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Turntable, platter floating on mercury

This turntable was described by Jacques Marteau in the french revue L'Audiophile n37 (Winter 1986).
Heavy platters have many advantages like a big inertia which gives low wow and flutter and a low resonance frequency. The counterpart is the extreme pressure reached by the contact point of the axis. To overcome this problem, the steel platter floats on mercury and is self-centered through a particular usage of its belt.
The idea came after observing in a lighthouse an enormous Fresnel lens weighing two tons that turns easily while floating on mercury.

Warning: mercury is dangerous when swallowed or inhaled (like water, mercury gets in air and this could be very dangerous in a closed ambients). 
Although this project seems interesting, I strongly advise you NOT to build it. 
Mercury is also extremely polluting for the environment. 
Pay attention to your jewels, mercury dissolves gold ...

Platter support

The steel platter floats on the mercury. To avoid dangerous mercury vapours, a thin layer of liquid paraffin is deposited on the mercury. The buoyancy calculation is not straightforward, it's quite difficult to obtain the expected result at the first attempt.

Platter centering

The floating mat can move freely on the mercury's surface. To avoid this problem, an auto-centering system was designed.
The identical pressure of the belt on four opposite points, centers it.

The first prototype used bearings but they did a disturbing noise even under small lateral forces.
The belt has a 5mm diameter and the contact "points" are 5cm wide.

Platter section

Steel was chosen because it does not react with mercury. The upper-side of the platter is made of aluminium to avoid magnetic influences with the cartridge. The platter weighs 25kg.

The Turntable without its platter

In the next picture, you can see the tank and the various cylinders containing the power supplies and the engine.
The cylinders and supports are grooved and filled with lead for a heavier weight and better damping.

The Complete Turntable

Beautiful and effective ...

Another idea

A mixed solution combining a traditional axis and a platter floating on mercury can be used. That would permit to reduce the pressure of the axis contact point while maintaining a heavy mat. The self-centering system could also be completely avoided.

Another way of stopping mercury vapors by Deon Cruywagen:

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