Rod Smallwood rodsmallwood52 at btinternet.com
Wed Dec 2 13:08:19 CST 2015

Sorry forgot to use feed back from the tape.
Usually a timing track or a phase locked loop clock drived from the data 

Don't worry

On 02/12/2015 17:50, tony duell wrote:
>> 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

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