This is a little functional twin-cylinder compressed air engine. This engine can run on every low pressure. Just blowing into the inlet is plenty of pressure to let it run.When using higher pressures the engine can produce a little bit of power. The engine will have to be glued together when using higher pressures otherwise the engine may go plop* and fall apart.
The valves are pneumatically closed, so there won't be any valve-float.
The valves will have to start opening when the piston is just past the apex. Around 85 degrees sould be perfect to make the engine run well.
The timing between the pistons doesn't really matter. 180 degrees of rotation between the pistons is best. When one piston is at the top the other one should be at the bottom.
Assembly should be quite easy to figure out.
If it don't fit, its not in the right place.
You can also use the pictures provided to help with the assembly.
Have fun printing, good luck assembling and I hope your new engine runs. :)
Hobbyking 1.75mm. PLA
The assembled engine without the flywheel.