Hint W9 - Ratchet
The K'NEX ratchet restricts any K'NEX axle so that it will rotate in one direction only.
This can be useful, for instance, when building a clock with a pendulum, or when using an axle to wind up a rubber band.
The photo on the left shows a K'NEX axle on which a ratchet is being fitted, as follows:
1. Attach the four lugs on the back of the ratchet outer bronze to a white connector.
2. Place the ratchet inner black inside the ratchet outer bronze.
3. Push a K'NEX rod through the two parts of the ratchet and the white connector, so as to form an axle.
4. Attach an interlocking clip tan to the axle, and slide its projecting lug into the edge of the hole in the ratchet inner black.
The axle can now be turned in one direction only.
To change that direction, reverse the ratchet inner black.