[Coco] STATUS - Re: Resurrecting a CoCo (26-3001) with a 26-3029 FDC.

[Gene Heskett]

On Sunday 14 September 2008, wdg3rd at comcast.net wrote:
>Does anyone have any details on how to fabricate new head load pads?  It's
> not so critical for my 5.25" drives (I have several spare drives), but the
> 8" CDC drives on my TRS-80 Model 2 really need replacements, and that
> machine is older than any of the parts managers at the computer stores
> around north Jersey. --
>Ward Griffiths    wdg3rd at comcast.net

An old felt hat might have the raw material if its thick enough.  Or check the 
sewing stuff's shelves at Wally World for those little green dots with waxed 
paper covered contact cement on one side, intended for bottom of furniture 
foot padding.  I don't have any idea if that glue will be good long term, but 
its worth a try.  I put some larger versions of that made from a coarse brown 
felt, at Lowes in sheets about 1/8" thick, cut to size, on the bottoms of the 
legs of the gun cabinet I made last year, and they have stayed in place well 
as I've slid it around on an engineered hardwood floor. 30 years from now?  
No way to tell and I doubt I'll be here to check.

I think those may also have had a drop of some almost wax-like lubricant 
melted into them to reduce friction, but that thought doesn't come with any 
real recommendations.  A small sliver of paraffin laid on it, and a hair 
drier used to melt it in till it disappears might be the general idea.  You 
do NOT want it to wet the disk surface cuz that will raise the friction of 
its turning inside the sleeve.  Any 8" disk today will turn at 2 or 3 times 
the torque it took 30 years ago anyway.  Just as in videotapes, they should 
be stored cold & at very low humidity.  Hot, high humidity conditions 
multiply the abrasiveness of the coatings many times.

You'll also have problems from the hub rosette in those drives, they shrink 
and warp with age because of the pressure applied when closed, this results 
in both reduced drive torque as the disk can slip, and poor disk centering, 
causing both edge damage to the disks holes, and eccentric tracks that a 
stepper driven head positioning system cannot track.  So those drives are 
best parked with the disks removed and the levers 'open'.  And generally, 
using only disks with hub reinforcement rings.  If you have stuff on 
un-reinforced disks, I would attempt to back them up to disks with the hub 
rings.  If you can lay the drives down so that the pressure rosette enters 
the disk from below which would take gravity out of the picture, you may be 
able to read even disks with damaged hubs.

As for replacement rosette's?  Today I expect you would have to have them made 
by a friendly machinist, I think I could make one out of HDPE if I had to.  
And I don't think I'd cut the fingers in my version, I'd just machine to size 
with a taper on the entry side.  Much stronger that way.

Good luck, Ward.  Those drives were the single biggest reason we retired an 
old character generator 15 years ago, even after I had replaced both of them 
with double sided Shugart's with direct drive spindle motors.

-- 
Cheers, Gene
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