Max RPM of a Flywheel: Calculating Friction & Drag-Free

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    Flywheel Rpm
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Discussion Overview

The discussion revolves around calculating the maximum RPM of a flywheel, particularly in the context of Stirling engines. Participants explore the implications of excluding friction and drag in their calculations and consider the relationship between flywheel speed and engine power output.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the maximum RPM of a flywheel while excluding friction and drag, suggesting that energy builds up as the flywheel turns.
  • Another participant argues that without considering friction and drag, there is technically no maximum RPM for a flywheel, questioning the relevance of the inquiry.
  • A later reply acknowledges the initial misunderstanding and connects the flywheel's speed to the power output of a Stirling engine when coupled to a generator.
  • One participant states that the maximum RPM is defined by the point at which the flywheel would disintegrate due to centrifugal forces.
  • Several contributions provide examples of high-speed flywheels and their recorded tip speeds, highlighting the extreme limits of flywheel technology and the conditions under which they fail.

Areas of Agreement / Disagreement

Participants express differing views on the concept of maximum RPM without friction and drag, with some suggesting that it is a non-issue while others provide examples of physical limits based on material failure.

Contextual Notes

Participants discuss the implications of excluding friction and drag, but do not resolve the mathematical or physical assumptions underlying their claims. The conversation includes references to specific high-speed flywheel records, which may not be directly applicable to the original question.

JakeMLaBonte
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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 each other 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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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, got to 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.
 
The maximum revolutions per minute of a flywheel is the rpm when the flywheel flies apart.
 
Google found..
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...
http://www.cnet.com/uk/news/fastest-man-made-spinning-object-clocks-in-at-600m-rpm/

Scientists at the University of St. Andrews in Scotland spun a man-made sphere of calcium carbonate at 600 million revolutions per minute.

The sphere was only 4 micron in diameter so although it was doing 600,000,000 rpm the tip speed was only 125m/s.

Edit: I'll let someone work out the g-forces.
 

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