Algodoo

This piston pump can vary it's stroke, and therefore vary the displacement/amount of fluid it pumps. It also has the ability to reverse the flow, and pump in the other direction. The large gear on top is only to show how fast it is pumping and in which direction, and the graph is to show this. The controls are the up and down arrow keys to vary the displacement. Please rate and comment.
EDIT:
Updated with frequency changer by blugain, seems to work fairly well on 200 Hz, but if your computer can handle 500-1000 then it should work even better. Controls are z and x keys to change frequency.