Replace roller rubber on HP 9825 tape drive

[Dwight K. Elvey]

>From: ard at p850ug1.demon.co.uk
>
>> 
>> > Hi Tony
>> >  I'm proposing an experiment for you since I know that
>> > you are the type that would actually try it.
>> 
>> I am going to try this, although probably not tonight...
>> 
>> However, even if it does bahave as you suggest, it still doesn't explain 
>> _why_... I will have to think about this some more...
>
>Sorry to follow up my own message, but I spent last night thinking about 
>it, and I think I now understand it.
>
>The things that are important are (a) the belt is elastic and therefore 
>stretches, and (b) the drage from the spools means that the tension in 
>the belt is not the same all the way round. There is more tension in the 
>belt on the takeup side than on the supply side. 
>
>Supppos that a certain length of belt has gone past the supply spool (and
>thus wound off that length of tape). As it goes round the takeup spool the
>belt will be stretched a little more, so it will move the surface of that 
>spool by more than the amount that the surface of the supply spool was 
>moved. It will try to wind more tape onto the takeup spool, thus 
>tensioning the tape.
>
>For obvious reasons this effect is small. It helps to have the tape 
>fairly well tensioned before using the cartridge. If you're reassembling 
>a defective one, I'd tension the tape as much as possible by hand.
>
>If you could make a cartridge with the belt round the outside, and with 
>the drive roller possitioned far enough forward to let the bead get in 
>contact with the tape (inside the loop formed by the belt), it wouldn't 
>work. There'd be more movement on the supply side, the tape would get 
>ever more slack.
>
>-tony
>

Hi
 That is why I mentioned to Joe that you need to pull on
the supply side tape a little to get it to take up the slack.
That is what I recall doing when I replaced the bad roller.
I don't recall how I got the last little bit of slack
out of the tape. I remember holding onto it with a ChemWipe
to keep my finger oils off the tape but that only works
until is gets close. One still needs to suck in the last
bit of slack before putting it into a machine.
 Like I said, it was counter intuitive to pull on the supply
side to get the take-up side to suck in the tape but that
is what I recall.
 It wasn't until now, years later, that I thought about
how it could work. Thinking about how the Bernoulli's
principle worked with a elastic band helped to figure it
out. The more stretched band at the take-up has to have a
higher surface speed.
 It should be fun to confirm by the spool experiment :)
It was a fun thought experiment anyway.
Dwight