Alright. I need a motor that is capable of pumping air into a piston filled with compressed air. The motor needs to pump the air into the piston at a constant speed, as the piston is being used to raise up a load. The problem is that the weight of the load on the piston will be between 10-200 lbs. Since the weight of the load will change the pressure of the air in the piston, I'm concerned that it will also affect the speed at which the motor is able to pump in the air. I've already calculated that the motor needs to be at least 1/2 horsepower. Is there a way I can make sure the speed of the air pumped into the piston is constant?