[bojan]

Hi,
this solution of Az drive with friction rollers may be interesting for someone...
I designed it this way because I wanted the specific reduction ratio (it is visible on the pic that rollers provide for reduction 1:3) and some degree of "self-aligning" at the same time, to allow for larger tolerances in positioning of the rollers and axles. This solution was sort of forced upon me, because I was using various parts from waste.. and it turned out pretty well.
Why two rollers? I tried with just one (forced between the driver and driven disk by spring), but that solution turned out bad, because when the telescope was driven in one particular direction, the roller was pushed out and the friction was decreased to the point of not moving at all in that direction.
The most important thing here is that both rollers are identical, and the tension between the rollers is sufficient, which is provided with two springs (another one is below the rollers and not visible on this image).