Author Topic: Strictly.... “ Hot Air “  (Read 58730 times)

Online Jasonb

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Re: Strictly.... “ Hot Air “
« Reply #540 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

Offline Alyn Foundry

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Re: Strictly.... “ Hot Air “
« Reply #541 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.




Online Jasonb

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Re: Strictly.... “ Hot Air “
« Reply #542 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:

Online Jo

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Re: Strictly.... “ Hot Air “
« Reply #543 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
Enjoyment is more important than achievement.

Online Jasonb

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Re: Strictly.... “ Hot Air “
« Reply #544 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

Offline Alyn Foundry

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Re: Strictly.... “ Hot Air “
« Reply #545 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.

Online Jasonb

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Re: Strictly.... “ Hot Air “
« Reply #546 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.

Offline Alyn Foundry

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Re: Strictly.... “ Hot Air “
« Reply #547 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.

Online Jasonb

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Re: Strictly.... “ Hot Air “
« Reply #548 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.

Offline ettingtonliam

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Re: Strictly.... “ Hot Air “
« Reply #549 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!