Maybe it's been done?
My ramp-door trailer is under a carport, but the ramp sticks out from under when it's down.
If I'm out working on it and it starts raining, I'll grab the ramp spring and turn it to slowly raise the door like a drawbridge.
It takes very little force to do this.
What about putting a sprocket on one end of the shaft and rigging up a small electric motor with a chain to power it?
I think with the proper gearing it might work.
I plan to enclose the door mechanism with a removable cover, but it would be nice to be able to raise it from inside.
Maybe a hand crank?
Hmmm...
Thoughts?