The limitation of flywheel speed mostly depends on the tensile strength of the material in the wheel and the density. So if the wheel is enclosed in a vessel which is highly pressurised, say with air*, the pressure will compress the flywheel and reduce the apparent tension. That means it should be able to spin faster without distruction.

*I originally thought of superfluid Helium (friction-less), but that only goes up to about 25bar... not enough. And it is only friction free up to a certain velocity.
-- Ling, Mar 01 2016

If the environment is non-frictionless, then the flywheel will get hotter even before you spin it up to a higher-than- normal speed. Hotter materials tend to be less strong than colder materials.... (Colder materials tend to be more brittle, but that is actually related to a different thing, "toughness", than "strength".)
-- Vernon, Mar 01 2016


Wouldn't a fluid be the best for this?
-- bungston, Mar 01 2016


This is actually (contrary to my first reaction) not such a dumb idea.

However, you'd need fearsome pressures to have any significant effect, and I suspect the greatly increased drag would offset any advantages.

For instance, the tensile strength of good steel is something like 1600MPa. If you had a pressure of 160Mpa (1600 atmospheres), you'd get a 10% increase (and a ~5% increase in maximum speed), although the liquefaction of the gas would be a bit of a problem.
-- MaxwellBuchanan, Mar 01 2016


Instead of pressure from external gas could one use a fixed magnet for a flywheel, with an external fixed magnet around it opposing the field from the wheel? The field from the external magnet should oppose the centrifugal force which wants to pull the wheel apart. It should not slow the rotary motion.
-- bungston, Mar 01 2016


Again, the forces you could apply would be very small compared to the existing tensile strength of a steel flywheel. As mentioned above, getting only a 10% increase in the effective burst-force of the flywheel would require applying an external force of 1600 atmospheres, or about 12 tons per square inch.
-- MaxwellBuchanan, Mar 01 2016


Alternatively, you could use Schrodinger's Flywheel to store infinite amounts of energy.

If the flywheel is utterly isolated from the rest of the universe, it has no rotational reference. Hence, it can spin at an infinite rate without experiencing any centripugal forces, just as a rocket, when cruising, experiences no acceleration.

Of course, getting energy in and out of the system would be tricky.
-- MaxwellBuchanan, Mar 01 2016


Or, just spin the universe really slowly. With its huge inertia it ought to store a few Joules (x10^alot).

One of my old ponderings: If I fire little thrusters to rotate my spaceship, and set the frame of reference as my spaceship, then I am rotating the universe? Since I input so little energy this cannot be so. The other way to tell is that I am flung to the outside of the spaceship. How does my spaceship know the universe is there?
-- Ling, Mar 01 2016


//If the flywheel is utterly isolated from the rest of the universe,// and all the parts of the flywheel are utterly isolated from each other, even at the sub-atomic level, it can neither experience any forces nor have the experience of being a flywheel.
-- lurch, Mar 01 2016


//If the flywheel is utterly isolated from the rest of the universe, it has no rotational reference.//

I don't think that's true - I think anything anywhere other than on the rotational axis would feel an apparent force ('centrifugal force').
And there's an experiment you can do with a bucket of water as a demonstration.
-- Loris, Mar 02 2016


If the parts are isolated from each other I think the essential flywheelness disappears.
-- bungston, Mar 02 2016



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