Hi Me and my friend is starting a project to building a flywheel system with aim for energy storage. This is a small budget experiment to see how long flywheel can hold energy with our design. One problem we face is finding a suitable motor, we plan to use induction motor to avoid eddy current lose, but most of the induction motor under 1kW has max rpm around 3500, a bit low for our purpose. Is there cheap induction motor that can deliver 6000rpm or above? provided we can ignore bearing friction, can we ramp up rpm by increasing drive frequency? Also, we plan to rip out original bearing of the motor and connect the motor rotor to flywheel rotor with a shaft, both inside a vacuum. Would there be a heat dissipation problem to this approach? Since I'm new to all this, any help would be appreciated.