File:Cable drive moving apature.PDF

Stepper motor driving standard rod with many lengths of cable wrapped around it, the cable secured by a screw in the middle of the cable. When the rod rotates, the gear drive rotates a spreader bar or thread layer. This has two holes that the cable goes through. The gear driven short threaded rod causes the spreader bar or threading control to move up and down the rod laying down cable being taken up in such a way that it never over laps, and pulling old cable off the same way. This should be more reliable, albeit more complex, than using threaded rod only for the main shaft and depending on the cable to remain in the threads.