Author Topic: Doppelmotor - Double Acting Stirling Engine  (Read 3741 times)

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
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


Offline crueby

  • Full Member
  • *****
  • Posts: 11370
  • Rochester NY
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!

Online Dave Otto

  • Full Member
  • *****
  • Posts: 3885
  • Boise, Idaho USA
    • Photo Bucket
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

  • Global Moderator
  • Full Member
  • *****
  • Posts: 4543
  • Switzerland
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

  • Guest
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

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
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

  • Full Member
  • ****
  • Posts: 76
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

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
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

  • Full Member
  • ****
  • Posts: 1080
  • Stirling Engine Maker Darfield Canterbury N Z
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

  • Full Member
  • ****
  • Posts: 859
  • Raleigh,NC. USA
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

  • Full Member
  • ****
  • Posts: 825
  • Lancashire, UK
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

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
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

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

Online Dave Otto

  • Full Member
  • *****
  • Posts: 3885
  • Boise, Idaho USA
    • Photo Bucket
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #13 on: April 16, 2020, 09:04:13 PM »
Nice looking parts Yogi!

Dave

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
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

toolznthings

  • Guest
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #15 on: April 18, 2020, 01:32:37 AM »
Great work and progress  :ThumbsUp:

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #16 on: April 18, 2020, 09:47:08 PM »
As promised, today's part is the cylinder sleeve.
The sleeve is turned from 416 stainless (thanks Brian).  ;) Turning the outside and inside diameters to full length and parting off.




Finishing to length.




Milling the notches for the air passages.




The finished sleeve.




The sleeve installed in the cylinder.




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


Offline Craig DeShong

  • Full Member
  • ****
  • Posts: 859
  • Raleigh,NC. USA
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #17 on: April 18, 2020, 11:24:37 PM »
Lov’in this build.  Your building an interesting hot air engine.

If I might ask, why are you using paper when holding a work piece in your mull vice?
Craig

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #18 on: April 19, 2020, 02:06:00 AM »
Thanks Craig. I'm using paper in the vise to protect the finished surfaces. My plan is to have the engine done in a "as machined" finish. I'm very picky, especially on aluminum parts, not to make any unnecessary marks in subsequent machine operations. That's probably not the easiest way to finish an engine, but it is my preferred look. 

Yogi

Offline AlexS

  • Full Member
  • ****
  • Posts: 165
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #19 on: April 19, 2020, 10:35:29 AM »
Great work! Looks like art to me your building engines.

Offline Plani

  • Full Member
  • ****
  • Posts: 76
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #20 on: April 19, 2020, 09:24:41 PM »
Very nice Parts  :ThumbsUp:
And great progress!!  :ThumbsUp: :ThumbsUp:
Keep them coming  :popcorn:

Plani

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #21 on: April 20, 2020, 10:29:49 PM »
Thank you guys for the compliments!  :cheers:

The next series of parts are all relative similar in the way I'll be machining them. I'm also grouping parts together that require the same tooling to be a bit more efficient. I will keep the description to a minimum, but I'll post a picture of each operation. If there are any questions, things are not clear, or this format is not working out, please let me know.

I'm starting with the short bearing block and the support for the swing.

Op. 1: Milling the contour to full depth.






Op. 2: Milling to thickness.






Op. 3: Removing the corner radius on each mounting pad. That's required for the screw head clearance.




Op. 4: Drilling the mounting holes.






Finished parts.




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



Offline zeeprogrammer

  • Full Member
  • *****
  • Posts: 6790
  • West Chester, PA, USA
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #22 on: April 20, 2020, 11:40:49 PM »
Every time I look into one of your threads, I do it with trepidation.

The finishes you get are so awesome I struggle with trying to achieve that or just going away.

I'm not going away but neither is the struggle.  ;D
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #23 on: April 21, 2020, 10:20:27 PM »
Oh Zee, the last thing I want is to discourage anyone... I don't know what to tell you. Rigid machines, I guess...  :LittleDevil:

Today's part is the lever.

First, milling one side to full depth.




The part turned around, the second side is finished to thickness and the relief is milled. I drilled and reamed all the way through the stock on the first operation, which allowed me to set the part zero position in the bore.




To mill the slot in the fork, I stood the part up in the vise. That's definitely not the best workholding method, but with light cuts it turned out ok. (I do have a slitting saw arbor on order, as we'll have to do this again  ;))




The finished lever.




Thank you for following along, and check back tomorrow for more.
Yogi

Offline zeeprogrammer

  • Full Member
  • *****
  • Posts: 6790
  • West Chester, PA, USA
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #24 on: April 21, 2020, 11:19:45 PM »
Oh Zee, the last thing I want is to discourage anyone...

You're not. Your work is inspirational...as is the work (play) of so many members here.

But sometimes...  ;D
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #25 on: April 22, 2020, 11:05:43 PM »
I understand Zee...

Today's series of parts are the tall bearing block, the two supports for the lever, and the eccenter strap.

These parts are made very similar to the last few parts. First operation is to machine the profile to full depth.








To finish the parts to final thickness, I used a set of soft jaws to hold the parts.








The bearing block and the supports are drilled and tapped.






The finished parts.










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

Offline Craig DeShong

  • Full Member
  • ****
  • Posts: 859
  • Raleigh,NC. USA
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #26 on: April 23, 2020, 08:16:14 PM »
Very nice work Yogi.  I must admit I’ve never used ‘soft jaws’.  I can see where, for holding odd shaped parts they could be quite useful.  I assume these are ‘throw away’ fixtures you add to the mill vise.  Could you explain how they are attached to the vice?

Thanks
Craig

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #27 on: April 24, 2020, 12:59:18 AM »
Thank you Craig.
The soft jaws (or machinable jaws) are aluminum jaws that are mounted in place of the hard jaws in the vise. They are getting used up.
I'm a big fan, and use them for holding odd shapes a lot. Another benefit of soft jaws is it lets you locate the work. As you have to machine the jaws, you can use the same part zero point for the part program. Again, that's very handy on odd shaped parts.






Yogi

Offline Craig DeShong

  • Full Member
  • ****
  • Posts: 859
  • Raleigh,NC. USA
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #28 on: April 24, 2020, 02:33:37 AM »
Thanks Yogi.  I just looked on Mc Master Carr and found them.  They aren’t cheap  ::) but I might get a few pair because I can see a few places in the past where they would have been a real benefit to have.

I’ll probably have an opportunity in the future to need them and when you need them, that’s not the time to be thinking about ordering a pair.
Craig

Online Dave Otto

  • Full Member
  • *****
  • Posts: 3885
  • Boise, Idaho USA
    • Photo Bucket
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #29 on: April 24, 2020, 02:53:35 AM »
Hi Craig

Check monsterjaws.com they have pretty good prices on soft jaws.

Dave

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #30 on: April 24, 2020, 03:34:32 AM »
I second Dave with monsterjaws.com (also selling on eBay). I couldn’t buy the aluminum for what I can get the jaws from them, and they are reversible.


Yogi

toolznthings

  • Guest
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #31 on: April 24, 2020, 01:56:09 PM »


The best out there. Lathe chuck soft jaws, too.   :ThumbsUp:

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #32 on: April 25, 2020, 11:21:58 PM »
Up next the cylinder heads.

The two cylinder heads are identical, with the exception one has a bore for the piston rod.

The first side is turned and parted off.






Chucking really gently on the register, the second side is cleaned up.






Drilling the mounting holes and milling an air passage.






Finished cylinder heads.




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

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #33 on: April 28, 2020, 10:24:14 PM »
The next parts are the connecting rod, and the links for the displacer and power piston rods.

The process for making these parts is the same as before. Milling the profile, setting up soft jaws, finishing the second side...


















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

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #34 on: April 30, 2020, 12:41:37 AM »
Work continues... Today we have the crank disc.
Made from 416 stainless (thanks Brian). First side is turned.




Parting off.




Gently chucking on the outside diameter to clean up the second side. Before machining, checking the run out with a dial indicator, as it would be very easy to chuck the piece crocked.




Drilling and tapping for a set screw.




...and drilling and reaming for the crank pin.




The finished crank disc.




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

Online Dave Otto

  • Full Member
  • *****
  • Posts: 3885
  • Boise, Idaho USA
    • Photo Bucket
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #35 on: April 30, 2020, 01:12:12 AM »
Beautiful work Yogi!
I'm enjoying your progress.

Dave

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #36 on: May 03, 2020, 11:54:27 PM »
Thank you for the compliment Dave!  :cheers:

Next, the gland nuts. The first operation is to face, bore and cut the thread. The nut has a 15 degree chamfer on the hex, as it is commonly seen on nuts. I machined that chamfer on both sides in this first set up.




Over on the mill, using a collet block to mill the hex.




Back on the lathe, I could pick up in the groove I cut earlier to finish parting off.




Cleaning up the face after parting off.




...and the finished gland nuts.




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

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #37 on: May 04, 2020, 09:43:04 PM »
Both the power piston and the displacer pistons have packing glands in the design. Both are quite similar, but not identical with few dimensions being different.

I was able to turn pretty much the entire part in a singe operation. Doing it this way I could guarantee the concentricity of the bore to the outside diameter and also the thread, and with that to the nut.

Here the glands before parting off.






This is how the parts came off the machine.






The only turning on the second operation was to clean up the burr left from the parting operation and breaking the edge.




Drilling the mounting holes.




The finished glands:




Unfortunately I have to go back to work and this project will have take a break. My original plan to have the engine finished by now didn't quite work out, but I still feel like I made a lot of progress and the goal of a pleasant distraction definitely worked. The drive to finish it, even if it was a lofty goal, did the trick with many quality hours spent in the shop.

Everyone stay safe and stay tuned for the continuation of this project.
Yogi

Offline Admiral_dk

  • Full Member
  • ****
  • Posts: 1900
  • Søften - Denmark
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #38 on: May 04, 2020, 10:17:51 PM »
I think we all enjoyed your build so far - so we will be back when you get time to continue  :cheers:

Per

Online Dave Otto

  • Full Member
  • *****
  • Posts: 3885
  • Boise, Idaho USA
    • Photo Bucket
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #39 on: May 05, 2020, 12:45:26 AM »
The glands look great Yogi, nice work as usual!

Glad that you get to go back to work, please stay safe. When they sent everyone to work from home at my job, I figured that I might also get some extra shop time too. Not much I can do from home except to check email and attend Zoom and MS Teams meetings, because I work in a shop. Well that didn't happen, they got approval for me and my two coworkers to continue to come into work.
It certainly has been different working in a ghost town; actually kind of nice in someways.

Dave

Offline Plani

  • Full Member
  • ****
  • Posts: 76
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #40 on: May 06, 2020, 04:25:42 PM »
Really nice parts you made there! They're looking fabulous!

In the mean time stay safe and healthy, looking forward to see more updates.

Plani

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #41 on: June 01, 2020, 01:53:54 AM »
Thank you gents for the kind comments. It's very much appreciated.  :cheers:

I can report some more progress on the engine whit the completion of the flywheel.
Corrosion resistance is always a consideration when I choose material for an engine. Steel would be the go to material, but I would want to address the possible corrosion. I decided to go a different route instead, with a two part flywheel, with an aluminum center hub and a bronze rim to get the required mass.

The shape of the aluminum stock, which was left over from another job (cut free from a bigger piece), wouldn't allow me to chuck it in the lathe. To be able to chuck it, I milled 3 flats at 120 degrees to hold it in the 3 jaw chuck.










Roughing some more material away to get to a good staring point.




Turning the first side.




Next, I machined the first side of the bronze rim. I machined a small shoulder which will locate the center hub in the rim.




Installing a set of soft jaws to finish the second side.




Still in the soft jaws, the rim is finished turned.




Milling the spokes.




The finished assembled flywheel. The center is a shrink fit in the rim.




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


Offline Roger B

  • Global Moderator
  • Full Member
  • *****
  • Posts: 4543
  • Switzerland
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #42 on: June 01, 2020, 08:18:33 AM »
That's an impressive looking flywheel  8)  :wine1:
Best regards

Roger

Offline Zephyrin

  • Full Member
  • ****
  • Posts: 489
  • near Paris, France
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #43 on: June 01, 2020, 08:26:57 AM »
beautiful finish on all these parts, immaculate...wow
 

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #44 on: June 22, 2020, 08:12:02 PM »
Thank you gents for the kind comments!  :cheers:

The next part is what I call the swing.
First operation is to mill the contour to full depth.




The part turned over in the vise, the remaining stock is milled away and finished to final thickness.




Milling the fork ends using a slitting saw:




The last operation is to mill a pocket for the eccenter.




The finished part.




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

Online Dave Otto

  • Full Member
  • *****
  • Posts: 3885
  • Boise, Idaho USA
    • Photo Bucket
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

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
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

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
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

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
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

  • Full Member
  • ****
  • Posts: 825
  • Lancashire, UK
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #49 on: July 05, 2020, 05:50:35 PM »
 :popcorn: :popcorn: :ThumbsUp:         Terry

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
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


Online Dave Otto

  • Full Member
  • *****
  • Posts: 3885
  • Boise, Idaho USA
    • Photo Bucket
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

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
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

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
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

  • Full Member
  • ****
  • Posts: 1900
  • Søften - Denmark
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:

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #55 on: December 01, 2020, 06:34:46 PM »
Thank you for kind comment Per!  :cheers:

And here the long awaited video:



For this first test run, I'm using a couple of alcohol burners because that's what I had on hand and was easy for a test set up. The alcohol burners are not easy to regulate though. The engine got a pretty good clip going at full heat. That was alright for the first start but I would like to run the engine relatively slow in permanent operation. I will be using a gas (butane/propane) burner for heat, which I will be working on next.

Thanks everyone for following along and stay tuned to finish the engine.
Yogi


Offline cnr6400

  • Full Member
  • ****
  • Posts: 827
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #56 on: December 01, 2020, 06:45:23 PM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:

Offline Jo

  • Administrator
  • Full Member
  • *****
  • Posts: 13839
  • Hampshire, england.
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #57 on: December 01, 2020, 06:58:12 PM »
 8) Nice

Jo
Enjoyment is more important than achievement.

Offline crueby

  • Full Member
  • *****
  • Posts: 11370
  • Rochester NY
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #58 on: December 01, 2020, 07:27:00 PM »
Awesome!

Online Dave Otto

  • Full Member
  • *****
  • Posts: 3885
  • Boise, Idaho USA
    • Photo Bucket
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #59 on: December 01, 2020, 07:54:19 PM »
Congrats Yogi!
Beautiful work and interesting motion.


Dave

Offline Bob

  • Full Member
  • ****
  • Posts: 10
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #60 on: December 01, 2020, 10:09:02 PM »
Nice work.

One question, does the piston float axially on the piston rod?

Bob

Offline Admiral_dk

  • Full Member
  • ****
  • Posts: 1900
  • Søften - Denmark
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #61 on: December 01, 2020, 10:25:58 PM »
It runs very well but it sounds very energetic, like it would need a load and be able to pull it well too  :praise2:    :cheers:

Offline yogi

  • Full Member
  • ****
  • Posts: 448
  • Duncannon, PA USA
    • Yogi's Workshop
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #62 on: December 02, 2020, 03:16:10 PM »
Thanks everyone for the kind comments! It’s very much appreciated! :cheers:

Bob, no, it does not. Could be a potential problem with stacking tolerances, but worked out fine.


Yogi

Offline tvoght

  • Full Member
  • ****
  • Posts: 933
  • Indiana
Re: Doppelmotor - Double Acting Stirling Engine
« Reply #63 on: Today at 12:01:40 AM »
Outstanding work on this engine, Yogi! Do you intend to show your work on the gas burner(s) here? That's something I'd like to see.   --Tim