Talk:Flywheel

Flywheel Material
What is the flywheel made out of will you please tell me Because I have to do a report on it. So if you can send more information on the flywheel.

There is no one "flywheel material". A flywheel's inertia depends on both the mass of the matrial used to create it, and the distance of each piece of material from the centre of rotation. So, for say a backup power generation application (where the flywheel stores kinetic energy which can later on be used to generate electrical energy) a design using a heavy material with the mass concentrated far away from the centre is preferable.

However, by moving the mass away from the centre, the tensile strength needed to hold the material in place (and stop the wheel from ripping itself apart) increases. Note that in the animated GIF currently on the page most of the mass is concentrated in the flat rim on the edge of the wheel. Additionally the wheel has most of the material in between the 'spokes' removed, which lightens the wheel by removing mass where it is least effective (i.e. closer in to the centre )

--202.159.206.45 09:58, 19 November 2005 (UTC) Why do we call a flywheel, a flywheel?--202.159.204.26 15:47, 27 October 2005 (UTC)

Please Help!
Can anyone explain The Flywheel Theory to me in its simplest terms? I am really trying to understand the basic idea behind it so that I can compare it to being a sales rep. Any explanations offered would be greatly appreciated Thanks.
 * A flywheel requires some impetus to get it going, the same applies to a sales rep.Gregorydavid 00:13, 20 March 2007 (UTC)

A flywheel in its simplest form is essentially a mechanical device that stores rotational kinetic energy when it gets it, and releases it when it is required.For example in a simpe 1 cylinder engine, the crank shaft rotates 180 degrees when the piston moves down (caused by the fuel ignition), during which the flywheel stores some of the energy. In order for the piston to move back up,the energy which was stored in the flywheel is now used.

Sandpit
I cut this error from article. Gregorydavid 00:02, 20 March 2007 (UTC)

i dont know what a flying wheel is. sorry people

Disambig
I have removed the link to pitch in the following sentence:

"...A vehicle with a vertical-axis flywheel would experience a lateral momentum when passing the top of a hill or the bottom of a valley ( roll momentum in response to a pitch change).."

This is to reduce links to disambiguation pages. Hopefully one of you wise people who know which pitch it is referring to can either let me know which it is, or correct the link to the appropriate pitch! =) Marc 09:20, 11 May 2007 (UTC)

Overlapping Image
The white flywheel image overlaps some of the text of the preceding paragraph for me. If I weren't going to bed right now I'd fix it. 202.10.86.59 15:42, 12 June 2007 (UTC)

Leonardo Flywheel
The Leonardo flywheel is more interesting than the former caption told, so i changed the wording. As the balls fall down from lower centripetal force, the I of flywheel structure decreases as r^2, so that the rotation rate decreases much more slowly than in a rigid design, as sqrt(E/r^2) instead of sqrt(E) where E is the remaining energy in the flywheel.

Please help!
If a flywheel is attached to a generator,the generator's torque is effected,especially at the start of torque,isn't it? —Preceding unsigned comment added by 218.249.29.234 (talk) 07:23, 16 September 2008 (UTC)

main purpose of flywheel
this is used 4 balancing

EnergyCalculations
Hey,

did anyone check these? I find an factor 4 from diameter squared instead radius squared and another 10...

Bye —Preceding unsigned comment added by 82.238.217.104 (talk) 16:16, 26 January 2009 (UTC)

I LIKE THIS —Preceding unsigned comment added by 194.50.118.230 (talk) 13:25, 6 May 2009 (UTC)

I have added and mass in the following section:
 * For a given flywheel design and mass, it can be derived from the above equations that the kinetic energy is proportional to the ratio of the hoop stress to the material density.
 * $$E_k \varpropto \frac{\sigma_t}{\rho} $$
 * This parameter could be called the specific tensile strength. The flywheel material with the highest specific tensile strength will yield the highest energy storage.

My understanding are that the maximum energy stored is proportional to the volume and the tensile strength. For a given geometry it is independent of the mass and density but for a given mass it is then of course inversely proportional against the density. The maximum energy stored are of course also dependent on the geometry, with a maximum for a thin walled cylinder. For a given geometry (fixed shape and volume) and tensile strength the maximum centripetal force per unit of volume is fixed. The energy and the centripetal force both increase with the square of the velocity so for example four time the density gives half the velocity but since the energy is mass times velocity squared the energy is the same. I still think the section is unclear and misleading, I hope some one finds a better wording. Gr8xoz (talk) 16:30, 27 March 2010 (UTC)

Rimmed flywheels
I've cleaned up this section some, but I sense that the entire section belongs elsewhere (i.e., in a different article). Lambtron (talk) 19:19, 5 October 2011 (UTC)


 * I agree. In case you're not aware there appears to be a group of Indian students who've been told to add stuff to WP and have been copy-pasting lots of stuff with little guidance. Much has already been reverted as copyvio (e.g. Band brake). DexDor (talk) 19:29, 5 October 2011 (UTC)

Blanked all IEP edits
I have blanked all the edits made by WP:IEP students on this page, as they all seem to be copied from textbooks. This is part of an ongoing effort to clean up the IEP edits. The students (

,,, for this page) have been notified. Manish Earth Talk •  Stalk 04:39, 28 October 2011 (UTC)

Thick-walled empty cylinder
It used to read "I = (1/2) m (rexternal^2 - rinternal^2)", I changed the - sign into a +.

Reasoning behind the - sign would have been that "whether you shave some material off the inside or the outside, the difference rexternal^2 - rinternal^2 decreases, so I decreases, and that's what actaully happens."

However, that reasoning looks wrong to me. First, the shaving would lower m, and second, if you set rexternal = r, rinternal = 0, you do get the solid result of I = (m/2) r^2, but if you set rexternal = rinternal = r, you get I = 0, not the thin-walled I = m r^2. The + sign would give the correct result.

This is only a semi-educated guess. Can anyone check the formulae please? - ¡Ouch! (hurt me / more pain) 08:57, 8 November 2011 (UTC)

This isn't right. You have to subtract the empty part of the cylinder from the outer dimension as you would when calculating the definite integral. I've put the formula back accordingly. Daniel Hooper~enwiki (talk) 04:00, 18 May 2022 (UTC)


 * @One.Ouch.Zero is correct, it is a + and not a -, see http://hyperphysics.phy-astr.gsu.edu/hbase/ihoop.html. You can also calculate the integral if you need to be convinced ;) I corrected the formula accordingly. 212.126.165.68 (talk) 14:26, 2 February 2023 (UTC)

Theoretical Energy vs. Manufacturer's Specs
The table in the "Examples" section is misleading since it uses a theoretical maximum energy capacity, rather than the actual energy capacity of the devices which it references. For instance, the actual energy capacity of the last flywheel is 3000kW-sec, or 3MJ (found here) — Preceding unsigned comment added by 173.246.15.78 (talk) 01:31, 6 December 2011 (UTC)

Misuse of sources
This article has been edited by a user who is known to have misused sources to unduly promote certain views (see WP:Jagged 85 cleanup). Examination of the sources used by this editor often reveals that the sources have been selectively interpreted or blatantly misrepresented, going beyond any reasonable interpretation of the authors' intent.

Please help by viewing the entry for this article shown at the page, and check the edits to ensure that any claims are valid, and that any references do in fact verify what is claimed.

I searched the page history, and found 6 edits by Jagged 85 (for example, see this edits). Tobby72 (talk) 16:14, 19 January 2012 (UTC)

Engine flywheels
I have heard that a flywheel that spins at double the engine's speed absorbs imbalences in the engine components (you can at least mention this use). Because there are some inefficiencies with this method, there is a certain car company (at least the one i guess) that uses a combination of flywheels at different RPMs to attain the same effect - how does that work? Charlieb000 (talk) 17:15, 2 April 2015 (UTC)


 * A flywheel is axially balanced (it's a symmetrical wheel). If it isn't, deliberately, then it's a balance weight not a flywheel. A flywheel absorbs rotating oscillations and transients, but it can't do anything about linear vibrations. To reduce torsion transients even more, there are now dual mass flywheels.
 * I think you're thinking of the balance shaft used in a few four-cylinder engines. These engines do have a vibration component that's at twice the crankshaft speed, which can be compensated by a shaft with an eccentric weight on it, running at twice crankshaft speed. This in turn introduces a sideways vibration! The latest idea is the system used by Audi for the VW TDi engine, which has a pair of counter-rotating balance shafts geared together. These still compensate for the vertical vibration, but balance out their own sideways addition.  Unfortunately Audi screwed the engineering of a minor component within this and they fail expensively at 60k miles, often destroying the engine. Andy Dingley (talk) 17:45, 2 April 2015 (UTC)

Juggernaut.
This article also should speak of the dangers of flywheels. If the bearing seizes or the pedestal gives way, the rotor of an industrial-sized flywheel or motor most literally turns into a Juggernaut, that is godess Khali's unstoppable war chariot running amok. The rotor of an electric locomotive's motor-generator set gladly ruins the whole factory building, if it breaks free during full power test (did happen at Ganz-Mavag Hungary). Possibly worse outcome than a boiler explosion, if we compare with steam locomotives, but happens less frequently.

Allegedly, a carbon-in-vacuum flywheel proposed as an alternative for battery-based KERS for family sedans, couldn't withstand the designed 60k RPM and exploded at Volvo during tests and then the chassis looked like as if hit by an IED. 82.131.132.180 (talk) 21:00, 25 April 2015 (UTC)
 * This sort of safety aspect is another reason for the use of vacuum. With a vacuum flywheel system it's possible to use contra-rotating flywheels mounted very close to each other, without windage problems. This cancels out their overall momentum, so that a catastrophic failure destroys itself in-place, rather than turning the housing into a spinning projectile. It also allows them to be fitted with brake surfaces. If there's a partial failure of the bearings, contact between them can dissipate energy as localised heat (destructively), rather than releasing it around the test cell as kinetic energy. Andy Dingley (talk) 21:19, 25 April 2015 (UTC)

Fitness applications
I have seen flywheels described as being incorporated into fitness machines like rowers (horizantal pulls) or for pulling down/back the 'ski-erg'. I am wondering if a section explaining fitness machines for cardio or strength/endurance for arms and such could be created. Not sure what references could help build it. Seems like a good alternative for people with leg injuries or movement restrictions. Ranze (talk) 23:53, 25 May 2015 (UTC)

Table of energy storage traits
Very difficult to understand what this section means, why should a battery have an angular velocity? I propose to include a table to compare maximum energy densities, Oscar

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1 g, 1.964 m radius flywheel?
Can we think of more realistic flywheels, please? Darsie42 (talk) 10:16, 19 June 2019 (UTC)

Team-B-Vital Improvement Drive
Hello all!

This article has been chosen as this fortnight's effort for WP:Discord's #team-b-vital channel, a collaborative effort to bring Vital articles up to a B class if possible, similar to WP:Articles for Improvement. This effort will run for up to a fortnight, ending early if the article is felt to be at B-class or impossible to further improve. Articles are chosen by a quick vote among interested chatters, with the goal of working together on interesting Vital articles that need improving.

Thank you! Rema goxer (talk) 22:00, 13 May 2022 (UTC)


 * Remagoxer, sure thing! CactiStaccingCrane (talk) 08:56, 14 May 2022 (UTC)

India Education Program course assignment
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