After seeing a Ringbom engine operating at a hobby machinist gathering and being intrigued with it, I decided to build one myself. I already had a booklet about them in by library written by Dr. James Senft. According to the information in the book they were invented by Ossian Ringbom in 1907. However there is no evidence that any of the engines were ever built. Using a patent drawing Dr. Senft had worked up a set of construction drawings for a miniature working model, which I used as a basis for this model, except I doubled the size, and changed some of the materials to be able to use what was on hand.
The cold end of the displacer cylinder was machined out of solid stainless steel. The hot end is a piece of drain pipe or tube. The displacer is a small shaving soap container. The power cylinder is a piece of automobile shock absorber, and the flywheel is a roller that I picked up at a swap meet, etc. etc. It is rather strange. Below operating temperature, both starting and stopping it rocks back and forth in half revolutions.
However after it reaches operating temperature it runs in full circles, and it will run either direction.
In this video it is running at about minimum operating temperature. Slightly more heat and it will run faster.