KeyRing of a combustion boxer-engine with turning crankshaft and moving pistons.
In this design the pistons of each opposed pair of cylinders move inwards and outwards at the same time. Like all BMW boxer engines.


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


Assembly
- Use some oil or grease between moving parts for a smooth operation.

- Build the crankshaft using the crankshaft alignment tool. 
  Apply glue.  I use Loctite Super Glue-3 Power Gel.
  Attention for the orientation of the piston rods: upper piston rod upside down!

- Click the pistons in the cylinders, placing the assembled crankshaft in the crankcase.



- Screw the winding button on the back of the crankshaft.


Operation
Turn the winding button on the backside of the crankcase.
The pistons of each opposed pair of cylinders move inwards and outwards at the same time.


Other keyrings in the same series:
Engine KeyRing by Bootjevaarder | Download free STL model | Printables.com
V-Engine KeyRing by Bootjevaarder | Download free STL model | Printables.com