Joerg said:
Good idea. But mechanically it might be almost as complex as a specially
made idler wheel that grabs into the knurls. If only the knurls are deep
enough to be considered "teeth" one could simply use a 2nd potmeter of
same type.
Unless the knurls are actual teeth (on both wheels) you are going to
have to arrange to have some side force applied to maintain friction.
This will be a combination of a spring plus the force applied to the
idler by the operators thumb.
Either using a second pot or an idler wheel, the idle shaft will have to
be free to swing against the main pot wheel. If it is bolted down, any
wear of either wheel's surface will result in proper contact being lost.
Of course, for actual gears, both shafts can be fixed.
There is one alternative (if the device has the space internally). Drill
a small hole in both the main and idler shafts (which can be fixed) and
pass thin nylon string through one, wrap it around the shaft a few times
and then around the other in the opposite direction. Bring it back to
the main shaft and tie it to the loose end with a small tensioning
spring in line. If there isn't enough room laterally, the string between
the two shafts can be routed around a third shaft to provide enough free
travel to incorporate the tension spring. This is how they used to
couple radio tuner knobs to the variable cap. shafts.
