Wish to spool 5/8" rope onto a revolving drum. The drum is approx. 2' long,with a 12" diam and the axle is 2" diam. The spooling mechanism (similar to a fishing reel) goes back and forth through a moving eye mounted on a nut on a threaded rod. The rod is driven by a DC (reversible) 12 V motor. As the rope layers build on the drum the eye needs to move faster as the drum speed is constant. Micro controllers are beyond my scope. How may one control the motor speed turning the threaded rod to accomplish an even spooling automatically?