12 Jun
2013
12 Jun
'13
11:29 a.m.
Hm, Tony....
Sure, and there are evenb official HP scheamtics for the 7900. there is,
of course, the very minor problem that it's a twin platter drive (one
fixed, one removable), with separate secor transducers, so the
modification would have to be switched in only when the remvoeable pack
was selected. That's trivial to do.
Mod modifyign the pack is easy too. It's jsut a matter of remving the
hub, putitng it in a dividing head, careully lining up a sutiable
slitting saw with one of the existing slots, then rotatign it by 1/24th
of a turn, cutting a an extra slot, rotating it by 1/12th of a turn
cuttign another slot, and so on. And the resulting pack would then work i
nan unmodifed drive, for exampel on somebody else's machine
Actually, that is an issue with modifying the drive rather than the pack.
A modified drive can;'t read 'original' packs, and the packs recorded on
the modified drive can't be read on an unmodified drive. You cna't
exchange packs with friends unless they also have the modification
fitted.
I also need a few 24 sector packs, for an HP7900
drive. Those should be
easier to make than 16 sector ones, in that it's 'just' an extra notch
midway between the existing ones.
Hm, I will follow the electronic path for RK05
drives now.
But you could modify any drive where you have schematics for.
> You don't need a complete hub IIRC> The sectorign ring is a separate part
> fixed on by 4 rivets. It should be possible to jsut replace that.
Really? I remember the whole thing consisting of two
parts. But I
might be wrong.
I could have sworn that it was a separate part, but it looks like _I_ was
wrong. All the RK05 packs I've just looked at have the sectorign slots
cut in the main part of the hub. Oh well. I am now tying to think where I
saw a separate sectoring ring.
Makign a new hub is not goign to be easy. The 2 faces (the one that
lovates on the spindle flange and the one that carries the actual disk)
have to be very parallel. I think the tolerance on the central conical
hole it sight too, and that is too small to be able to use a boring tool
ot make it. I think you'd need a special tapered reamer.
Modifiyign the drive would thus appear to be a lot more practical for 16
sector machines. For HP 24 sector ones, cutting the extra notches seems
quite possible. I must give it a go, if I can ever get my 7900 to work again.
Be warned if you do take the bpack apart that the
platter is not
automatically centroed on the hub. You ahve to put the platter in place,
fir the clamp ring, then put the hub on a suitable spidnle and use a dial
guage to centre it up. A right pain to do...
I did it. I did not have any tools
for centering. I did it as good as possible.
The first result was too "excentric", I did it again. The drive will happily
work with a badly centered disk. But it makes too much vibrations...
A centering cone or anything alike would be great... cost
would be the programming and setup of the CNC that turns the hubs. Then
Can't anyone turn by hand any more?