The toughest problem in this build was the crankshaft mounting. The original bearing bolts worked loose under roughly 120 kilograms of dynamic force, so the maker cut a larger opening in the frame and welded in a rigid, concentric steel pipe bearing housing. That is a serious fix, and it shows the kind of stubbornness this project needed. The engine is number 8 in the series, a homemade three-cylinder radial design the maker calls true DIY, sitting on a welded steel triangular frame.
Everything was built from repurposed pneumatic cylinders, precision steel pipes, plate steel, and copper, with brass plumbing fittings, ball bearings, and rod end bearings, also known as heim joints. The wooden flywheel is weighted and was balanced. Steam lines started out glued and leaked, so they were replaced with threaded and soldered rigid copper pipes. The maker also designed a synchronized triangular linkage mechanism to actuate valve gear reversal across all three cylinders, which to me is the standout piece of engineering here. Prototyping was done with Lego Technic liftarms, and the welding was done with a TIG welder, plus a bench drill press, angle grinder, belt sander, blowtorch, files, and a hole saw along the way.
The finished engine runs continuously on shop air, runs at high speed in demonstrations, and reverses direction using the manual linkage handle. Two things remain open. There is minor leakage from the cold Teflon cylinder seals, and the engine is not yet in its final home: the maker plans to install it into a replica 1916 Harley-Davidson bicycle frame using an organic Rankine cycle fueled by butane and hot water. An underground shop space is also being excavated to house a metal lathe.
Project by The DIY Science Guy. Watch it on their YouTube channel: