Author Topic: Doppelmotor - Double Acting Stirling Engine  (Read 3725 times)

Offline yogi

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Doppelmotor - Double Acting Stirling Engine
« on: April 10, 2020, 11:29:55 PM »
It's been a while since I have been able to contribute to the forum. But the time has come to start a new engine. I know I have a couple of other engine projects that are not quite finished yet, and I'm expecting to receive some flak for that...  ;)

I felt like building an engine that's not overly complicated and if everything goes as planned should be finished in a reasonable amount of time is exactly what the doctor ordered, especially with what's going on in the world right now.

The engine is designed by my brother. It's always been one of my favorite designs of his. Speaking to him about his design, he took inspiration form a 1927 Stirling Brothers engine. Below is a video of his engine running.



The starting point for my build is a set of thermos bottles I picket up a the local close out store. My original plan was to use the outer shell of the thermos, but after modeling the engine in CAD, they would have been too large (maybe in a later build). Instead, I decided to use the inner shell.






To cut the thermos open, I used a Dremel tool.






To square the end, and getting both shells to the same length, I carefully chucked it up in the lathe and used the Dremel mounted in a tool holder for the cut.




The flange is made from brass.




Test fitting:




The finished silver soldered hot ends.





Thanks for following along, and stay tuned for more.
Yogi


Online crueby

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #1 on: April 10, 2020, 11:56:02 PM »
Nice start on a very interesting design!  Were there any problems silver soldering between the thin shell and the thicker ring? Must have taken some careful heating. Will be watching along!

Offline Dave Otto

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #2 on: April 11, 2020, 01:37:54 AM »
Cool project Yogi.
Sometimes you just need a little break to work on something different.

Dave

Offline Roger B

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #3 on: April 11, 2020, 07:56:05 AM »
That's an interesting design  :ThumbsUp:  :ThumbsUp: and good use of available materials for the displacer cylinders  :wine1:
Best regards

Roger

toolznthings

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #4 on: April 11, 2020, 06:37:57 PM »
Looking super  :cartwheel:
Nice work on the canisters.  :ThumbsUp:

Brian

Offline yogi

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #5 on: April 11, 2020, 11:30:48 PM »
Thank you guys for the kind comments. It's very much appreciated.  :cheers:

Chris, I didn't have a problem with the difference in material thickness for the soldering. I applied the heat from below onto the flange. That seem to work out quite alright, even though it's definitely not my best soldering job I have done...  :embarassed:

Offline Plani

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #6 on: April 12, 2020, 09:39:32 PM »
Nice Project Yogi!
Looking forward to see this one come together.

Plani

Offline yogi

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #7 on: April 13, 2020, 09:16:12 PM »
Thanks you for the kind comment Plani!  :cheers:

We continue the with the base plate. First, the plate it milled to width.




The top of the plate is faced, drilled and counter bored.




...and the same operation for the bottom of the plate.




Here the finished base plate, top and bottom, after deburring and tapping:







Thanks for following along, and stay tuned for more.
Yogi

Offline Ian S C

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #8 on: April 14, 2020, 05:47:14 AM »
Going to be watching closely on this one, it looks to be a close lay out to my Ross Yoke ALPHA motor,but bigger, I have a large(for me) cylinder liner 4" bore x 8" long, that could make the two cylinders for an ALPHA Motor, I have some stainless cannisters for the hot cap. I may pinch some of your ideas Yogi.
Ian S C

Offline Craig DeShong

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #9 on: April 14, 2020, 10:30:36 PM »
Boy that’s a lot of holes :). Interesting to see for what they’ll be used.
Craig

Offline scc

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #10 on: April 14, 2020, 10:44:34 PM »
Excellent!  I'm intrigued :popcorn: :popcorn:        Terry

Offline yogi

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #11 on: April 16, 2020, 12:33:09 AM »
Thank you gents for the kind comments!  :cheers:

Ian, I'm looking forward to what you will come up with...   ;)

The next part is the cooler.
Starting with the first side, turning the face and finishing the inside diameter.




For the second side, I turned a set of soft jaws to hold the part from the inside.




Here the two coolers fresh off the lathe:




To make the two coolers fit next to each other, they need a flat milled for clearance.




Since I had to drill the hole pattern multiple times, I set up a 1-2-3 block in the vise. With a second 1-2-3 block, I could then align repeatedly against the milled flat. This was very fast and easy.








The two finished coolers top and bottom:




Thanks for following along, and stay tuned for more.
Yogi
« Last Edit: April 16, 2020, 12:38:32 AM by yogi »

toolznthings

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #12 on: April 16, 2020, 01:24:13 AM »
Major progress and nice work  :ThumbsUp:

Offline Dave Otto

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #13 on: April 16, 2020, 09:04:13 PM »
Nice looking parts Yogi!

Dave

Offline yogi

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #14 on: April 17, 2020, 10:10:28 PM »
Thank you Brian and Dave!  :cheers:

Today's part is the cylinder.
In the lathe, both faces and the bore are turned to size. The cylinder will be getting a sleeve (probably tomorrow ;)) so the piston is not running in an aluminum cylinder.




Over on the mill, the holes to mount the cylinder and the air passages are drilled.




On each face, the holes to mound the cylinder heads are drilled and a notch for the air passage is milled.




The finished cylinder:




Thank you for following along, and stay tuned for more.
Yogi