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Help with project design please Answered

I am building what amounts to a miniature winch.  I have a small, but powerful, battery powered gear-motor, which can wind thread or wire onto a spool.  My problem is the motor shaft does not turn freely because of the gears so I need to find a way to allow the wire to spool freely out before it is then wound back under power.  One-way bearings do not work because they are designed to allow a shaft to rotate freely in the same direction it turns as it does when under power, like a helicopter rotor.  I need the shaft to turn under power in one direction but to spool out freely in the opposite direction.  Suggestions?

Christopher Taylor


Could you use/design a clutch? Something where you can disengage the spool from the gearing so that it spins freely, then reconnect it when you want the motor to wind it up.

Thanks. I did think of a clutch. The winding-in feature is RF controlled and I will not be able to easily access the device once it is placed and working.


Ah. Blargh :-(

What about a ratchet? Essentially, an axle within an axle: A narrow spool piece with a gear on one end is what is attached directly to the motor shaft. The wire-spool itself slides onto that spool piece with some clearance (or a teflon or ball bearing support), with a ratchet hook that engages the gear mentioned above.

...No, that doesn't work. Relativity bites :-( The spool turning clockwise with the shaft still is exactly the same as the spool being still and the shaft turning counterclockwise. If the ratchet can slip when you unwind the wire, then it will slip when you engage the motor.

This is a great engineering problem.

But doesn't the shaft turn with the spool in that case? The few fishing poles I've used have a button or lever which disengages the ratchet. When the line runs free, the whole assembly (spool, shaft, and crank) turns. If you release the ratchet button, everything stops.

Hmmm, seems so. My chalk line handle also spins.Clutcheting ratchet it is then.

If you've already got an RF control to turn on the winch, could you have the same control engage the clutch (e.g., a simple solenoid)?