Hello from David in Emsworth, Hants.
I finally finished my Thermo Pulse Hot Air Engine! An enjoyable project overall but frustrating at times.
This started with the drawings of the "Danielle" design by Jan Ridders, his "Thermo Pulse Mobile". I decided not to include the "mobile" arrangement, opting instead for a more conventional layout. I was unable to get the exact type of test tube specified so I scaled the stroke and the dimensions of the parts inside the test tube in proportion to the bore of my tube (to 95%). However it would not run. I even slightly melted the tube when I tried a more powerful gas burner! After looking at other engines on YouTube, reading some articles and trying some experiments, I rebuilt it to the Warbrook configuration at which point it ran.
I have retained some of Jan's design details. The tube support with its 'O' ring and the little silicone rubber tubes to retain the restrictor are very effective. My final restrictor has 9 holes and I am inclined to think its real function is as a cooler, conducting heat to the tube support. I feel the power is being restricted by the limited extent the heat can conduct through the glass.
My engine likes to run fast and I found that lightening the piston and balancing the crank were worthwhile improvements. It runs very freely but the piston rattles because the test tube is not quite cylindrical.
I have done some testing to determine the power needed to rotate the engine 'hot' and 'cold', under various conditions. This allowed me to optimise some proportions for best performance. Some of the results are quite interesting but don't really give any insight into how this type of engine works. I hope to publish the results eventually when I get time to write it up.
Some photos and a video below.
