KeyRing of a combustion engine with turning crankshaft and moving piston.
Release 2.0 d.d. 28-8-2025: improved clicking of crank cheek/crank case and piston pin/crank cheek.

Printing
No supports.
I printed with PLA+, layer height 0.15 mm.

Assembly
Use some grease or oil on the moving parts for a smooth operation.
No glue.
Click the piston in the cylinder, and the crankshaft in the crankcase.

Operation
Put your finger on the round button and turn the crankshaft.