Thanks for all the replies!

   The main reason for this inquiry was trying to incorporate inexpensive, ready made, planetary gear assemblies (e.g. power tools) which would not be high precision.

   Electrical preloading does work and it's being used in industrial machinery. However, one of the suppliers for the gears and motors for this application said the motor control is done by the CAM software...
   
   Finding an affordable CAM capable of doing that would make this approach worth looking into.


   Mechanical preloading ( gears + springs, etc) are only recommended for slow speeds.

Even if you could get this to work (and I have my doubts) why would you?

Surely, you'd end up with exactly the same effect that is achieved far more simply and cheaply by the old trick of using two pinions fixed slightly out of phase on the same shaft.

Ian

Yes, that should work but, from what I read so far, it only works for slow speeds.

 Maybe use a wide Rack or 2 of them, side by side ? But that would increase the cost as well.