# RPM of a Flywheel

## Main Question or Discussion Point

Hey guys, new to the forum. I am wondering how to find what the maximum rpm of a flywheel could be. I was looking at stirling engines, and trying to compile all the equations that apply to calculate the rpm of the engine. I know the equation for the expansion of gas in the cylinders and the force applied to the pistons, however I know that as the flywheel starts turning, the energy carried with it and the continued force applied builds upon eachother until it reaches its maximum rpm. Excluding the impact of friction and drag, I was wondering how you calculate the max rpm.

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russ_watters
Mentor
Welcome to PF!

I'm not sure you're asking the right question: excluding friction and drag, there is no maximum rpm for a flywheel. But why would you even care about that? Are you looking for the power output of the engine? It is a completely separate issue...

Wow, gotta say, feeling pretty dumb right now, didnt even realize that until I wrote it out. And yes. I though if you were to hook stirling engine to sone type if generator, that the speed the motor rotates plays a factor.

Doug Huffman
Gold Member
The maximum revolutions per minute of a flywheel is the rpm when the flywheel flies apart.

CWatters
Homework Helper
Gold Member
http://www.ctgltd.com/product/flywheels

The fastest flywheel CTG manufactures has a rotational tip speed in excess of an incredible 1,000m/s!
Not sure if this is out of date but...

http://www.guinnessworldrecords.com/world-records/fastest-rotating-flywheel/

The fastest rotational speed for a ring or disc-shaped object was achieved by scientists at Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA, on 9 December 1985. Using an air turbine, the Demo 1C flywheel was spun up to a tip speed of 1405 m/s (5,058 km/h 3142.9 mph), at which speed it failed due to the stress on the materials involved.
5000 km/h is about four times the speed of sound.

Not exactly a flywheel but...