I am looking for a cheap (preferably under 2000 USD) electrical motor that can spin freely in either direction when the motor is unpowered. The motor will be used as an alternative source of power to a hand-cranked ferry.
There are three cranks: one on the ferry + one at each docking station. All three cranks are connected - when one turns, all turn the same direction.
At this point, we're just looking for a quick proof-of-concept hack that interferes minimally with the current operation of the ferry. What we have in mind is a small electrical motor mounted near each of the two cranks on shore, directly connected to the crank axles using belts or bike chains. To keep it as simple and cheap as possible for this quick proof-of-concept, we were hoping to find a motor that spins with minimal resistance in either direction when unpowered.
Our first idea was to use a direct drive brushless motor designed for bikes, since they presumably do not need a clutch to spin freely, but from what I have read, such motors don't like high load at low RPMs, so they don't seem ideal for our use-case. Our cranks will spin at about 30 RPM. The load varies depending on the weather, but rarely more than an adult person can crank with one arm.
Does anyone know of an off-the-shelf product that meets our requirements?
I have googled for a geared motor with an internal magnetic clutch that automatically releases when the motor is unpowered, but I've found no good candidates so far.