The rotor has magnets spaced around it, the same pole facing
towards the outside. As the rotor magnets move past a piston,
they repel the piston due to its embedded magnet.
The distance between the piston and the rotor can be
adjusted by supporting the piston with some adjustable-
magnets, which repel some piston-embedded
magnets added for this purpose.
Changing this distance adjusts the stroke length of the pump.
For use as a pump you can use way valves.
If you use cams to control the valves you can run it as a
hydraulic motor or as a pump.