Author Topic: Doppelmotor - Double Acting Stirling Engine  (Read 3457 times)

Offline Dave Otto

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #45 on: June 23, 2020, 12:42:06 AM »
Looks very nice Yogi!
Good to see that you are getting some shop time.

Dave

Offline yogi

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #46 on: July 02, 2020, 03:38:16 PM »
Thanks Dave! Yes, shop time comes at a premium in the summer month...  ;)

I have a few more parts to show, starting with the rod end forks.

Milling the contour:




Milling to final thickness:




Finishing the fork, drilling and tapping:




Finished:




The crankshaft is next:
Not much to it. The only thing worth mentioning is, to prevent the set screw from marring the shaft, I'm milling a flat on the shaft for the eccenter. Similar with the crank disc (post #34). To allow it to be adjusted for the displacer timing without chewing up the seat, I turned a relief groove.








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

Offline yogi

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #47 on: July 03, 2020, 06:58:24 PM »
For the eccenter, I first turned the outside diameter.




On the mill, the eccenter is dialed in and bored out.




Back on the lathe, to part off.




The second side is cleaned up after parting off.




Drill and tap for a set screw.




Finished eccenter.




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

Offline yogi

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #48 on: July 05, 2020, 01:40:16 PM »
I have a couple more parts finished.

The piston is made from bronze.








The four posts are milled to length, drilled and counter bored. The counter bores are for some bracing to add some stability.




The ends are drilled and tapped.




...and the finished posts.




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

Offline scc

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #49 on: July 05, 2020, 05:50:35 PM »
 :popcorn: :popcorn: :ThumbsUp:         Terry

Offline yogi

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #50 on: November 06, 2020, 09:28:35 PM »
I'm finally able to share some more progress on the build after having a crazy busy summer at work.

The last parts needed are the displacer pistons. I have been contemplating these pistons for quite some time, but I couldn't push them off any longer. Ideally the dispacer is made from a material that doesn't transfer heat easily and isn't too heavy. Thin wall stainless tubing comes to mind. Of course, finding stainless tubing in the right dimension is next to impossible.
What I came up with instead, is to assemble the piston out of multiple parts. The tubing will be machined from stainless steel with 0.5mm wall and will be threaded at both ends. To make machining more manageable, the tube will be assembled of two pieces. The top and bottom will be made from aluminum. I allow for a 1mm gap between the hot cap and the displacer.
To better illustrate my plan, see the CAD rendering below:




I sourced a piece of 312 stainless steel tubing off eBay that had pretty close dimension of what I needed.
First operation was to finish the inside diameter and thread one end.




To hold the part for the second side machining, I cut a thread on a scrap piece.




Ready to machine the second side.




Now the tricky bit. As I was machining most of the material away, down to 0.5mm wall thickness. I decided to machine to final dimension only short sections at the time. This will leave a bit of a mark on the transition of each section. Since the displacer is not going to be seen, I was more than willing to accept that.




Success! I was quite skeptical at first and was relieved that my plan worked.




The finished tubing sections times four.






Thanks for following along and stay tuned for more displacer parts.
Yogi


Offline Dave Otto

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #51 on: November 06, 2020, 10:45:03 PM »
Hi Yogi

Continuing to make progress; the parts look nice!
Good to see you back in the shop.

Dave

Offline yogi

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #52 on: November 21, 2020, 08:38:10 PM »
Thank you Dave!  :cheers:

To continue with the displacer pistons, the tops and bottoms are next.

Turning what will be the inside of the top with the thread.




Parting off:




The same steps were used on the bottom piece. Turning the inside with the thread, and then parring off.






To hold the parts to turn the second side, I cut a internal thread on an off piece.




With the parts threaded in place, the second side is finished.






The finished parts.






The last part needed for the displacer piston assembly is a connector piece for the tube sections. They were turned, threaded and parted off. No second operation needed.








The connector piece installed on one of the tube section.




The finished assembled displacer pistons.




..and the displacer pistons together with the the hot caps.




Next I'll start assembly of the engine, as I have made all the parts needed to get the engine together for a test run.

Thanks for following along and stay tuned.
Yogi


Offline yogi

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #53 on: November 23, 2020, 03:17:37 PM »
Before the assembly starts, here a quick picture of all the parts...




Yogi


Offline Admiral_dk

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Re: Doppelmotor - Double Acting Stirling Engine
« Reply #54 on: November 23, 2020, 07:46:05 PM »
Great family shot  :ThumbsUp:

Looking forward to the video  :cheers: