[Jared]

It may just be simpler to use a transmission which cannot backdrive, like a worm gear. They provide large amounts of reduction in a small amount of space, and do reasonably well with large amount of torque. We plan on using a 10:1 worm reduction in our elevator for exactly these reasons.

If you'd like more details on the worm drive we're using, let me know and I can send you some specifics.