Author Topic: Another breath engine (Huff and Puff)  (Read 3235 times)

Offline Roger B

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Another breath engine (Huff and Puff)
« on: April 06, 2019, 01:56:28 PM »
I have been inspired by Doc's start and Marv's version of the Huff and Puff and will make a version. I need to convert the drawings to metric and a have a question regarding imperial dimensioning conventions. The drawings from Doc's link use imperial fractions, imperial decimals and number drill sizes. The number drill sizes seem obvious, you use that size drill.  For other dimensions fractions and decimals are used, the crankshaft is 0.0625" and the hole in the flywheel is 1/16". Are fractions used for stock sizes and drill sizes and decimals for machined sizes? Am I reading too much into this?

The metric conversion will require some thought regarding the port sizes and positions and the dimensions of the piston valve to maintain the timing.
Best regards

Roger

Offline Florian Eberhard

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Re: Another breath engine (Huff and Puff)
« Reply #1 on: April 06, 2019, 02:06:09 PM »
Hi Roger

I have got a conversion table flying around from my stuart feed pump build - i could scan it and send it to you if you want?

Florian

Offline Jasonb

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Re: Another breath engine (Huff and Puff)
« Reply #2 on: April 06, 2019, 02:21:39 PM »
Quite often on imperial drawings fraction and decimal are both used as a way of indication tolerance, with the decimal needing to be a tighter tolerance than the fraction.

In practical terms for an engine like this then silver steel/drill rod or ground mild steel will do for the shaft as that is likely to be off the shelf and close to 0.0625"  size. Most won't have a 1/16" reamer so the hole can be drilled with a 1/16" drill and the flywheel loctited to that.

In your case you will be better off using nearest stock sizes for both these items that doing a direct conversion so 1.5mm rod and a 1.5mm drilled hole will do.

Alternatively if you have a bit of lung capacity to spare then a simple way to do it is to allow 1/32 or 0.03125" on the drawing to equal 1mm which will give a slightly larger engine but most sizes will be in 0.5mm or 1.0mm increments.

Offline JC54

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Re: Another breath engine (Huff and Puff)
« Reply #3 on: April 06, 2019, 08:02:06 PM »
Hello all, I have just converted a simple beam engine (Beam engine with a twist) from imperial to metric and as Jason says go to the nearest available metric sizes for shafts and fittings. Doing it this way saved me a lot of problems, head scratching and frustration. Perhaps not strictly correct but some dimensions I left until engine was nearly built and made parts to fit..  ::) I wish I could understand this CAD stuff. John :old: :DrinkPint:
When the Fun Stops,, Stop!

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #4 on: April 07, 2019, 08:20:42 AM »
Thank all for your feedback  :ThumbsUp:

Florian, thanks for the offer however I have a copy of Harold Hall's Metal Worker's data Book which has conversion charts and details of the American threads.

First thoughts:

Cylinder bore 1/4"  6mm
Valve bore 1/8"     3mm
Piston rod 3/32"    2.5mm Is this a bit large for a 6mm bore?
Crankshaft 1/16"   1.5mm Would 2mm be a better choice?
Fixings 0-80          M1.4 

I can adjust the piston stroke (1/4") and the valve stroke (1/8") to keep the port and valve geometry correct.
Best regards

Roger

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #5 on: April 07, 2019, 02:28:08 PM »
I have started to set out the cylinder block and valves. I had to change the port angle from 45° to 40° to compensate for the slightly greater distance otherwise both ports would have been connected to the inlet at the same time. With the valve in mid position both ports are slightly open to exhaust. Is this sensible or should I adjust the dimensions to have everything closed at mid position?

PDF attached
Best regards

Roger

Offline Jasonb

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Re: Another breath engine (Huff and Puff)
« Reply #6 on: April 07, 2019, 02:47:37 PM »
You could reduce the distance between the piston and valve bores to compensate for the reduced diameters which should allow you to keep the angles the same and therefore the openings. off the top of my head the 7.5mm would come down to about 7.25mm

2mm piston rod should be ok

Offline bent

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Re: Another breath engine (Huff and Puff)
« Reply #7 on: April 08, 2019, 07:34:22 PM »
Y'all are pretty short winded...my son can blow hard enough to run my PM #3 (3/4 bore and stroke).  Of course, he's a trombone player ::)

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #8 on: April 12, 2019, 03:27:38 PM »
Thank you Jason. It all comes down to where I make the changes. If I change the bore centers I may have to change the crank/eccentric as well. I may end up doing this anyway  :headscratch: If I reduce the piston rod to 2mm I will probably have to change the little end (as George has done). A 0.8mm slot in a 2mm is possible but a little tight. I will draw up some more this weekend and see what it looks like.
Best regards

Roger

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #9 on: April 14, 2019, 07:53:01 PM »
I had a look at reducing the centers to keep the original port length and this seemed to give reasonable timing (PDF below). I thought about the little end and decided to try putting the 0.8mm tang on the piston rod and making a 2mm square slotted end on the con rod. Having drawn it could I make it? I took an small piece of 2mm thick brass, marked it out, drilled the little end 1mm and drilled and reamed the big end 1.5mm. I tried to cut the slot with a 0.8mm slitting saw but ended up with a slightly off center ~1mm slot  :facepalm:
The next step was to mill either side of a piece of 2mm stainless steel rod to produce a 0.8mm tang. That went OK as did marking and drilling a 1mm hole. The trial assembly was not so good, the 1mm hole in the conrod was 1.2mm one side and around 1.1 the other side  :(
I will try again with a 0.5mm slitting saw and starting with a 0.8mm hole.
Best regards

Roger

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #10 on: April 16, 2019, 07:51:22 PM »
I tried plan B for the conrod using the other half of the piece of brass. The slot was slightly under 0.8mm and central  :) The sides were then milled down to give a central thickness of 1.5mm. This could have been the original of 1.6mm (1/16"). One side of the little end was milled to size and the rod was cut away from the supporting piece. The other side was milled to size and with a little bit of work on the slot it all fitted together nicely  :)  :wine1:
Best regards

Roger

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #11 on: April 16, 2019, 07:57:18 PM »
As the Hobbymat was in milling mode I used my Proxxon FD150 to turn some 4mm od 1.5mm bore filling buttons to finish the big end and sides of the conrod. These were hardened and then clamped together around the big end with a short length of 1.5mm silver steel in a tool makers clamp. The big end and the sides were filled to shape. So small  ::)
Best regards

Roger

Offline Admiral_dk

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Re: Another breath engine (Huff and Puff)
« Reply #12 on: April 16, 2019, 09:19:59 PM »
I knew from reading here about the builds of this engine that it is small - but seeing the conrod on your thumb nail really brings the size into context  :ThumbsUp:

Nice work Roger.

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #13 on: April 20, 2019, 07:03:17 AM »
The cylinder blank, 11 x 11 x 20 was milled from 12mm square brass bar. The frame, 19 x 28 x 27.3 was cut to size from a bit in the offcuts box. The cylinder was set up in the 4 jaw independent chuck for drilling and reaming the piston and valve bores. I used a floating reamer holder as I have one. The frame was then set up, taking care due to the slightly different sides and the piston rod hole was drilled and reamed 2mm. Next the spigot that locates the cylinder was turned to 6mm.
Best regards

Roger

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #14 on: April 20, 2019, 07:07:48 AM »
Next the piston rod was cut to length and threaded M2. The piston was turned from 7mm brass rod tapped M2 and Loctited onto the piston rod. It was finished to 6.2mm, the final sizing being done with it fixed to the rod to ensure concentricity.
Best regards

Roger

Offline b.lindsey

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Re: Another breath engine (Huff and Puff)
« Reply #15 on: April 20, 2019, 01:53:27 PM »
Moving right along Roger. The conrod looks great but really small as Roger said. I love it!!

Bill

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #16 on: April 21, 2019, 12:45:44 PM »
Thank you Bill, I think you mean Per  :)

The piston was finished to size, but what is a snug fit? It's different for a fuel injection component or a breath engine. After I had turned the cylinder cover I tried to quantify this. Dry the piston fell straight through and with the cover in place it fell in a few seconds.


With a drop of light oil the piston just sat there with or without the cover  ::) Obviously what the comments about lubrication being a problem meant  :thinking:

I then started on the flywheel and excentric. I have decided I will try and cut the recesses in the flywheel with a 4mm end mill on the RT rather than attempting to make a small trepanning tool. The next steps for the excentric are also on the mill so time to change modes again.
Best regards

Roger

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #17 on: May 01, 2019, 11:33:53 AM »
The flywheel was centred in the Proxxon RT and the recesses were milled with a 3mm end mill, plunging in the middle and then finishing to 4mm with 0.5mm cuts either side. The back of the excentric was milled to size with the RT set vertical. The RT was then moved to the Proxxon drill to drill the bore 0.4mm and ream 1.5mm. The RT was then set vertical again to drill and tap for the M1.4 fixing screw. Finally the flywheel was set at 30° in the normal vice for drilling and tapping M1.4. The hole position was initially flattened with a 1mm end mill so the tapping drill did not wander.
Best regards

Roger

Offline gbritnell

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Re: Another breath engine (Huff and Puff)
« Reply #18 on: May 01, 2019, 12:14:30 PM »
Roger, you're a courageous fellow tapping a M1.0 hole like that.
Nice work.
gbritnell
Talent unshared is talent wasted.

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #19 on: May 01, 2019, 05:37:59 PM »
Thank you George  :ThumbsUp: Not quite so brave, it's M1.4, and I find the little Proxxon drill makes a good tapping stand if you remove the drive belt.

As the little drill was set up the next stage was to drill the ports in the cylinder. It was set at 45° using a V block, the edge was found and the cylinder was traversed 0.65mm (half the port diameter). I started with a 1mm end mill followed by a 0.8 mm centre drill and finally a 1.3mm drill (all at 4700 rpm). This was repeated for the other port.

Back to the lathe to part off the excentric. This was then mounted on a piece of 1.5mm silver steel and the little spacer piece was machined on the front followed by facing the parting pip off the back. The flywheel was then clamped on the same stub using the tailstock centre and given a quick deburr/polish. The chuck was then changed to the 4 jaw SC to finish the inlet stub on the cylinder. Next step mill out the frame.

This engine is quite a challenge to work out the correct machining sequence so you don't remove a piece you need to hold for the next operation  :headscratch:
Best regards

Roger

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #20 on: May 02, 2019, 07:46:34 PM »
I took the bulk of the material out of the frame with a 10mm end mill. Unfortunately my 4mm ball nose mill was slightly too short so I had to tilt the frame to round the fillets. With the middle cut out I could drill the cylinder fixing holes and then move on to finishing the main bearing stands. I will leave the stands at full height until I have finished the main bearing holes to allow for easier location.
Best regards

Roger

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #21 on: May 05, 2019, 08:44:08 AM »
The main bearings were drilled 1.4mm and reamed 1.5mm. I decided it would be quickest to remove the rest of the frame with a hacksaw and then clean it up in the mill. Leaving the main bearing stands at full height made it easy to hold. Next I milled the inlet/valve area of the cylinder down to 6mm. I will have to decide whether to radius or chamfer the corners of the cylinder (probably once I know it works  ::) ). To complete the required machining of the base I milled the 6mm clearance slot for the flywheel.
Best regards

Roger

Offline b.lindsey

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Re: Another breath engine (Huff and Puff)
« Reply #22 on: May 05, 2019, 02:32:22 PM »
Am enjoying all the pictures Roger. Lots of work in that little frame!!

Bill

Online Kim

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Re: Another breath engine (Huff and Puff)
« Reply #23 on: May 05, 2019, 03:27:05 PM »
Nice work Roger!  That is just a lot of itty-bitty-little machining you're doing there :)  :popcorn:
Kim

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #24 on: May 05, 2019, 08:26:52 PM »
Thank you both  :)  :) I'm never sure if I post too many pictures of each machining step  :headscratch: I know I like to see how others set up to machine things and the set ups they use.

The next step was the cylinder fixings. I drilled the 3 holes in the cylinder cover using the Proxxon RT and then spotted all the hole onto the cylinder. Unfortunately I broke the plug tap in one of the cover holes  :facepalm: I took a quick family shot before putting the cylinder in the alum solution.

While this takes place I moved onto a few other bits. I was able to get some  M1.4 x 6mm cap head screws which are fine for the cylinder fixing but too long for the cover. I also need a couple of M1.4 grub screws for the flywheel and excentric. I tapped a piece of 4mm square silver steel M1.4 and then milled a 0.6 mm step 0.2 mm over the centre line. After hardening I cut the screw down to 3mm and the used the guide to cut a slot for the grub screw using an Xacto razor saw with a 0.4mm wide blade.
Best regards

Roger

Online Kim

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Re: Another breath engine (Huff and Puff)
« Reply #25 on: May 06, 2019, 05:14:35 AM »
Sorry about the broken tap  :'(   I certainly feel your pain there.  Hopefully the alum will work for you.
Kim

Offline Jo

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Re: Another breath engine (Huff and Puff)
« Reply #26 on: May 06, 2019, 03:11:31 PM »
I'm never sure if I post too many pictures of each machining step  :headscratch: I know I like to see how others set up to machine things and the set ups they use.

I like to see other people's set ups as well: You can always learn something new or an easier variation of how to do something than you normally use :ThumbsUp: When Vixen visited on Friday we were talking and he likes the technical discussions about the engines and their history and is less interested in the step by step stuff. But then again we did sit chatting for a few hours on how to set up to machine his Propeller hub  :noidea:


Bummer about the tap  :(

Jo
Enjoyment is more important than achievement.

Offline Vixen

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Re: Another breath engine (Huff and Puff)
« Reply #27 on: May 06, 2019, 06:22:35 PM »
I'm never sure if I post too many pictures of each machining step  :headscratch: I know I like to see how others set up to machine things and the set ups they use.

It is always interesting to see other peoples set-ups and the special techniques they use. That's how we all learn. As Jo said, we spend a long time discussing the merits of various ways and set-ups to machine the tapered spline in the Jupiter's propeller hub. Hopefully there will be one that's works better than the rest.

I am also interested in how you use the alum to remove the broken tap. I have tried to do it in the past but without success. I seems that the word alum means different things in different places and not all work at dissolving broken taps or drills.

Please can someone identify the type of alum which works and where to buy it from.

Thanks

Mike

It is the journey that matters, not the destination

Offline Florian Eberhard

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Re: Another breath engine (Huff and Puff)
« Reply #28 on: May 06, 2019, 06:48:20 PM »
I took a quick family shot before putting the cylinder in the alum solution.

Hi Roger

In Case the alumn doesn't work, you can still try sulphuric acid. Thats what I used for removing a broken drill from my cochran boiler and that worked pretty well!
(Look here, answer #137: http://www.modelenginemaker.com/index.php/topic,5740.135.html )

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #29 on: May 06, 2019, 07:38:11 PM »
Thank you all for the interest  :ThumbsUp:

Alum (I will get the exact formula tomorrow when I am at work as that's where I got mine from) does work but you have to use it at a fairly high temperature ~80°C. I was able to remove a broken HSS tap from an aluminium conrod previously, the current tap is reducing in size but it takes time. As far as I know it won't touch Tungsten Carbide (for those who use expensive taps).

I have made a few other small pieces with the Proxxon FD 150, the crankshaft, clevis pins for the piston rod and valve and the blank for the valve. Next step is back to the Proxxon mill to finish the valve and excentric rod. I did think about redesigning the excentric rod to give an adjusting screw but hopefully it won't be needed.

The clevis pins and rings are kept in a plastic bag as one sneeze and they are gone  ::)
Best regards

Roger

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #30 on: May 07, 2019, 02:47:33 PM »
Alum is potassium aluminum sulfate KAl(SO4)2·12H2O.
Best regards

Roger

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #31 on: May 11, 2019, 12:25:58 PM »
The holes in the valve rod were drilled with the Proxon drill and then this was exchanged for the mill. The flats were milled in the valve and the hole for the pivot was drilled 0.8mm and then 1mm. I have left the valve in the vice to cut the slot for the valve rod using the Hobbymat mill.
Next the excentric rod was milled to 1.5mm thick leaving about 10mm at 2mm thick so it could be held for profiling. The tongue was milled down to 0.8mm thick. To finish off the ends of the rod I could either make a fixture for the RT or some filling buttons  :thinking:  Probably filling buttons.

The broken tap has almost completely gone  :) 
Best regards

Roger

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #32 on: May 12, 2019, 10:20:10 AM »
I decided to make two filling buttons to fit in the excentric bore so I could use them to hold it as well. A piece of 8mm silver steel was turned down to 5.5mm for 0.6mm and then parted off at 1.5mm. The 3mm hole in the middle in just to allow me to hold them for hardening but also makes parting off easier. The excentric rod was then filled to shape with a selection of small files.
Next up was the crank disc. The blank was turned from 11mm brass rod (I didn't have any 10mm) and drilled 1.4mm and reamed 1.5mm. It was them moved to the Proxxon drill, centred, offset 3.2mm and the hole for the crankpin was drilled and reamed. Finally the disc was Loctited onto the crankshaft.
Best regards

Roger

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #33 on: May 12, 2019, 04:18:01 PM »
Good news  :) The broken tap has completely gone. I washed the cylinder with hot water, ran a tap down all the threads and gave it shot of maintenance spray.

The slot in the valve was cut with a slitting saw in the Hobbymat mill.  Next up I drilled the locking wire holes in the two pivot pins. They were placed on the drill table and picked up with the vice using an length of 1.5 mm ss to balance the load. The vice was centred with a 1.5mm spike, centre drilled  and then drilled 0.5mm. They are temporarily held together with some 0.2mm copper wire. I will use 0.5 mm wire for the final assembly.
Best regards

Roger

Online Kim

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Re: Another breath engine (Huff and Puff)
« Reply #34 on: May 12, 2019, 04:33:39 PM »
Don't sneeze!    ;)  :popcorn:

Great work on all those fiddly little parts, Roger!  You've got to be getting close now...  how many more little parts could there be in an itty bitty engine? :)

Kim

Offline Admiral_dk

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Re: Another breath engine (Huff and Puff)
« Reply #35 on: May 12, 2019, 09:01:35 PM »
I know that what you are building in this small size isn't easy, but I can't wonder if it isn't almost like a walk in the park after the precision demanded in a small real diesel  :noidea:

I suppose that it can also be seen as another way of honing the skills demanded for doing the diesel ....

No matter what angle I choose to view this - you are doing just fine  :cheers:   :popcorn:

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #36 on: May 15, 2019, 08:17:37 PM »
Thank you both  :)

Kim, The only bit left was the crankpin, just a little piece of 1.5 mm silver steel.

Per, there are several things behind making this little engine. Firstly I liked it  :) Then it was more practise and learning more about the little Proxxon lathe and mill. Finally it was something I could finish in a short time scale  ::) I think that the diesel will take another couple of years before I am happy with it and can move onto the Junkers.

So faced off the crank disc, Loctited the crankpin in place and put it together checking for free movement at each step. I used a couple of 1mm drills for pivots at this stage. I need to check the clearance between the valve pivot and the frame, it looks a little tight. The cylinder cover is just pressed in not screwed down. Obviously I had to try it and success  :whoohoo:  There is no lubrication other than residual maintenance spray on the cylinder and valve bores.


Happy  :)  :)  :)
Best regards

Roger

Offline Ye-Ole Steam Dude

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Re: Another breath engine (Huff and Puff)
« Reply #37 on: May 15, 2019, 08:46:55 PM »
Hello Roger,

The engine runs really well and a good job on your part. Hang in there with the diesel :ThumbsUp:

Have a great day,
Thomas

Offline b.lindsey

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Re: Another breath engine (Huff and Puff)
« Reply #38 on: May 15, 2019, 10:44:11 PM »
Very nice. Going to have to make one of these after finishing up some other projects first. Well done Roger :whoohoo:

Bill

Online Kim

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Re: Another breath engine (Huff and Puff)
« Reply #39 on: May 16, 2019, 05:58:44 AM »
Wow!  Runs a treat!  Now to get rid of the drill bits sticking out the sides  :Lol:
Kim

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #40 on: May 19, 2019, 06:48:33 AM »
Thank you all  :ThumbsUp:  :ThumbsUp:

I dismantled the engine to sort out a few details. I filled a small flat on the crankshaft to give better grip for the flywheel grub screw. Two small cutouts were filled in the frame and the cylinder cover to reduce the obstruction of the ports. The cylinder and frame were rounded off using a 1.5mm radius cutter with the fixed jaw of the vice as a location surface. I made a couple of 5mm filling buttons for the main bearing stands, using the clamp that held them in place to take the cutting load so as not to risk bending the stand.
Best regards

Roger

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #41 on: May 19, 2019, 07:21:15 AM »
I reassembled the engine checking for free running at each stage. I will have to remake the two clevis pins, the valve one is too long and the cross hole is off centre in the piston rod one. I put a small amount of light oil on the crankshaft bearings and gave it a blow  :)


I have attached my drawing as PDF and DWG below if anyone is interested (note: they are more electronic back of an envelope sketches than professional grade drawings like Brian Rupnow's)
Best regards

Roger

Offline Jo

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Re: Another breath engine (Huff and Puff)
« Reply #42 on: May 19, 2019, 12:39:51 PM »
8)

Ideal engine to let the kiddies blow round to get them interested in our models  :)

Jo
Enjoyment is more important than achievement.

Offline b.lindsey

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Re: Another breath engine (Huff and Puff)
« Reply #43 on: May 19, 2019, 01:48:03 PM »
Fantastic Roger!!  I love it  :cartwheel:

Bill

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #44 on: May 25, 2019, 07:55:45 AM »
Thank you both  :)

Nearly there. I turned up a neater air connection from 6nn hex brass that takes a more sensible sized pipe and then started on new clevis pins.
Best regards

Roger

Offline Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #45 on: June 10, 2019, 08:25:00 AM »
So I finally stopped traveling for long enough to finish off the clevis pins. As expected the swarf gnomes got one which I had to remake  ::) I also ground a new parting tool with an offset blade to minimise the overhang from the chuck.

Back to the two cylinder engine  :)
Best regards

Roger