Ringbom 1: A Ringbom Stirling Engine

[tvoght]

Ringbom One is a Ringbom Stirling I designed myself. I have been campaigning it at my favorite expositions since perhaps 2018 (with some teething problems in that first year), but this is the first time I've shown it here.


<a href="https://www.youtube.com/watch?v=XbbSIu0Qswc" target="_blank">http://www.youtube.com/watch?v=XbbSIu0Qswc</a>

For those wondering, the displacer of a Ringbom Stirling is not driven by a mechanical linkage, but by pressure variations within the engine. The video shows some unusual characteristics of such an engine.
A Ringbom is slightly harder to design than one with a mechanically linked displacer because the expected pressure variations must be at least estimated, and the area of the displacer rod and mass of the displacer figure significantly in the performance of the engine.

What I found was that a Ringbom is also much more difficult to troubleshoot when things aren't going right. The lack of a mechanical displacer linkage means that one can never be quite sure where the displacer is positioned at any given time during the engine cycle. I struggled for months with a problem that finally turned out to be frictional stick points between the displacer rod and its bushing. The symptoms I saw did not do much to point me to the root cause.  Having finally worked that out, it is actually a fine running engine.
--Tim

[gldavison]

Excellent job Tim, and a very good runner too.

Gary

[Dave Otto]

Thanks for sharing Tim!
That’s a nice running and looking engine.

Dave

[MJM460]

That’s running really nicely, Tim.  Seems to be providing some significant power as well.  A very interesting principle.

Now for the build log?

MJM460

[Chipmaster]

Wasn't aware of that type of Stirling engine - fascinating, and a good video.
Thanks
Andy

[Art K]

Tim,
That is a nice running engine. I can imagine how it would be difficult to sort out running problems, given how they are sensitive to friction. It does seem weird watching the displacer moving with out any linkage.
Art

[tvoght]

Thanks everybody for your comments!
Gary, you have seen the engine before. One thing I forgot to mention is that it is quite a bit louder than a typical Stirling engine...
Dave, I appreciate any favorable comment from a master builder of Stirling engines. I got to see your collection of Stirling fans that one year in Portland. My jaw is still gaping a little.

MJM460, I know you like to talk thermodynamics, and I brought some amateurish analysis into play here. PV = mRT and F = ma  yada, yada, yada.
Art, I first ran this engine the morning before I left for the NAMES show in 2018. It was running great and I was so happy. I packed it up for the show and when I got there it would hardly run at all except for a couple of minutes at a time when nobody was watching.  I took it to the 2019 show thinking I wouldn't even bother setting it out. I did though and played around with it, and it suddenly started running well at the show. By show's end, it was running like a top.

Andy, you just don't see a lot of Ringbom builds around, and that's why I wanted to show this one around.


As for a build log, I have pictures, but not a lot of time right now. MJM460's prodding got me thinking though, and I think I can do a decent log that at least hits upon the high points. Since things are kind of slow around here right now, it seems the right thing to do. Stay tuned. I've already gotten a couple of parts written up.

--TIm