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Hi,
Thanks for the comments.
Yes the friction drive is home made. The R.A. wheel has a stiff dimpled rubber glues to it and the drive is spring loaded to place pressure on the R.A. wheel. There's a cable release for disengaging the drive.
The motor itself is a crouzet one revolution per hour 12v DC synchronise timer. I picked this up from a second hand shop years ago.
The main thing in this design is to have good balance, so as to not put too much strain on the gear box.
I recently made the same drive for the 16" scope, originally I had a chain drive with an extra worm wheel drive inbetween the motor and the friction clutch. Too much back lash and torsional forces!
So I simplified it to the straight friction drive, less things to go wrong in the drive chain. The drive is reasonably accurate, but does need some controlling, hence the rheostat on the observatory scope.
Cheers,
Justin.
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