OT: Archiving data/video/movies/photos/oral history

From: William Donzelli <aw288_at_osfn.org>
Date: Sun Jun 4 21:14:20 2000

> But plastic gears, at least the plastic gears found in consumer-grade
> stuff will crack as well due to said external forces.

Modern plastics _do_not_ suffer from mechanical and dimensional
stability. They will not just "go bad" due to age, like older plastics
and brasses.

> Perhaps I've been very lucky, but it all my years of repairing machinery
> I have _never_ found a metal gear/pulley/etc that's suffered in this way.
> Stripped teeth, sure. Wear due to lack of lubrication, sure. But not
> stress-induced cracks.

You've been lucky. Also, keep in mind that many of these cracks can not be
seen, and do lead to teeth being easily stripped.

> Yes, but the problem is that the gears in modern units are not made of
> 'today's brass'. Or 'yesterday's brass'. They are made of today's
> plastic, often a cheap-n-nasty plastic. A plastic that cracks if you look
> at it wrongly, if it gets one drop of oil on it, or whatever.

No! As stated before, modern plastics are not cheap-and-nasty. In 50
years they will be the same as they are today. If gears are used
improperly, maybe beyond their capabilities (too thin, poorly formed
teeth), that's a design issue, and they will wear out. So will the finest
brass gears. But my last point about using a found CD-ROM 50 years from
now in fairly _unused_ condition is important, as any wear inducing design
flaws will not have been given to chance to work their evil.

> Yes, that is the issue. We're considering what will be available in 50
> years time (or whatever). And most consumer-grade stuff simply won't be.

Certainly it will, it small caches (or singles) found in warehouses,
estate sales, hackers that never threw the stuff away, etc.. No, they
probably won't be so common that they could be found in days in any city,
but they will be far from unobtainable.

> Perhaps you can name a single CD-ROM drive that's built with 'today's
> brass' and 'today's stable plastics'. And which comes with as much
> internal data as you find in 60-year-old Hallicrafters/RCA/etc repair
> manuals.

If the things work (or most of them - hell, even if the survival rate
is just 10 percent in 50 years), no repair manuals will be needed. If you
get a bum unit with no manual, go to the next one and see if it works.
You will get a good one.

> Again you're missing the point. I don't doubt that an expensive unit
> today would last even longer than the 28 years that my N1500 has gone.
> But there simply aren't any such units about (Every VCR I have looked in
> recently has had a much poorer build quality than that N1500). There may
> be a few 'professional models that will last, but from what I've seen of
> other equipment, I doubt that.

You have to compare the N1500 to today's high end and professional
models, and not the regular stuff. Your N1500 was far from "commercial
grade made for the masses".

> It very much is the issue if you want a workign unit in 50 years time.
> Nobody realistically expects to take a 50-year-old unit off the shelf and
> turn it on. We expect to have to do minor repairs.

And why will all 50 year old CD-ROMs go automatically bad? Will it be
because of the materials of the chassis changing? Well, no, not really.
Will it be because of the chips going bad? Well, some will, but certainly
not all (no fineline geometries here). Will it be because of corrosion?
Well, certainly some, but many will be found in a stable environment. Will
the lubrication go bad? No, modern lubricants are very stable (easy to
change, anyway). Will the motor go bad? Probably not - motor technolgy is
quite mature.

So exactly what do you think is the aspect that will damn all CD-ROMs to
a broken state 50 years from now?
 
> Well, while it may take a lot less time to change one ASIC than to recap
> an old radio, I doubt it's going to be as easy to get the parts.

If they are not bad, why replace? Why assume that every chip will have
gone bad?
 
> You seem to think that old brass gears in the tuning drive of said old
> radio might well develop stress cracks. You're probably right. But
> cutting gears is well within the capability of a well-equipped home
> workshop. Makeing undocumented ASICs certainly isn't.

There will be plenty of donors.

> Seriously, what has that got to do with it? Running the unit may cause
> wear on mechanical bits, but surely it shouldn't start a process that
> causes the unit to die, any sooner than it would have done, when powered off
> and packed away. If it does, then why doesn't the factory burn-in test
> start this decay process?

The decay due to time alone is getting _very_ minimal, thanks to the modern
materials. Use is the thing that will kill these units, far faster than
time alone. "No use" results in "very little decay". "Daily use"
results in "quick fatigue".

William Donzelli
aw288_at_osfn.org
Received on Sun Jun 04 2000 - 21:14:20 BST