ard at p850ug1.demon.co.uk
Wed Sep 7 10:56:32 CDT 2016
> The other question is the disassembly of the pack and the installation
> of the new hub. How is that done? What are the concentricity
> requirements for the platter? Is there a mating surface (exterior cylinder
> surface on the hub) or are platter and hub aligned in some fixture and
> then clamped to hold the platter in position? Clearly the pack would be
> reformatted, so a small amount of runout would be ok, but it would have
> to be small enough that the vibration is controlled.
I looked into this a couple of years ago with the intention of making
a 24 sector pack for an HP7900 (actually part of an HP9880). Starting
from a 12 sector pack of course.
This project got interupted by a house move and I've not gone back
to it yet, but I did discover there is no alignment ridge or anything
between the hub and platter. The platter fits on the flat top of the
hub, there is a clamping ring that is then screwed down to anchor
My intention was to put the hub on a spare spindle (I happen to
have a load of RK05 drive spares), put the platter on, turn it round
by hand and use a lever-type dial gauge to get minimum run-out.
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