Using a cylinder as a tank

[Hydros]

Here's one with a large hydraulic cylinder being used as a high pressure tank.

You might be able to get up to 2000 PSI of tank pressure.

This sytem would have external gears and the coil spring would be inside of a four bolt cage. One side of the cage would have the bolt threads and nuts exposed to allow the end plated to compress the coil.

You would use another pump hooked up to also compress the coil then use a slowdown or valve to lock the system.