Preventing a bicycle freewheel from freewheeling!
You might want to do this if you want to try fixed-wheel riding on the cheap. I wanted to do it for another reason - making a transfer shaft (jack-shaft) for a homemade trike project. I worked out a way using two old freewheel clusters, but because the driven rear wheel is on the right, I needed to stop the freewheels freewheeling.
First, how does a freewheel work?
This diagram shows a simplified view. The green centre part is driven by the chain, and the red pawl locks into the blue, notched outer part, which is attached to the wheel. If you pedal backwards, or coast, the blue part turns faster than the green, and the pawl just skips over the sloping notches making a click-click sound that most cyclists know so well.
Here is an assembled freewheel, here part of an old 5 speed cluster.
here you can see the fine thread that the retaining ring screws into
the outer bearing balls
the various parts
the inner balls. Note 2 balls have been used to lock the pawls (there are two pawls, one on the hidden side). I stuck the balls in with grease. Because we are locking the freewheel we don't need a full number of balls in the inner race. Just enough to keep everything aligned, say 90% of the balls.
here's one of the pawls seen from above
and "spiked" with 2 balls each
here you can see the ratchet teeth. The pawls engage with these teeth
this is from another freewheel. The balls were too big to lock the pawls, so I used some short 2mm pins (cut from old drills).
and yet another freewheel with 4mm diameter pins.
You have to experiment to see what fits.
freewheel: locked, and assembled minus three of its sprockets, which were not needed. I used a piece of PVC water pipe as a spacer for the 2 smaller sprockets. They are only needed to hold the assembly together.
another shot of the pawls from above
and a freewheel removal tool held in my steel vice.
This page tardus.net/freewheel.html Last updated: 11 Aug 2021