This is just something I made for fun. It's a locomotive style reciprocating (1/2 stroke cycle) steam engine.
I didn't originally design it to run, just be a model. But after some careful sanding and filing, as well as liberal amounts of graphite, it does run on compressed air.
I may modify it at some point. ...Give it a larger piston and larger valve ports.
Here's a quick video if you want to see it run (Sorry about the aspect ratio).
I've included the nine (9) parts as STL files. And Also a Rhino model file if anyone wants to modify it.
The AirEngineComplete.stl is simply for the image.
It should be fairly self explanatory to put together. The shaft on the flywheel is a little bit too long. So unless you plan to use it as a power takeoff you'll probably need to cut it down.
As always I'm happy to help answer questions etc.