Quote Originally Posted by EddyCurrent View Post
Just thinking very quickly about control, it may not be good enough for your requirement though. (trying to keep it cheap and simple)

The base would be a simple motor and gearbox
The screwjack would be simple motor operated.

The base would rotate at a constant speed.
At each full turn it will trigger a switch that will move the screwjack a small amount using a timer to run the motor.
2 limit switches will indicate when the hammer is at each end of it's travel.
It should be programmable. There are certain moments that the hammer needs to spiral towards the center, otherwise waves of material rize due to accumulated tension and at a certain moment everything will wrap if not controlled.