It's very unusual to see a bar-heavy motor assist.
In the UK I have built quite a few motor-assist
counterweight sets, using an
electric chain hoist to control the descent of an arbor-heavy set.
The idea being that you take the
arbor up to the
gallery, then rig a motor above it and attach the hook to
arbor. Then you take the weight on the motor and
release the brake (not re-applying the brake until the motor is removed). You fill the
counterweight arbor to it's max load. Now the bar
flies in when you run the motor up, and
flies out when you run the motor down. The benefit of this is that you can hang modular sets or
LED walls on the fly bar and lift it section by section without having to add more weight each time you lift it. Once the whole thing is in the air, you can then remove the motor hook and still fly it in and out like a normal bar. Then you just re-attach the hook for the
load-out.
