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David Kerzel, Pompano Beach, Florida david@FloridaAME.org

Stirling Cycle, Modified Ringbom configuration, for low differential temperature operation First posted 7/15/2003

One of the members, John A Hastings, sent a picture of a Ringbom engine. I wrote him to find out what it was and how it worked because it does not appear to have enough parts. He recommended books written by James Senft about Stirling and Ringbom engines.

The Ringbom is a derivative of the classic Stirling. It uses internal pressure to move the displacer rather than a second crank. The original patent, from 1907, had a extra hole to prevent pressure from building up inside the engine when heat was applied. Eliminating this hole makes it "modified" and more efficient.

I had purchased Jerry Howell's full size low temperature stirling hard to find parts and was going to build his engine. I became consumed with the simplicity of the Ringbom so I modified one of the plans in the Senft book "Miniature Ringbom Engines" to use Jerry's parts. Then I started to simplify the design to make it as simple as possible.

This should be a simple quick project. I will post in progress pictures. If it works the plans will be posted.

The engine will have glass cylinders and the cylinders will be the only support between the top and bottom sections. 7/4/2003

The heat exchange disks are made from 1/8 aluminum. They could be turned and the holes layout done later, a better edge finish would probably result.

I like the rotary table and just dialing in the numbers. I rough cut the disk on the band saw, held it to the wood disk with double sided tape, drilled the outer holes, and used #2 wood screws to hold it more securely when milling the edge.

7/13/2003

It looked like a good idea, but it turned out to be a lot of work to make the flywheel from rectangular stock.

8/10/2003 All the main metal parts are complete. Next will be fitting andgetting the [istonsand displacer to work.