Model Engine Maker

Engines => From Kits/Castings => Topic started by: Alyn Foundry on October 26, 2017, 06:21:49 PM

Title: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 26, 2017, 06:21:49 PM
Hello All.

I thought a dedicated thread for all engines that use expanded air might be a useful addition to the forum.

Some will remember that I used to sell a half scale replica of the Robinson number 4 hot air engine, production stopped when Rhuddlan foundry closed. The main reason was that nobody could make the highly complicated mould that used 3 different cores just to make the platform. The other problem arose when the price of Aluminium scrap topped the £1000.00 per Ton mark and four of my Aluminium master plates were stolen from Buckley who produced the cylinder castings.

Thanks to Andy ( Chipmaster ) we have had some new cylinders cast and I have just finished or should I say refinished my old Robinson Hot Air Engine that became a cylinder donor to an old customer several years ago.

Some pictures and a video to come later....

As this is an open thread please post any “ Hot Air Engine “ related builds or pictures of your engines here.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 26, 2017, 06:30:33 PM
Some pictures and a video to come later....

 :pics:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 26, 2017, 06:32:56 PM
Indeed Jo.   ;)
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 26, 2017, 06:36:54 PM
Top picture is the first half scale engine to be built by the Alyn foundry.

The lower picture is perhaps the earliest surviving Robinson patent engine built in the 1880's before Robinson's themselves. It's air cooled !!
Title: Re: Strictly.... “ Hot Air “
Post by: b.lindsey on October 26, 2017, 06:51:41 PM
Nice pictures. Are both of them cast iron? They sure look to be. Very nice!!! As for the thread, are you looking for both stirling as well as atmospheric engines Flame Lickers)?

Bill
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 26, 2017, 06:52:05 PM
A kit....
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 26, 2017, 07:06:15 PM
Nice pictures. Are both of them cast iron? They sure look to be. Very nice!!! As for the thread, are you looking for both stirling as well as atmospheric engines Flame Lickers)?

Bill

Hi Bill.

I think my last post showing the ru... em patina tells you they're Iron.  :)

The lower picture is an original 130 year old engine at full scale.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 26, 2017, 07:11:55 PM
Graham, looking at the first two photos you posted the only major difference that I can see if teh valve on the end of the model cylinder, linkages look very similar. Are there any other variations that I can't see?

Must admit I like the look of the original engine, not sure if it is the shape or the bare iron that tickles my fancy :thinking:

I would think supporting the core(s) for the water space was quite difficult, the air passage not so bad as it can be supported at either end
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 26, 2017, 08:00:02 PM
Graham, looking at the first two photos you posted the only major difference that I can see if teh valve on the end of the model cylinder, linkages look very similar. Are there any other variations that I can't see?

Must admit I like the look of the original engine, not sure if it is the shape or the bare iron that tickles my fancy :thinking:

I would think supporting the core(s) for the water space was quite difficult, the air passage not so bad as it can be supported at either end

Hi Jason.

Indeed, the simplicity of the air cooled engine is amazing.... I too like the unpainted theme.

The valve in the later design was a governor, a simple disc in the air tract that was held open by a light spring. As the air passed more rapidly the disc would be drawn forward against a step and close the power cylinder completely.... Not a good idea, so a couple of small holes were used in the disc to diminish the dead stop condition.

The water jacket core was a nightmare !!  Supported by " Chaplets " they used to " Blow " regularly to start with, but a newer resin bonded sand was used and we produced well over 200 kits.

Pictures are great, video even better !!   ;)

AHQKtDbZUXA
Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Ian S C on October 27, 2017, 11:39:04 AM
one of our machinery club guys brought a Robinson over from Australia about three years ago, quite an impressive motor.
Ian S C
            (http://)
Title: Re: Strictly.... “ Hot Air “
Post by: b.lindsey on October 27, 2017, 01:16:49 PM
That is quite a large engine and beautifully restored as well.

Bill
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 27, 2017, 01:31:40 PM
Hi Ian.

Thanks for your input.

Do you know the bore and stroke dimensions? I believe the number 6 was 10” bore and the largest that Gardner’s of Patricroft built.

Note the extra cooling tank that doubles as the main bearing support.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: scalemodel on October 27, 2017, 08:19:23 PM
When I was 19 many years ago I brought a rider Ericsson from camdam minature steam services which I built, at the time they hadn't got any firebox castings in so they said they would send one I'm still waiting!! But that's another story

When the rider was done I brought a set of castings off the engineers emporium for their robinson engine which is quite a big model, not long after I brought these I got into model traction engines and the robinson never got started.
I may push the castings on or swop them for some other castings maybe steam related.

Just thought I would share my hot air experience

Jonathan
Title: Re: Strictly.... “ Hot Air “
Post by: Ian S C on October 28, 2017, 11:49:23 AM
I have not measured the bore, but I would say it's near enough to ten inches,  It should be at a show near here in a few weeks, if I remember, I'll run a tape over it.
Ian S C
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 09, 2018, 03:25:24 PM
Hello All.

Number 3 son Alan started on his Robinson hot air engine some nine years ago. School, college and an apprenticeship kinda got in the way....

However....

-kNKswjpc20
That’s a short run to test before painting, more to come.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on January 09, 2018, 03:49:36 PM
Lets hope he has not bought quick drying paint for it :Lol:

Looking good, have the boys made any more progress on their RLEs?
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 09, 2018, 04:05:41 PM
Hi Jason.

Hmmm.... trying to find a warm place to spray without upsetting mama is the problem.

Alan's about a third of the way through and Mathew about a quarter. I'll try to post some photos on the R.L.E. thread that Jo started.

Meanwhile, a few pictures showing the complexity of patterns and core boxes for " JUST " the engine platform.

Cheers Graham.

Picture 1.

Showing all the parts. The big plate makes an impression for the platform outside core. Picture 2 shows the platform pattern now split to allow removal from its box. Picture 3 showing the air passage and displacer cavity core box. Picture 4 showing the water jacket core box and " Robinson Patent " cores.
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on January 09, 2018, 06:19:29 PM
I started working on castings for the Robinson hot air engine last October.
Graham suggested that I add some pictures of a platform casting that I have been working on. Some defects called cold shuts only became apparent as I milled the upper surface of the casting and there is a porous blowhole underneath.

I started off milling the underside of the platform casting flat.
(https://farm5.staticflickr.com/4664/38702403185_ebc714d274_z.jpg) (https://flic.kr/p/21XZW6x)WP_20171106_10_37_17_Pro (https://flic.kr/p/21XZW6x) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

I could see a depression to the left of the casting but it didn't concern me at that stage...
(https://farm5.staticflickr.com/4628/24730935497_f04df65814_z.jpg) (https://flic.kr/p/DFovvB)WP_20171106_12_48_09_Pro (https://flic.kr/p/DFovvB) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

Ready to mill the top of the platform flat
(https://farm5.staticflickr.com/4628/24730934897_bbeddab9c6_z.jpg) (https://flic.kr/p/DFovkg)WP_20171106_13_10_37_Pro (https://flic.kr/p/DFovkg) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

Then the cold shuts were revealed....
(https://farm5.staticflickr.com/4664/24730934527_f6b7214b57_z.jpg) (https://flic.kr/p/DFovdT)WP_20171106_15_51_38_Pro (https://flic.kr/p/DFovdT) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

I filled the air passage in the casting with thinners to test for porosity and it leaked like a sieve...
(https://farm5.staticflickr.com/4673/27821572329_36a91d8ece_z.jpg) (https://flic.kr/p/JouQax)WP_20171108_12_17_23_Pro (https://flic.kr/p/JouQax) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

Graham agreed the casting was scrap and he would resurrect the patterns so we could have some more cast.
I have continued to work on the other castings

Cylinder, I started by milling the base flat.
(https://farm5.staticflickr.com/4703/38702404375_5bbc391236_z.jpg) (https://flic.kr/p/21XZWs4)WP_20171104_12_35_43_Pro (https://flic.kr/p/21XZWs4) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

Then boring it out
(https://farm5.staticflickr.com/4613/27821572669_e644c5b206_z.jpg) (https://flic.kr/p/JouQgp)WP_20171106_13_25_43_Pro (https://flic.kr/p/JouQgp) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4715/24730934407_e3b931575b_z.jpg) (https://flic.kr/p/DFovbP)WP_20171127_11_28_43_Pro (https://flic.kr/p/DFovbP) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

Lapping the cylinder using fine Timesaver compound
(https://farm5.staticflickr.com/4651/39598440891_e237d9c1b4_z.jpg) (https://flic.kr/p/23kbmTv)WP_20171230_15_32_21_Pro (https://flic.kr/p/23kbmTv) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

Machining the displacer cylinder insider and out then forming a groove for a large O ring seal...
(https://farm5.staticflickr.com/4610/38702399715_db5014dd0e_z.jpg) (https://flic.kr/p/21XZV4H)WP_20171231_15_56_14_Pro (https://flic.kr/p/21XZV4H) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4706/38702393265_b7d1df30e1_z.jpg) (https://flic.kr/p/21XZT9v)WP_20180103_15_42_33_Pro (https://flic.kr/p/21XZT9v) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4708/39598435751_f36731b120_z.jpg) (https://flic.kr/p/23kbkmT)WP_20180103_16_04_20_Pro (https://flic.kr/p/23kbkmT) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4747/39598435621_ee8fa06a9b_z.jpg) (https://flic.kr/p/23kbkjD)WP_20180103_16_19_56_Pro (https://flic.kr/p/23kbkjD) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

This is the engine as at yesterday afternoon
(https://farm5.staticflickr.com/4648/38702390965_46138fc79d_z.jpg) (https://flic.kr/p/21XZSsR)WP_20180107_19_41_31_Pro (https://flic.kr/p/21XZSsR) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4758/38890260224_54a11504cf_z.jpg) (https://flic.kr/p/22fAKs1)WP_20180107_19_43_33_Pro (https://flic.kr/p/22fAKs1) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

I'm expecting Graham to pick me up on the use of screws to hold the flywheel on the crankshaft, they will be replaced by discreet grub screws........

Andy


Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 10, 2018, 11:40:18 AM
Good morning Andy.

It’s your engine, your prerogative.   :)

The 3/32” wide keyway is the smallest one on the range of kits I produced but I duly bought a broach back in the day.

A tool like that will last a lifetime, if cared for, well maybe more! As I was also providing a machining service at the time the £30.00 cost soon disappeared.

The gib head key was just an 1/8” one carefully milled down from my stock of 200, I used to do them in pairs as the tapers then cancelled themselves out.

Your progress is excellent and your workmanship also. I can’t tell from the photograph but how deep is the
“ O “ ring groove in the “ hot pot “ ? I used to make mine with quarter depth in both “ hot pot “ and platform which gives an ideal thermal separation,  the “ O “ ring itself becoming the register for alignment.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on January 10, 2018, 05:00:54 PM
Good evening Graham.
I spent all my pocket money on castings so I don't have any broaches  :(. I reckoned two grub screws 120° apart would suffice instead of an authentic look.
The groove is 0.15" deep so the O ring is about 0.050" above the surface of the cast iron displacer cylinder AKA 'Hot Pot' to be compressed and seal against the platform.
(https://farm5.staticflickr.com/4765/25744831458_140d704a9b_b.jpg) (https://flic.kr/p/FdYZss)O Ring Groove (https://flic.kr/p/FdYZss) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

For alignment i'm relying on the three 1/4" Whitworth studs that secure the base to the platform, they almost touch the displacer cylinder flange so there is virtually no movement. It didn't occur to me to machine grooves in the hot pot and platform.
Will make the piston next.

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on January 10, 2018, 05:12:02 PM
I spent all my pocket money on castings

:facepalm:

Tell your wife I said she needs to give you need more pocket money so you can buy more castings  :ThumbsUp: (or broaches  :naughty: )

Jo

In the meantime if you hear of any casting sets I am willing to consider buying them to keep them safe  :mischief:
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on January 10, 2018, 05:57:50 PM
Yes Jo, if only all women saw things the same way as you !

if I become aware of any casting sets in need of saving I'll let you know  ;D

Andy



Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on January 10, 2018, 06:06:17 PM
This Tesco Tuna tin will be the displacer after the contents have been consumed.
I may need to bore out the displacer cylinder / hot pot further to achieve optimum clearance.

(https://farm5.staticflickr.com/4768/39569275002_78ee6df1cb_z.jpg) (https://flic.kr/p/23hASTm)WP_20180103_16_09_43_Pro (https://flic.kr/p/23hASTm) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 10, 2018, 06:36:15 PM
I spent all my pocket money on castings

Jo

In the meantime if you hear of any casting sets I am willing to consider buying them to keep them safe  :mischief:

Hi Jo, are you joking or being serious?

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 10, 2018, 06:45:43 PM
Hi Andy.

I’m not sure if the “ O “ ring modification was put in writing in the construction notes as I have mislaid them.

As you can imagine the “ O “ ring will perfectly register the two components whilst both acting as a seal and thermal barrier.

What weight is the Tuna can with contents? My supermarket no longer sells the 185 gram tin which is the correct depth. I’m using a tinned Crab meat here, sadly the contents, I’m told leave a lot to the imagination!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on January 10, 2018, 07:01:21 PM
In the meantime if you hear of any casting sets I am willing to consider buying them to keep them safe  :mischief:

Hi Jo, are you joking or being serious?

Cheers Graham.

Graham how long have you been a member on this forum  :stickpoke: when have you not seen me looking to help out casting sets by providing them with a loving home  :noidea: my usual supplier has run out of desirable ones (that he is willing to sell me  :wallbang: )


I decided that I would take Alan's recommendation on my new year resolution about buying casting sets so I will be buying fewer not more :mischief:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on January 10, 2018, 07:25:06 PM
Hi Graham,
I'm using the photographs of your plans that I took in your kitchen and I haven't seen construction notes but I'm content that the three 1/4" Whit studs will do the job, they'll have to now !

Tesco Tuna Chunks in Spring Water 160g net weight, contents very good. Will the height of the tin be critical?

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 10, 2018, 08:07:21 PM
Hi Jo.

How desirable does the Alyn Foundry half scale Robinson hot air engine sound?

Because....

I have 90% of one here, well might be 80%, I’m not sure yet. Alan tells me we haven’t got a flywheel.

As you know, thanks to Andy we got some cylinders cast, and they have machined up nicely. The next part is to see if they can manage the horrendously complicated platform casting. I have loads of the other parts left over.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 10, 2018, 08:11:38 PM

Tesco Tuna Chunks in Spring Water 160g net weight, contents very good. Will the height of the tin be critical?

Andy

Hi Andy.

The working depth of the “ Tuna can regenerative displacer “ is 45mm. Anything less in depth might not work.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on January 10, 2018, 08:31:41 PM
How desirable does the Alyn Foundry half scale Robinson hot air engine sound?

:naughty: I have been hoping to add a couple of Sterling's to the collection.. You will have to see how much of a set you can find...  ;)

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on January 10, 2018, 09:24:41 PM
Hi Graham,
the Tesco Tuna tin is 38mm deep, if that won't do and I can't source a tin of the appropriate size then I'll fabricate a lightweight regeneratice displacer using thin brass sheet.
How are you getting on with the platform patterns? I'm confident the AJD foundry will produce sound castings  :cheers:

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on January 11, 2018, 08:02:48 AM
Just had a look through mine: John West & Waitrose (160g) are 37mm high and Asda is tallest at 41mm (185g)  :-\.

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Ian S C on January 11, 2018, 09:25:51 AM
If you can't get the right size of tin can, lookout for a stainless steel container, stainless cup, mug, kitchen containers. Another way is thin walled stainless tube, with a cap TIG welded on one end to form a cup.  Steel, stainless or not is always better than brass.
Ian S C
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on January 11, 2018, 10:28:41 AM
Hi Ian, yes I'd prefer stainless but getting it welded at a low price would be a problem for me, in the past I think you've mentioned that you have a friendly TIGer.

Jo - oooh Waitrose - posh stuff, I'll take a ruler next time we go shopping and look at a wider range of tinned food.

Searching the Internet I saw images of Sirena and John West tinned tuna 185g sold in Australia. The proportions of those tins looked much deeper than UK equivalents.

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 11, 2018, 11:20:18 AM
Good morning, early birds.

Yes, Ian has nailed it....

A lot on non running hot air engines have used “ Cuprous “ based materials for the displacer piston. The highly thermally conductive material will equalise, very quickly the temperature differential that’s needed for these types of engine to run.

So....

ASDA sell a tinned Crabmeat,  “ Kingfisher “ I think? The tins are exactly right and light enough for the job.
The regenerative packing material is a couple of Stainless Steel pan scrubs neatly stuffed inside before soft soldering the lid back on.

I say “ neatly “ because after sealing the piston you need to carefully hold and then drill through the soldered top at 5/16” or 8 mm and then push a 2 BA clearance drill through the bottom. The final part of the job is to provide passage of the air through the regenerative material. I have inherited a set of specially ground drill bits that have a point and then two sharpened edges that neatly cut to their diameter.
I place 4 holes through the top and then rotate by 45 degrees to place the 4 holes through the bottom.

Regenerative displacer piston, finished!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on January 11, 2018, 01:58:16 PM
Andy why can't you silver solder a stainless one, easy to do with Tenacity No5 or HT5
Title: Re: Strictly.... “ Hot Air “
Post by: Zephyrin on January 11, 2018, 02:12:24 PM
we immediately spot a hot-air engine builder  in a grocery store, he does his shopping with a caliper.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 11, 2018, 02:24:11 PM
we immediately spot a hot-air engine builder  in a grocery store, he does his shopping with a caliper.

Hi Zephyrin.

Indeed, I was very carefully scrutinised by a little old lady whilst measuring the various tinned fish products! She actually asked me what I was doing.

Upon providing my answer a look of total blankness appeared. It was all I could do to stop myself laughing!

Cheers Graham.

PS.  Yes Jason, a very light gauge SS tin, Silver soldered would suffice.
Title: Re: Strictly.... “ Hot Air “
Post by: Perry on January 11, 2018, 02:56:38 PM
 :lolb:
we immediately spot a hot-air engine builder  in a grocery store, he does his shopping with a caliper.

Hi Zephyrin.

Indeed, I was very carefully scrutinised by a little old lady whilst measuring the various tinned fish products! She actually asked me what I was doing.

Upon providing my answer a look of total blankness appeared. It was all I could do to stop myself laughing!

Cheers Graham.

PS.  Yes Jason, a very light gauge SS tin, Silver soldered would suffice.
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on January 11, 2018, 07:09:32 PM
Andy why can't you silver solder a stainless one, easy to do with Tenacity No5 or HT5

Yes Jason I could have a go at soldering up stainless steel but I'd have to obtain the material which might take longer than using a tin.

Meanwhile, because I don't like crab meat a friend who does is going to buy a tin of Kingfisher crab meat from Asda tomorrow and bring the empty tin over on Saturday. I've given him the dimensions.

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 12, 2018, 02:23:20 PM
A sight unseen since 1991.

5VW0Zi-f7g0
Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on January 13, 2018, 08:51:30 PM
A Kingfisher Crabmeat tin is a close fit.
My friend brought round the empty tin this morning. it is 47mm deep as recommended by Graham and the diameter in particular the top rim is a close fit in the displacer cylinder = 3.4" bore. If I'm successful turning it into a displacer I'll bore out the cylinder to suit.
P.s. my friend enjoyed the crab meat.

(https://farm5.staticflickr.com/4615/25800290218_8b6865bfc8_z.jpg) (https://flic.kr/p/FiTepY)WP_20180113_17_58_57_Pro (https://flic.kr/p/FiTepY) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4603/25800290608_044c1001e6_z.jpg) (https://flic.kr/p/FiTewG)WP_20180113_17_57_19_Pro (https://flic.kr/p/FiTewG) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4766/38774907925_a93ce66b79_z.jpg) (https://flic.kr/p/225pxeg)WP_20180113_17_58_45_Pro (https://flic.kr/p/225pxeg) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

I spent the afternoon lapping the piston
(https://farm5.staticflickr.com/4709/38774907635_a861127b87_z.jpg) (https://flic.kr/p/225px9g)WP_20180113_18_00_59_Pro (https://flic.kr/p/225px9g) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on January 14, 2018, 09:18:59 AM
:thinking: That tin has a draft angle on it, I thought the sides needed to be parallel if it is ok the an alternative may be to buy the tins of Salmon.

Did you notice that Graham mentioned castings to me and then he has gone quiet, not even a pic of them  :disappointed:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on January 14, 2018, 10:18:40 AM
I think the angle on those spun/pressed tins is so minimal it is not worth worrying about.

It's coming along nicely Andy and is probably the only time getting crabs from a friend is welcome :-[

I wonder what size tin would suit a 24mm bore Robinson :thinking:
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on January 14, 2018, 10:56:27 AM
Yes Jason I agree with you.....about the draft of sides of the tin, don't know about the rest  :LittleAngel:

I haven't noticed whether the tins are tapered. The displacers I made for my Rider Ericsson and Heinrici hot air engines have a clearance within the displacer cylinder so that the air can pass freely.

As for a 24mm bore Robinson perhaps a small paint tin would suit.

Jo - you might be waiting for new platforms to be cast like me. The platform on my engine is no good because of cold shuts and blow holes. Graham is repairing the patterns and we've agreed to meet up when he's ready and I'll take the patterns to the AJD foundry in Brierley Hill.

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 14, 2018, 11:25:41 AM
Good morning.

The tin does have a slight taper but as the air on this engine is supposed to travel through it rather than round it, no problem!

Andy, progress is slow but sure. If you recall I mentioned that the water jacket core box that was used many times by the lads at Rhuddlan was wrong? The core was actually longer than the casting!! They never told me about the problem, they just removed the excess in the core shop. This fault only became known when my father in law and I tried to mould a platform at the Buckley foundry. In trying to shorten the cast Aluminium box I managed to break it.

Jo, I have many spare Iron castings for this engine but no platforms, cylinders or flywheels. And I don’t have a full set of Gunmetal linkages. In making inquiries about more links it seems the Brass foundry has mislaid my patterns at the moment.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 15, 2018, 07:58:51 PM
Hello All.

I found this hidden away on a shelf in the workshop a few days ago. I'd almost forgotten I'd built it.

_0MZLg5v4zc
Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Perry on January 15, 2018, 09:32:15 PM
thats so entertaining, nice marble stirling  :ThumbsUp: nice
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on January 16, 2018, 10:18:42 AM
Soldering tin lids back on.
I had a practice at soldering the lid back on to a tuna tin yesterday using an electric soldering iron and 60/40 blowpipe  solder. The tin was stuffed with steel wool to simulate the recommended stainless steel pan scourers.

Hi Graham - is that how you made your displacers and how many 1/8" holes did you put in your displacers?

Andy

Title: Re: Strictly.... “ Hot Air “
Post by: Bluechip on January 16, 2018, 10:29:40 AM
Not quite 'Off-Topic' but sort of relevant:

www.ebay.co.uk/itm/Tattoo-Stainless-Steel-Cotton-Disinfection-Container-Tank-Alcohol-Canister-J7/292397617230?_trksid=p2485497.m4902.l9144

I wonder if these would be suitable for displacers ?

Probably nowhere near the size required for this engine but perchance for others.

Dave
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 16, 2018, 11:06:30 AM
Good morning Andy.

Yes that’s exactly what the finished regenerative displacer piston should look like before drilling the holes.

On the two recently built and rebuilt engines we went for 4 holes at 1/2” diameter placed 90 degrees offset between the top and bottom.

The most delicate part of the operation is to get the displacer piston rod hole accurately centred and drilled without it snagging the Steel wool within. About a week ago Alan came in from the workshop holding what looked like something that had been through a shredder, yes, it had snagged, an hour or so’s work wasted.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 16, 2018, 11:56:12 AM
Update.

Despite a recent break in at the Brass foundry that I’ve used for over 30 years now, my wooden patterns are safe.

I’ve ordered 6 sets of “ link motion “ castings for the half scale Robinson hot air engine. They’re being done in Brass this time as they very rarely do Gun metal these days.

I’m now in the process of getting the relevant patterns together for a small run of of castings. I’m hoping to have 6 kits available from a mixture of leftovers and new Iron parts within a month or so.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on January 16, 2018, 01:17:02 PM
Hi Graham, pity I recently sold my Weirauch HW80 air rifle which would have put neat .22 holes throgh the tin.   :)
Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on January 16, 2018, 04:22:01 PM
If Graham advocates 1/2" holes then you may as well get a tin, drill the holes and prize out the contents before poking the scouring pads in via the holes, saves all that soldering :)
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on January 16, 2018, 06:26:44 PM
Yes Jason I thought about removing the contents through 1/2" holes and inserting stainless steel scouring pads in the other direction but the material might fall out through the holes.
 I expect Graham has tested these options and will comment. The plans state "Cover both faces with 1/8" holes leave 1/2" band around circumference un drilled". Perhaps Graham has found fewer 1/2" holes more effective. I haven't found any pictures of Robinson regenerative displacers.
Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 16, 2018, 07:02:16 PM
Hi Andy.

Drilling 4 holes either side is far less time consuming than many 1/8" holes, otherwise there's nothing to be gained!

Here's a picture of the internals from a 1905 book, Modern engines and power generators.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on January 17, 2018, 12:49:48 PM
Thanks Dave, well spotted those stainless steel tins would be useful to hot air engine builders. The 9cm tin is closest to my requirements.
Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 23, 2018, 06:33:35 PM
Wonderful service!!

Look at the contents of a surprise parcel that arrived by courier this morning.

We're one step closer to a small run of Robinson hot air engine kits.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on January 23, 2018, 06:49:04 PM
Castings  :naughty:

I can tell you know how to chat up a young lady Graham  :embarassed:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: b.lindsey on January 23, 2018, 06:51:24 PM
I think you should reserve one set for shipment to the USA.  :naughty:

Bill
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on January 23, 2018, 07:14:38 PM
Castings  :naughty:

I can tell you know how to chat up a young lady Graham  :embarassed:

Jo

Jo I think Graham swings both ways as he has just sent me some photos of castings :-*
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on January 23, 2018, 07:29:06 PM
Jo I think Graham swings both ways as he has just sent me some photos of castings :-*

I think he knows you better than he is letting on  :lolb:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 25, 2018, 04:14:14 PM
Hello All.

I’d like to share a little nostalgia with you. The following pictures are of a Robinson platform that my father in law and I moulded 10 years ago. It was one of the last Iron castings to leave the Buckley Iron foundry when they closed. The casting wasn’t a very good one, there was a nasty gash across the upper part and the “ air port “ core had broken and breached to the water jacket.

Sadly my father in law has since developed Alzheimer’s disease and as a kind of comfort Mathew decided to try and use his grandad’s handy work.

A big lathe makes the job look easy.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 25, 2018, 05:44:42 PM
As a follow up....

The gash in the platform quite literally, disappeared!

But the photograph shows the breach into the water jacket quite clearly.

We have milled down through the top with the intention of gluing a rectangle of Steel into the neat slot, pre drilled, of course.  ;) The beauty of this is that the cylinder sits and hides all the remedial work, only we and the entire readership of MEM will ever know.  :)

Jo.

Please note my special coating process is already starting!   ;)

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 29, 2018, 07:12:31 PM
Some sad news.

Alan, Mathew’s grandad passed away this morning....

He took over Alyn Foundry for a few years whilst I recuperated from my own health issues, he will be sorely missed.

Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: RayW on January 29, 2018, 07:50:33 PM
So sorry to hear your sad news Graham. Without Alan, many of the Alyn Foundry engines wouldn't exist today, so we all owe him a big debt of thanks.

Best wishes
Ray
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on February 06, 2018, 12:40:37 PM
Here are three links to YouTube videos of my recently completed Robinson Hot Air Engine.

Running in
AcvF79pigrg
Fitted with governor, spring compressed
bEiQ2Sm8W28
Running with governor spring loose
wpUjZJWogA8
Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on February 06, 2018, 01:17:46 PM
All rather good though I think I like the slow speed of the running in video best.

I suppose it's time for a lick of paint now, was there a factory colour for these?
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on February 06, 2018, 01:23:07 PM
Nice runner. Especially are there are no nasty bits trying to chop off thumbs  :)

I thought they are supposed to be a stove or range top engine Andy  :noidea: all of Grahams ones run on his range  ::) . I wonder if they would run on my log burner if they didn't have the legs on the base  :thinking:

Jo

Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on February 06, 2018, 01:32:09 PM
Could always make a base like this and use up your twigs Jo :)

(http://www.stationaryengine.org/Rallies%202005/Barleylands/robinson_barleylands_2005.jpg)
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 06, 2018, 01:46:16 PM
Well done Andy.

We just need to get a replacement platform for you in the not too distant future.

As for operation on gas flame that was exactly what the “ squat “ base was originally designed for. There were other bases produced to run on coal with a firebox, grate and chimney.

Love Jason’s picture of either a number 5 or 6 I noticed several foil packages under the firebox, baked spuds for tea!!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on February 06, 2018, 01:49:44 PM
Nice little model of a similar engine here by a man after my own heart ;)

http://birkpetersens.blogspot.co.uk/2012/06/robinson-type-hot-air-model.html
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on February 06, 2018, 05:05:58 PM
Now that my engine runs I'll take it apart and polish the gun metal linkages like this one owned by a friend.

Graham I believe you built this, but the protective coating has been amended.
(https://farm5.staticflickr.com/4705/28338454269_bea8fb9628_z.jpg) (https://flic.kr/p/KbaZa8)DSC04659 (https://flic.kr/p/KbaZa8) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

(https://farm5.staticflickr.com/4721/25247013747_4af417f8d6_z.jpg) (https://flic.kr/p/EsZxAt)DSC04660 (https://flic.kr/p/EsZxAt) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

Jason, I agree I prefer slow running :old:.

Jo,
I can understand you thinking they were meant to sit on gas hobs. However, I'm not allowed to bring engines in the house.
 
Nice runner. Especially are there are no nasty bits trying to chop off thumbs  :)
Jo

Agreed but the base does get hot enough to burn your thumbs instead.

Andy


Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 06, 2018, 06:25:47 PM

Graham I believe you built this, but the protective coating has been amended.

Andy

Hi Andy.

Yes, if it’s  MC’s?

Grrrrr..... they never left me like that in the past....  :)

But time and a constant flow of ground water through the workshop doesn’t help at all!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on February 06, 2018, 07:03:14 PM
Yes correct Graham, that one with the modified surface treatment belongs to MC.

Quote
Grrrrr..... they never left me like that in the past....  :)
Cheers Graham.

Yes I reckon some folk don't appreciate the care that went into acheiving the original factory finish.

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 21, 2018, 08:49:45 PM
" Graham
Not strictly from rejects, but definitely Robinson related. A few weeks ago I managed to acquire an unmolested set of castings for the Robinson hot air engine, still I think, in the original packaging. There is one drawing, is that all? I don't quite understand how the displacer piston goes together, what material did you use. I was thinking of thin wall brass tube with sheet brass end pieces, made to be a slack (maybe 30 thou) fit in the hot end cylinder. How hot does that get? Can I use soft solder on that displacer piston?
The other bit I don't understand is what seems to be a governor valve in the end of the cold cylinder. How does that work?

Regards

Richard "

Hello Richard.

We'd love to see some pictures of your acquisition, I'm hoping they look better than with my now famous " Special coating " ?   ;)

Yes, only one drawing. This was an emulation of how Gardner did theirs back in the day.

The displacer is best made from a ready made lightweight Steel tin, the process and utilisation of same has been covered in previous pages.

Yes it's a governor and it works by air trying to pass the disc and drawing the disc onto a shoulder that then closes the transfer port. A couple of small holes drilled through the disc prevent the engine from stopping dead.

Please use this thread to detail your build progress and feel free to ask any questions that may arise.

Cheers Graham. 
Title: Re: Strictly.... “ Hot Air “
Post by: Mcgyver on February 22, 2018, 02:14:44 AM

As this is an open thread please post any “ Hot Air Engine “ related builds or pictures of your engines here.

Lots of hot air here, just ask my wife.

I didn't see any Rider Ericsson models, so thought I'd put some up of one I made, probably 10 years ago now.  Its great runner, pumps water well.  A few deviations from the drawings, the power cylinder I machined and then lapped the bore.  For the piston I shrunk some bronze rings on the AL piston and turned them in situ.  My thinking was to get good performance it needed minimal clearance, minimal contact area between the cylinder and piston (rings) and both should be very round, straight and smooth

(https://i.imgur.com/SRo8akg.jpg)

(https://i.imgur.com/P93Qyue.jpg)

(https://i.imgur.com/Kl6AeAk.jpg)

(https://i.imgur.com/OsKFYBM.jpg)

(https://i.imgur.com/bCDSZXj.jpg)











Title: Re: Strictly.... “ Hot Air “
Post by: Perry on February 22, 2018, 07:48:01 AM
Hello Mcgyver, what a beauty you have there. Very attractive in that green paint.   :ThumbsUp:
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 22, 2018, 11:05:46 AM
Hello Mcgyver.

Many, many thanks for posting the pictures of your Rider Ericsson hot air engine. It looks lovely, what scale is it?

I have a set of un started castings, well apart from the finished flywheel.... :) Mine has the 11” diameter one.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on February 22, 2018, 01:17:40 PM
Watch out Graham Jo will be after those :mischief:
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on February 22, 2018, 01:21:25 PM
Watch out Graham Jo will be after those :mischief:

We are still waiting for pictures of his Welsh  Casting Gold Mine  ::)

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Mcgyver on February 22, 2018, 02:43:03 PM
It looks lovely, what scale is it?

I have a set of un started castings, well apart from the finished flywheel.... :) Mine has the 11” diameter one.


Thank you, its 1/4 scale irrc.   11" sounds about right for the flywheel.   

The full size were made in different sizes - I couldn't tell you what size the model is of.  A while ago I visited a chap in the Muskoka area who had a great collection of full sized mechanical things including two Rider Ericsson engines.  Here's some snaps I took.  Digging them out reminds me of the of a few finishing bits I haven't gotten around to yet on mine.

(https://i.imgur.com/qHz6HCA.jpg)

(https://i.imgur.com/wOmhkcu.jpg)

(https://i.imgur.com/cvupapX.jpg)

(https://i.imgur.com/gRisW76.jpg)

(https://i.imgur.com/w2nXFOK.jpg)





Title: Re: Strictly.... “ Hot Air “
Post by: b.lindsey on February 22, 2018, 02:49:00 PM
That is a lovely R.E Mcgyver. Still one of my favorite engine!! I agree it looks good in the green also.

Bill
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 22, 2018, 04:39:57 PM
Hello All.

Finally, the weather has improved here and I ventured out to the workshop.

Geof of the Anson engine museum asked me to make him a Robinson for the upcoming 150th anniversary of L Gardner and sons engine business.

Pictures of the start on a rejected platform with very poor lettering.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on February 22, 2018, 05:42:24 PM
Here are some pictures of my crab meat tin displacer. To avoid tangling the drill with the stainless steel scouring pads when drilling the central hole, I soldered a small tube inside the tin to keep the scouring pads away from the drill.
(https://farm5.staticflickr.com/4658/40379023712_202d110480_z.jpg) (https://flic.kr/p/24wa3Y1)P1070307 (https://flic.kr/p/24wa3Y1) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4610/40379023302_a2698d2736_z.jpg) (https://flic.kr/p/24wa3QW)P1070311 (https://flic.kr/p/24wa3QW) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

and here are three pictures of the governor with small holes to avoid bringing the engine to an abrupt halt.
(https://farm5.staticflickr.com/4721/39712397874_4d4cd18270_z.jpg) (https://flic.kr/p/23vfqk5)P1070400 (https://flic.kr/p/23vfqk5) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4614/38612199300_eaafa71c9d_z.jpg) (https://flic.kr/p/21Q2BC9)P1070399 (https://flic.kr/p/21Q2BC9) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4631/39712397644_4ea5708663_z.jpg) (https://flic.kr/p/23vfqg7)P1070401 (https://flic.kr/p/23vfqg7) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

The shaft is peened over the disc to retain it and the disc is sucked against the flange that can be seen in these pictures
(https://farm5.staticflickr.com/4620/40379023082_8d8d056061_z.jpg) (https://flic.kr/p/24wa3M9)P1070394 (https://flic.kr/p/24wa3M9) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4721/38612198430_1ebe4fa307_z.jpg) (https://flic.kr/p/21Q2Bn9)P1070396 (https://flic.kr/p/21Q2Bn9) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

This part of the engine gets very rusty. what are your governors like Graham?  :stickpoke:

Andy

 


Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 22, 2018, 05:54:39 PM
Hi Andy.

Poke, poke....

Ahem, I didn’t fit one to mine! :)

However, your excellent photos should help with Richard’s recent enquiries immensely.

Whilst supping my mug of “ roseylee “ I was thinking about a couple of other hot air engines that you rarely see like Hayward Tyler and Bailey. Has any member here built or scratch built any models ?

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 22, 2018, 08:25:08 PM
Anson " commission " update.

Overall time 2 hours give or take.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Perry on February 23, 2018, 11:19:37 AM
Hello Graham and all. Since my first try on stirling engine  http://www.modelenginemaker.com/index.php/topic,6504.0.html   I found great interest on this topic and would definetly like to build more hot air engines in future.
I’d like to take advantage of this hot-air dedicated thread and ask few questions :


1.   Lubrication

Beautiful, above pictured Rider Ericsson may be a perfect example and I would like to understand what is the lubrication practice for power piston and displacer piston rod and how to ensure that oil will not get to the bottom of the hot cap after some time.

In my experience with my brave little stirling is that after some running time (hours) tiny amounts of light oil, that I use to lubricate displacer piston rod, will leak trough gland and find its way down to hotcap bottom, this resulting in oil burning/smoking inside and affecting engines performance. ( I dont lubricate power piston at all)

Is this not an issue with full size hotair engines and larger models?

2.   Regenerative displacer piston

Grahan, watching your progress with Robinson engine made me thing about this topic, I’d like to understand, if in this scale, does the regenerator actualy add anything to the  performance of engine.
Specificly,if the enlarged „dead volume“ introduced by the regenerator does not take away the bebefit of the regeneration. Fully enclosed displacer piston would not create this additional dead volume.

And sub. question to this topic: why is stainless steel wool/mesh a good choice for regenerative purposes? I undrstood that SS is good for displacer piston due to low thermal conductivity.Isnt good / high thermal conductivity a property that is desired for good regenerative function? Would cooper mesh be usable / better / poorer option ?


Many thanks for all answers

Perry
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 23, 2018, 11:56:18 AM
Good morning Perry.

You have raised some interesting questions.

Re. Lubrication.

As we all know the smaller you get in size with a hot air engine the less power you have, even the lubricant can cause drag. Luckily the half scale Robinson is large enough to cope with ordinary engine oil.

Over a long period of time oil does get into the hot end and “ cook “ but never really caused any problems as we ran them at outdoor rallies.

Re. Regenerative displacer piston.

You raise a good point about the use of Stainless Steel as opposed to a Cuprous material. The thermal efficiency of say Copper would be far superior but according to record Robinson’s used perforated Iron sheets.

Whether or not the use improves performance, I cannot answer with any confidence, but....

We tried both a sealed empty tin and a fully stuffed open tin displacer in the same engine. We found with the sealed tin the engine wouldn’t exceed a certain RPM no matter what the heat intensity was. With the stuffed and open tin the engine would accelerate with higher heat.

Our conclusion was that the air in the closed system had to get around the small space of the sealed piston causing drag whereas with the stuffed piston the air could move much more freely.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Ian S C on February 23, 2018, 12:40:36 PM
For the regenerator you do not want the heat to be conducted from one end to the other. Andy Ross in his experiments with regenerators found that the best he could come up with was stainless steel foil with dimples on it to separate the rolled sheets. Stainless wire and mesh have been used, you have to be careful with some engines if you use stainless(or non)steel wool as it can break up and the bits get in the wrong places.
Ian S C
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on February 23, 2018, 02:14:13 PM
"Whilst supping my mug of “ roseylee “ I was thinking about a couple of other hot air engines that you rarely see like Hayward Tyler and Bailey. Has any member here built or scratch built any models ?
Cheers Graham."

Hi Graham, someone has scratch built a model of a Bailey engine, see below. By the way I heard you on BBC Radio 4 at 11.00 this morning.

I took a few pictures of a Bailey engine held in Birmingham's Reserve Collection which I visited a few years ago. It was impossible to get a good picture.

(https://farm5.staticflickr.com/4630/39542054655_0cdf76b8ed_z.jpg) (https://flic.kr/p/23fcne2)Bailey Lehmann 1882 hot air engine [1] (https://flic.kr/p/23fcne2) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4607/39542054325_2395e74306_z.jpg) (https://flic.kr/p/23fcn8k)Bailey Lehmann 1882 hot air engine [2] (https://flic.kr/p/23fcn8k) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4713/39542054015_02c9014b0d_z.jpg) (https://flic.kr/p/23fcn2Z)Bailey Lehmann 1882 hot air engine [3] (https://flic.kr/p/23fcn2Z) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4748/39542053685_963d4f6c34_z.jpg) (https://flic.kr/p/23fcmWi)Bailey Lehmann 1882 hot air engine [4] (https://flic.kr/p/23fcmWi) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

In 2015 this superb model of a Bailey engine was displayed by the builder at the Stirling Engine Get Together at Kew Pumping Station.
(https://farm5.staticflickr.com/4696/39542134655_1f56a4e257_z.jpg) (https://flic.kr/p/23fcM1k)P1030710 (https://flic.kr/p/23fcM1k) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4769/38627473420_691f1a96d5_z.jpg) (https://flic.kr/p/21RnU63)P1030711 (https://flic.kr/p/21RnU63) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4768/40438375721_e4464360c7_z.jpg) (https://flic.kr/p/24Bpffv)P1030713 (https://flic.kr/p/24Bpffv) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr
(https://farm5.staticflickr.com/4706/38627473100_d213c2fc45_z.jpg) (https://flic.kr/p/21RnTZw)P1030714 (https://flic.kr/p/21RnTZw) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

This is a video of the model
(https://farm5.staticflickr.com/4654/25567497907_c4ca1975bb_z.jpg) (https://flic.kr/p/EXj7nr)Model Bailey Hot Air Engine at Stirling Engine Rally, Kew 2015 (https://flic.kr/p/EXj7nr) by Andy (https://www.flickr.com/photos/116764188@N08/), on Flickr

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 25, 2018, 07:06:58 PM
Many thanks for those pictures Andy.

Meanwhile, back in another area of what became an icebox....

Lapping of piston to cylinder using the material that makes the piston yoke.

Closeup of milled yoke.

Cylinder, piston and yoke.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on February 27, 2018, 02:49:48 AM
Hi
I think I've managed to attach some photos of my Robinson casting set. If you can't see them, I'll try again.

I've got some queries about the linkage mechanism. The drawing shows pin diameter of 0.3125" (5/16") for all the linkage pins except the one on the big end which is dimensioned as 0.250" (1/4"), even though diagramatically it is drawn as larger than the others. The bosses on the castings are barely 3/8" dia, so putting a 5/16" hole in them  will pretty much destroy them. Should the pins be, in fact, 3/16" dia, and 1/4" (or even 5/16") for the big end?

Richard
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 27, 2018, 11:11:25 AM
Hi Richard.

The pictures are there,  thanks.

Do you know what age the castings are? The drawing was later marked with an erratum as the pins were labelled as 5/16” when, indeed they should read 3/16” !

I hope the recent pictures Andy posted will help you get started? I’m hoping to be finished with my contract for the Anson Engine museum by the end of the week, weather permitting.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 27, 2018, 01:28:50 PM
Taking shape.
Title: Re: Strictly.... “ Hot Air “
Post by: Bertie_Bassett on February 27, 2018, 01:50:30 PM
looks good, and i see you are still maintaining the special coating  :ThumbsUp:


may have already been asked but would one of these engines work on top of a wood burning stove? the blanking plate on the top of mine looks like a perfect place for one driving a small fan. could even drop the hot end into the fire itself to aid things.  might all get too hot and equalise too quickly though ?
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 27, 2018, 04:28:42 PM
Hello Bertie.

A former customer managed to run his Robinson on a single “ nightlight “ candle, his engineering was impeccable!

Every moving part had been polished and he specified a particular lubricant, the name escapes me but something like “ Formula 1 “ is ringing a bell?

Our engines will run for hours on end so long as the water is replaced and I’m almost 100% certain that they’d drive a fan sat on top of a wood burning stove.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on February 27, 2018, 04:38:57 PM
Graham
The drawing with my castings is dated 1991, and the envelope containing it has the Alyn foundry address in Wrexham, and a telephone number which doesn't start '01' I can't now remember when the '01' prefix to a number replaced the earlier '0' prefix.
Were there any other changes to the early drawing?

Richard
Title: Re: Strictly.... “ Hot Air “
Post by: Bluechip on February 27, 2018, 04:54:24 PM
Richard

Numbers changed '95 -ish. Can't remember the exact date, know I was in Stuttgart at the time and was baffled as to why I couldn't dial UK .

IIRC If you dialled the old code in UK a recorded message told you to redial with the  '1' in, but 'Cellnet' ??? on mobile didn't do it for out of UK calls.  :headscratch:   Just said unknown number  ... helpful barstewards ...  :rant:

I think they completely changed some codes like Coventry ??

Dave

EDIT Found it. 16 April 1995 ...

Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 27, 2018, 05:42:26 PM
Hi Richard.

Well it’s definitely an early kit..... Ffordd Lerry or The Old brewhouse?

Regarding the drawings they were accurately drawn at full scale enabling you to take measurements directly from the paper!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on February 27, 2018, 11:01:09 PM
OK, if you say so Graham!
I was firmly brought up in 'do not scale' drawing offices. Not that we didn't, sometimes, when no one was looking.
I'm impressed with dimensioning to 4 places of decimal though. Have to up my normal standards to build the Robinson now.

Richard
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on March 01, 2018, 01:10:46 PM
Oy, Oy....

Wot's going on ere then?

 ;)
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on March 01, 2018, 01:16:13 PM
Are you breeding them?

Think I may have a puppy here ;)
Title: Re: Strictly.... “ Hot Air “
Post by: crueby on March 01, 2018, 01:20:28 PM
Are you breeding them?

Think I may have a puppy here ;)

The one on the right is a canibal - eating the one on the left!   :o
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on March 01, 2018, 01:51:15 PM
Are you breeding them?

Think I may have a puppy here ;)

Hi Jason.

You'll have to teach me how to do that, there drawing malarkey!

On a serious note your choice of material for the platform will need carful consideration.... Aluminium really is a " No No " far too conductive for long runs.

Don't forget that we're hoping to produce a small run of 6 sets later this year, once I can get my car started.... An already faltering auxiliary electric Diesel pump has now ceased to work due to the cold weather, argh.... Stranded.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on March 01, 2018, 06:54:16 PM
Thanks Graham, although aluminium or brass would be nice and easy to cut it out of I think it will be in steel as that has similar conductivity to iron and it will allow me to silver solder the round cylinder to a flat base that has been milled out for the passages and a sheet metal top.

Will probably also do a steel cylinder again for easy soldering and CI piston
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on March 04, 2018, 04:00:01 PM
Hey there Jo.

Look what I found, one of my castings WITHOUT that " special " coating.   ;)

Things are coming along smoothly just the displacer piston to finish.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on March 04, 2018, 04:25:54 PM
Hey there Jo.

Look what I found, one of my castings WITHOUT that " special " coating.   ;)

:o

Are you sure it has been correctly aged  :thinking:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on March 04, 2018, 04:51:01 PM
Hey there Jo.

Look what I found, one of my castings WITHOUT that " special " coating.   ;)

:o

Are you sure it has been correctly aged  :thinking:

Jo

Hi Jo.

By " it " should have read " they " .... Yes a bag of four was found lurking in an original Buckley foundry Polypropylene sack in almost perfect condition.

Minimum age of 12 years normalisation.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on March 07, 2018, 06:38:04 PM
I've nearly finished it !!   :)

 kJ30ubhD_Fg
Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on March 07, 2018, 08:01:14 PM
Looks Good Graham, I suppose the simpler linkage produces far less friction then the parallel motion.

Shame you got all those linkages cast as they seem surplus to requirements now ;)
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on March 08, 2018, 11:41:53 AM
Looks Good Graham, I suppose the simpler linkage produces far less friction then the parallel motion.

Shame you got all those linkages cast as they seem surplus to requirements now ;)

Thanks Jason.

Very probably, but the consensus is that the parallel motion looks far more pleasing.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on March 08, 2018, 03:20:36 PM
Hello All.

It seems to be a bit " one sided " on this thread, surely there are others building hot air engines? C'mon let's see em....

As a kitchen range is a little overkill for the average rally scene I will be showing my method of providing a neat little burner for the Robinson to run on. All you need is a proprietary made gas burner, Primus, Sievert etc and some bar stock. More to come....

Cheers Graham.

Title: Re: Strictly.... “ Hot Air “
Post by: Jo on March 08, 2018, 03:31:45 PM
Hello All.

It seems to be a bit " one sided " on this thread, surely there are others building hot air engines? C'mon let's see em....

I am still waiting for my castings  :(

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Bluechip on March 08, 2018, 03:48:34 PM
Hello All.

It seems to be a bit " one sided " on this thread, surely there are others building hot air engines? C'mon let's see em....

I am still waiting for my castings  :(

Jo

I'm still waiting for it to warm up ...  :old:

Dave
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on March 08, 2018, 03:50:14 PM
I won't be needing castings but will be a bit later in the year before I get round to starting mine.

Plan to have the base that was used for coal firing with a chimney and hope a tea light or mamod fuel tablet will provide the heat.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on March 08, 2018, 06:04:59 PM
I won't be needing castings but will be a bit later in the year before I get round to starting mine.

Plan to have the base that was used for coal firing with a chimney and hope a tea light or mamod fuel tablet will provide the heat.


Hi Jason.

Yes that'll look really nice.

An old friend who departed nigh on 20 years now built his engine upon an actual Coal fired arrangement. He fabricated the firebox from some Steel tube and it really looked " the business " ! With a little cast Iron door, firebrick lined and a grate. His collection was dispersed, I wonder who has it now?

Jo.

There's a trip planned for the Midlands within the next few weeks.... Patterns for hot air engine, Sphinx and anything anyone might be interested in?? Just PM me.   :)

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on March 10, 2018, 11:33:26 AM
Good morning Richard.

I moved your post here.

“ Speaking of oiling, what if any were the arrangements for the hot air engine? Did it have a cylinder oiler and a lubricator on the crankshaft bearing? Oil holes in the various links and rods?

Richard “

You see many models “ adorned “ with fancy Brass bits n bobs but having had the privilege of working on many original engines, they were pretty basic.

The cylinder has no provision for a lubricator, link motion has simple “ centre drill “ cups on each pivot point. The crankshaft bearing was done in the same manner as the link motion.

Over the last couple of days I’ve been running the Anson Robinson for hours at a time using ordinary engine oil. I discovered that by adding a little Paraffin/ Kerosene to the cylinder lubricant the engine speeded up quite dramatically, even oil viscosity makes a big difference!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on March 10, 2018, 06:41:49 PM
Update.

After several hours of running the Anson Robinson I noticed that the displacer piston rod was rotating, annoyingly.

Closeup of the improved con rod roller attached, no more side to side!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on March 10, 2018, 08:00:07 PM
Another (more elegant  ;)) solution might be to have a fork shape to the rod end with the slot sized to just clear the conrod.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on March 11, 2018, 07:26:37 PM
This came up on e-bay, I want one of these all "mental" engines  :LittleDevil:

https://www.ebay.co.uk/p/All-Mental-Mini-Hot-Air-Stirling-Engine-Motor-Model-Educational-Toy-Kit/24007868729?iid=302500551515&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D43781%26meid%3D8546616a601446ce86f4c692622a55ff%26pid%3D100005%26rk%3D5%26rkt%3D6%26sd%3D142174725524%26itm%3D302500551515&_trksid=p2047675.c100005.m1851
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on March 31, 2018, 03:28:09 AM
I've done a bit towards the Robinson, by filing up the gunmetal linkage castings and marking out for drilling/reaming. Haven't made my mind up whether to paint them, in which case they are probably good enough now, or polish them, in which case there is more to do.
Having read this and other sections of the site, I'm disappointed that my iron castings don't have Graham's Special Finish. if I sent them back, do you think he'd do it?

The steam guys seem to get pretty worked up about what grade/material to use for O rings used with steam at about 180C. Any advice about O ring material to use on that big one between the 2 halves of the displacer cylinder? For that matter, now asbestos is unobtainable, will a thick piece of Hallite/Klingerite jointing material be OK between the base casting flange and the flange on the lower half of the displacer cylinder?

Richard
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on March 31, 2018, 11:43:55 AM
Hi Richard.    ;)

Great to read you've made a start on your engine.

Regarding the " special " coating it would take years of standing in a damp workshop to achieve!

Mathew is here today to " hopefully " finish his engine, the one who's base was moulded by his grandad and I. We're hoping to get 5 half scale Robinson's together working for the Anson Engine museum Easter opening event tomorrow.

I've managed to drill through the section of Iron that was blocking the " air port " and by press fitting a piece of 15 mm Copper water pipe, Tlnned and Lead loaded the breach between the water jacket and port.

The " O " rings I used/use are a special " high temperature " compound and I still have several on stock, please message me.

The drawing shows the " O " ring fully recessed but I changed my mind as I built a few more. I now machine to one eighth depth in each part, platform and hot pot. This allows for a half thickness gap separation to reduce heat transfer, but the " O " ring also accurately registers the two components as well.

I'll post some photos of Mathew's progress later today.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on March 31, 2018, 11:59:37 AM
Hi Graham
Thanks for the reply (its Richard, not Ian by the way)

Given the weather I think a couple of days outside would do for the special coating! We used to 'season' castings outside for about 6 months, partially to let the casting stresses ease out, partially because the rust would lift off any casting sand left on. Did mean that when you started machining, it wasn't just black cast iron dust, but a good amount of orange rust flying around. These castings of mine are over 20 years old now so I think they've been well seasoned even without the rust. I shall go over them with a big old file first, then give them a coat of red oxide primer, before starting work on them. The primer helps prevent any oil getting into the surface texture, I always think.

I will PM you about the O ring.

Richard
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on March 31, 2018, 01:09:59 PM
Hi Richard.

I agree 100 % about painting, wished I'd done it several times.... I now have a collection of prototypes that won't take paint no matter what's been tried to remove the ingrained oil.

As promised, a photograph of my repair on Mathew's platform, more to come as the afternoon progresses.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on March 31, 2018, 05:28:42 PM
Getting there....

Assembly ready for the alignment stage.

All clamped and ready for drilling the main bearing pedestal and cylinder. As the displacer rod hole is the only thing that can't move the whole setup is aligned around it.

Just a few more holes to be drilled, tapped and clearanced, a run scheduled for a little later this evening.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on March 31, 2018, 09:26:09 PM
Graham
What are the 2 lugs for on the flange of the base casting in the 2nd photo?
What was the difference between the water cooled version and the air cooled one?
Did the full size one have a separate cooling tank, or did it just rely on having the water in the base topped up from time to time?

Richard
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on April 01, 2018, 07:21:13 PM
Graham
What are the 2 lugs for on the flange of the base casting in the 2nd photo?
What was the difference between the water cooled version and the air cooled one?
Did the full size one have a separate cooling tank, or did it just rely on having the water in the base topped up from time to time?

Richard

Hi Richard.

Sorry for my late reply, I have just returned from the Anson Engine museum, where a record 5 half scale engines were seen!

The lugs are where, theoretically, the two fixing bolts for the main bearing pedestal would be threaded.

The air cooled version, I assume you're referring to a picture I posted earlier in this thread? That engine was actually built by another company under license and is simply a " heat sink " with ventilation holes.

No, the number 4 uses the the cored space only for cooling. The number 5 had a hopper that doubled as the main bearing support, it was the number 6 that needed a separate cooling tank.

It would seem that as greater power was needed each size had a bigger cooling requirement.

Cheers Graham.

PS.

I just found this....

e1SwR0SugeA
That was me, right at the end removing one of ours from the platform of the " majestic " number 6.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on April 02, 2018, 06:18:34 PM
Graham
I think we are talking about 2 different things. The lugs I'm on about are the 2 hinge like lugs on the front of the circular flange at the bottom of the base casting. I can't understand how they would have anything to do with the main bearings, they aren't anywhere hear them or line up with them. I'm puzzled (easily done, I'm told). I've looked at lots of photos on  this sitge and can't see these lugs on any of the other engines.

Richard
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on April 02, 2018, 06:25:45 PM
Could be the casting runners that have not been cleaned up yet.

EDIT, just looked back through the thread and it is indeed where the runners fed the iron into the casting as you can see from the patterns.

(http://www.modelenginemaker.com/index.php?action=dlattach;topic=7561.0;attach=76707;image)
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on April 02, 2018, 06:51:05 PM
Hello Richard.

I'm pretty sure Jason's " nailed " it! I thought you were referring to the two small lugs on the top underside.

We never, ever let our castings near anyone with a grinder, quickest way to a scrapper! Instead we made specially shaped runners that could be snapped off from the running system leaving the last bit for the model engineer to " fettle " .

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on April 02, 2018, 07:10:24 PM
these bits
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on April 02, 2018, 07:26:58 PM
Show how stupid I am!
Title: Re: Strictly.... “ Hot Air “
Post by: Admiral_dk on April 02, 2018, 09:52:36 PM
Well we are not stupid just because we haven't got a clue about the answer to something and that is why we ask :stickpoke:

It's when you can't learn something that the term gets more appropriate .... though even that definition is fraught, as we know that there are different ways to learn something, and only one or two usually works for one individual and they are most likely not the same ones that work for a different person ....

That said - I do certainly know how it feels to fell stupid  :-[ we all been there.

Best wishes

Per
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on April 07, 2018, 10:27:24 AM
Graham
I've tried to message you about the big O ring for the Robinson, but it doesn't seem to work, not for me anyway. How do I get in touch?

Richard
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on April 07, 2018, 11:05:01 AM
Good morning Richard.

My sincerest apologies, the last couple of weeks have  been very busy due to school holidays and my full time carer duties. I'll contact you today via email.

I visited Andy ( Chipmaster ) yesterday and was shown his collection of Alyn Foundry engines, amongst others. His craftsmanship is of a very high quality and his recently completed Robinson hot air engine ran almost silently!

Andy is helping me coordinate with the foundry that's going to, hopefully, produce a small batch of castings for us from the patterns pictured above.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on April 20, 2018, 12:58:03 PM
Graham
What do you use these days for the jointing/insulating material between the lower displacement cylinder and the tripod base. Its shown as asbestos string on the drawing.

Hope you are getting over your chest infection

Regards

Richard
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on April 20, 2018, 04:32:26 PM
Hello Richard.

We're quietly getting better, thanks.

Regarding the insulation, on the last 4 we haven't used anything but you could probably use the " sealing rope " that's made for " wood burning " stoves.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on June 04, 2018, 07:04:15 AM
Graham
What clearance do you use between the displacer piston and the displacer cylinder bore? The can I am using for the piston gives an OD of around 3.280", and the cylinder bore will probably clean up to around 3.300". The drawing shows a bore of 3.400.

Richard
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on June 04, 2018, 11:33:29 AM
Good morning Richard.

The bore diameter isn't too critical. The bigger the clearance the less air travels through the regenerator piston and the quicker the engine will run.

I'd aim for the smallest clearance that ensures the displacer piston doesn't rub against the cylinder walls.

For those of the readership here interested, I had a phone call from the foundry. They are about to cast a platform in the next day or so. They have successfully cast some of the other parts like the flywheels and bases but these are child's play by comparison, I'm keeping my fingers crossed for a positive outcome.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on June 04, 2018, 11:57:22 AM
Thanks for the update Graham, hope those cored parts come out OK

I got a few more "castings" from my foundry too ;)
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on June 05, 2018, 09:35:11 AM
Thanks Graham.
I think I'll go for a bore of 3.300" giving 10 thou clearance all round If it isn't enough, then its easy to bore out a little more later.

Richard
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on June 07, 2018, 05:19:15 PM
For those of the readership here interested, I had a phone call from the foundry. They are about to cast a platform in the next day or so. They have successfully cast some of the other parts like the flywheels and bases but these are child's play by comparison, I'm keeping my fingers crossed for a positive outcome.

Any news yet on how the platforms came out or any other bits of interest?

J
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on June 07, 2018, 05:50:07 PM
Hi Jason.

Sadly no, it seems a bereavement may well have put things on hold for this week.

The tally is mounting I'm expecting the total weight to exceed 100Kg by the time they have completed my order.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on June 14, 2018, 11:51:14 AM
Hello All.

Some minor setbacks, see attached.

First picture is how the cores are laid out in the mould before closing and pouring.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on June 14, 2018, 01:12:11 PM
Bit hard to see from the photos but has the iron not flowed down to the cylinder end of the casting?
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on June 14, 2018, 03:07:08 PM
Hi Jason.

Yes and by the looks of it trapped core gas was the prime culprit.

The guys at Rhuddlan used a little trick called a " run off " they ran a channel off from the opposite end of the " in gate " . This channel carried both metal and gas away whilst the core " fumed " and fresher metal replaced the gassy stuff.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on June 19, 2018, 08:16:54 AM
Graham
My drawing shows the flange of the displacer cylinder as 4 5/8" dia. The studs fastening the main casting (the one the foundry is having trouble with at present) to the tripod base pass outside this flange, and presumably help to centralise the displacer cylinder. The drawing shows them as 1/4" dia, on a 4 27/32 PCD. Should this be 4 29/32 PCD, otherwise they foul the flange?

Regards

Richard Wilson
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on June 19, 2018, 11:41:38 AM
Good morning Richard.

I've built many of these engines over the years, the drawing was made from the first. One modification was the practice of making the " O " ring groves one eighth the thickness of the ring in both the platform and the " hot pot " . This both accurately registered the 2 components and ensured a good thermal barrier.

I've recently discovered several inaccuracies that strangely were never reported, you've reported another!

Ideally you would like to see the nuts flat on the platform flange and not overhanging the edge. By using the registering method above you could always reduce the " hot pot " flange diameter a little.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on July 03, 2018, 10:59:51 PM
The hot air engine progresses but slowly. I've machined the tripod base and the displacer cylinder, now progressing to the platform.
I've got a Denford Synchro 280 lathe which swings 11 1/2" over the bed, so its not small by home workshop standards. I had the devil of a job setting the platform in the 4 jaw to machine the underside. When the cored out cylinder was running true (as near true as a sand casting can be), the outer corners of the platform clouted the back Vee on the bed, and the pivot shaft for the chuck guard. The chuck guard pivot was no problem, I don't use it anyway, so off it came.
I had to radius the corners of the platform (big file!) to get clearance for the bed, but thats OK now, only just skimmed the edges of the end letters of 'Robinsons Patent'.

Thinking about it now, maybe I'd have been better off setting it up on the mill and using the boring head.
The other solution would be to grind off that back Vee, it doesn't do anything near the chuck as the tailstock is the only thing that runs on it. If I thought I could do it neatly, so it looked almost as if it was made that way, I think I would, I'm just afraid of ending up with it looking like a butchered job.
Now to start machining it. Theres a few surface blow holes, so I'm hoping they don't open up as I get below the surface.

Richard
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on July 22, 2018, 10:21:40 AM
Well the temp of the hot air in my workshop has reduced the amount of time I have been spending in there but I have now got all the linkages machined for "Wee Robbie" Quite fiddly little bits to do, most of the pivot holes are 2mm and the adjusting bolts on the split big end M1.6. mostly done on the rotary table and all cut for solid (sorrry Jo no JBWeld)

(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC02931_zpsbpjkgxzu.jpg)

Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on July 22, 2018, 11:09:18 AM
Good morning All.

First I'd like to apologise to Richard as today is the first time his recent post was seen by me. This forum moves very rapidly on occasions.

Jason, to the untrained eye your little " Robbie " looks almost cast! Very nice.

I'm sure a few of us would like to know how you put together the platform fabrication, did you take any photos?

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on July 22, 2018, 01:17:18 PM
If it runs I will do a full build thread and post some drawings  (subject to Graham's OK)

Basically it was all milled out of a slice of 100mm CI and a 2mm steel plate set into the bottom to which the upper cylinder half was silver soldered.

(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC02877_zps2gnz7tjq.jpg)

(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC02878_zpsglyoiypu.jpg)

(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC02880_zpsqwv2wmkt.jpg)

(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC02887_zpsonqweqhp.jpg)

(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC02888_zpszn9frzav.jpg)

Title: Re: Strictly.... “ Hot Air “
Post by: Dave Otto on July 22, 2018, 04:54:02 PM
Very nice Jason!

I would love to see a build thread on Wee Robbie


Dave
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on August 06, 2018, 09:42:51 AM
Graham
On my drawing, the displacer chamber is dimensioned as 2 3/4" long, +1/16", - 0.0". The lower chamber is shown as 1 1/2" long, with a 1/16" gap between the halves, so by inference, the upper part is 1 1/4" long. After a good cleaning cut across the flange, mine is 1 3/8". I don't want to take more off the flange, so do I just live with the increased clearance, or do I make the displacer 1/8" longer? I haven't made it yet.

Advice would be gratefully received.

Richard
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 06, 2018, 11:17:20 AM
Good morning Richard.

In a word, yes.

This hot air engine is quite forgiving on tolerance, in certain areas. Obviously piston to bore fit is far more critical.

Just keep on going.    :)

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 22, 2018, 06:26:52 PM
To all interested parties.

I had a phone call this morning.

The foundry rang to let me know of its success, a sound casting from the rather tricky patterns.

Photos to follow soon.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on August 22, 2018, 06:28:26 PM
 :whoohoo:

Jo &  :pinkelephant:
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on August 22, 2018, 07:44:04 PM
Me too :whoohoo:

Andy

Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 24, 2018, 11:26:46 AM
This " happy bunny " !! :cartwheel:

Took me back 20 years!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 24, 2018, 11:28:03 AM
Oops.

Technical hitch.... :)

Six more on order!
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on August 24, 2018, 11:38:16 AM
 :thinking: You must be having one of those upside down days.

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on August 24, 2018, 11:41:11 AM
No, He's just had to have a lay down after all that excitement, it was making him see double :lolb:
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 24, 2018, 11:58:23 AM
Well....

They've been a long time in the making.

The website said that my session had timed out, I resubmitted, four pictures not two was the result.

A cracking looking casting though, don't you think? The choice of sand makes all the difference.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on August 24, 2018, 12:03:55 PM
So what type of sand did they use in the end? Also the top surface looks a lot smoother than the sides what would be the likely reason for that?
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 24, 2018, 12:26:51 PM
Hi Jason.

They used a CO2 gas bonded sand that has very low fume characteristics. They made the two cores from it too.

The difference in finish was caused by " pattern drag " as has been shown very early in the thread the mould cavity is also made up in a kind of core box itself. My patterns are getting a little tired after over 200 runs. The top is formed from the sand that makes up the top box. This is part of the plate which is " dead flat " with just four prints for the water jacket core to register with, the two oval and two round holes.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on August 24, 2018, 12:38:08 PM
Thanks Graham, that would explain the vertical shape of the "grain" caused by the pattern being withdrawn
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on August 27, 2018, 10:24:52 AM
Question for those with running engines. How full should the piston be with the wire wool?

I have managed to turn mine from solid 303 stainless ending up with a 0.4mm wall thickness and have put eight 3.0mm holes top and bottom. I used some of the long curly swarf to put inside but if held upto the light I can see some daylight at the other end so do I need more. Or should I try with some fine wire wool?

Engine almost runs just not quite enough to sustain running.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 27, 2018, 11:38:28 AM
Good morning Jason.

Could be insufficient displacement.

On the last couple of engines I've built I used those cheap Stainless Steel pan scrubbers as filling, tightly packed too.

Hot air engines are akin to clocks however. An old horological friend used to say " tight enough to work, loose enough to run " makes sense doesn't it?

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on August 27, 2018, 11:51:25 AM
Hi Jason,
Have a look at the pictures I posted on this thread 22/2/18, I put two stainless steel pan scourers in the displacer. They would have been Spontex or Tesco brand. The scourers were unravelled and packed into the displacer to the extent that the tin lid of the displacer had to be held down when it was soldered in place.
I also followed Graham’s advice and put four half inch holes in the top and bottom of the displacer instead of 1/8 or 3mm holes.
Looking forward to getting my replacement platform casting  :whoohoo:

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on August 27, 2018, 01:23:33 PM
Thanks, I'll give it another go with more packing.

I stuck with the 3mm holes as mine is only 35mm internal dia x 16mm internal depth.

I may also skim a thou or so out of the bottom cap as I think there could be a little friction there when assembled, engine spins freely but not loosely with the cap off.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 27, 2018, 01:35:26 PM
Hi Jason.

I forgot to ask, does the engine have the characteristic compression/vacuum feel when cold?

Also how or what are you using as your thermal barrier between the platform and the hot pot?

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on August 27, 2018, 02:20:16 PM
Hi Graham, while I recover from this cold I have been doing a bit of casting fettling  :-X

I can report that the ends of the legs on the Robinson base were a bit hard and had to be fettled with a belt sander rather than a file. Those new arms are cleaning up ok.

And I decided as it was an easy thing to start I would have a little clean up of the hot pot. I assume it would be best to wait until I have a displacer cylinder so that I can get a nice tight fit on the bore  :thinking: which means I will need to buy a tin of Crabmeat.

Graham I have some rubber o-rings of 3.5mm diameter in my collection but nothing 4.75mm diameter did you say you had any spare?  :mischief:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 27, 2018, 02:49:51 PM
Hi Jo.

Looking good!

Yes I have a spare " O " ring, in fact I forgot to put it in with the kit. I sent them as a matter of course as they became more popular.

Now, don't forget that the " Crabmeat " displacer piston is a very loose fit. You're looking for a few Thou between it and the side of the machined casting.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on August 27, 2018, 03:10:24 PM
Now, don't forget that the " Crabmeat " displacer piston is a very loose fit. You're looking for a few Thou between it and the side of the machined casting.

I've been looking out a few recipes for disposing of the crabmeat I think a Crab linguine with chilli & parsley with a nice dry white New Zealand Sauvignon Blanc from Marlborough might be the way to go  :LickLips:

The other option I thought of was to empty two Tuna tins out through the bottom so that the tops are kept intact that was they are stronger for turning and drilling. The two tins are then joined around the mid line where they both taper so that you do not have a soldered on top  :noidea:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on August 27, 2018, 05:09:36 PM
Hi Graham

Yes I do have a compression bounce on the engine when cold, more so at the top of the stroke than the bottom, hopefully you can see it here

LoCLNsTY0Vo
I've just put a washer between the cap and base on each of the three mountings until I get something more suitable for insulation, may be letting heat out around the edge and adding to the heat in the bed.

Well I changed to some wire wool, skimmed a thou or so out of the hot cap to get a bit more clearance, ran an airline into the bed to cool it and took a small blowtorch to Robbie's bottom and can now add another notch to the workshop doorframe :pinkelephant:

Still needs a bit of tweaking but at least it runs. Sorry the video is a bit jumpy but I had the blowtorch in my right hand and camera in my left.

XT8Nn3nbPfU
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 27, 2018, 06:03:53 PM
Aye, another notch indeed.

In your first video you could clearly see both the vacuum and or the compression, it depends upon your point of view.

A good thermal barrier is essential on these engines otherwise they just won't run. When I was at the Anson for the 150 years of Gardner exhibition earlier this year Geoff had managed to gather a whole set.

What was really interesting was that up to the number 4 just simple around the top cooling was used. The number 5 had a small tank that also doubled as the crankshaft bearing. The number 6 was fully tank cooled with the cylinder included!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on August 28, 2018, 06:57:42 PM
Hi Jason, I didn’t realise your Wee Robbie was so small. However, it is an impressive runner having no knocking.

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on August 29, 2018, 04:04:47 PM
JB how does it compare in size with the Bruce Robinson Hot air  :thinking:

My flywheel has a hole  :wallbang: 

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on August 29, 2018, 08:13:20 PM
Not sure of the bore of the Bruce one but mine is certainly smaller. ;)

Probably not quite half the size.

Just put the hole in the right place to help counterbalance the weight of the piston :LittleDevil:
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on August 30, 2018, 07:59:26 AM
Just put the hole in the right place to help counterbalance the weight of the piston :LittleDevil:

I was thinking if I put on the flywheel so that when the power piston is fully out the hole is at the bottom it would not be as noticeable especially after the JBWeld filler goes off ;)

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 30, 2018, 11:15:56 AM
Damn, damn.... DAMN!!

Never, ever had this kind of problem in the past. What if I had interested parties overseas? I wouldn't dream of sending something out with potentially hidden flaws. Sadly this effort is already tarnishing my reputation.

The foundry is, as I write, replacing the faulty flywheel castings. But with what? More of the same?

Jo, a little dust from the swarf mixed with the filler helps disguise the finished repair.   ;)

Hopefully your " O " ring arrives today, late, but that's the new improved postal service. It cost £1.01 to send first class and still didn't get there the day after. And the price, who the hell came up with the penny?

All I can say is that you shouldn't have any problems with the other castings they're genuine OEM !!   :)

Ok, sorry for the rant....

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on August 30, 2018, 12:09:04 PM
Royal Snail  :disappointed: As we have stamp collectors in the family I normally "recycle" stamps  :-X Its amazing how many do not get franked these days. I can't remember when I actually paid for one. I'll keep my eyes open for it but the new postie doesn't normally turn up until about 2pm  :-\

The displacer cylinder is due to be delivered around dinner time  :cartwheel: Thanks to Dave for convincing me that having home deliveries of groceries is a good thing = less time tediously walking round shops, sitting in traffic jams and no Diesel used  :ThumbsUp:


While I wait for the grass to dry I have been making a little swarf in the workshop  :naughty:

Jo

Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 30, 2018, 12:24:48 PM
Jo, I hope I've caught you in time.

You really need to do all the other faces before the bore.

I squashed my first cylinder oval using the vice to mill the flat faces. Once learned never forgot.


Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on August 30, 2018, 12:42:23 PM
:headscratch: I had to mill the base flat and square to be able to hold it in the four jaw. It might still be a bit tall but until I know where the bore is I have nothing to measure off of  :noidea:


Just taking the last boring cut before starting on the back face about 1mm to come off of there before doing the 25.4mm hole. Then it can be turned round and possibly mounted on a mandrel.

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 30, 2018, 01:45:12 PM
Hi Jo.

Never mind the head scratching, I've machined many a rough casting, but in this case you did the right thing. Once bored you can expand your 3 jaw into it and do the tail end.

Don't worry about the height it doesn't matter much. In fact most of the engine doesn't matter much either! The only really critical part is the piston to bore fit. Oh and of course the crankshaft. And definitely the displacer rod hole.

As I've written recently they need to be a tad " slack " just remember Eric's words.   ;)

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on August 30, 2018, 04:32:39 PM
His usual term is "a rattling good fit"  ;)

The cylinder was turned round and the other end counterbored for the governor cover but it has not been finished as the displacer cylinders arrived and some Sticky Wotsits to go with my coffee  :naughty:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 30, 2018, 04:52:16 PM
Okay, which are the " sticky whotsits " ?

Has your " O " ring arrived yet?

And no, that wasn't the one you wrote about some weeks ago!    ;)

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on August 30, 2018, 05:06:21 PM
The best Sticky wotsits are made by Thorntons  :LickLips: but they only come in packets of 9 and Mike proved that a packet has a very short life expectancy - under 1 min with him around ::) . So these are being quality tested to see if they are up to acceptable standards. The Waitrose own ones went down ok at Bristol  :thinking: But I found the chocolate a little solid on the shortbread ones 

Has your " O " ring arrived yet?

:ShakeHead:

Royal fail-ed, so much for first class  :toilet_claw:

Ah the other phrase that Eric uses I am sure I have not written that down on the forum  :hellno:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: zeeprogrammer on August 30, 2018, 05:28:54 PM
and some Sticky Wotsits to go with my coffee  :naughty:

Coffee? In the background I see some  :wine1:
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 30, 2018, 05:37:44 PM

Ah the other phrase that Eric uses I am sure I have not written that down on the forum  :hellno:

Jo

Dear Jo.

Some of us have longer memories!!   ;)

http://www.modelenginemaker.com/index.php/topic,7664.msg171010.html#msg171010

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on August 30, 2018, 05:54:29 PM
and some Sticky Wotsits to go with my coffee  :naughty:

Coffee? In the background I see some  :wine1:

Zee, that makes everything loosen up :LittleDevil:
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on August 30, 2018, 07:23:50 PM

Ah the other phrase that Eric uses I am sure I have not written that down on the forum  :hellno:

Jo

Dear Jo.

Some of us have longer memories!!   ;)

http://www.modelenginemaker.com/index.php/topic,7664.msg171010.html#msg171010

Cheers Graham.

That's the somewhat cleaner version of the real expression  :-X 

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on August 31, 2018, 02:02:00 PM
More swarf has been seen in the workshop  :naughty:

And Royal Snail finally arrived from far away lands  ::) Thankyou Graham  :ThumbsUp:

Jo

Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on August 31, 2018, 04:46:19 PM
Phew!!

Be very careful with that Jo, I'm waiting on a phone call from the original supplier. They don't have any record of them at that particular size.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on August 31, 2018, 08:32:29 PM
It's coming along well Jo, will this one be considered safe enough you you to play with alone?

Spent a bit more time on mine this evening and got a couple of 10min runs on the blow torch before things got a bit too warm. Also started working on a gas burner, it's still a bit too orange a flame which makes a bit of soot so will make a few alterations to get a bluer flame. The burner is much quieter than the blow torch and the engine itself makes very little noise which is nice. The Jumping about was only because it was not sitting firmly on the fire bricks.

wdpskBAPUHE
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on September 01, 2018, 06:23:24 AM
I thought those little engine ran on night light power  :noidea:

It's coming along well Jo, will this one be considered safe enough for you to play with alone?

Actually any engine running is going to have to be re-evaluated as my running crew has come up with a new excuse to save his thumbs in that he can't visit any more  :(  I think this engine might be safe enough for even my thumb to be allowed near and it needs to be running before 24th November  ;)

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on September 01, 2018, 07:30:53 AM
I did try a tea light, you can just see it on the left at the start of the video but my alternative base does not allow enough air in so it goes out or burns very weakly. I've ordered some Mamod fuel tabs to try, that is what Dave was using on his at Bristol, Might also try some meths :DrinkPint:

The gas is clean and practical and uses the same small camping gas bottle and hose that I use for CHUKY
Title: Re: Strictly.... “ Hot Air “
Post by: Bertie_Bassett on September 01, 2018, 07:40:34 AM
looks like a nice runner Jason  :ThumbsUp:

once iv got my workshop rebuilt something similar is on my 'to do' list
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on September 01, 2018, 12:11:35 PM
Good morning.

I had one customer that informed me of a successful run using a night/tea light candle. He was a master at model engineering.

Every moving part had been hardened then mirror polished. He had turned several grooves into the piston to reduce drag.

The major difference was that he had reduced the thickness of the hot pot bottom to thousandths of an inch.

A handy burner for this engine can be made by using either the Primus 8842 or the 8719 as a perfect gas mixer. The chamber can be made from any piece of off cut metal you have around 40 mm diameter.

Cut it deep enough so that the burner can be press fitted into a hole drilled into the side. Bore out a cavity to around 36 mm diameter leaving a couple of mm left at the bottom. Counterbore the opening to 38 mm at 1 to 2 mm deep. The gas ring is made from metal that fits the counterbore. I used to use my Gardner chimney top turned upside down for this. The upturned edge provided a barrier to wind that would otherwise blow the flames out.

I often wondered if the matrix from one of those portable gas heaters cemented in would work. Never tried it myself. With Diamond hole saws now readily available it might be worth a try?

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on September 02, 2018, 02:39:26 PM
Bluechip and I have just had a little fondle of the hot pot for my engine and Dave agreed with me that as drawn it is going to take a fair while to get the pot anywhere near hot enough to run so it is probably worth reducing the thickness of the bottom a tad.

I also noticed that I fitted the cylinder for the displacer before I ate the contents and the displacer tins seem to have expanded now that they have had their caps removed  :noidea:


I have not yet got as far as thinking about the gas ring I have enough problems that I have found I have plenty of 3/16 Whit taps but the only dies I have in that size are blunt  :wallbang:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on September 02, 2018, 02:50:58 PM
Single point them :LittleDevil:

I was wondering if one of the small cheap camping gas rings would do for these larger engines, just take the legs off and you have a burner about 40mm across, I have one you can try when the engine is made.

https://www.ebay.co.uk/itm/Super-Mini-Portable-Camping-Gas-Powered-Butane-Propa-Stove-Burner-Cookout-Picnic/132482835729?hash=item1ed897a511:g:gYsAAOSwokJaalOc
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on September 02, 2018, 04:23:46 PM
Hi Jo.

Regarding the hot pot base thickness.

You have three options really. The first is to leave it as thick as possible. This makes the heating time the longest but the advantage is that on a windy rally field it won't stop running.

Reduce the thickness a little and have an engine that starts and runs reasonably quickly.

Or go wafer thin for almost instant start and stop.

The choice is ultimately yours.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on September 02, 2018, 04:58:59 PM
I was going to give it a try as it is then look to go thinner later :)

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on September 03, 2018, 07:50:16 AM
Last night I was sent a couple of extracts from an original No5 drawing, it shows the power piston with a number of grooves along it's sides and I think the curved bottom of the pot is given as 3/8" but it's a bit hard to read but looks to be that compared with other dimensions so would equate to 3/16" on the half scale model
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on September 03, 2018, 11:13:39 AM
Hi Jason.

The grooves in the piston will reduce the friction to a degree but we found that our engine ran just as well without them.

Regarding the curved hot pot bottom I naturally assumed it was done that way to increase the heating surface area. We didn't try to copy this but the thickness of our casting would allow the builder to put a slight radius into the bottom of the outside, you could even round off the bottom corner too.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Ian S C on September 03, 2018, 01:27:44 PM
The groves on the piston form a labyrinth seal, and i supposed to increase performance, but I'm not too sure. Only disadvantage 'v found was when I thinned the skirt of a piston a little too much, and the skirt fell off. Skirt thickness I was aiming for was about 1 mm, the groove about .25 mm, well it was a bit of old window weight after all.
Ian S C
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on September 05, 2018, 07:52:51 PM
Yesterday I was talking to Graham about castings and heating Robinson Hot Air engines. Graham suggested I added some pictures of the propane burner I made for my engine on MEM as they are cheaper than buying Primus / Sievert 8842 burners.
A few years ago having bought a commercially manufactured ceramic burner to suit a Stuart 504 boiler I thought I could save money by making my own. At the time I found it difficult to obtain the honeycomb ceramic material for a reasonable price. However, it now it is widely available particularly on ebay. I have also used the ceramic honeycomb material salvaged from Super Ser portable gas heaters but it is difficult to remove the material in one piece.
The pictures of the burner I made for my Robinson Hot Air engine show how simple it was to make. The brass body is held together with silver solder and the ceramic material is sealed round it's edges with fire cement. the optimum flame is obtained by adjusting the gas / air mix by moving the jet in or out of the Bunsen type mixer tube.

Gas jets threaded 1BA are available in a range of sizes from several suppliers including,
Chuffed2Bits http://www.chuffed2bits.com/page9.html
Forest Classics https://www.forest-classics.co.uk/ceramic-burners/round-burners/bix-001-2-diameter-x-1-deep-round-burner


Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on September 06, 2018, 11:06:00 AM
Good morning Andy.

Many thanks for posting your pictures.

I suggested the use of Primus/Sievert burners as all the " headache " of getting the air to gas ratio correct has been done by the manufacturer. They aren't cheap however and your solution is far less expensive.

Viewing the flame sees perfect combustion.

I take it the tank is refillable? Butane?

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on September 06, 2018, 12:35:06 PM
Andy, what dia is the burner? if about 40-50mm the little camping stoves I posted a link to above would do similar

There is a drawing for a burner to go with Sandy's 3" vertical boiler which is almost identical to your burner should anyone need a drawing, it's in the plans and drawing section.
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on September 06, 2018, 05:54:17 PM
My burner is 38mm diameter Jason which was the diameter of an old plumbing fitting that came to hand from my scrap brass box. As can be seen in my pictures and your Wee Robbie videos it can be awkward getting a burner to fit beneath the Robinson with its squat proportions. As my burner is quite close to the bottom of the displacer cylinder it only produces a gentle flame consequently it takes a few minutes to heat the engine up enough to start running but that suits me because the engine will keep running at a slow speed. I also wanted to have a gap beneath the burner to avoid scorching the wooden base.
I think the camping burner in your link would have to be modified or you’d have to raise the engine considerably to fit it beneath the displacer cylinder.
Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on September 18, 2018, 07:10:52 PM
Hello All.

Today was the day to visit and pick up some Robinson HA platform castings that had been cast at a different foundry.

We were met by the floor manager and given the " tour " of the works. This foundry can claim over a 150 year heritage and has some very experienced staff. I was immediately drawn to the " Greensand " area and was watched " hand " testing the sand which was well " tempered " and silky.

Our castings had been made using a CO2 bonding system that produces " zero " fume.

I have to say that these platforms are probably the best castings I've ever seen and the first to be made without " Chaplets " ( metal parts to prevent core shift ) being used.

The attached picture shows an un fettled casting other than shot blasted.

I'm rather tired.....

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on September 24, 2018, 10:36:03 AM
Something is missing  :noidea:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on September 24, 2018, 10:58:50 AM
Something is missing  :noidea:

Paint :LittleDevil:

Coming along well, is that the heat resistant gasket I can see under the tin can? I need to sort a thinner version for mine which did get some paint on it yesterday :)
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on September 24, 2018, 11:08:04 AM
Yes that is the rope gasket.

That is the 6mm diameter version, I was fitting the larger version to my log burner yesterday before I started cremating the brown stuff  >:D

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on September 24, 2018, 11:31:18 AM
Just ordered a metre of 3mm at the vast sum of £1.13 delivered :)

Feels like you just got your woodburner done just in time, we had our first frost this morning :(
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on September 24, 2018, 01:22:30 PM
Something is missing  :noidea:

Jo

Hi Jo.

What a " dark horse " you are! That's excellent progress.   :ThumbsUp:

It saddens me that you're going to have to wait until next month for the platform casting.

I noticed that you have even split the big ends on the connecting rods, I used to " dummy " those!   :LittleDevil:  As Jason has mentioned perhaps a coat of primer wouldn't go amiss?

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on September 24, 2018, 04:41:13 PM
Thankyou Graham,

The final item for today is crab a-la Robinson  :wine1:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on September 24, 2018, 04:53:17 PM
Bon appιtit

       :wine1:
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on September 24, 2018, 05:29:42 PM
Do you sprinkle with Parmesan or swarf :thinking:

I should be so lucky, fitted a new Neff oven on Saturday morning and did not think it was getting very hot, turns out the fan assist does not assist :cussing:
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on September 24, 2018, 06:26:03 PM
Seafood with cheese  :headscratch: and to think this is the boy who won't eat my bacon butties or cakes :noidea:

I think it is best we don't let you near the kitchen  :hellno:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on September 24, 2018, 06:50:47 PM
So does that mean I won't be able to try and make all those recipes for crab and cheese dishes I found on the net :-\

At least I don't eat my pasta with a knife :LittleDevil:
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on September 24, 2018, 06:59:24 PM
Ask any Italian what they think about those pasta dishes  ::)

Yes pasta is eaten with a fork and finished with scarpette or those from south London use the side of their finger rather than a knife  :disappointed:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on September 24, 2018, 07:29:11 PM
I just let the dogs lick the plate :Lol:
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on September 24, 2018, 07:47:01 PM
I am so pleased I don't live in your house  :facepalm2:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on October 07, 2018, 01:06:42 PM
Did some fettling and rough machining on my new platform casting for the Alyn Foundry Robinson Hot Air engine yesterday. Graham / Alyn Foundry brought it over a couple of weeks ago, its one of a new batch by the Barr & Grosvenor Foundry in Wolverhampton UK. You can see by the photographs so far so good - no cold shuts or blow holes but chilled around the edges.

Perhaps anyone else machining one of these castings might check how the lettering 'Robinson Patent' on the end of the casting lines up before they start. On my casting the lettering on the end lined up perfectly with the top which was why I mounted the casting upside down on parallels and milled the round flange first. I milled about 0.080" off before it was machined all over the surface.

When I turned the casting over to mill the top it was flat all over and only needed about 0.015" off to clean up the entire surface. I wish I could avoid the swirl machine marks left by my cutter, I guess they could be a symptom of a worn seventy plus year old milling machine so I might use my shaping machine to finish the top of the casting.

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 07, 2018, 01:16:21 PM
Looking good.

I wonder if any more are cast in the future if the foundry are able to anneal the castings, I can't see it would add that much to the final cost and could just be done on the ones with thing sections rather than say a chunky flywheel. It is not so much of an issue when flattening the surfaces where carbide tooling can be used but if you need to start drilling or tapping near a hard spot it will soon throw things off or blunt tool.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 07, 2018, 02:20:26 PM
Many thanks for the update Andy.

I haven't had a chance to get into the workshop recently however I'll try one in the Le Blonde soon.

I wonder if those edges are showing because of a " speed " issue? Obviously using the lathe and a single point cut at lower speed might see something different ?

Regarding a " planed " finish, yes that would certainly make the engine look more authentic as most Robinson engines were done that way originally.

Jason, those castings were fairly expensive to make. Adding a cost for annealing them might prove too much for a potential customer to bear. If my sample shows similar signs of hardness having been machined in a different fashion then we might have to consider that option.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 07, 2018, 07:32:03 PM
Hello All.

I finally got out there....

Mounted in my large 4 Jaw chuck the photo shows the top half ( cold end ) of the displacer cavity bored to size and the displacer piston rod hole also bored and lapped to 8 mm diameter.

No sign of any " chill " on the mounting flange.

It'll be a chuck change tomorrow, back to the 3 Jaw for facing the top.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Ian S C on October 08, 2018, 12:27:52 PM
For those without a shaper you could probably draw file some parts.
Ian S C
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 08, 2018, 07:39:57 PM
Indeed, Ian.

And this casting machined like Butter!

Using the lathe I found little if any " hard " spots and a single pass produced the attached.

Hmmm, perhaps yet another engine to come?

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 08, 2018, 07:48:11 PM
I wonder if that will fit in Big C's four jaw or I need to get the little faceplate out  :thinking:.

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 08, 2018, 08:02:10 PM
I wonder if that will fit in Big C's four jaw or I need to get the little faceplate out  :thinking:.

Jo

Well Jo, if I knew who or what " Big C " was I might be able to help.

My Le Blonde has a 7 and a half inch swing the platform passes  comfortably over the saddle arms. The whole job can be done in under an hour and that's including the change of chucks.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 08, 2018, 08:55:22 PM
Should not be a problem getting it in your chuck, would even fit mine as it is gripping the inside of the recess, however it may only turn through 270degrees on mine before there is a loud bang as it hits the bed.  :-[

Or do you think the faceplate will be needed to keep it withing the masters gap?
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 09, 2018, 01:24:14 AM
I wonder if that will fit in Big C's four jaw or I need to get the little faceplate out  :thinking:.

Jo

Well Jo, if I knew who or what " Big C " was I might be able to help.

Big C is my Colchester Master which has a 6 1/2" swing across the bed without taking the gap out. Little C is my Cowells ME lathe :D

Should not be a problem getting it in your chuck, would even fit mine as it is gripping the inside of the recess, however it may only turn through 270degrees on mine before there is a loud bang as it hits the bed.  :-[

Or do you think the faceplate will be needed to keep it within the masters gap?

I was rather thinking I might need to use the face plate with the top surface bolted against it to turn the underside of the casting as Big C only has a 10" 4 jaw chuck. The three jaw will easily hold the bottom once it is turned but the shape of the casting might be close even over her bed  :thinking:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 09, 2018, 08:07:42 AM
Quote
Big C is my Colchester Master which has a 5 1/2" swing

I thought your master was bigger than that, even my Warco can swing 11" :thinking: You seem to have lost 2" of swing somewhere as most are 6.5" ctr height or is it the imperial sizes confusing you :LittleDevil:

I suppose if you can have the jaws at 45degrees around the round part of the top rather than one gripping the end with the letters you stand more chance of getting it in the 4-jaw
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 09, 2018, 08:10:58 AM
Yes corrected the size.
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on October 09, 2018, 11:21:53 AM
Here's a picture of the Robinson HA Platform casting attached to the faceplate of my Colchester Chipmaster.
The Chipmaster has a 5.1/2" swing over the bed which the casting misses by about 1/4"  :).

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 09, 2018, 12:04:31 PM
Thanks Andy so it should be Easy-peesy then  :)

JB must have one of those special undersized 5 1/2" lathes  :-X

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 09, 2018, 12:29:57 PM
No mine is oversize as 280mm equates to 11.023" :LittleDevil:
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 14, 2018, 03:15:13 PM
I got the burner and base for my wee Robbie finished off so thought a couple of pictures were in order, seems like blue is the popular choice for these engines. All fabricated or cut from solid except the flywheel which is off a Stuart 10 size engine.

(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC03206_zpsavljvhhg.jpg)

(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC03207_zpsjskiapdn.jpg)

(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC03208_zpsnoqaf1a8.jpg)

(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC03209_zpssoifzepy.jpg)

(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC03210_zpsej6arw1h.jpg)

I did try it with Mamod fuel tabs without the base and it ran OK on them going nearly the full 10min burn time before slowing as the engien got a bit hot, I was nor running any cooling water. However the style of base I made would not work with the tablets as there was not enough air and the flame soon went out.

So a change of firing method was needed, I settled on a modified camping gas stove as this draws it's air from outside or in this case up from under the raised display base and also offers more control over the flame not to mention less of a smell.

(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC03204_zpsd0jaygtx.jpg)

(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC03205_zpsznblotcg.jpg)

As seems to be the usual case the engine did not want to run once it was all back on the base, I eventually traces this to teh flywheel being a bit close to teh bearing and rubbing but not before I had tried it with a bit more heat than I should which resulted in a scorched base and one of the joints opening up :'(

Anyway the base repairs can wait, here is the video. Ruler make sit look a bit shorter than it is but still only 4 1/2 " from back of cylinder to front of chimney, the consequence of a small lathe  :LittleDevil:

oWf9DnTIIJI
J
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 14, 2018, 04:18:42 PM
Hi Jason.

A very nice runner, well done!

I'm guessing that the " hot pot " is quite thin as the engine came to a halt very quickly after the flame was extinguished?

Have you thought about solid fuel? Obviously no good for indoor running but at a rally smoke issuing from the chimney would be quite eye catching.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 14, 2018, 04:29:18 PM
Thanks Graham.

I did thin the base of the pot but the engine was also starting to get a bit hot all over so expect that also contributed to it loosing speed.

Not sure if I would get a good draft for solid fuel, the Mamod tabs go out straight away as the chimney does not take the fumes out fast enough even with the firebox door open.
Title: Re: Strictly.... “ Hot Air “
Post by: Dave Otto on October 14, 2018, 04:48:16 PM
Very nice Jason!
Are you going to offer plans?

Dave
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 14, 2018, 05:02:31 PM
Not Sure, I need to talk with Graham first as I based my design on his drawings but if I do they will be here and free.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 14, 2018, 05:32:30 PM
Not Sure, I need to talk with Graham first as I based my design on his drawings but if I do they will be here and free.

There's no need to ask, Jason.

The Robinson hot air engine would, in patent speak be considered " prior art " and " fair game " for copying. But thanks anyway.

Very few would know that I had to get written permission from Gardner's to be allowed to put the name on our half scale engine replica. I was also informed that if our standards dropped they reserved the right to revoke that permission at any time!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 14, 2018, 05:55:48 PM
Thanks graham, I did not want to tread on anyones toes particularly as your version of this engine is back in limited production.

I'll get the working 2D drawings tidied up and probably do a separate build thread here, as I said above drawings will be free as a way of saying thanks for the info and help through this thread.

j
Title: Re: Strictly.... “ Hot Air “
Post by: Roger B on October 14, 2018, 07:57:25 PM
Looks good and runs well to me  :praise2:  :praise2: I'm sure that plans will be appreciated  :ThumbsUp:
Title: Re: Strictly.... “ Hot Air “
Post by: ShopShoe on October 15, 2018, 02:25:52 PM
A very Nice Runner and Great Looking.

I like the colors you have chosen.

Thank You for posting.

--ShopShoe
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on October 22, 2018, 05:55:53 PM
My Robinson running with a new platform casting and some pictures showing the old defective casting and one of the new platform.
HJR9YdzE6RY
Now I have to decide on the colour scheme.

Andy

Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 22, 2018, 06:42:43 PM
Hi Andy.

Beautifully quiet and running slowly, excellent work!

I'm guessing you'd allready finished it before now, ready for the washed out event last weekend?

It's always hard to find a colour for an engine, Red's and Greens predominate.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on October 22, 2018, 07:17:18 PM
Thanks Graham. Yes, I had machined the new platform over a week ago except for drilling and threading the holes for the cylinder and crank support studs but not in time for the Broomy Hill rally. However, I displayed and ran the engine ran all day with its old platform.
Did you find a new source for the large O ring seal between the displacer cylinder and platform? I noticed that mine had suffered slight damage inflicted by the edge of the groove it sits in so I will be looking for a spare.
Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 22, 2018, 08:16:35 PM
Hi Andy.

Despite several phone calls to my original supplier we've drawn a blank. They were made from Silicone, Orange in colour and were 4 inches ID with an approximate 1/4" thickness.

The firm are now saying that at that thickness the starting ID is 4,1/2 inches progressing upwards.

I don't know if they made me a batch specially at the time but it seems they don't have a record either. Not surprising I suppose as it was over 25 years ago!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 22, 2018, 08:45:36 PM
Fleabay have silicon O-rings of about 100 OD of various thicknesses:

https://www.ebay.co.uk/itm/VMQ-Silicone-O-Ring-OD-30mm-to-100mm-Select-Variations-5-7mm-Cross-Section/283144176410?hash=item41ecb5431a:m:mZacR6jypu31TFLVkTQUOGg:rk:30:pf:0

https://www.ebay.co.uk/itm/6mm-Section-Select-OD-from-30mm-to-300mm-VMQ-Silicone-O-Ring-gaskets/281766787443?hash=item419a9bf973:m:maqqO72A3H2jHWB1Kvllj8Q:rk:24:pf:0

https://www.ebay.co.uk/itm/7mm-Section-Select-ID-from-76mm-to-200mm-VMQ-Silicone-O-Ring-gaskets-DORL-A/112930746431?hash=item1a4b32703f:m:majvyf8caTGdvORQ2zbUZMw:rk:31:pf:0

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on October 22, 2018, 09:10:47 PM
Thanks Jo, I’ll check those sources.
Have you started work on your platform casting?

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 23, 2018, 07:01:46 AM
I used a vitron ring on my small one and it does not seem to have been affected by the heat.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 23, 2018, 07:22:10 AM
Thanks Jo, I’ll check those sources.
Have you started work on your platform casting?

Andy

:disappointed:

I'm still Log splitting  :facepalm:

I can't see me getting back into the workshop until Thursday at the earliest  :(

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 23, 2018, 07:26:59 AM
I suppose if the grooves are already cut you need the same size as there is nothing to stretch them over and don't confuse the ID and OD :ShakeHead:

Also why look for odd sizes, just put BS 345 into google and get exactly the same size as Graham specifies

First hit

https://simplybearings.co.uk/shop/p512828/BS345-5.33mm-Section-100.97mm-Bore-VITON-Rubber-O-Rings/product_info.html

Though I usually use Sealforce

https://www.ebay.co.uk/itm/Imperial-Silicone-70-Shore-Rubber-O-Rings-5-33MM-Cross-Section-BS339-TO-BS365/322012190084?hash=item4af96c1584:m:mquNkdktn48uj7y_P5sUGNA:rk:6:pf:0
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on October 23, 2018, 10:09:46 AM
Morning Jason, thanks for helping. I thought Simply Bearings £12.83 for two + post was a bit too much.
Before looking at your post I found a firm called Eastern Seals in Ashington, UK who appear to be able to supply BS345 silicone O rings at £0.59 each. Minimum order £5 so at that price I'll buy a few for spares. Graham might be interested in some too.

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 23, 2018, 10:18:43 AM
I think the other two suppliers prices are about the same when you take off the "free postage" but if you can get several for the £5 minimum then they can no doubt post the lot for what the others charge for one.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 23, 2018, 11:22:11 AM
Whoa there, Neddy....

BS 345 when studying the tables is a 4" nominal ID with a 4,3/16" OD.... ONLY 3/16" thick!!

Further checking sees exactly what my original supplier said that at a 1/4" nominal thickness the starting
ID is 4,1/2" ....

As I posted yesterday perhaps they made a " special " batch as I did order over 100 units.

Cheers Graham.

Edit....

Following Jason's eBay link a metric, close equivalent is available at approximately 101mm ID with a 5.5mm thickness. But that's not a 1/4" either!!
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on October 23, 2018, 11:44:06 AM
Well the plans I followed specified a 3/16" BS 345 O ring, here's an extract from your plan that I photographed!!

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 23, 2018, 11:59:47 AM
Hi Andy.

Well.... you can't argue with that, can you?    :lolb:

We did however use a different tack on later builds by only putting a 1/4 of the groove in each of the Iron parts to leave half the remaining thickness as a thermal barrier.

I'm not able to measure the last remaining " O " ring at the moment but will post the results later.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 23, 2018, 12:14:03 PM
I just measured mine and it is 5mm diameter.

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 23, 2018, 12:50:27 PM
A nominal 3/16" O ring Which BS345is  has an actual cord diameter of 0.210" or (5.33mm for Jo)and her's sounds closer to that than it does to 1/4" Nominal which has a cord of 0.275" or 6.99mm

You could try a Metric 6mm ring which is a true 6mm cord and 100mm ID if you want to get close to 1/4" actual diameter
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 23, 2018, 03:45:47 PM
Well....

It would appear that an apology is needed here, a " cap in hand " emoji etc.

The last " O " ring on stock measures a smidgen over 5mm, 5.2 to be precise.

I was absolutely convinced they were a 1/4" section, so you guys n gals, carry on regardless!!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 23, 2018, 06:03:36 PM
Another set of Robinson castings have been discovered hiding in plain sight on my dining table :thinking:

They look very good quality (the foundry is somewhere on the Fens but that was all we were allowed to know ::) ) The pictures on the drawings and the instructions do not match. The pictures with the drawings suggest that there are two spinnings which there are not  :ShakeHead:  There is a very nice Brass engine plaque  :) Yes this is another very nice casting set from Polly Wobbles  :ThumbsUp:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 23, 2018, 06:45:52 PM
The brass spinning for the displacer piston is not the best material as it conducts too much heat, make one from stainless. That is what Irish Dave did when I suggested it to him and what I did on Little Robbie, about 0.3mm wall or less will do nicely.

As a bonus Dave's stainless one tipped the scales at 34g rather better than the Polly one which was 93g
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on October 23, 2018, 06:49:11 PM
Another stupid question. I've machined the base casting apparently successfully, with no signs of the dreaded cold shut lines. Now I've just machine the undersides of the cylinder and bearing castings, taking off just enough metal to give a clean flat surface. The drawing shows a dimension of 1 25/62" (1.390") from the top of base to the centreline of the cylinder and crankshaft. In both cases, this would result in a bore which was markedly offset in the casting. Using a dimension of 1 5/16" gives a much better looking result.
1 25/64" looks an odd size, and it is that size for, presumably, a very good reason, but what that reason is, currently escapes me.
Can you see any problems if I lower off the centreline by 5/64"? The only issue I can see is if the ends of the levers operating the displacer rod end up too low and bash the top of the base. I can always put packing pieces under the cylinder and bearing castings if I have to.
Looking ahead to when its finished, do these engines 'self start' when heated enough, or do they need assistance for the first turn or so?
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 23, 2018, 06:56:54 PM
I had to alter the bottom to the centre line of the cylinder on mine as well Graham said it did not matter the motion would take out the minor differences.

These engines are not self starting you need to give them a twirl

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 23, 2018, 07:26:09 PM
Hi Richard.

I would suggest just to remove what is necessary from the cylinder base to get it flat. Then proceed to bore the cylinder concentric to its outside, as cast form. These engines are very forgiving as regards measurements the only critical area being piston to bore.

They do require to be hand started and if when everything is fitting well will just need a single pull over TDC.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 23, 2018, 07:38:25 PM
Hi Jo.

Re your quoted comment.

 " There is a very nice Brass engine plaque "

If I was informed correctly, many years ago. The engine kit you have was copied from a museum exhibit where someone had mistakenly fitted a Robinson Gas engine number plate to a hot air engine.

I have seen many original examples of Robinson hot air engines over the years but never, ever seen another with an identification plate.

However, a bit of " Bling " can make all the difference!!   ;)

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 23, 2018, 07:58:38 PM
That will be this one in the Science Museum complete with wrong plaque which the Polly version is based on.

https://collection.sciencemuseum.org.uk/objects/co61992/robinson-air-engine-1914-hot-air-engines
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 24, 2018, 04:43:34 PM
Tgs has started skimming off the bottom of the base.

There is a bit of a line across the face so I have filled it with JB weld and will give it another skim in the morning. There probably won't be any JB left by the time the machining is finished but better safe than sorry.

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 25, 2018, 10:41:55 AM
One side skimmed flat. You can see on the first cut (red arrows) that the edges are hard and shiny. when machining you can hear the cutter going through these and it sounds a bit like the cutter is loose but everything is actually ok.  The bit marked with green is still low so another cut was needed.

Second cut and you can see that the low bit is just about visible but it is small enough that the casting can be turned over to machine the other side. The JB weld has nearly vanished and hopefully when it is turned it will all go and all that worry was for nothing.

Turning it over I have used four clamps to hold it down onto some parallels and to prevent it ringing have added a machinist's jack under the over hang.

I am trying to ignore someone who is trying to side track me by getting tonight's castings out early  ::) it must be time to go and make some more Cast Iron dust.

Jo

Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 25, 2018, 04:52:16 PM
I decided that those sharp edges were going to be a bit hard so I used a smaller carbide cutter to remove them before getting the big face cutter out again.  First facing cut and there are more hard bits and I still have another cut to come off which took it down flush  :)

I am planning to turn the bottom on Big C but she is currently finishing off another job so in the meantime I thought a little assembly was a good idea to see what the engine is going to look like before some :wine1:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 25, 2018, 05:10:53 PM
As most of those red bits arrowed are just the thin flash which you would expect to cool first would it have been easier to dress it with a grinder first. That's what I tend to do and remove the runners and any parting lines too.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 25, 2018, 05:14:20 PM
Hi Jo.

Well.... the home straight is nearly in sight!

If I may offer a tip once you have the displacer rod hole completed?

Having built quite a few of these over the years I found the easiest way to get the engine looking right was to set the crankpin at either TDC or BDC and move both the cylinder and bearing yoke until the vertical links look, well " vertical " ! Using a couple of engineers clamps you can then lightly hold both cylinder and bearing yoke whilst rotating the flywheel. This will find the optimum position of " looseness " for the assembly before final spotting and tapping the four holes.

Now go and enjoy that  :wine1:  you deserve it.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 25, 2018, 05:32:40 PM
Thanks Graham, I'll try that.  :)

JB the reason that there are all those hard bits is because the outside of the casting is rather thin around the water jacket/tank, especially the edges of the holes. The hardness is continuing into the casting.  Thankfully there will be no more machining on that surface and I have to decide if I want to polish it  :thinking:


In the meantime I have some tricky castings to work out how to hold... another  :wine1: is required 

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 25, 2018, 06:36:55 PM
Bling name plate last week, polished cast iron this week, must be that mobility scooter car making you all flashy :LittleDevil:

Just went with the finish straight off the machine which is most likely how they were originally left.


(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC02881_zpstv6iaxuk.jpg)
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on October 25, 2018, 07:32:29 PM
I usually go over new castings with the angle grinder to remove the flash and remains of the runners, then a big old bastard file to get rid of the sand texture as much as possible. It makes them nicer to handle, and after a couple of incidents cutting myself quite badly on sharp edged flash, safer as well.
I just went for facing both sides of the base on the lathe, without facing it off on the mill first. I used a brazed carbide tip tool (a good UK make not those Chinese ones) and didn't have any trouble at all with hard spots. Its a tricky casting to hold in the 4 jaw to face the bottom, but I got there in the end.

Thats a useful tip about setting the cylinder and bearing block, Graham. Hopefully, I should be doing that soon (Soon for me means months rather than years) as the next jobs are boring the cylinder and the bearing housing.

Richard
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 26, 2018, 02:59:01 PM
I am pleased to say that the platform casting fits nicely in a four jaw chuck for boring  :)

If anything it is a little small as I had to pack the sides with some bits of Ali to avoid the ends of the jaws hitting in the centre of the chuck. 

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 26, 2018, 04:14:14 PM
I only reverse the one jaw.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 26, 2018, 04:39:22 PM
I tried that to start with but by reversing all of the jaws I could tap the casting down on them and knew the bottom was parallel  ;)

The top half of the hot cylinder has been bored out, the bottom surface faced and the piston rod hole drilled and reamed. I need to make the piston rod next  :thinking:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on October 26, 2018, 05:04:10 PM
I have received the silicone O rings, they are perfect and only cost £10.66 for ten including delivery.
Here's a picture of a new O ring fitted and the remaining nine spare.
I recommend  https://www.easternseals.co.uk/ for the supply of O rings, their prices are so low. :)

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 26, 2018, 05:30:59 PM
They look good Andy.

The old one looks rather squashed  :o

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on October 26, 2018, 06:15:10 PM
The old O ring is still pliant and serviceable but looks scorched where it has been in contact with the bottom of its groove in the hot pot.
Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 26, 2018, 07:04:57 PM
Hi Both.

So Jo, are we looking at a run this weekend? With just a simple part to finish, two holes, one tapped.
Nothing to seriously maim or injure??   :)

Andy, those " O " rings look great, just like mine did!!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 26, 2018, 07:52:17 PM
I also need to make the piston & some more fixings Graham and Saturday is gardening day  :noidea:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 28, 2018, 11:50:22 AM
I've turned down the end of the piston rod where it goes through the regenerator piston and added a washer to give it some support. The bottom has had a 3.2mm hole drilled in it and been beaten flat with a hammer. Overall the piston seems to hold together ok without soft soldering  :thinking:

Graham mentioned drilling 4 1/2" diameter holes in the regenerator, I don't have any suitable drills that size so I chose to drill six holes using a 10mm wood drill bit. To avoid getting cut fingers the loose lid was screwed onto the bottom of the tin for drilling :paranoia: These wood drills work well in thin material and happily cut one piece at a time

I have stuffed the inside of the piston with some wire wool for now, and it looks piston like, I am not sure if it really needs to be soldered together  :noidea:

Graham's drawings show the length of the mounting hole to the top of the regenerator as 63.5mm I decided to play it safe and do some measurements and yes it looks about right  :ThumbsUp:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 28, 2018, 12:28:05 PM
I did not solder mine but do have a machined recess in the edge of the piston that the lid is a good fit in which ensures the piston stays central so no risk of it rubbing on the sides of the base or cap.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 28, 2018, 02:01:59 PM
Hi Jo.

To coin Baldrick.... I have a cunning plan.... I like it!!  No need to solder as the washer retains the top cover.

It makes for a little extra machining but it should work. My only reservation is that the edges need to be a close fit otherwise the outside diameter might just rock sideways.

Are we there yet?    :)

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 28, 2018, 04:02:59 PM
Not this weekend I have had too many phone calls interrupting my workshop time  :ShakeHead: The worst offender phoned up numerous times to let me know that he did not buy me the set of castings he said he would try to buy for me but they went for a lot less than I was willing to pay  :rant: And to really annoy me he has brought another three sets of Stuart castings (6A, 600 and Sandhurst) for a song, this is the same supplier who has not made a single model engine for over 8 years >:(

As for the Robinson: I've drilled a few holes and started studding. But currently I have studs without any nuts, its not good if your studs have no nuts  :embarassed:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 28, 2018, 04:24:57 PM
I gave up on the string and made a couple of washers from Exhaust manifold gasket, you can tighten things down a lot more easily and get even pressure all around the o ring which keeps the top and bottom bores in line.

You can buy A4 size sheets online that come with both the metal faced and plain "paper" gaskets, paper is easy to cut.

Which casting set were you after?
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 28, 2018, 04:29:46 PM
I will give it a go... I do have the proper glue for it but the end will have to be dealt with  :thinking:

I wanted the Stuart Major Beam engine casting set and was willing to pay a lot more than they £200 they sold for. I would have even paid buyer's commission for them so he lost out on making a handsome profit :stickpoke:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 28, 2018, 04:48:04 PM
£200, someone went away very happy.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 28, 2018, 05:18:37 PM
It wasn't me  :hammerbash:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: 10KPete on October 28, 2018, 06:08:19 PM
I had no idea that the engine castings competition was so intense there! Has this been only for out-of-production castings?

 :shrug: :shrug:

Pete
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 29, 2018, 07:33:57 AM
I had no idea that the engine castings competition was so intense there! Has this been only for out-of-production castings?

:noidea:

My supplier is a model engine collector who also likes dealing to fund his habit. Both the Stuart 6A and Major Beam are still available from Stuarts but they will cost you a four digit sum of money   :toilet_claw:

https://www.stuartmodels.com/item/61/stuart-major-beam-unmachined

https://www.stuartmodels.com/item/57/stuart-6a-unmachined

Jo

Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 29, 2018, 07:41:06 AM
I think the reason Jo is unhappy is that there was no intensity to the competition, if only one person is bidding the casting set will go for the starting price rather than two or more bidders competing which pushes the price up.

Next time you will have to get the mobility scooter dusted off and go yourself.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 29, 2018, 07:54:37 AM
Jo is unhappy as he promised to bid on the Major Beam for me, I told him how much I was willing to go up to and now he keeps wasting good workshop time phoning me up telling me that he did not do what he promised and even worse he told the chap next to him that if he did not bid on it he would bid on it for me so this chap was the only bid on it and he won it  :rant:

I am not a member of that club it is a couple of hours away for me so not a sensible one to join.

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: 10KPete on October 29, 2018, 08:00:30 AM
 :paranoia:

Pete
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 30, 2018, 12:07:35 PM
All squared up and bolted down.

I think that the propane burners on my range are too wide as they are totally missing the hot cap on the engine so I need to find an alternative burner.


The engine is bouncy, but not running and has a tendency to suck in its piston when stopped so I might need to set up it cold and then put the power piston in to maximise the pressure  :noidea:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on October 30, 2018, 12:52:15 PM
Hi Jo.

Wonderful, it's now complete, well done.

When cold the engine should feel as if there's a vacuum trying to pull the piston back as you turn the flywheel, but you should also feel a compression too!

Your gas ring does look a little bigger than my small one but you surely must be able to turn the flames right down so they just lick around the edges of the cap?

I wouldn't worry about trying to get a bit of positive pressure in the system, it'll soon leak away via the various loose bits. Oh, and they don't heat up and run that quickly initially either, first runs can take up to 30 minutes, this time gets less and less as the engine beds in and loosens.

Good luck, eager to see movement, cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 30, 2018, 01:06:24 PM
I found mine needed a lot of flywheel flicking at first, as it warmed through you could tell it was taking longer and longer to come to a halt and eventually it took off.

If you do feel the hob is too big stand it on a couple of bricks and gently play your blow torch on it's bottom.
Title: Re: Strictly.... “ Hot Air “
Post by: Gas_mantle on October 30, 2018, 03:26:45 PM
Looks good Jo  :)

Is it worth buying a ceramic burner set up and permanently attach it?
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 30, 2018, 05:08:01 PM
Or Jo's moths may prefer a camping stove particularly if a few have been let loose today on yet another set of castings.

https://www.ebay.co.uk/itm/UK-Outdoor-Folding-Gas-Stove-Cooker-Hiking-Picnic-Stainless-Steel-Gas-Burners/132711963938?hash=item1ee63fdd22:g:cSEAAOSw2gdbUiqC
Title: Re: Strictly.... “ Hot Air “
Post by: Gas_mantle on October 30, 2018, 05:15:59 PM
Or Jo's moths may prefer a camping stove particularly if a few have been let loose today on yet another set of castings.


.... or better still get some mucky old coal  ;)
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 30, 2018, 05:24:47 PM
Or Jo's moths may prefer a camping stove particularly if a few have been let loose today on yet another set of castings.

:headscratch: I must have missed something.

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 30, 2018, 05:26:25 PM
Coal is no good to Jo, she has not got a fire hole or chimney, unlike me :) besides she like to burn wood ;)

(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC03061_zpsjjw20uju.jpg)

(http://img.photobucket.com/albums/v156/jasonballamy/Engineering/Robbie/DSC03060_zpsdlv6l0ij.jpg)
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on October 30, 2018, 05:28:04 PM
Or Jo's moths may prefer a camping stove particularly if a few have been let loose today on yet another set of castings.

:headscratch: I must have missed something.

Jo

I thought that dancing pink thing in the other thread was due to a new purchase, maybe I was wrong as you would have had to pay full price which is not like you :LittleDevil:
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on October 30, 2018, 05:57:26 PM

thing in the other thread was due to a new purchase

I thought I mentioned someone didn't buy the Stuart Major Beam engine he promised to pick up for me, this is the second time in two months he has messed me around when I was trying to buy casting sets  :cussing:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 01, 2018, 12:23:38 PM
I have fully dismantled the Robinson and found that as well as bubbling a little water out from under the power cylinder some had got down into the hot end  :ShakeHead: , the worse bit being the rusty wire wool in the regenerator :facepalm2:

Following a visit to Waitrose I have, as instructed, purchased some pan scourers made of stainless steel swarf an am going to try re-assembling with two of those in place of the original wire wool.

Following a bit of a polish of the platform I think we are ready for another re-assemble and test heat  :)

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 01, 2018, 12:40:18 PM
Did you not put any sealant between cylinder and base :facepalm:

If you are blowing bubbles then you are leaking air as well as water
Title: Re: Strictly.... “ Hot Air “
Post by: Bluechip on November 01, 2018, 12:53:46 PM
I have fully dismantled the Robinson and found that as well as bubbling a little water out from under the power cylinder some had got down into the hot end  :ShakeHead: , the worse bit being the rusty wire wool in the regenerator :facepalm2:

Following a visit to Waitrose I have, as instructed, purchased some pan scourers made of stainless steel swarf an am going to try re-assembling with two of those in place of the original wire wool.

Following a bit of a polish of the platform I think we are ready for another re-assemble and test heat  :)

Jo

Hi Jo

If that was me [ ? ]  I shall allow myself a little   ' TOWDJA'    :) 

I can't remember where or when I saw the info. about steel wool  but it did point out the following:

It breaks up and clogs the engine.
It rusts.
It is too tight usually and slows the engine due to restricted air-flow.

Dave

Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 01, 2018, 01:12:14 PM
But then again my little one runs fine with wire wool, though don't use the 0000 grade.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 01, 2018, 02:08:53 PM
My apologies....

I failed to mention the application of a film of Acetate cure clear Silicone between the cylinder and platform castings.

This will ensure both an air and watertight seal. And.... You don't need to wait for it to cure either!

We have tried many " fillers " for the regenerative piston, both Iron and Stainless Steel works well. Water getting into the system will obviously cause corrosion so that's why we went down the stainless Steel route.

I'm pretty sure we'll see motion very soon.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 01, 2018, 02:26:47 PM
If that was me [ ? ]  I shall allow myself a little   ' TOWDJA'    :) 

It was thanks Dave  :) I haven't heard of that type of beer :DrinkPint:  :thinking:


I've put a gasket under the power cylinder.

Before final assembly I decided to test the piston fit and vacuum caused by moving it out:

dI6N2w9r9I8
Once I have had my cuppa it might be worth a bit more assembly.

Jo

P.S. Thanks for the spare O rings Andy  :ThumbsUp:

Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 01, 2018, 02:27:28 PM
As an afterthought.

Don't over tighten the three nuts that join the platform to the base, finger tight only.

As an experiment, once you have got the engine running nicely a few times, you could wrap the displacer piston in Aluminium foil. By sealing the regenerator the air has to pass by the sides this really slows the engine down!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 01, 2018, 02:40:13 PM
Hi Jo.

It seems our posts crossed.

That looks almost a perfect seal, good!

One issue I could see from your video was that the big end has been rubbing on the crank disc, this needs slight attention to reduce the friction.

Please don't use 3 in 1 oil as a lubricant best with a little dab of Diesel oil or a very light mineral oil.

This is getting exciting!!
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 01, 2018, 06:37:24 PM
That cuppa is taking a while, I fear it may have changed to a glass or two by now
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 01, 2018, 07:22:39 PM
:embarassed:

The engine was put back together... I was busy warming up the hot pot with the torch and the phone rang  :facepalm: by the time I got back the top end had heated up and the power piston was a bit sticky at the inner end :headscratch: ... So I left it to cool down.

Having gone indoors I found a nicely chilled Elephant sitting with a bottle of wine, the ingredients for a rather nice meal  :LickLips: and a box of lonely castings, all of which was clearly an attempt to discourage me from going back out to the workshop  :shrug:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: 10KPete on November 02, 2018, 12:14:12 AM
I sounds like you have some very powerful forces at home....
 :wine1:

Pete
Title: Re: Strictly.... “ Hot Air “
Post by: Bluechip on November 02, 2018, 10:52:53 AM
If that was me [ ? ]  I shall allow myself a little   ' TOWDJA'    :) 

It was thanks Dave  :) I haven't heard of that type of beer :DrinkPint:  :thinking:



TOWDJA  =  I told you.    :ThumbsUp:

I think you need Stuart to give you lessons in 'Ilson', a similar language to Esperanto but a lot more abstruse. :lolb:

Dave
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 02, 2018, 11:17:49 AM
 :thinking:

Update on the engine: The seizer was caused by rust in the power cylinder  :o Andy had warned me that he had similar problems after he had left his engine after the first few runs. It has been cleaned up but I am going to have the afternoon making swarf on the Wall  :ThumbsUp:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 02, 2018, 11:33:13 AM
Look on the bright side Jo, you may have discovered the recipe for Grahams famous brown coating :LittleDevil:
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 02, 2018, 11:55:51 AM
Hi Jason.

Not really, that's the non permanent version! There's also my rather secret recipe, it really lasts.

Well Jo, I'm a little disappointed. You're so close to the finishing line the suspense is killing me!

Over time the engine will " ingest " some of the lubricant, get heated and coat the internal working surfaces. This stops any further corrosion from damp air. Although in your case I think water had got transferred into the " air port " via the two cored holes under the cylinder mounting flange.

Never mind the Wall, that tape is only a few " thou " away from you.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Gas_mantle on November 02, 2018, 12:30:33 PM
Having got this far Jo you really have to show us the engine running  :)
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 04, 2018, 04:19:34 PM
A bit further  :thinking: After the rust in the cylinder it seems to have lost that nice bounce  :(

VxMBti_KYno
I need to make up some sort of burner as I have been having problems heating the engine with the torch and it has weakened the Loctite joint on the crankshaft  :Doh: Initially I thought it was the flywheel that had come loose but  :ShakeHead:

It is so close  :wallbang:

BS_GhlHIkDY
Time for a strip down again  ::) But that will have to be tomorrow after a bit of rotovating with that little side and face cutter they dropped off yesterday >:D

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Gas_mantle on November 04, 2018, 04:22:52 PM
There can't be much that needs doing to it Jo, it's on the verge of running now  :)
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 04, 2018, 04:33:14 PM
That looks a lot of heat and it seems a bit tight at the point where it stopped in the second video but you are almost there.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 04, 2018, 04:52:50 PM
Well done Jo, I'd call that a run.

You definitely have far too much heat at the moment and heating up the sub base won't be aiding either.

The full size engines did have a tapered keyway into the crank disc, these were hammered in tight then machined flush. At half scale we didn't think this was needed but you could perhaps use a small taper pin instead?

I'm truly looking forward to a more lengthy video!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Dave Otto on November 04, 2018, 04:52:58 PM
Almost there Jo, looking good. :ThumbsUp:

Dave
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 04, 2018, 04:54:51 PM
Jo are the links on the crank pin hitting the vertical links? think I can hear a slight knock when they come close and that is where the engine came to a halt
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 04, 2018, 06:10:25 PM
No the end of the screw on the crank vertical link was hitting the crank web where the crank had slipped out of the disc  ::)

In the meantime we have been looking at another Robinson  :-X

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 05, 2018, 01:57:28 PM
Good grief Jo!

Are you a Gemini by any chance?

You haven't finished the bigger one yet.

Have you ever tried doing any " metal spinning " ? I used to make Brass spinnings to mend/replace parts for Tilley lamps. It might be an interesting exercise to try to make the displacer piston for the smaller engine from some thin stainless Steel sheet.

The method is simple, find a suitable solid blank of the right diameter, preferably polished, the " chuck " Cut a disc from your sheet Steel that roughly corresponds to the top and sides. Mount the form tightly in the strongest lathe you have then press the disc against it using the tailsock fitted with a rotating centre and a centred thick washer. You also need a vertical peg firmly attached to a horizontal bar that can be fitted into the tool post. This is your leverage point for the form tool.

I learned a few secrets from a local spinner, use a non ferrous form tool for ferrous materials and vice verse for non ferrous materials. The lubricant is nothing more than Fairy household soap ( Green ) block and dissolved in Paraffin.

The next stage requires a little courage but if you've done any wood turning in the past then you're half way there! The form tool needs to be both strong and long because you're forcing the metal to move over the form. Bring the lubricated polished end against the metal and by pushing and leaning against the peg you start to create heat. You can now start to manipulate the metal by pushing it away from you, the flat quickly becomes a cone. Keep forming the cone to a tighter and tighter angle until you can start moving the metal along the length of the " chuck " whereupon you've finished. Hopefully you've got some excess metal in the length to allow for a neat " parting " using a sharp pointed tool. The top cover can be done the same way but your " chuck " will need to be the diameter of the finished outside diameter of the body spinning.

I would certainly recommend a few practice attempts at forming metal in this way but the results can be quite rewarding. The spinning firm I visited were very approachable the boss said, 5 years to learn the trade, 7 years to learn the Art!!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 05, 2018, 02:05:59 PM

 if you've done any wood turning in the past then you're half way there!


That will put her off before she even tries it :Lol:

It would also be good practice for when the BB1 Cylinder covers need spinning :LittleDevil: I enjoyed doing it for my Fowler

As it happens Tiley are in the next unit to the timber merchants that I use for my hardwood.
Title: Re: Strictly.... “ Hot Air “
Post by: crueby on November 05, 2018, 02:34:43 PM
Graham, I have never tried it with steel, but did make some clock pendulum bob covers from brass. I had to stop a couple of times and re-anneal the sheet partway through forming over the outer edge, but it worked quite well.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 05, 2018, 03:57:29 PM
Hi Guys.

Annealing, particularly with certain Brasses is almost a must. However, the choice of the Brass in the first place helps as there are many particularly suited to spinning.

Attached is a picture of our most ambitious spinning, one done professionally I must add. I did however make the collapsible chuck. The finished item fits the very popular collectable Tilley PL 53 storm lamp.

Alongside the Bronze and Steel " pushers "

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Roger B on November 05, 2018, 07:41:52 PM
That looks nearer to running than my diesel  :ThumbsUp:  :ThumbsUp:  A little bit more fine tuning and you will have a runner  :wine1: ( and not be sprayed with unburnt diesel oil  ::) )
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 18, 2018, 04:20:05 PM
On the Polly Robbie the governor casting is not a casting  :disappointed: It is a bit of flat steel. So using the bit out of the centre of the base I set about making a Cast Iron governor part. First the centre was turned up with a shoulder to fit into a 16mm hole and then the bit of spare cast Iron faced and had the centre fitted. These have been loctited together


I had every intention of not only finishing this bit but also machining the cylinder when Bluechip arrived this morning. After a very nice visit by Dave, thanks Dave   ;D , I discovered that Dave had left a box of bribery goodies for Surus  :headscratch: but the sun was out....Minx has been getting restless and wanted to go for a drive.... so we visited my supplier who had a workshop Elf for me  :naughty:. On arriving home I discovered that someone thought I already had a workshop gnome so I was not (currently) allowed an Elf as well  :( so he has added them to his collection and given me the box of Jaffas as a consolation prize :noidea:

I will have to try again tomorrow to do some more on the Polly Robbie.

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 19, 2018, 04:44:11 PM
Update on my Alyn Foundry Robinson: I am still thinking about a design for the burner. I have some bits and pieces that I could make something out of  :noidea:

In the meantime I have been machining up a cylinder  :naughty: the fist step was facing the bottom and back to give me something to square up with. Mr Silky then squared it up in his four jaw and bored the cylinder, turned it round and bored the governor hole (the Polly design does not have a governor  :( but mine will) Check the cover fits before taking down.

Mounted back in a vice the governor face was skimmed again to square it up to the bore. At this point I found the spacing of the threaded mounting holes left a lot to be desired so chose to move them in from 19mm offset to 16mm offset. I also drilled the cover while everything was set up.

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 19, 2018, 04:55:08 PM
The governor cover was marked on the inside face with a marker and hacked down to leave some material. then the outside was filed first on one side then the cover turned round and you can see how far out of symmetrical the casting is. One side was much wider than the other so there was a fair bit to file off. To make sure there was plenty of material under the bolts I used buttons under the screws ( sorry no pic  :-[ ) and marker pen to show the progression of the filing.

I should mention that this casting like the others in this Polly kit has some hard bits: one of those was the mounting point for the governor cover

At the end of the day I have a cover that fits and a cylinder ready for a bit more work  :)

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Admiral_dk on November 19, 2018, 10:37:00 PM
Quote
At this point I found the spacing of the threaded mounting holes left a lot to be desired so chose to move them in from 19mm offset to 16mm offset.

Looks like you made nice progress after finding a "compensation mod" that worked, as the end result won't give it away for anybody that haven't build one themselves  :cheers:
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 22, 2018, 04:50:29 PM
Thanks Per,

The Power Piston came as a slightly over length piece of Cast Iron. At 42mm diameter the spare material represented a useful piece of material for 38.1mm diameter piston rings should I need them so I decided to start by turning the gash end down to 38.5mm diameter and to hold the material by that for making the piston. The entire piston was turned in a collet leaving about 0.05mm extra for lapping with, ignoring the hole shown on the drawing it was tapped to take the small end and then parted off. The piston is still at this stage slightly over length and will not fit into the bore although it "thinks about starting".

Piston turning was done on a simple jig - a piece of spare steel turned down and threaded to match the piston with a shoulder, the piston was then screwed onto this and pushed tight against the collet and the end turned to length. Pulling the jig out of the collet allowed the piston to be lapped. My chosen lap was a stone held in my fingers and rubbed over the outside of the piston making sure it was in contact with the entire piston length at all times. As the piston comes down it is important to check the fit. Sometime you will find it goes in so far - this is either an indication of a non parallel piston or that the bore on the cylinder has a slight taper. To find out which one turn the piston round and try it in the other way. As you can see this one fits in both ways round the same distance which means there is a slight taper on the bore of the cylinder that was caused by using a car brake drum hone rather than one of Smelly's hones. This can be corrected with a little more honing of the cylinder. Finally the piston slides in and all is well.

I was hoping that someone would have come up with some ideas for making the burner using the bits I have for the bigger Robinson by now  :(

Jo


Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 22, 2018, 05:25:45 PM
Jo, did you just externally lap the piston down until it fitted the cylinder or did you lap the piston into the cylinder? EG run the two together.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 22, 2018, 06:03:42 PM
The final finish was done together.

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on November 22, 2018, 06:11:48 PM
Here's another one that runs  :mischief:

ajBDy7FamYYt=9s

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 23, 2018, 11:32:59 AM

I was hoping that someone would have come up with some ideas for making the burner using the bits I have for the bigger Robinson by now  :(

Jo

Good morning Jo.

All the family are " down " with a flu like virus that's been hanging on for weeks, I'm still feeling pretty rough.

I made a very simple gas ring that used the upturned top from the Gardner hot tube chimney top. Using a scrap lump of Steel round bar, a little larger in diameter to that of the chimney top simply bore out a cavity that's smaller than the top then counter bore for 3mm deep at the top's diameter. You can then drill a hole into the side and insert a " Primus " burner for correct mixing.

Andy, ( Chipmaster ) gave me a piece of ceramic removed from a portable gas heater on my last visit but I've yet to try this as an alternative to my 18 hole original design.

Nice paint job Andy!!    :ThumbsUp:

You were making more noise than the engine!!   :)

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 23, 2018, 01:45:34 PM
Jo If you want to keep the height of your burner down then thread the top of a block of metal to take the "gas ring"  and fit the other part which I assume has the jet in it and takes a hose on the opposite end into the side of the block with a suitable extension piece between to bring the plastic valve out to where it won't melt.

Hope you get it made ready for tomorrow :LittleDevil:

Talking of things melting, given that you had the loctite fail on your crankshaft is it a wise thing to be using loctite on your two part governor fabrication as that is likely to get hotter than the crank should.

J

PS I just got some castings :cartwheel:
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 23, 2018, 05:41:52 PM
 
Jo If you want to keep the height of your burner down then thread the top of a block of metal to take the "gas ring"  and fit the other part which I assume has the jet in it and takes a hose on the opposite end into the side of the block with a suitable extension piece between to bring the plastic valve out to where it won't melt.

Yes that was as close to a design I got before I had to go off for an important meeting this afternoon, just got back and will have to see if I can bring both in the morning ::)

The crank failed due to not having an appropriate burner  :disappointed:


Surus tells me he is looking forward to receiving his castings tomorrow (don't forget them or I won't hear the end of it  :Doh: ) And he is not coming tomorrow as the owner of "his" Stuart Major castings will be there and none of us want to see blood   :hellno:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 23, 2018, 06:47:41 PM
Only one set of castings in my package.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 25, 2018, 04:16:37 PM
:facepalm: Its been hell I didn't come home with any castings yesterday  :disappointed: so I was in trouble :paranoia:


Having completed my penance I have been out in the workshop and machining the platform for the Polly Robinson. This fits nicely in a four jaw chuck and can be turned in the same way as the Alyn Foundry base. Yes this casting (like all of the Polly Castings) has hard spots so a good carbide tipped tool was needed for turning  ;)

The top was skimmed to allow it to be held square and then the bottom could be faced and have the bore cut for the other part of the platform which is integral in Graham's castings.

the water space is covered over with a very nice laser cut part which even has the screw holes marked out for holding the base on. the sides of the casting had a little more draft angle than the plate allowed for so once squared up so that will have to be filled and due to the temperature I will use JB Weld. I am also considering holding the sleeve part of the casting to the main platform with JB Weld to avoid having to drill through from the top  :thinking:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 25, 2018, 04:22:06 PM
:facepalm: Its been hell I didn't come home with any castings yesterday  :disappointed: so I was in trouble :paranoia:

The little man would not have wanted them anyway especially once he found the sand in some of the voids :censored:
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 25, 2018, 05:15:56 PM
The little man would not have wanted them anyway especially once he found the sand in some of the voids :censored:

It was another casting set he was hoping for - My supplier encouraged Alan to bring one of the Stuart Major Beam castings along to the meeting and to put it on my display table  :slap:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 27, 2018, 05:19:20 PM
A bit more progress on the Polly so it is best I add to the "features" list of the Polly model/drawings:

The two brass castings for the Arms do not match the drawings  :ShakeHead: This does not actually matter and there is little point trying to change them. And as the Displacer Link is already too wide in the gap of the arm there is no point in thinning down the end of the displacer rod.

The power piston drawing does not show the piston being threaded for the Gudgeon Block (or a nut to attach either)

Both Laser cut arms are ok but the location of the centre pops for the holes for bushes needs pushing over to be more central.

Both mounting plates at the bottom of the crank bearing and the cylinder castings are undersized in one direction but they are dimensions that do not matter.

I am not sure if I really need all of the fixing screws that came with the kit :noidea: As I normally make my own fastenings I am tempted to make my own again as the ones provided would need cutting down anyway. I am still wondering if I really need to drill holes in the top of the platform to attach the lower piece or if JB Welding it together would be sufficient. I am tempted to give it a go and if nothing else if it fails it will give Jason another reason to  :stickpoke: my build  :-\

Jo

P.S. As you can see someone had to check one of his casting sets was still all present and correct  ::) I am hoping to be allowed to fondle them later  :)

Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 27, 2018, 06:00:54 PM
Never mind Jason   :stickpoke:  ing....

Have you managed to repair the " true " half scale engine yet?

I'm sure we're all waiting eagerly for the video.   :)

Cheers Graham.

Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 27, 2018, 06:14:17 PM
I have to make a burner Graham and to do that I need gas jets. Which I forgot to order  :facepalm:

The engine is back together and passed the test on Saturday when he tried poking it.

Jo

P.S Did you get the PM?
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 27, 2018, 06:15:55 PM
Don't be silly Graham she can't repair the 1/2 scale engine until the RLE has been repaired.

I suppose the JB Weld will be fine after all its only going to sit in a dark corner almost finished with the rest :LittleDevil:

Why can't you unscrew the jet from that old gas ring that you had a t the weekend,
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 27, 2018, 06:36:25 PM
Why can't you unscrew the jet from that old gas ring that you had a t the weekend,

Size matters  ::)  I am waiting for Jerry at Clevendon Steam https://www.clevedonsteam.co.uk/products.html to come back to me on the delivery...

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 27, 2018, 06:38:03 PM
Could have got them next day from forrest, and more choice of Size as it matters and they also have the smaller No3 which you will need :facepalm:

https://www.forest-classics.co.uk/ceramic-burners/gas-essentials-and-jets

Cheaper via their e-bay site but slower postage


https://www.ebay.co.uk/itm/NEW-NO-3-GAS-JET-1BA-THREADI/202067603909?hash=item2f0c2af1c5:g:~y4AAOSw3~5ZzQYV:rk:2:pf:0
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 28, 2018, 08:44:17 AM
And even cheaper from Jeremy  ;)  They should be in the post later today then we just have to wait for Royal Snail  :disappointed:

Why do I need the little No 3 jet :headscratch:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 28, 2018, 08:52:07 AM

Why do I need the little No 3 jet :headscratch:

Jo

I thought the whole reason for making a burner was that your hob was too big and your torch bigger still :facepalm2:

A No8 would be what you would use on a burner for a 3" vertical boiler but you don't want to be getting anywhere near that much heat so the smaller jet is the better bet.

Did you see the size of the flame on Norman's burner he was using for his Polly, not much more than a large candle flame, and mine runs on a similar flame without the base, the only reason I went with the ring was because it draws in air lower down and even then I can't set the flame as low as I would like without it going out.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 28, 2018, 09:01:19 AM
My hob burners are a larger diameter than the hot pot on the 1/2 sized Robinson so they heat the stand rather than the pot. The torch needed a better mount but was only for a quick test. So the plan is to make a long term solution for each engine.

But it will all have to wait until I get some time... there is so much to do when you are retired  :facepalm:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 28, 2018, 09:14:12 AM
Regarding that old camping gas ring you had. the 5.8mm dia thread is most likely to be the Euro standard M6 x 0.75 if you wanted to use that, not the BA size I thought.

Happens to be the same thread as that hose I had on my engine, had you mentioned it before I could have brought my taps along with me for you to borrow.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 29, 2018, 04:10:35 PM
The ceramic proved to be easy to cut and file  :)

The bigger burner is finished and a second has been started. I didn't get far as it is Thursday  :naughty:  :wine1:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Bluechip on November 29, 2018, 05:53:53 PM
Ah :)  That's cute ..  does anything stick the ceramic in or just a close fit ??


it is Thursday  :naughty:  :wine1:

Jo

Yeah, me too after this mornings escapade. I feel I owe it to myself ....  :facepalm:

Dave
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on November 29, 2018, 08:54:08 PM
I'm boring the Robinson cylinder and have just noticed that the drawing shows a 1/8" wide semi circular groove undercut at the end of the bore. Doing it isn't a problem, but I'm just curious what its purpose is.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 30, 2018, 07:18:07 AM
I would have thought it allows the piston to clear the end of the bore so you don't wear a ridge at the end, same sort of thing you see on cross head guides etc. Also makes it easier to lap as you are not working into a corner.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 30, 2018, 10:46:00 AM
Good morning Richard.

If you look closely inside the cylinder you should see the grove " as cast " at the bottom end.

It's sole function is to allow the tip of the cutting tool to clear before bottoming.    ;)

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on November 30, 2018, 11:23:47 AM
Thanks Graham
I've only taken one roughing cut through as yet, with about another 1/8" to go. I did notice that the boring bar started cutting fresh air towards the end of the bore, but didn't realise that was deliberate!

Jasonb has a good point about it giving clearance when honing towards the end as well.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 30, 2018, 01:42:09 PM
I have finished off the smaller burner just in time as the nice lady from Royal Snail has just dropped off those exceedingly cheap jets from Jeremy  :cartwheel:

This morning I started tackling the Hot cap and the Displacer which come as flat pieces of brass  :thinking: the first job was to turn them round using a super glue chuck and a safety tailstock support. I tried knocking the corners off the piece of brass before turning but I came to the conclusion that that was a waste of time.

We have discs  :) I need to make a hole in one and decide if I want a displacer or regenerator  :noidea:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on December 01, 2018, 02:57:59 PM
There is a little too much bonking going on around here   :embarassed:

A0s0VvEQVZs
I am going to have to sort that out but once it had cooled down I thought I may as well try a tea light  ;)

IyDsfIYnyRw
Must stop that bonking it is not good  :disappointed:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Gas_mantle on December 01, 2018, 03:17:28 PM
Great stuff, well done  :)

It runs fast on the tea light, you got me interested in making one now  :)
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on December 01, 2018, 03:31:37 PM
Well worth the wait Jo.

Very well done!   :ThumbsUp:

Have you been able to ascertain where the knocking is coming from? At this moment I think Andy's engine is the quietest I've ever heard running.

As a " by the way " I have 3 sets of castings left if anyone is interested.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: b.lindsey on December 01, 2018, 03:42:02 PM
That worked Jo. Could the displacer be hitting on the bottom of it's stroke?

Bill
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on December 01, 2018, 03:57:35 PM
Thanks. I have tracked down the bonk - the power piston had unwound itself on the mounting and was catching the bottom of the power cylinder  :disappointed: So I need some sort of thread lock to discourage it from doing that again.

No more playing today its getting late.

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on December 01, 2018, 05:04:14 PM
Running well Jo, what colour are you going to paint it. Choice of VHT can be a bit limited.

You may have room for a locknut to stop the wrist pin block unscrewing, should go into the passage at the end without having to touch the casting
Title: Re: Strictly.... “ Hot Air “
Post by: Admiral_dk on December 01, 2018, 06:29:49 PM
That engine is running very well on a candle  :praise2: and this time Jason can't tease you about not finishing it either  :whoohoo:
Title: Re: Strictly.... “ Hot Air “
Post by: zeeprogrammer on December 01, 2018, 06:55:25 PM
 :ThumbsUp: Congrats!

I've been looking around for an engine that will run off a tea candle. I can't say that's an engine for me but it tells me it can be done.

Given a tea candle, is VHT paint necessary?

Looking forward to seeing what you choose.
Title: Re: Strictly.... “ Hot Air “
Post by: Chipmaster on December 01, 2018, 07:09:17 PM
Another Robinson HA is running. LittleAngel:
I added a locknut to the wrist pin block on my engine.

Andy
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on December 02, 2018, 01:11:27 PM
Hello All.

Running so soon on a " tea light " Jo is a serious testament to your engineering skill, very well done.  Months of running are normally needed to " bed in " the different parts.

My own preferred method for the wrist pin block is a dab of Acetate cure Silicon as this serves to seal and lock the item.

Regarding paint, the only component that actually does get very hot is the base. The platform, theoretically shouldn't get hotter than 212/100 degrees because of the water.

Jo, one more video please, after you've had time to both repair and paint the engine.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on December 02, 2018, 04:04:29 PM
Big R is going back together Graham. I have tried some nut lock on the power piston thread  :noidea: She will have to wait for another day for her next run.


In the mean time I have been having fun  :paranoia: The hot end and displacer on middle R is made up. Of course bending up the outside wrapper using the rollers leaves a flat at the end of the metal  :facepalm: Then you have to shorten it once rolled to get a snug fit. Even then it needed wiring.

And even that did not totally work and first the bottom slipped, then the top, then I melted the corner of the piece of 0.5mm rolled brass and had to add a repair piece. I think this piece would be better if it was spun  ::).

And there is another one of these to solder up and that one cannot be patched  :toilet_claw:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on December 02, 2018, 04:29:45 PM
When you come to do the other one Jo leave the disc oversize and then you just have to file it off flush rather that faff about trying to line it up when its hot
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on December 02, 2018, 08:48:02 PM
When I'm rolling up something like that, I try to get the end inch or so to roughly the right radius over a former, then put it through the rollers.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on December 05, 2018, 02:42:48 PM
fEsdmUCUjZc
:thinking: It still seems to have a bit of a knock but it is better.

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on December 05, 2018, 02:55:22 PM
It's running well, did you look to see if those big end links are touching the vertical links, may not show when flywheel is turned as things are being pulled apart but could clash when you move the piston which pushes all the links together.

Painted as well :cartwheel: and the shade of your favorite  :wine1:
Title: Re: Strictly.... “ Hot Air “
Post by: b.lindsey on December 05, 2018, 04:06:43 PM
Looks great Jo. Love the color too!!

Bill
Title: Re: Strictly.... “ Hot Air “
Post by: zeeprogrammer on December 05, 2018, 04:34:32 PM
Nice one Jo.  :ThumbsUp:

I'm still amazed it runs on a tea candle.
Title: Re: Strictly.... “ Hot Air “
Post by: Kim on December 05, 2018, 04:53:49 PM
Congratulations, Jo!  That is really nice :)
And running on a tea candle is pretty cool indeed!
Kim
Title: Re: Strictly.... “ Hot Air “
Post by: Roger B on December 05, 2018, 07:26:23 PM
Splendid  :praise2:  :praise2: As the others have said just a tea light is pretty impressive  :wine1: (that's your glass for Thursday  :stir: )
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on December 05, 2018, 08:52:25 PM
Thanks Guys  :)

Another engine to put away into the collection. Hopefully I might be able to swop it for another set of castings  :naughty:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Dave Otto on December 05, 2018, 09:45:29 PM
Nicely done Jo, I like the color too!

Dave
Title: Re: Strictly.... “ Hot Air “
Post by: Steamer5 on December 06, 2018, 06:17:33 AM
Very nice Jo. You just need to scale the candle down to see how little it needs

Cheers Kerrin
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on December 07, 2018, 11:28:53 AM
Thanks Guys  :)

Continuing on with the Polly Robbie...

The Displacer Cylinder  :facepalm2: I ended up having to turn shoulders on the two ends, wire the outer and keep the whole lot together using a piece of threaded rod. Easy flow wouldn't run so I ended up using some even higher percentage silver solder (=lower temperature melting) to do the joining. Its together  :paranoia:

Do I want to do it again  :hellno:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on December 07, 2018, 04:31:36 PM
The main part of the engine that still has to be finished is the platform this requires a hole drilled along the length of the casting for the passing of the heated air. Then the parts have been joined together with JB Weld. And finally the hole taken through the other part.

Now I just have to wait for it all to go off :drinking-41:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on December 09, 2018, 04:10:44 PM
The Links: are soft and they do not match the drawings, they are however about the right length. I decided on redesigning to use the supplied links and not to use smooth pivots or attempt pinning with 10BA screws but to make screwed pivots.

Before drilling, reaming and tapping the holes it was necessary to pack between the arms.  I couldn't find any easy way to stop the arms bending all over the place to let me mill out the centre slot so I used a needle file and did it by hand  ;)

Another Weekend is over  :-\ so its another week in the Workshop to look forward to  :ThumbsUp:

Jo

Title: Re: Strictly.... “ Hot Air “
Post by: 10KPete on December 09, 2018, 04:47:09 PM
 :ThumbsUp: :ThumbsUp:

 :popcorn:

Pete
Title: Re: Strictly.... “ Hot Air “
Post by: b.lindsey on December 09, 2018, 04:54:07 PM
Got to love retirement eh Jo? Like an endless weekend  ;)

Bill
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on December 09, 2018, 06:22:38 PM
Retirement is hard Bill  I have to keep looking up the Dilbert cartons to remind me what I am missing so I don't  forget  :noidea:

I reckon I am over the worst bits of this engine so I have been asking Surus to see if he has started thinking about the next set of castings I can have out of his collection ;D

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on February 06, 2019, 02:13:19 PM
Just to wake up this thread, cos its been ignored since early December.
I know there was a lot of discussion about a year or so ago about making the diffuser? piston for the Alyn Foundry version from tin cans.
To be honest I wasn't ever too keen on that, and although I have made one that way, it isn't something I'm proud of, even though its hidden away inside the engine.
I'm thinking of a brass one, 2 flanged end plates and a barrel, probably 26G brass, soft soldered together, though it could be silver soldered if necessary. Yes, I've got the stainless steel pot scourers ready to stuff it with. It will be a bit heavier than the tin can version, but not that much.

Any thoughts?
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on February 06, 2019, 03:13:42 PM
I recall Graham saying that brass was not a good material as it conducts heat too easily. On the small one I made the piston was machined from stainless bar and I know somebody who had a job to get a Polly one going until he ditched their brass pistion and did the same as me. At your size starting with stainless tube may be a better bet.

Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on May 31, 2020, 12:00:39 PM
A recent find from the Gardner archives, courtesy Geoff Challinor Anson Engine museum.

The number 6 is indeed a " formidable " hot air engine.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on June 22, 2020, 04:12:24 PM
Hello All.

I've discovered that the " construction notes " for the half scale Robinson hot air engine have been misplaced.

Can anyone help find a former customer that might still have a set please?

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on June 22, 2020, 04:25:50 PM
I've discovered that the " construction notes " for the half scale Robinson hot air engine have been misplaced.

There should have been construction notes   :thinking:  I didn't get any   :disappointed:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on June 22, 2020, 04:47:19 PM
I've discovered that the " construction notes " for the half scale Robinson hot air engine have been misplaced.

There should have been construction notes   :thinking:  I didn't get any   :disappointed:

Jo

Yes Jo, three A4 sheets of them....

Hopefully someone might be able to find them?  A gentleman named Nigel McBurney ( hope I've spelled his surname correctly? )  bought several from me. I dropped out of the scene following my heart attacks, lost track of many friends and contacts.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on June 22, 2020, 04:50:39 PM
Managed to make my version without any notes, probably easier to direct any potential builders to threads on here that are likely to have a lot more info
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on June 22, 2020, 08:59:50 PM
Jo,

Graham has possibly just realised as I have just agreed to have a set of these castings off him

Construction notes would certainly be useful for idiot like me.

I have just printed out each of the views from the .pdf onto A3 sheets so I can try and read the dimensions

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on June 22, 2020, 09:17:45 PM
This thread is the construction notes  ;) . My build started here: https://www.modelenginemaker.com/index.php/topic,7561.msg181544.html#msg181544

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on June 23, 2020, 12:05:28 AM
Jo,

Just finished reading all way through and making a few notes on the plans.

Yours looks very good and runs well on that candle.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on September 19, 2020, 05:29:30 PM
Hope to start my Hot Air engine in the not too distant future.

Spent most of last few months finalising the sale of my Dad's house (plus sorting out Pension and Insurance claim stuff for him), am part way through having bathroom completely rebuilt (had to move wall and next week will have to fit new skirting and architraves to the doors, prior to plumber installing everything.), sorted out my machine tooling a little bit (into a Versatool cabinet), helping eldest daughter with her new house and garden, and have almost finished installing a crane to pick up the indexer and rotary tables for the Milling Machine.  At the moment the crane flexes the 48mm vertical steel tube it is mounted on and so needs a further support under the swinging arm.  Material is cut to length and ready for machining.

I have been though this thread again and adding to the notes I have made on the plans.

I notice everyone skips over anything concerning the brass/gunmetal parallel linkage.  Has everyone just spent a number of hours with small files and filed them flat and filed the bosses to a cleaner shape to remove as much of the casting marks as they wish.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on September 19, 2020, 05:50:50 PM
I notice everyone skips over anything concerning the brass/gunmetal parallel linkage.  Has everyone just spent a number of hours with small files and filed them flat and filed the bosses to a cleaner shape to remove as much of the casting marks as they wish.

Yup that is about it. The actual lengths do not matter  other than the pair of links must be the same distance between the pivots.

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on September 19, 2020, 06:01:11 PM
Rather than hours with a file you could ream the holes and then mount them on the rotary table and give them a good clean up, not a lot of difference to how I cut mine from solid. A corner radius milling cutter would leave a small internal fillet around the bosses if you want to keep the cast look.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on September 19, 2020, 07:34:11 PM
Jo, Jason,

Thank you both for quick responses.  I quite like the idea of the rotary table option but will find something to practice on first.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on September 19, 2020, 09:56:02 PM
I cleaned them up with files and a Dremel, then superglued the link pairs back to back for drilling/reaming.  I've turned some buttons from silver steel to act a filing guides for the bosses.

The rotary table is overthinking the problem a bit IMHO.  :hammerbash:
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on November 07, 2020, 09:06:28 PM
Finally started my Robinson Hot Air Engine.

Decided to start with the brass linkages.  Cleaned up with combination of files and the die filer.  Recommendations for the drop links to the regenerator and the con rods is to drill and ream them as pairs.  Cleaned the back faces of all of them with file and abranet on die filer table.  Miked up the bosses on the Regen links and it was touch and go as to whether I could get them to the requisite 0.2969. :(  I machined the boss faces on the small Cowells mill.  Basically nice and easy to see to work and in the warmth in my office. :)  The final dimensions were about 4 thou shy, but this will not cause a problem.

The con rods need to be .250  thick so clamped them flat on the table, used cigarette paper to align cutter with table top and dropped the knee 0.249 to give me the .250.  Repeated exercise for the second con rod.

Then came the fun bit.  Trying to superglue the pairs together.  The Regen pair took two attempts and the conrods three.  The first attempt on the conrod ended up in the gas hob to warm it up to separate the pair.  Eventually I was happy with them.

Back up to the Cowells Mill to clean up the sides of both pairs.

Tomorrow will hopefully drill and tap the holes for big end bolts and try and find a thin slitting saw blade to split the big ends.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on November 08, 2020, 09:07:41 PM
Conrod was quite an awkward thing to mount because of the taper along its length.  After a bit of thought I remembered a Myford vice I have which has a swivelling section which can be used with the moving jaw moving jaw.  Was able to rest it on a paralllel and clamp up tight.  Then mounted the vice to angle plate on mill table.  I had made a couple of filing buttons and used one to locate the centre of the small end and put in a small dimple with a drill.  The Big end I had used calipers to find the center.  The only way I could think to get it vertical was to use the laser edge finder to pick up the line on the vertical face and the dimple in the big end. A sheet on white paper held at 90 degrees to the conrod enabled me with a magnifying glass to centre the laser The vice needed a few light taps to get this correct.  But eventually got there.

Centralised the X axis DRO on the glued split line, and the zeroed the Y axis on the center of the rod. Used a 1/4" endmill to create flat platforms on the what would become the big end cap.  Then swapped to 2.3mm drill to to drill two holes per cap ready to tap 2BA.  Went to depth of 8.5mm but this turned out not to be deep enough I found a bit later.  Tapped the holes to depth. Then drilled clearance hole to depth of big end cap.  Then hunted for thinnest slitting saw blade I had.  I had an arbor I had made for the Cowells mill and this just gave me enough depth to be able to line the blade up on the centre of the dimple in the small end.  Hand magnifier and bright light needed for this.  I had to remove the clamp I had in place whilst drilling to be able to use the slitting saw.  Lowered the knee 1.625inches and cut of the big end cap. This was when I found the drilled holes were not quite deep enough.  Was able to go round them all again with 2.3mm drill and then tap. All OK.  Cleaned edges of big end cap and refitted it temporarily with some long 2BA bolts with a nut and washer fitted to pull the cap down.

Next job drill and ream big and little end.

Anyone who has any better ideas as to how I could have mounted this up to machine it, please shout up.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 09, 2020, 07:22:09 PM
Progressing nicely Colin. :ThumbsUp:

For the folk interested in the historical....

The first Robinson patent was issued in the late 1880's. I have attached some early written information. It would appear that the firms Norris and Henty and Potts and company were some of the first manufacturers.

The last picture is of 3 different sizes listed in the literature.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on November 12, 2020, 09:00:39 PM
Taken 3 days but finally got the brass linkages drill, tapped and reamed as necessary.

The superglue trick is all very well so long as it does not separate whilst drilling.  Which it did.  Carefully stepping up drill sizes and it suddenly snatched separated the glue but luckily the conrod in this case stayed with the drill.  My temporary big end bolts took a bit of a hammering.  Carefully reassembled back in vice and continued.  Unfortunately not too carefully.  What I had not notices was the lower conrod had tipped slightly.  Only spotted this after reaming the holes (0.250") and wondering why it appeared to be at an angle.  Bugger :censored:  Luckily was able to get the miniature boring head to bore the holes out from the required 0.250" up to just under 0.2812 (9/32") and then reamed 9/32".  Will now have heavy duty crankpin. :D

The two long straight links also separated the super glue and I ended up with a bent link.  Judicious use of arbor press restored it to straight.  I drilled/tapped and reamed these as individual links rather than as a pair.

Everything else went well.

One thing is certain it takes a damn sight longer to set these little things up to machine than the actual machining itself.

Now to make the pins.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 13, 2020, 12:38:21 PM
They look very nice Colin.

That's undoubtedly the most tedious of the engines construction out of the way, however I found the pin making equally so too.

The rest is fairly easy but don't forget to do all the facing operations on the cylinder before boring.   ;)

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on November 13, 2020, 08:22:25 PM
Graham,

I've been making the pins today.  Its taken me almost all day to end up with 4 pins.  There were also 2 that I buggered up, one just at the last step prior to parting off.  :censored:  Once I had worked a sequence out I was okay with them.  Just need to sort out slitting saw for the screwdriver slots and champfer the edge of the screws.

Quick question for you. I don't quite understand how the link to the piston should look.  Is the link offset to one side of the brass boss in the piston, as it looks to me in the drawing.  Or should it be central between two lugs on the brass boss.  Also is the pin joining the two screwed similar to the other pins on the linkages.  Could do with seeing a plan view.  Also the link to the top of the cylinder, Is this pinned similarly.

What material is used for the link down to the regenerator piston?

Thanks,

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 13, 2020, 08:29:01 PM
This is how I interpreted it, yes another pin
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on November 13, 2020, 08:31:59 PM
Jason,

Thanks for that.  Its what I would have expected but not quite what the drawing appears to show.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 14, 2020, 11:44:19 AM
Good morning Colin.

I've just been looking at the drawing and yes, there's a few omissions that I could well have related to in the missing write up.

The small end fork is shown with a " ragged " edge telling you that it's a " cutaway " of the complete item made from Hexagonal Brass bar stock.  ( labelled )

The cylinder pivot pin is made the same as the others but not threaded. It is simply retained by a 1/16" split pin and washer.

The displacer piston rod is made from 5/16" Silver Steel ( ground stock/drill rod ) and needs to be as snug a fit as possible through the platform casting. A 3/16" cross drilled and reamed hole attaches it to the Brass links you've already finished.

Now, if a mistake during the boring of the displacer rod hole is made, no need to worry. As 8 mm is only a few thou away from 5/16" you can always upsize.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on November 14, 2020, 01:17:29 PM
Graham,

Many thanks for those answers.  Now you have mentioned it the the raggedy edge shows up like a sore thumb.  I just had not spotted that on the drawing.  :Doh:

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on November 15, 2020, 02:12:27 PM
Ah, brass hex for the piston gudgeon housing. Makes sense. All it says on my drawing is 'Hex bar stk'. How is the gudgeon pin fixed? A split pin either side?
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 15, 2020, 02:21:55 PM
Hi Richard.

You could do either, make a pin the same as the cylinder top pivot or, as you say pin, washers and split pins.

I think I posted a reference to Gardner's hand sketched parts list on the previous page, you could always make a more elaborate yoke if you wanted to.

Cheers Graham.

Edit.... No, two pages back....
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 15, 2020, 02:23:26 PM
If you ream the gudgeon pin hole in the carrier with a hand reamer and only go part way through you can leave a taper in one side and the pin will press into the taper  :)

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on November 18, 2020, 10:31:57 PM
My flywheel is now machined.  Came out slightly undersize once it was cleaned up as did one of the bosses (by about 4thou).  There is a large boss on one side and a short boss on the other.  Which way round are these intended to be, i.e. which is on the outside.  I am going to attempt fixing flywheel with a gibhead key as per the plans.  As the flywheel needs a tapered slot, I need to be sure which way round to fit it.  Going up from 3/32 key to a 2.5mm key.  Only 4.6thou bigger, but at least have suitable slot mill for the keyway in the crank.  Never done a keyway before and this is a rather tiny one.  Setting the cutter up is a bit delicate to get the 1 in 100 taper.  This is tomorrows task.  But I may try to make the key first to see how I get on.

Graham,
I have your build notes for this engine, with a couple of modes suggested by Nigel McBurney.  Will get copies to you in near future.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 19, 2020, 11:27:10 AM
Good morning Colin.

I received your email this morning, thanks.

The reduced length of boss is butted up to the main bearing pedestal, with running clearance.

I'm puzzled, are you going to " broach " the keyway in the flywheel hub? There's two ways....

Proprietary keyway broach with bush or set up the flywheel with the correct angle under a slotter and cut it that way? The taper is always put into the flywheel hub, the crankshaft carries the corresponding slot in parallel with the shaft.

I'm aware that I don't use my broaches correctly, I push them to the last cutting tooth before pulling back and then re push with the shim in place. The proper way is to use a tapered slot bush and push the broach right through.

The propriety bushes are useless for this job as they're far too short, only supporting the broach half way. I made longer ones years ago.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on November 19, 2020, 12:47:35 PM
Graham
I'm sure you've covered this before, but my drawing suggests that the governor valve and the bore the the end of the cylinder are both 1" dia. Instinct suggests that the valve is slightly smaller, say 15/16", so that when it activates its sucked into the bore, but with a 30 thou annulus all round to choke the engine and slow it down. Otherwise, slightly larger, say 1 1/16" but with a few 1/8" air hole drilled in it.

Even though I've done most of the engine, if you do get hold of a copy of your build notes, I'd appreciate a copy, if only to see where I did it wrong!

Do these hot air engines run either way round? I presume they are not self starting, but need a good pull to get them going.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 19, 2020, 01:10:45 PM
A couple of small holes in the governor will stop it plugging the cylinder hole

http://www.modelenginemaker.com/index.php/topic,7561.msg167581.html#msg167581

Should just need a gentle flick to start it off, they almost start moving by themselves as they get upto temp, one way only.

oWf9DnTIIJI
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 19, 2020, 01:33:38 PM
Graham
I'm sure you've covered this before, but my drawing suggests that the governor valve and the bore the the end of the cylinder are both 1" dia. Instinct suggests that the valve is slightly smaller, say 15/16", so that when it activates its sucked into the bore, but with a 30 thou annulus all round to choke the engine and slow it down. Otherwise, slightly larger, say 1 1/16" but with a few 1/8" air hole drilled in it.

Even though I've done most of the engine, if you do get hold of a copy of your build notes, I'd appreciate a copy, if only to see where I did it wrong!

Do these hot air engines run either way round? I presume they are not self starting, but need a good pull to get them going.

Hello Richard.

Actually the governor disc should be slightly larger in diameter than the hole through into the cylinder. This creates a firm seal. But.... The problem is that when it operates is stops the engine dead. To soften the governor Gardner placed a couple of 1/4" diameter holes ( at full scale ) through the disc, so as Jason suggests a couple of 1/8" holes drilled will work just fine.

They run in one direction only, pull the flywheel away from the cylinder opening.

Please PM me your email address, definitely got it somewhere but just remind me. I'll send on the PDFs to you.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on November 19, 2020, 03:04:09 PM
Graham, Following my chat to Nigel McBurney who has made a number of these engines he has made a couple of mods to them to help with running. One is a change to the pins on the linkage rods. They are fully reamed both sides and a sleeve type nut put on from the back. His other mod is to the governor valve assembly. He has fitted an adjustable brass sleeve in the casting and the governor rod slides in this bushing. The sleeve is then used to control the distance between the governor valve and the face of the casting in which it runs. I sent the copy of the schematic for this to you with other stuff this morning. He had these mods described in Model Engineer Vol. 179, No.4050, 12-25 Sept 1997.

Thanks for reply re flywheel boss.  I intend (hope) to machine the key way in the flywheel on the lathe. I have ground a suitable cutter and have just ground some gauge plate down to a fraction under 2.5mm. Now going to shape the gib head key and try it in crankshaft prior to cutting jetway in flywheel. Will use the carriage on the lathe with cross-slide set to give 1:100 taper. That’s the plan. Whether it works or not I have no clue.

My mate Tom has a spotter for his XYZ (Bridgeport clone), so this is a possible last resort. Unfortunately I do not have enough space to swing the head 180 degrees so that I could fit it to mine.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 19, 2020, 03:41:28 PM
Hi Colin.

Yes, I saw the mods but, if you're making a " true " replica of the Robinson then the modifications are non original.

For the link motion assembly an old clockmaker adage comes to mind...

      " Tight enough to work, free enough to run "

I've never done a keyway on the lathe so I'll be interested to know how it turns out for you, lots of patience will be the " key " to success !!  ;)

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 19, 2020, 06:40:35 PM
Colin. you can't use the carriage to cut a tapered keyway as the movement is along the lathe's axis. There is a way to do it by taking out the topslide leadscrew and making a lever feed for that or making a complete slotting attachment. carriage works fine for straight cuts

I usually make a bush with a tapered slot and use a keyway broach.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on November 19, 2020, 09:20:05 PM
Jason,
Thanks for the reminder.  Of course it only works for straight keyways. :Doh:  I think I meant using the topslide,  :old:but I guess that would be rather slow.  I do have a slotting attachment but it is somewhat on the large size  :ThumbsDown: 

Need to rethink.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on November 19, 2020, 09:23:30 PM
Take the bulk out using the carriage, then just use the topslide to add the taper. It takes for ever doing the whole thing with the topslide.
To be honest, with these small engines I tend to make the keyways parallel and fit a tight parallel key. Naughty me!
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on November 19, 2020, 09:52:21 PM
Liam,
That may be the way to go.  I do have a slotting attachment for the Myford, which came from a mate of mine but have never used it.  It is quite bulky and the current toolholders are designed for larger bores than 5/16", so would need to make a suitable holder for the cutter I have ground up.  It has a tenon key on it to locate it in the cross-slide and hopefully parallel to bed travel.  If I use this to take out most of the material  then as you say the topslide only has to remove a very small amount.  Will need work out the best method set the1:100.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 20, 2020, 07:37:26 AM
Will need work out the best method set the1:100.

Colin

Bit of flat bar, parallel if you have one in the toolpost and clock it true along the lathe axis as the carriage is moved. Now put two marks on the bar 100mm apart and adjust the topslide until your dti shows 1mm movement between the two marks as the carriage is moved.

To do the matching tapered key put equal packing either side of your vice such as 123 blocks and lay a 1.5mm drill on one of the blocks. use a rule as a parallel resting on block and drill at the 150mm division and then set your gib material on that.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on November 21, 2020, 09:03:08 PM
Jason,

Your technique worked great.  Took a long time to setup, about 1hr, I have a big Bison vice and took me ages going through all my 1-2-3 blocks and parallels to get the height right so that only 5/64" was gripped in the vice jaw.  Ended up with combination of 4 parallels/123blocks and a 20thou plastishim each side.  I doubly checked the height with digital height gauge to be certain equal heights prior to adding 2mm drill to the equation (needed 200mm to get across the vice).  Machined nicely but went very slowly and surely.

Cut 2.5mm keyway in crankshaft.  Cocked up, initially picked up 2mm drill and did full slot with that, and realised,   :facepalm: when key would not fit and went over with 2.5mm slotmill.

Key fits firmly in slot, so pleased with that.  Flywheel will be Mondays job.  Wife comes out of hospital tomorrow after haveing a second knee replacement so think my time in workshop may be curtailed a little.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on November 23, 2020, 06:47:55 PM
There are 4 core holes in the top of the engine bedplate, going through into the water space. 2 of them are under the cylinder, the other 2 are open to fresh air. Obviously one is needed to fill the water jacket, but is there any good reason why the other 3 can't be plugged?
A 3/8" BSP plug looks to be about right. It would avoid having to rely on sealant under the cylinder flange stopping leakage into the air passage. Maybe I'm just worrying unnecessarily.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 24, 2020, 11:55:17 AM
Good morning Richard.

The simple answer is no....

We just used a " lick " of Silicone sealant to seal the two surfaces prior to bolting the cylinder down.

As for the " visible " holes I'm guessing your platform is our early version? We since made them oval to be in keeping with those that Gardner built. They were never plugged.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on November 24, 2020, 12:19:04 PM
We had a discussion ages ago about the likely age of my castings, and I think we settled on it being about 1991.

Richard
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on November 24, 2020, 12:47:43 PM
They must date from before Graham perfected his special coating  :thinking:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on November 24, 2020, 01:36:41 PM
Indeed, when I got them they were still in the original box and packaging, and entirely free from Graham's Special coating.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on November 24, 2020, 09:17:15 PM
Jason,
You mentioned making a tapered bush.  Any hints on ensuring I get the depth correct for the broach.  I have managed to source a suitable broach with parallel bush.  I have made a bush, which is longer in order to cover the full length of the flywheel bore.  I have made a collar to go round it with machined flats on either side, which once it has a slit (wider than the required broach width) in it will support/clamp the bush in the vice.  I can use the collar as a support guide to set at the appropriate angle as before.  I can then mill the slot for the broach in the bush.

Thanks,

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 24, 2020, 10:12:05 PM
Hi Colin.

As you have bought a broach and bush set which should have included a shim for the second and final cut? You can use the original bush as your " datum " for the correct depth. You can then upend it by the required angle.

Alternatively you could use my method and that is to push the broach to the last cutting tooth, retract the broach, fit the shim and re push it to the same spot as before. The cutters are set at the right taper themselves.

I have always worked " dry " with cast Iron but you could use a light smear of cutting fluid to ease the progress.

We use the small fly press here to push but an arbour press will work equally well.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on November 24, 2020, 10:46:33 PM
Graham,

The broach set does include 1 shim (0.03205).  Are you saying the actual cutting taper on the broach is 1:100?  So by pushing the broach in to the same position you will end up with taper, rather than pushing all the way through to get a parallel slot.

I have a couple of arbor presses (1small - 1/2ton, and a larger one which is either 2 or 3 ton).  Also have flypress or hydraulic press. I think the larger of the two arbor presses would be the best option.

Lots of learning curves here, never having used a broach before.  :headscratch:

Thanks,

Colin

PS Like the V twin CHUK
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 24, 2020, 11:00:12 PM
Hi Colin.

Well if it's not, ( 1:100 ) it's pretty damn close. I've used the method described above for every keyway I've ever done over the last thirty odd years or so.

The " key " to success, pardon the pun, is to watch, very carefully what the broach is doing as you push. If things " ain't  " square you're very likely to snap it like a Carrot.

I'm still using the same 3/32"  " A " series broach that was bought to build the prototype Robinson 29 years ago.

Good luck, cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 25, 2020, 07:32:11 AM
Graham's method probably gives a taper that looks like a flight of stairs if you were to enlarge it enough with multiple points of contact for the key and it seems to work for him.

I tend to hold the bush in my vice so the slot is milled top to bottom using the Y axis so you have the top and bottom making contact with the vice jaws and then use a similar method to the key by packing under the vice, just don't over tighten it back down onto the table.

Depth of slot make it the same as the parallel bush at the point of entry eg just under the flange and getting deeper towards the end otherwise the broach won't enter the hole. If in doubt make it a bit deeper and you can always add a bit of shim under the supplied one. MAKE SURE YOU BROACH FROM THE CORRECT SIDE.

I usually oil the broach/bush when cutting CI

I think you said you used gauge plate for the key so this won't apply but if you do any with rectangular key steel in the future then leave the key on the length of stock right until last, that way you have something to pull it in and out with while checking the fit. Moles on the far end give you something to tap against to get it out without

(https://hosting.photobucket.com/albums/v156/jasonballamy/Hit%20n%20Miss/1-3rd%20Galloway/.highres/IMAG2400_zpsfada20ac.jpg)
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on November 25, 2020, 08:58:28 PM
Jason and Graham,

Thank you for your advice.  I decided to go with Jasons option and make the tapered bush.  Setting up the taper was much easier this time.  Could not do it along the Y axis as the vice is just too big to manhandle, so went and used the support collar I had made.  All was going well till got down about 30thou when the 1/8" cutter I was using decided to shatter.  After much searching I found a new Clarkson cutter  (as opposed to the initial no idea where it came from cutter).  Slowed the cutter down and went very very slowly. 20th DOC each pass.

Tomorrow comes the acid test, broach the slot in the flywheel.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on November 28, 2020, 04:47:44 PM
Slot in flywheel broached nicely.  Its maybe little too deep (need to either take 15 thou out of bottom of broach guide or use a thinner shim.  It came with a 30thou.  I really needed a 15thou.  Reasonably happy for first ever keyway.

Used a length of 5/16" silver steel for the displacer rod.  Drilled and tapped the bottom for screw to hold the displacer piston, and then drilled reamed the cross-hole at the top to connect it to linkage.  I had found a really nice Eclipse 4" Magenetic V block on Ebay a few days earlier and it turned up Friday afternoon just in time to be used to hold the displacer rod for drilling/reaming.

The piston boss is made from 3/4" hex brass stock.  Put in 3 jaw on Myford and turned end down and then ran 2BA die up it.  Made a small silver steel mandrel and tapped it 2 BA.  This could then be mounted in collet chuck on dividing head on mill and the boss screwed into it.  Centered the boss and zeroed the DRO's, then turned dividing head through 90 degrees and set up to drill/ream gudgeon pin hole.  When drilled/reamed turned dividing head back to vertical and cleaned up the sides with 3/8" end mill and milled the centre out.  Cleaned up edges and ran reamer through to clean out and frays.

I had made gudgeon pin a few days earlier and just needed to cross-drill for split pin.  Decided this was going to be easier with tailstock drilling pad in the Cowells lathe.  Drilled out 1.7mm for split pin.

Next job is the bearing support.

I am still looking for suitable displacer piston, not managed to find the appropriate size of crabmeat tin.  I do have a sheet of 0.5mm stainless (and shortly some 1.2mm).  I am thinking of trying to make a piston from this.  How much does weight affect the piston. I assume it needs to be as light as possible.  Was thinking of 1.2mm for top and bottom and the sides from 0.5mm.  Wondering whether I can maybe glue the sheet to a board, and then trepan it out to size (85mm or just over) and whether feasible to turn the outer face down by 0.6 mill to act as a boss to locate in the stainless tube/cylinder.  Could punch the holes in top and bottom with 1/2" punch in the flypress, then hopefully few dabs of silver solder to hold together.  Does this sound feasible or am I in cloud cuckoo land.  I obviously need to source tin-can or make this prior to continuing with the hot end and main body.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 29, 2020, 11:33:53 AM
Progressing nicely Colin.

Regarding the displacer piston, hang on for a couple of days. I shall be shopping at ASDA next Tuesday I'll have a look for you.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on December 14, 2020, 06:35:48 PM
Been to my local ASDA and checked every tin of fish/crabmeat I can find.  At this point in time they do not appear to have the 145gm tin.  The nearest I can find is an ASDA Red Salmon 170gm.  This is 86.04mm diameter around the beaded end and 44.5mm tall.  The only problem is that it tapers down to the bottom of the can to as near as I can measure 78mm.

Is this too much of a taper to work.  Does it need a close fit at the top and bottom of the regenerator.  If so the only way I think I could use would be to remove the bottom of one can and the top from another and solder together where they touch and hope to get them lined up okay.  But would soft solder work, or does the hop end get too hot?

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on December 14, 2020, 09:52:43 PM
Base and Hot End now machined.  Calculation for location of groove for 'O' ring was not perfect, but as machined as rounded groove I don't think it will matter hugely.  The final position is just a tad deeper than the the rest. 

Cannot decide whether to start hacking the salmon tin apart or machining the power cylinder and piston.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on December 20, 2020, 06:36:22 PM
Decided to have a go at the Regenerator/Displacement piston. Decided to try the ASDA Salmon tin.
I did not want to cut the tin open and have it deform in any way. Mounted it rim side down in the large indexer and centralixed it with coax centering tool.  I did not want to use end mills or wood hole cutters and then remembered I had bought a set of Parkside diamond hole cutters from LIDL a year or so ago.  Had a look at these and they were nicely sized so picked 1/2" one and put a hole in the centre.  It cut a nice clean hole.  Off set the indexer by 1" in the Y axis, set indexer to 72 degrees and worked my way round till I had a ring of 5 equidistant holes.  Then removed the juice the salmon was packed with with a small syringe with a large bore needle.

To ensure that the hole in what was to become the bottom was perfectly centered I put a long centering drill in chuck, went down through the salmon layer till touched the bottom of the tin.  As soon as I felt the drill go through I stopped.  Removed the tin from the chuck and looked at bottom of tin.  Realised I had cocked up slightly.  The base of the tin had sprung and and although I had stopped as it broke through it had sprung up and the centre drill had left a larger hole than required. :ThumbsDown:  Luckily I had prepared for such eventualities by buying a second can of salmon. :ThumbsUp:

Repeated the exercise only this time used a 3.5mm drill to give hole size required.

Turned the can over and repeated to put another 5 holes but offset 36 degrees to the set on the other side.

Then spend 15 minutes removing the contents of the can and throwing in the bin.  I did not think the cats would appreciate swarf from the diamond cutter in their tea. :)

So now we have a regenerator/displacement piston with no soldering (silver or otherwise).   :cartwheel: I now need to turn down the rod on which the displacer is fitted and make a small shouldered washer for the top of the can.  Will also put a thin sleeve inside to separate the stainless steel mesh from the rod location to aid assembly.

Next step is power cylinder.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Dave Otto on December 21, 2020, 12:32:47 AM
That turned out quite well! Thinking outside the box or maybe the can. :lolb:

Dave
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on December 22, 2020, 01:52:05 PM
To ensure displacer can be assembled and dis-assembled easily I decided to insert a sleeve in the centre with a support bush at the top and turn down the diameter of the rod to .250.  The sleeve also prevents the can from being crushed and miss-shaped when fixing screw inserted from the underside.  This worked okay and then assembled it and filled with two stainless steel pan scourer pads.

Graham just asked what it weighs so swiped the cooking scales of wife and checked.  125gms as it stands in the third photo.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on December 22, 2020, 03:07:46 PM
Looking good Colin.     :ThumbsUp:

Here's mine.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on December 22, 2020, 05:24:24 PM
16 grams lighter.  Perhaps I should do some paring of weight.  Think I'll wait and see if works firt.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on December 22, 2020, 05:44:07 PM
I'm curious to know how you got the pan scourers in through those holes.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on December 23, 2020, 01:06:13 AM
Combination of stretching the scourer and handle end of old toothbrush, fingers and an Eclipse scriber. Fingers a bit sore by the end.  :)
Colin
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on December 24, 2020, 02:29:52 PM
If you excuse the expression, is it well stuffed? I mean is the pan scrubber material in all the hard to reach corners? Presumably the more material there is in there the better the heat transfer will be?
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on December 24, 2020, 03:08:59 PM
Definitely well stuffed  :Lol:

As I was feeding it in I was using the hooked end of a scriber to pull the contents internally around the can.  Filled it from two different locations.  It would be quite a struggle to get anymore in the can.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on December 28, 2020, 10:37:40 PM
Well it's taken best part of two days but now have a power cylinder. 

Once the base was flat and squared up drilled the two mounting holes and the two transfer port holes which allow air to pass between the power cylinder and displacement cylinder via the main body.  Then over to the large 4 jaw chuck.  I trued the cylinder up using the outer surface of the cylinder and then checked that the two machined faces on the base were square (in both directions) to the face of the chuck.  Faced the end of the cylinder, it was a little on the hard side.  Boring the cylinder was taking around 20 minutes for a return journey as I had it on the slowest feed I could get.  Again the first 1/8" was hard.  Gradually worked way out to just under the requisite 2.25" and left it overnight and finished off this morning.

Turned cylinder round and fitted in 3 jaw chuck to machine the governor end.  The 1" diameter hole which passes through to the main bore just cleaned up with about 20 thou to go.  The larger diameter bore then put in to a depth about 10thou past the pair of transfer port holes.

Over to mill to face of the governor flange and drill/tap the fixing holes.  Finally drill the 3/16" hole for the linkage rod in the two flanges on the top.  Was hoping to have plain hole one side and tapped hole the other but had to abandon this idea.  The holes were  bugger to drill as the material was hard, started to tap the lower hole but decided discretion was the better option and stopped before the tap snapped in the hole.  Drilled the hole out and passed a 3/16" reamer through it.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on December 31, 2020, 06:47:46 PM
I was doing really well, the piston was almost complete, fitted beautifully, just had to face off the boss on the top.  Put in 3 jaw on Colchester, coke can shim to protect it.  Really slow 5 thou DOC to clean up the face.  Tool dug in and threw piston out of chuck. :censored: :censored: :censored:  It changed shape slightly.  :censored: :censored: :censored:  Scrap :(  after taking my time.  Ordered new casting of GC.

Was going to abandon workshop and read a book but decided to make the governor plunger.  At least that bit went okay.

Happy New Year to you all.

Colin

Title: Re: Strictly.... “ Hot Air “
Post by: Dave Otto on January 01, 2021, 12:33:40 AM
Ouch, sorry about the mishap with the piston; hopefully the next one will go better.

Dave
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on January 01, 2021, 01:28:11 AM
That makes two of us.
Thx
Coli
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 01, 2021, 12:32:13 PM
New year greetings.

Colin, your piston doesn't look as bad as I was imagining during our telephone conversation.

There's a replacement on its way but in the meantime you could try a little " rescue " work.

I'd suggest getting it very hot in the forge, around a mid towards bright Orange for several minutes. Allow it to cool naturally. Make a suitable mandrel to pick up the thread you've put in the piston crown. You can now " clock " the crown diameter for truth. If you centre the mandrel you can add extra support with your tailsock rotating centre. By getting the piston hot it should have " grown " a little and also might have relaxed back to a more round condition. I use " radiused " tips for cast Iron, general work, as this gives a much smoother surface finish.

With any luck you should be able to remove a few thou and bring the piston back to size. Although the drawing shows a plain, flat side many of the full size engines had shallow reliefs to help reduce friction in the cylinder bore. That small " nick " in the side won't affect anything at.

The governor looks great, cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on January 02, 2021, 10:27:51 AM
Following Grahams advice the piston has had 20 minutes at 800degrees in furnace.  Just about to go and make a mandrel and see if can resurrect it.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on January 02, 2021, 05:09:44 PM
Having cooked the piston as per Grahams suggestion I was amazed by how much it had grown.  Just under 10 thou on diameter.  Made a 1/2" mandrel with 2BA thread and stuffed it in the collet chuck and screwed piston on.  It looked pretty true all things considered so proceeded to cleaned up the piston boss and face and then turned diameter back down to 2.2495.  It cleaned up reasonably well.  Can still see couple of marks in it, but going to go with it for now.

Last piece to machine is the main platform.  Will try this on big lathe tomorrow.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 02, 2021, 06:17:16 PM
Pleased to read things turned out well Colin.  :whoohoo:

Do take your time in setting up the platform as it will pay dividends later.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on January 05, 2021, 08:30:26 PM
Fettled the main casting and went to have chat with friend, Tom, who had his own engineering business for last 4 years.  Had a chat about brazed carbide tooling and borrowed a spare green grinding wheel of him.  His view was to mill the casting rather than turn in lathe.  Chatted about milling cutters and appropriate speeds.  Came back and set up in mill with flat side down resting on two parallels with couple of bits of thin card to get level.  I had what should be a nice 4 tip facemill cutter which fitted in my large Clarkson collet.  Ran it nice and slow but had a very rough, almost grooved, finish. :ThumbsDown:  Could not work out what was wrong  :headscratch:b and Tom came up for a look and bought his spare R8 3 tip facemill.  Swapped over to this and achieved a beautiful finish. :)

Looked at my facemill and found that for some reason two of the opposing tips were slightly lower than the other two.  Gave it a quick clean and it appeared a little better, but is now awaiting complete disassembly and a visit to the ultrasonic cleaner.

With a decent finish on the circular underside the casting was turned over and the top face milled.  This machined really nicely but needed a little more machining off than I expected to completely clean up.  Finished off with a 1.5thou cut with about 1/2" stepover.

Really pleased with the finish achieved.  Its about 20thou undersize on height but this should not cause any problems.

Next step is a bit of boring, drilling and tapping.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on January 05, 2021, 08:39:30 PM
Coming on nicely Colin  :)

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on January 05, 2021, 08:44:49 PM
Thanks Jo.  Happy New Year to you and hoping you are keeping well away from the dreaded bug.

With a bit of luck will get the cold side bored and the displacer rod hole done tomorrow and maybe even the three screw holes.  This will just leave the tapped holes for the bearing pillar and power cylinder.  I have bought paint and primer for it all, but need to do a little bit with some JBWeld on the 3 leg base prior to painting.

Colin



Title: Re: Strictly.... “ Hot Air “
Post by: Roger B on January 06, 2021, 08:23:03 PM
I have always been surprised how much things grow when heated with CI piston rings and silver steel  ::) It can be a good rescue operation  :)
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 07, 2021, 01:42:13 PM
There are many " roads to Rome " Colin but you're nearing the finish line.

Having not had a milling machine for several years after the lathe I discovered many tricks to get the job done. With the Robinson platform you can reduce the number of operations to a minimum.

Don't get me wrong, I wouldn't be without one these days and funnily enough the Denbigh has become a lathe on more than one occasion. Particularly when I had to machine flywheels of over 14" in diameter. It has an effective three foot swing....  ;)

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on January 07, 2021, 10:32:27 PM
Setting of the main casting in the 4 jaw chuck was fun.  By the time it was centred on the lower periphery the the casting missed the lathe bed by about 1/8".  Used a tailstock revolving centre to help hold the casting against the chuck jaws.  I was running at lowest speed 54rpm as did not like the idea of casting spinning too fast and having to take interrupted cuts.  The only downside is the bearings are very very noisy on that particular gear.  I felt the next gear up which is a lot quieter was a bit too fast for my liking (85rpm).

Trued the face up and then bored out the cylinder.  Took it out to 3.35inches and then removed tailstock center to enable me to measure with internal mike as I took next few cuts to 3.4".  Just before took the last cut I faced the inside top face.

Centred, drilled and reamed the 5/16" hole for the displacer rod.

Put the tailstock center back in and then machined the 1/16" O-ring groove on 4.1732" diameter.  Finished off with a cleaning up the periphery of the casting and putting a champfer on lower edge.

Off to the mill to use the DRO's hole positioning feature to do the three holes to mount to base.

In order to position the  holes to fix the power cylinder and the bearing mount, all the linkages etc are assembled and placed on the main casting.  The linkage to the displacer rod needs to be set vertical and this then positions the power cylinder which is clamped in place.  The bearing mount is then moved around until the whole assembly moves easily and does not jam up or get stiff in any position.  When this is achieved the bearing mount is clamped in place.  The holes are located on the main casing using transfer punches through the power cylinder and the bearing mount.

Just need to source some small headed 0BA and 2BA bolts to fix the two components.

Then have a choice: test then paint or paint then test.

Colin
 
Title: Re: Strictly.... “ Hot Air “
Post by: Admiral_dk on January 07, 2021, 11:04:03 PM
Nice to see it this close to running conditions - must give some satisfaction  :cheers:
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on January 07, 2021, 11:57:01 PM
Thank you. My wife will be pleased. She was whinging last night at 21:30 at the noise she could hear from the garage workshop.  The lathe was a bit noisy as I was doing the final clean up of the base.  She shouldn’t have gone to bed so early 😀

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on January 09, 2021, 09:50:17 PM
All masked up today and painted.  Base and hotpot then cured in furnace for 1hr.  The other parts all went in the kitchen oven.  Paint said 1hr at 200degreesC.  Ran it up to 100 for hour then took out crankshaft and crankweb as these locktited together and also the bearing mount with oilite bushes.  Then upped to 200 for 1hr for the remainder.  Once all cool assembled it all.  Only one minor cock up.  I had drilled the hoes in the power cylinder 2BA and they should have been for 0BA.  So quick trip to the drill to open them up.

Then proof of the pudding, does it work.  Yay, it does.  :cartwheel: Not for long as was trying it on the kitchen gas cooker.  The small burner was quite not hot enough and the next size burner put flame everywhere.  Took a fair few spins.  Will have another go in morning when cooled and this time will fill the casting water jacket.

Hopefully it will loosen up a bit more as keep going.

ColinXXtCOF5K700
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on January 10, 2021, 07:11:47 AM
Just keep beating it with the spoon until it runs how you want ;)

Looking good now it's all together and a nice shade of blue :)
Title: Re: Strictly.... “ Hot Air “
Post by: Zephyrin on January 10, 2021, 07:54:53 AM
nice built, runs easily too, beautiful engine...
You could maybe test copper scouring pad, probably much better as a heat exchanger.

with your heat source, you can watch if the milk does not overflow at the same time.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on January 10, 2021, 01:52:32 PM
Second proper run this morning.  Still on cooker burner.  Took about 15-20 spins before it started to run, but then kept going for 40 minutes till I stopped it.

Really pleased how quiet it is.  :cartwheel: :cartwheel:

JFWwwBYTHbY
Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 10, 2021, 01:59:39 PM
And yet another Robinson comes to life, well done Colin.

From the video you sent me this morning try checking the Gib head key in the flywheel. I have a feeling it's a little loose?

These engines can be a little pernickety initially but as the " high " spots wear they then settle and just improve with each run.

Zephyrin's comment is also quite valid as I've seen reference to the use of Copper in some of H Robinson's patents. But for the most part they used Iron " shavings " inside the displacer piston but over time they could rust and clog the action.

Looking forward to seeing your next video Colin.

Cheers Graham.

I see our posts crossed....
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 10, 2021, 02:05:35 PM
Great stuff.... :ThumbsUp:

The tapping I could hear yesterday has gone completely, lovely....

What's coming next Colin?

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on January 10, 2021, 02:52:25 PM
Now that is running nicely, even had to check my volume knob to see if it was turned down.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on January 10, 2021, 03:18:53 PM
Thanks Zephyrin, Graham and Jason.

I am really pleased at how silent it runs.  Whilst it was on the cooker how the metal of the hob was vibrating so put kitchen towel pads tp protect the hob surface and keep it a bit quieter.  Held it down with the wooden spoon but after the 40 minutes was getting bit cramp in hand so thats why I stopped it.

Need a proper wooden base and burner now, then can hopefully have a play at adjusting the governor.  When I manually closed the governor it stopped the engine but hopefully after a bit more running will be able to sort this.

Burner wise I guess the options are either camping gas type of burner or a ceramic burner.  What are the pros and cons of each type, if any.

Yesterday I was bought a 170gm Kingfisher Catch Shredded Crabmeat tin.  This one has significantly less draft that the one I am currently using.  Perhaps I will make another displacer and try Zephyrins idea of copper scouring pads.  Not that I have ever seen any, but then its not something I would normally go looking for.

What next says Graham?  Not sure to be honest.  Steam, Hot Air or I/C - I have castings for all three types sat in boxes.  Maybe the RLE.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 10, 2021, 03:55:57 PM
Well....

We're currently playing with a little £9.99 inc P&P hikers stove, available from eBay. This has a short length of Stainless Steel braided hose to which is fitted the canister adapter and control knob.

What's great is that by undoing 2 screws you're left with just the burner which can be mounted into any enclosure you wish to make.

We've discovered that by a small adjustment of timing CHUK 3 will run beautifully on a very clean Blue flame and we're in the throes of making a rectangular head to fit the stove body.

As an aside, I believe Andy ( Chipmaster ) is using a ceramic burner for his Robinson engine.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on January 10, 2021, 04:27:34 PM
As posted elsewhere the camping stove works on my smaller one when turned right down so would think it's OK for your larger one. You do need to make sure it can draw in air from the bottom so any wooden base will need to allow for that - just simple feet will do.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on January 15, 2021, 04:18:02 PM
Colin, have a look at the video I just poste din this thread for an Idea of the speed I use to turn cast iron

http://www.modelenginemaker.com/index.php/topic,10064.msg230889.html#msg230889
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 15, 2021, 04:47:14 PM
Did your replacement piston casting arrive Colin?
Title: Re: Strictly.... “ Hot Air “
Post by: Admiral_dk on January 15, 2021, 07:47:35 PM
I haven't got a clue about how I missed that you got it running and nicely too  :cheers:

Regarding the lack off noise from some Stirling Engines - just ask the US Navy about the incident where a Swedish Submarine 'sunk a US Carrier' during an exercise in the zeroes (2007 ?) .....  :mischief:
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on January 15, 2021, 07:58:09 PM
Graham.
Yes piston did arrive. Many thanks.

Admiral_dk
Very pleased how quiet it is

Jason
Thanks will have a look later

I am just finishing of a wooden oak base for the engine. Hopefully done by end of day tomorrow then can hopefully get a much longer run.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on January 16, 2021, 07:37:24 PM
Oak base finished and support for ceramic burner turned out of a piece of brass and then all assembled (just need three brass screws to mount it but shop had just shut).

Tried the no.3 jet but did not appear to be getting any gas, so switched to the no.5 jet.  Once warmed up turned the gas as low as could get then left the engine running on the bench whilst I did other stuff.

By tea time I thought I had better switch it off.  It had run without any issues for five and a quarter hours (5 1/4hrs).  The water level had dropped a bit but that was all.

Will try the no.3 again tomorrow.

Overall very pleased with it. :cartwheel:


Colin
9tDXDtyhrB8
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on January 21, 2021, 12:33:19 PM
There is a 1" dia. bore in the cylinder casting, and the brass disc forming the governor valve is also shown as 1" dia. Is the disc supposed to be an easy fit in the bore, say, 31/32" dia, or is it supposed to fit against the end face of the 1" bore, say, 1 1/16" dia?
Is it recommended to drill a couple of bleed holes in the disc to prevent the engine from coming to a complete halt when the valve closes?
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 21, 2021, 01:10:42 PM
There is a 1" dia. bore in the cylinder casting, and the brass disc forming the governor valve is also shown as 1" dia. Is the disc supposed to be an easy fit in the bore, say, 31/32" dia, or is it supposed to fit against the end face of the 1" bore, say, 1 1/16" dia?
Is it recommended to drill a couple of bleed holes in the disc to prevent the engine from coming to a complete halt when the valve closes?

Hi Richard.

There are small discrepancies in the drawing, make the disc just slightly oversized to the hole so that when it's drawn close it seals the opening.

Two 1/8" holes drilled through the disc will stop the engine grinding to an abrupt halt.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on January 21, 2021, 01:24:37 PM
this help
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on January 21, 2021, 01:30:14 PM
Thanks gents, just what I wanted to know!
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on January 25, 2021, 01:34:57 PM
I presume that the diffuser rod has some sort of crosshead block at the top, to take the pin at the bottom of the links. My 1991 drawing doesn't show anything. I'm thinking of a bronze block reamed 3/16" for the pin, and threaded onto the end of the rod.
What has anyone else done?
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on January 25, 2021, 01:42:58 PM
Liam,

I just drilled and reamed the diffuser rod for the pin which passes through the links.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 25, 2021, 01:51:28 PM
Hi Richard.

There's nothing " fancy " about this engine....

The 5/16" or 8 mm displacer rod has nothing more than the 3/16" diameter hole cross drilled and reamed to pick up on the bottom link pin. I always used to use a small centre drill to create an oil way and cup in the end to keep the pin lubricated.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on January 25, 2021, 03:09:17 PM
I went with the fancy option of a square block drilled and tapped for the rod, cross reamed hole and rounded over end
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on January 25, 2021, 04:44:59 PM
The originals weren't that fancy Jason. But it obviously works.

Here's a picture of the various " fancy " bits from Gardner archives.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on January 25, 2021, 05:36:56 PM
I don't really like the idea of a 5/16" dia cross drilled rod floating around in the 15/32" gap between the links, or the steel rod working on a steel pin . I know the amount of running its likely to do is minimal, but yes, what Jason did is what I have in mind.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on February 08, 2021, 01:40:13 PM
The full size engine was the Robinson No.4 wasn't it? Given the minimal power output of hot air engines, what sort of purposes were they intended to serve? I like my engines to have something to drive, so now my engine is approaching completion, I need to think of a suitable 'load' even if only for display purposes.

Were there Robinson No.s 1,2 and 3, and were they even smaller?

Was there a Robinson colour for their engines?
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 08, 2021, 02:36:00 PM
Hi Richard.

Yes, a Number 4. This, I believe was Gardner's size system. Your engine is a half scale replica of a Gardner built size 4 with " squat " base designed to be run on a gas ring. I believe they made a tall base too.

The number 6, Gardner's largest, weighed in at nearly half a Ton and developed half a horse power.

The smaller engines were ideally suited to light loads like sewing machines and Dentist drills. A small Coffee grinder might look rather nice too.

Attached picture is of 3 different sizes made to Robinson's design but by other manufacturers.

Cheers Graham.

Oops, forgot the colour question. I've seen many originals over the years mostly painted either Red or Green.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on February 08, 2021, 02:54:56 PM
Hmm
A half size working sewing machine is probably beyond me, though small ones do come up on ebay from time to time, at a price. A half size Victorian dentists drill doesn't appeal somehow.
Given that there was the Robinson 'chippie' gas engine, presumably for driving the spud peeler, I suppose theres no reason why a hot air engine couldn't do the same thing. Now, do we have any pictures of a suitable spud peeler?
I grow potatoes, so I wouldn't be short of ones to experiment with.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 08, 2021, 03:17:30 PM
The " ensemble " as seen at Beamish.

The engine in the picture is the full size type " X " that I scaled down in 1998/9.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on February 08, 2021, 03:42:34 PM
The tall grey thing beyond is the peeler/chipper is it? Do we have any idea about its inner workings?
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 08, 2021, 04:31:15 PM
Errm, no, but I could ask....

I'd like to think it's a chipper, judging by the outlet shute.

As our family enlarged the need for lots of peeled potatoes grew exponentially. We invested in a potato rumbler. 'Twas nothing more than a rotating bottom plate that had undulations and covered with a coarse abrasive. You filled it with potatoes and let cold running water through as the motor rotated the plate.
Care was needed as if forgotten the potatoes would literally vanish.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on February 08, 2021, 04:36:07 PM
Yes I think that is just the chipper, the peeler is a somewhat larger undertaking
https://www.modelenginemaker.com/index.php/topic,7440.msg166684.html#msg166684

You could just make a nice little water pump, I think the hot air engines were use don large country houses to pump water up into the storage tanks.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 08, 2021, 05:05:17 PM
Thanks for the reminder Jason. :ThumbsUp:

I've just been in conversation with Geoff Challinor at the Anson engine museum. It is a potato chipper and slicer. But of much younger age than the engine.

Regarding colour scheme it was noted that Gardner would also paint to customers own requirements so your choice is now much wider.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 10, 2021, 11:23:54 AM
Some photos from the Anson....

The " lineup "

Left to right, number 6 ( tank cooled ) number 5 ( water hopper serves as main bearing/crankshaft support )  and a selection of deep base number fours.

Works drawings of the number 4 Air Engine.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 10, 2021, 12:05:03 PM
There's more....

Gardner works drawing of a modified Paraffin burner that was fitted to their multi cylinder Paraffin engines.

Closeup of the burner fitted to a Gardner engine.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on February 10, 2021, 01:21:06 PM
That drawing says the full size engine is 4 1/2" bore, 4" stroke. 'Ours' are half size, 2 1/4" bore, 1 1/2" stroke,which doesn't seem to correlate. Or did Gardiner have different sizes to Robinsons?
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 10, 2021, 02:05:14 PM
Hello Richard.

This question has arisen several times in the past, without, I may add an explanation.

It's possible that our scale engine is a number 3 ( Gardner scheme ) or a Robinson but as yet there's no concrete evidence either way.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 10, 2021, 02:11:04 PM
The " plot " thickens lol....

A " badge'd " Robinson from the Anson collection.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 10, 2021, 07:15:16 PM
Recently obtained information.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on February 12, 2021, 04:56:37 PM
So what we've got is a half size model of a Gardiner 4B?

I know in practice this doesn't make the slightest difference, but before I :hammerbash: fix the crank disc to the shaft was there any preference regarding the alignment of the crankpin to the keyway in  the shaft, i.e. same side, opposite side or just as it happened to come?
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 13, 2021, 01:55:10 PM
In essence, yes Richard but ours has got an 1/8" more stroke ....

I was going to suggest take a look at the drawing but I've discovered that the keyway isn't shown. :facepalm2:

I would suggest putting it in line with the crankpin. Are you going to keyway the crank disc too? The full size engines had a tapered key driven in hard and machined flush. We use Loctite....

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on February 13, 2021, 07:15:44 PM
Thanks Graham
I wasn't going to key the disc when you said you used Loctite, but didn't Jo have a Loctite failure on hers? I thought of Loctite, and a 1/8" round pin, half in the crank, half in the shaft, isn't that called a Scotch Key?
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 15, 2021, 12:03:10 PM
Yes, a Scotch or Dutch key Richard.

I remember doing a commissioned restoration on a 1/2HP EEC gas engine. They had used Scotch keys to hold the flywheels to the crankshaft. One flywheel was either broken or missing so the other had to be removed to use as a pattern, I recall a most difficult task.

For the replacement I had to use a " dummy " shaft to get the hole drilled and then, very carefully ream the taper to match the original on the crankshaft. The method is very secure, if done properly but quite the expletive deleted when you need to remove one!

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on February 15, 2021, 02:35:58 PM
Ouch! I've never come across one using taper pins, plain parallel ones are usual. Once I thought I'd do the job properly and use threaded pins with a slotted end, so they could be removed easily when required. Wrong! The only way to get them out was to drill them out.
When I reamed the crank disc for this engine, I did it with a hand reamer in the tailstock chuck, so the shaft slid in nicely till it was about 3/16" short of coming right through. I used Locset, and a couple of thumps with my trusty copper hammer to bring the end of the shaft flush. I don't think thats going to move, so no need for Scotch or Dutch keys, I hope.
I'm just making the flywheel key now.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on February 15, 2021, 07:27:47 PM
Liam,

Are you intending to make the key tapered (1:100).  I found this an interesting exercise, a) making the tapered key especially as it is so small b) putting tapered keyway in the flywheel.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on February 16, 2021, 12:11:59 PM
Very probably. I've got a slotting tool which can be adjusted to cut at an angle, and the key is just a filing job till it fits. Mine are anyway.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on September 07, 2021, 04:39:07 PM
Great news….

After seriously long negotiations I finally managed to get the manufactures to reconsider doing the 185 gram Tuna tins. We had to compromise at 198 grams though…. I mentioned that the lack of this size of tin was severely hampering the construction of Robinson hot air engines.

Seriously though, it’s looking like Tuna Mayonnaise for tomorrow’s breakfast.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on September 07, 2021, 05:16:21 PM
Will be interesting to see what difference that extra 13g capacity makes ;)
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on September 08, 2021, 12:11:50 PM
Will be interesting to see what difference that extra 13g capacity makes ;)

My toast overfloweth….  :)
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on September 09, 2021, 05:47:11 PM
After a serious mishap with my latest build the foundry went into overdrive after a call for help.

My castings are ready 24 hours after the call. They sent me photos of the moulds. Take a good look at the second picture, what do you see ?  ;)

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Twizseven on September 09, 2021, 05:59:04 PM
Distinct lack of a route for the poured metal to reach its destination.

Colin
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on September 09, 2021, 06:24:14 PM
I think they have scooped a bit out in the first photo though maybe Graham did not want to to feed the underside of the cylinder rather than the foot?

The foot and underside of the cylinder look concave, understandable where sand has been scooped out and meets the cylindrical part of teh cylinder but foot should look flatter. The shadow may be fooling us, the two green bits are the only uncut part and look straight, the red marks are exaggerated scallops where they have cut the runners

J

PS We also need full details of this mishap :LittleDevil:
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on September 11, 2021, 12:09:12 PM

PS We also need full details of this mishap :LittleDevil:

Well, as we all make mistakes from time to time…. Not so much a mistake in this instance but an un noticed problem with the highly “ chilled “ top mounting lugs. It took several attempts to drill and ream the 3/16” hole and the bit must have followed the easiest route. The problem only became apparent after fitting the link motion.

The “ chill “ effect had also found itself in the three legged base. Even after several minutes in the gas Forge at around 850 degrees C followed by a very slow cooling ordinary HSS drills wouldn’t even mark the surface.

This casting has to have three holes at 120 degrees for 1/4” Whitworth tapping, 5.1 mm. The solid Carbide drill bit I ordered from eBay got lost in the post so I re remembered an old trick from my days at Chester UK.

Masonry bits are cheap as chips, with a really tough Carbide tip soldered onto a softer backing. Using my trusty Diamond in Borozon wheel I carefully re profiled the top cutting edge from the triangular top form to a single cutting face then gently removed the sides to get the desired 5.1 mm diameter. Back to the rotary table under the big drill press and within seconds the holes were through. I’ve never worked with such a tough casting, ever!!

Putting the threads in was also a serious challenge using a first taper Presto tap. Needless to say I will be needing a new one. I just managed to get a three to four turn start in each hole ( 1/4” thickness  ) before risking a breakage. This foundry is definitely NOT on my Christmas card list….

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on September 11, 2021, 03:40:37 PM
Temp sounds OK but would have thought a bit longer heating time needed.

Would the pivot on the top of the cylinder be less likely to give problems if you did not core the slot, makes it a bigger lump so should not cool as fast and easy enough to mill the slot.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 04, 2021, 06:28:09 PM
Jason.

Rather than further clutter Jo’s Bailey build I’m replying to your question here….

I’ve just finished speaking with Geoff from the Anson engine museum. There’s no record of any drawings for the Gardner vertical hot air engine and, it would seem they never applied for a patent for it. The only known example is currently owned by Adrian from Engineers Emporium.

I mentioned the vertical Robinson patent engine, here’s a picture.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on November 04, 2021, 06:38:49 PM
Thanks Graham, I might try contacting Adrian and seeing if he can take a few photos and give a couple of sizes. It's mostly the conrod(s) and detail at the top of the piston as that can't be seen otherwise it's reasonably straightforward.

The water jacket would be a steel fabrication, two side frames could be fabricated or CNC cut from solid and same for the flywheels from slices of CI bar.

I think the Gardner is more appealing to me than the Robinson.

J

PS how is your eye?
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on November 04, 2021, 06:53:45 PM

PS how is your eye?

Still sore Jason, so I’ve been unable to get out in the workshop.   ;)

I too favour the look and simplicity of the Gardner engine.     :ThumbsUp:
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 11, 2022, 07:38:25 PM
More on the Robinson vertical hot air engine.

It seems that there’s at least one survivor of his 1881 patent, built under license in New Jersey USA.

pQ6No2-cpuQ
I’ve also got the patent drawings. Just a tentative question to those interested in building hot air engines.

Would anyone be interested if patterns and castings were made for a half scale replica from the patent drawings?

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on February 11, 2022, 07:43:13 PM
Only if they came with a 13" swing lathe thrown in as a freebee :'(

That will limit your market. 1/3rd scale may suit people more as that gives a 8 5/8" flywheel. Even 1/4 scale would work with a 5 1/2" flywheel and 2" bore
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on February 11, 2022, 08:10:49 PM
This seems to suggest that Pearns made some, they also did a lot of steam pumps similar to teh Cameron pump I did some time ago

http://hotairengines.org/closed-cycle-engine/robinson-1881
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 12, 2022, 11:26:03 AM
Only if they came with a 13" swing lathe thrown in as a freebee :'(

That will limit your market. 1/3rd scale may suit people more as that gives a 8 5/8" flywheel. Even 1/4 scale would work with a 5 1/2" flywheel and 2" bore

I see there’s been a terrific response to my post….  :lolb:

Jason, I’m curious as to how you’ve come up with some of the dimensions? From the written patent specification perhaps?  I just look at the pretty pictures! 😃 I too am well aware of the practical limitations that models can present to the builder.

I’m in contact with the current owner of the engine featured in the video I posted yesterday. He’s volunteered to send me some dimensions and pictures over the weekend.

In the “ old days “ I found that the flywheel pattern was one of the most difficult and time consuming items to make, so was thinking about using the Robinson 4B hot air engine flywheel as a basis for the rest of the model.

Cheers Graham.



Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on February 12, 2022, 01:55:21 PM
Maybe you did not put "castings" in bold enough print or perhaps a cross stich pattern of the engine would go down better ;)

I read the description under the video 8)

26" flywheel, 8" bore, 5" stroke and 6ft tall

Interestingly much like some of the other hot air engines it does say that is the largest that Victor produced so maybe they did others eg 3" , 4 and 6" bore?

So have you spent the morning searching round all the local supermarkets looking for a container with that egg shaped bottom :LittleDevil:
Title: Re: Strictly.... “ Hot Air “
Post by: Jo on February 12, 2022, 04:42:52 PM
Maybe you did not put "castings" in bold enough print or perhaps a cross stich pattern of the engine would go down better ;)

I have discovered someone has OCD: I brought him a couple of 84L really useful boxes and since then he is trying to work out which castings should go in them  :pinkelephant:  I am concerned that if he finally chooses ones that are not Ali I won't be able to move them.

Those would fit in there very easily  :facepalm: The problems is the price of everything is going through the roof so it is not advisable to commit to anything before you know what it is going to cost  :paranoia:

Jo
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on February 12, 2022, 04:54:17 PM
Ah yes you would have to pay full price for them.

Though another good reason for keeping the size manageable or making from scratch which having looked at that video a few times would be quite possible
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 12, 2022, 05:45:51 PM
Thanks for looking in Jo.

Having just checked the membership here, it is a little over six and a half thousand. Having asked a simple question I would have expected a tad more response than just the two of you ! But not too worry….

I’m not particularly enamoured of this engine but have been asked about a possible model. The gentleman is a woodworker and is thinking about turning his hand to a spot of pattern making.

My new foundry is very reasonable on price provided I don’t want castings yesterday. They’re happy to find a corner in the box whenever possible.

Going back to this particular engine I’m thinking that the 7” diameter flywheel and 2-1/4” bore ( my scale Robinson 4B ) would be reasonably easy to build by most, if not all Stirling cycle enthusiasts.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on February 12, 2022, 06:07:52 PM
That would still make quite a large casting, if done as the patent drawing then it looks to be a one piece casting from the crank bearings right down to the top of the burner so 11-12" tall. The Victor is easier as it's in three pieces - yoke, cylinder and furnace.

Assuming a separate CI liner to form the water space you would be looking at about 8" of boring bar overhang to do the top and bottom registers in one sitting and need something to run the fixed steady against. Possibly cast it with a bar between the bearing housings so a ctr could be used to support the casting while a smooth area at the top of the jacket was machined to run the steady against.
Title: Re: Strictly.... “ Hot Air “
Post by: Alyn Foundry on February 12, 2022, 06:46:22 PM
I have to agree with you Jason.

However the patent drawings almost always don’t look anything like the finished product!

I agree that the engine would best be made in three separate sections, like the Victor. With such low power output the top bearing yoke could be glued to the top of the power cylinder and then make a mechanical joint between hot and cold ends.
The power cylinder liner could also be made to be glued in place with the water jacket formed by the core. A separate hot end then fitted in such a way so as to provide a thermal barrier between the two halves. I don’t think there’s any need worry about the shape of the hot end, something similar to that of the Heinrici engines would suffice.

Cheers Graham.
Title: Re: Strictly.... “ Hot Air “
Post by: Jasonb on February 13, 2022, 08:01:58 AM
If the "joints" were done right it would also be possible to add a few csk (top) and counterbored (bottom) screws to hold the three sections together which could then be filled with JBWeld and so be invisible under the paint. The flange on the CI liner could also be trapped within the lower joint. Add in a second decorative bead where jacket meets yoke and your joints are hidden too. Loctite would only be used to seal/retain the liner.
Title: Re: Strictly.... “ Hot Air “
Post by: ettingtonliam on February 20, 2022, 01:41:47 PM
Its been a while since I did anything to my Alyn Foundry Robinson hot air engine, but I suddenly got the urge to do the diffuser. I'd bought a couple of tins of some sort of fish from a supermarket a couple of tears ago, and at the time had cut the tops off, eaten the contents and washed the tins out. A couple of days ago I turned up a close fitting wooden plug so I could hold it in the lathe and cut the tins to length, one full length, one about 1/4" long to fit inside the other. Then I drilled 6 3/8" dia holes in each end with a sheet metal drill. I decided to fasten the 2 together with long 4BA studs nutted at each end, rather than soldering the joint. Its stuffed with 2 Spontex stainless steel scourers, and, complete with rod weighs 70 grams according to my kitchen scales.

Next is to re read Grahams build notes and line up the crankshaft pedestal and cylinder ready for bolting down!