LGP-30 Memory Drum Update

allison ajp166 at verizon.net
Wed Jan 4 16:43:36 CST 2017

On 01/04/2017 03:50 PM, Paul Koning wrote:
>> On Jan 4, 2017, at 2:48 PM, Kyle Owen <kylevowen at gmail.com> wrote:
>> On Wed, Jan 4, 2017 at 12:06 PM, Jon Elson <elson at pico-systems.com> wrote:
>>> Previous messages suggested the LGP-30 drum was plated with nickel. If
>>> there are amateur astronomers with a vacuum evaporator, it might be
>>> possible to get them to adjust their setup slightly to vacuum evaporate
>>> nickel on your drum, after refinishing the base.  You'd need a rig to
>>> slowly turn the drum while evaporating the nickel. Some other research labs
>>> at universities might have the necessary equipment, also - check with the
>>> Physics department (or electrical engineering).
>> Will the desired thickness be enough with sputtering or evaporation? For
>> modern hard drives, sure, but my gut instinct is that you'd want a thicker
>> coating on the drum. I'd suggest sputtering over evaporation since it will
>> probably adhere to the surface better. I'd think nickel electroplating
>> would take less time and effort, though.
> Electroplating sounds ok, I don't know about procedures.  You'd have to be careful that the electrolyte doesn't damage the drum body.
> Evaporation and sputtering are used to make well controlled thin films, but there's nothing I can think of that limits how long you continue.  A mirror is coated only to the point that its reflection coefficient reaches the limit of the metal used, more is not useful.  But here you could just keep going however long you need.
> As for adhering, both should produce good coatings if the substrate is clean.  I remember a test for good evaporative coating technique: coat a test piece, then try to rip off the coating with scotch tape.  It shouldn't be affected at all by that test.
> There are reasons for using sputtering vs. evaporation, but I don't remember them.  I think the Strong book I cited discusses the subject. 

Several things.  Getting aluminum clean and keeping it so means NO
oxygen, it develops a
oxide coating really fast.  Other metal might be used but your generally
limited to non magnetic
substrates (aluminum, glass, brass, bronze).

Also the thickness of the magnetic media, rate of travel (speed relative
to the head),  head
distance and gap are all interrelated. For heads of that era the gap
will be wide, the media
thick, and the rate of travel high.  Those factors determine bit density
(likely very low) and
the data rate is really low as the machine is slow.

If the drum is scratched then moving heads one gap width right or left
should do fine.

Plated media doesn't help with this save for its mechanically easier to do.


> 	paul

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