On the Emulation of TU58s

[Paul Koning]

> On Jun 16, 2015, at 3:20 PM, tony duell <ard at p850ug1.demon.co.uk> wrote:
> 
> ...
>> The actual tape movement as such, is all done by the small wheel next to
>> the head, which just runs the tape past the head.
> 
> Which is essentailly the same as the capstan in an audio tape recorder, albeit the computer
> drive doesn't have a pinch roller

Most don’t.  Some do.  I remember using IBM tape drives on a 360 Model 44 that were amazingly badly designed.

Part 1: two capstans spinning all the time, in opposite directions.  Solenoid-activated pinch rollers would press the tape against the capstan to set it moving.  The same solenoid-activated pinch roller moved in the opposite direction would press the tape against a non-moving “capstan" to stop it.

Part 2: vacuum columns — no surprise there.  But why on earth would anyone build a vacuum column that has the oxide side of the tape facing OUTward, rubbing the oxide against the column side walls?

Amazingly enough, those drives did work reasonably reliably, but I would never want such a beast in my shop.

	paul