> > Circumference and Diameter are linked by the constant Pi and therefore > are an entity. > Its a little more complex with a rubber wheel and its indented path.
Indeed. And that may even depend on the type of 'rubber' used and how it deforms when pressed against the cartridge drive wheel. Remember that the motpr on these drives is mounted on pivots, which allows it to move back as the catridge is inserted. So a soft rubber roller is going to deform more than a hard one. > However as we are using closed loop control > when the measured term equals the target term there you are. I disagree with that. The tacho disk is on the bottom of the motor spindle. So the control electronics will count pulses from that and control the motor voltage to get the _motor_ turning at a constant speed. The drive roller in question is between the motor and the tape drive belt in the cartridge (effectively), so while the motor speed might be constamt and correct, the tape speed need not be if the roller is not right. I wondered about using the 'tyres' used on the idler wheels in VCRs, etc (which are still available). Unfortuantely they are sold by the machine they fit, not dimensions, so I don't know if any are a suitable size. And of course the is no shop that still sells things like that (only mail-order :-() so I can't go in and look at them, make measurements, etc. If the O/D is correct then that is all the really matters. If the I/D is different then it would not be hard to turn a different hub. I'll go back to the first question (as I also have 4 of these drive units, 2 in a standalone TU58, 2 in an 11/730 CPU, that need repairing). Does anyone have a UK source of tubing or whatever that will work -tony
