Ideas for a mechanism to rewind my clock

[bosr]

You may want to look into a sprag clutch design similar to the one shown at this link.

http://www.f150forum.com/f38/2011-transmission-weirdness-76812/index2/

[gaston gagnon]

I should have posted this before but if that can help, here is a sketch of the winding mechanism.
When the clock operates normally, the string goes up and the spool rotates freely CW (view from the right.
When rewinding, the motor forces the spool to rotate CCW therefore rewinding the string on the spool.

The  question is What mechanism should the ? be replaced with to produced the anticipated results?
So far, we have look at ratchet, sprag clutch and one way bearing to no avail. Neither allow the motor to rewind the spool
Thanks,
More ideas anyone?
Gaston