During my sophomore year, I took part in a group project to design and construct an air-powered motor. Each team was given a stock of metal and very minimal budget with which to construct the motor.
We decided to maximize torque, reasoning that we would be able to continue moving the cart with lower air pressure, making the most of our air supply. Since the piston bore was set by our supplies, we gave our motor the longest stroke we could and chose a 2-piston format. Our minimal budget went towards a 4-way solenoid valve and batteries. The valve was controlled by brush-style contacts mounted to the crankshaft.
I did almost all of the SolidWorks modelng, manufacturing, assembly, execution of the solenoid system, and debugging. In the end, we were very pleased to report that our motor performed as we intended.