Tape Drive & Tape Archival questions...

[Tony Duell]

> > Can you recomend any places to start looking (usual disclaimers, of 
> > course). I collect names of companies that sell useful stuff for 
> > hacking/restoration.
> 
> I just go to one of the local electronic stores.  They have

You're lucky to have a local electronics shop, and it sounds like you 
have more than one. 

> a wall display of assorted belts, each individually packaged
> (to justify the price?  :< ).  Of course, they have no information
> as to *applications* so it is wise to know what you are looking
> for before walking in.

Again, you're lucky. Over here, there are companies who sell 'belt kits' 
for particular models of VCR, with no information as to the sizes of the 
belts each kit contains. Great if you want to fix that machine, not so 
good if you want a belt for something else. I don't know of any place in 
London that will let you match up a belt (or who will supply a belt by 
dimensions).

> > FWIW, there's a program in the HP67 Mechanical Engineering Pac (which 
> > will also run on the HP41 series with a card reader) that calculates belt 
> > length given the diameters of the pulleys and the coordinates of their 
> > shafts. It assumes the belt goes round the outside of all the pulleys, it 
> > gets the wrong answer if one pulley is outside the belt (which would be 
> > done if that pulley needs to turn the opposite way)[1].
> 
> The problem with many of these belts is they usually ride in
> a groove cut in the circumfrence of the pulleys.  It seems
> like the depth of that groove is typically half the "diagonal"
> thickness of the belt (assuming a square cross section)

Sure. But doesn't that imply that the centreline of the belt lies on the 
circumference of the pulley? Which means that said program would 
calculate the correct size of belt (assuming it's measured around the 
centreline).

In any case, for the sort of belt we're talking about here, there should 
be enough 'stretch' to get it to fit.

> 
> So, one more bit of math involved.  It's often easiest to bring
> an old belt -- even if broken -- since the packages are

I've had blets turn to a sticky rubber blob (like the rollers in the 
other thread), then you can't match it up.

-tony