Neumann VMS spindle bearing

[evildrome]

Hi All,

Does anyone know how Neumann constructed the spindle bearing for the platter?

I saw something on someones site (forget who) and it seemed to be a high accuracy, plain oil lubricated bearing.

I get how that works but not how it could be driven from below like on a VMS.

Or VMS's work a totally different way?

They are direct drive from below, right?

Cheers,

Wilson.

[opcode66]

It is a standard bearing. Relatively large. I have a spare. I can take measurements if you like.

[evildrome]

Thank you, that is a very generous offer but for the moment I was just interested in the type of bearing.

I would have thought any normal bearing would be avoided due to ball / roller noise.

TBF I am constantly surprised by a great deal of things!

One imagines that there are two bearings? One for axial and one for thrust (platter support) loads ?

A photograph might be quite illuminating actually if you have the time.

Thanks!

Wilson.

[opcode66]

Ok. You're the expert.

I actually own a VMS70...

[evildrome]

Er...no. I'm not the expert.

That's what " I am constantly surprised " means.

It means that things are done in a way for record lathes that surprises me.

My background is in machining of large metal parts. I am used to the physics of machinery designed for high cutting forces.

As the cutting forces for record lathes are nearly negligible, the design of these machines is quite unusual (to me!).

I am, in the venacular, "a noob".

[dmills]

Indeed, I keep expecting angular contact ball or crossed roller bearings and slideways (All with significant preload), being as that is what I would be thinking for a precision lathe spindle in the machining sense, but nope, generally nothing so hardcore!

Hell I was wondering about magnetically levitated air bearing spindles, (Modern magnets are pretty much magic for this sort of thing) and an oillite brush can (if you blow the oil out of it with compressed air) make a decent basis for an air bearing given the small loads involved.

Got me wondering about what a thoroughly modern lathe would look like now, crossed rollers on both the platter and the head, or maybe air bearings on the spindle?

Maybe vacuum holddown up the middle of the bearing shaft?

Brushless AC servo drives everywhere?

Video microscope or high speed line scan camera so the computer can point out where there be problems?

LMS equalisation for linearity, record a set of tones on one blank from each batch and then pull them back into the computer so it can figure the corrections for that specific set of blanks (and how the corrections need to change across the radius)?

Fibre coupled laser heating of the record surface just ahead of the cutter?

Or way out of left field, do it in a vacuum on a silicon disk and use photolithograthy, then hydrofloric acid etch before metallisation by CVD? TI recently closed their old 5 inch wafer process line so there is bound to be kit kicking around.... It would be utterly MAD, but awesome to be making records with an upcycled semiconductor fab line!

Regards, Dan.

[evildrome]

Hi Dan,

Some interesting ideas.

I think air bearing spindles are out. I made one and it is *noisy*.

I think ball screws are out for the same reason.

I like the idea of laser heating... that definitely could work and would be very doable.

You can get cheap 15W lasers that burn wood. The question is, can you control the power output?

Do these things have an "on" voltage and there's no way to make them less powerful?

You could, I suppose make a defocusing lens arrangement to spread the heat out & blinds to stop it going anywhere you don't want.

Lots of possibilities...