This turntable was described by Jacques Marteau in the french
revue L'Audiophile n°37 (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 ...
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.
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.
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.
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.
Beautiful and effective ...
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:
