Old, but not "Classic"

From: jpero_at_pop.cgocable.net <(jpero_at_pop.cgocable.net)>
Date: Thu Nov 12 16:31:50 1998

> Date: Fri, 13 Nov 1998 01:30:35 +0000 (GMT)
> Reply-to: classiccmp_at_u.washington.edu
> From: ard_at_p850ug1.demon.co.uk (Tony Duell)
> To: "Discussion re-collecting of classic computers" <classiccmp_at_u.washington.edu>
> Subject: Re: Old, but not "Classic"

> >
> > < > technologies. (FWIW, I found out that zip drives uses shappire
> > < > bearings to carry the heads, that is from newsgroups so don't take
> > <
> > < Is there any particular problem with jewelled bearings? Watchmakers have
> > < been using them for centuries, and the methods of making and installing
> > < them are well known and documented.
> >
> > They been used in analog meter movements of quality for over 40 years
>
> Longer than that, actually. They were used on the compass needles of some
> tangent galvanometers :-). That probably means they've been used on
> electical meter movements for getting on for 100 years at least.

I'm Horology buff and this jewel thing, even longer time than many
think about 300 years. Jewelled movements is VERY desireable than
having anything else using hardened steel pivots in hammered-hardened
brass bearings. Before around 1925 my guess crimped in loose jewels
but after that, pressed in jewels. That technology was possible when
jewels can be ground perfectly round and parallel sides with hole
exactly in the centre, jewel material much stronger and purer than
native jewels full of flaws and cracks easily. You can do hand
install those pressed in jewels. I did that few times.
Ball/roller bearings is another best bearings for some specific uses.

> Of course some quality meters used taught-band suspensions instead of
> bearings.
>
> > and I've repaird them. Not much majik. They are a good precision low

I echo that, no majik there.
 
> No majik at all. There are plenty of books on watch repairing which
> describe the construction, installation, etc of jewelled bearings. I've
> never done it myself, but it's not something that is exactly new technology.

Correct I have few books on this including the old style repairing.

>
> > friction bearing. However I doubt they would be used in a ZIP as they
> > never had a good reputation for shock resistance. they would however be
> > low drag and help conserve power.

Not the that, your both statements is right and would might make
sense because that head bearings would shatter if the drive is
dropped and jewels can be made more closer in tolerences and last
long time. Can't do that with bushings at all, hint: WD,
miniscribes and few brands that used that.

>
> Yes, but in a desktop machine, power is not exactly short. In other words
> whether it takes 0.1W or 10W to move the heads is not a major
> consideration. So a jewelled bearing is probably not appropriate here.

I think less friction is best to give best tracking and seeking with
what little power you can use. This drive is sucking less than 500mA
at run time. 1A is surge current to kickstart the spindle,
unlock/undock the heads. Remember, that zip was designed to have
battery power when it first came out and might be still true.
 
> Jewelled bearings have 2 advantages. Firstly they are low friction -
> important in a watch escapement (where friction -> timekeeping errors) or
> a meter movement. And secondly they are accurate - the spindle runs true,
> but a good metal bush bearing can do that as well. Neither are major
> problems in a desktop servo-tracked disk drive.

Don't forget the bearing wear is extrended to hundreds years than
just plain brass and steel but perfectly fine in well designed gears
because they only rolls into and out together. Spindle still use
ball bearings not jewels! Hehehe... But those babbit and steels does
their job just fine because lube kept 2 parts by wedge action apart
becaues of lube pressure and high enough rpm. Think: skating
happens because of that water layer between ice and steel.

I had to rebuild brass bearings types in anything and often those any
movements not *that* old even younger than me! Time waster and
murder on those steel pivots. In worst cases that simply wore out to
a thin stem with a mushroom head that breaks off! Dress the steel
pivots and burnish them, dry polishing with a hard burnisher stick,
hand ream out those worn holes to size to accept the pressed in brass
bushing then ream the pivot holes to size that only allow less than 5
degree wiggle or jewels if desired. The ream tool is 5 sided with
sharp edges long, slow taper made of hard flexiable tempered steel in
many sizes.

>
> > Allison
>
> -tony

Jason D.
email: jpero_at_cgocable.net
Pero, Jason D.
Received on Thu Nov 12 1998 - 16:31:50 GMT