Thanks for the input guys. To answer the questions - it's a 17v cordless drill powered by a 12v battery, and a big heavy steel sliding gate.
I've built the hardware and the drill has more than enough power to open/close the gate so I know it's not a silly idea
. The drill turns a capstan with rope wound around it (to open/close the gate) with a gear ratio of 1:4
I 3d printed the capstan and the gears, as well as other parts, in ABS. Anyways, for those non-believers, it does work and works very well, I just want to replace the thick 1 strand copper cable with more flexible (less brittle) cable.
I'm going with the 8 AWG cable, I bought some and it looks thick as. I'll give it a go and will post a video up of my gate when it's done for all you non-believers