Tables That Feature Bearing Friction

Dertonarm, Are you saying that the vertical magnetic suspension of the La Platine per se simultaneously offered a form of eddy current braking of the rotation of the platter in the horizontal plane? If so, why would that not also be a feature of the current version of the La Platine? (I am going to check my physics books to verify that such a phenomenon would occur, but for now I accept the principle, if that's what you meant.)

Lewm, two magnets rotating in a horizontal = planar sphere do indeed produce an eddy current field.
The Platine Verdier folks and dealers will hate me for this .......anyway:
The current La Platine does feature somewhat lower quality magnets (compared to the old Focal magnets used till 1990/91 - that particular magnet was no longer available when Focal changed to the "6-tablet-magnet" - design invented by J. Mahul for the 15" woofers in early 1991) - thats why they promoted the ball to be inserted in the top bearing shaft hollow. To stabilize the vertical movement of the platter (in mid-90ies production was a tendency to instable magnetic field and often in loss of magnetic force causing many Platines in europe (and I suppose elsewehere too) to "oscillate" (= being unstable in height of platter)). To solve this problem the "top ball bearing shaft" was introduced (well, the hollow was there before, so they just put in the ball - smart move). That particular problem never occured with pre-1991/92 Platines. However the eddy current brake effect is no longer as dominat as it was in the original version with much better and more homogenous magnets.

Thanks. Very interesting, indeed. I do recall hearing rumors about La Platine platters "falling down", due to loss of magnetic field strength, but none of my (two) friends who own the table have had that problem. There are a few other brands that now sport magnetic suspensions, but as far as can tell from photos, none of those has magnets of nearly the same size as found even in the current La Platine. Nor are the platters as massive.

As to my knowledge all La Platine Verdier sold after 1995 do already feature the ball supported bearing. So those can't actually "fall down", as the vertical position is already determined by the ball bearing and no longer by magnetic force. The Platine verdier was imported and introduced to the USA fairly late (it was originally a DIY-project presented in french L'Audiophile magazine (with detailed schematics and description how to built) in the late 1970ies and the first offical built retail version was tested in summer 1980 in a german magazine). I do not know, whether there were any Platines delivered to the USA via the offical importer before 1995.

Thanks for qualifying your position, Dertonarm. I understand now that you are referring to a specific approach taken by Verdier. That approach as you have outlined it does seem to be unique, but costly and hard to control from a manufacturer's point of view. As you documented there were other issues with this approach, so perhaps it wasn't all that to begin with. Seemed to be a good idea.

The eddy current breaking is a solid, proven approach. The problem is that it still seems to be beyond the financial means of most of us, so we are left with belts or idlers. To Chris's point, the non-compliant mylar belts and lower torque motors do sound very good. This type of belt along with a decent control mechanism can provide speed stability that is better than most belt drives and I believe it is very close to your average idler. I suspect this is because we are starting with a no-cog DC motor and the mylar provides a much tighter coupling to the platter than any stretchy belt. But that is going off on a different topic.

If nothing else this discussion should show that the designer must take the entire drive chain into consideration, regardless of whether the bearing or motor is chosen first. They still have to work together to produce a speed stable platform.