Ksor, I just ran my beam engine and counted the revolutions. It's about 50 to 60 RPM.
I got a little dizzy and lost count a few times! :big:
It's single acting and very slow because the power stroke pushes air UP under the piston, and gravity pulls the piston DOWN.
The pressure can be adjusted so the motor will run even slower, probably slower than any other design of motor.
-MB