[MrForbes]

You are not stating the obvious, you are stating a point that is rather hard to see. Thanks!

when we were picking the motor/gearbox for our arm we were looking at speed reduction first. 256:1 and 125:1 gearboxes were the only ones that would do what we needed....and we still required another stage of chain reduction. Then, looking at the torque, we though we were ok as far as driving the arm, but the backdriving problem led us to use a gas spring to counterbalance it. It turns out that this also greatly reduced the torque needed to move the arm, which probably is why the gearbox survives.