unusual model engineers Stirling engine. 

You definitely used some more unusual designs for everything you could here. The short stroke piston isn't super torque, but I like it as a design and I love the funky crank.

love the linkage and the idea of a diaphragm power piston

How clever is that ball linkage in fact how clever is the whole design.

What an amazing engine David. Never seen one with a linkage like that before.

Yes it took my fancy, was purchased on eBay, made the small gas burner and it works well 😊

How to make a crank, without making a crank, X2.