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# Self-geared flywheel

A bit like a non-governing governor.
 (+2, -1) [vote for, against]

Another idea here involved a pedal-powered flywheel, and an annotation suggested that gearing would be needed to help get the flywheel up to speed.

Gearing, however, is a clunky solution. There is an eleganter way.

The MaxCo. Self-gearer Peddlable Flywheel has a relatively lightweight carbon-fibre rim. Five heavy lead weights are mounted on sprung arms, so that they sit inside the ring.

At low speeds, the spring arms keep the weights close to the hub of the flywheel, so that they have little rotational inertia. Starting the flywheel is therefore relatively easy.

As the speed builds, so the springs of the arms are compressed, and the weights swing out closer to the rim. At full speed, the weights are hard up against the rim, contributing the greatest possible moment of inertia and allowing the flywheel to store the greatest possible amount of energy.

Of course, some energy is wasted in compressing the springs but, as you ease off the pedals and the flywheel slows down, this energy is recovered and contributes to the residual spin of the flywheel.

 — MaxwellBuchanan, May 11 2016

Suggestulated by: Flywheel_20pedal_20mulcher
[MaxwellBuchanan, May 11 2016]

bicycle with speed governor
[xaviergisz, May 11 2016]

Flywheel physics https://en.wikipedi...ki/Flywheel#Physics
It appears that the variable-inertia flywheel was considered by one Sr. L. da Vinci... [8th of 7, May 11 2016]

Indeed this is more eleganter. Brilliant!
 — whatrock, May 11 2016

I think this might be brilliant, but sort of the opposite of useful for a normal flywheel. In an engine, you need the mass at low RPM, if you could find a way to reverse the effect... Anyhow, it lead me to staring at diagrams of dual mass flywheels and pendulum style centrifugal absorbers. I'm now confused and want a BMW diesel all at the same time.
 — bs0u0155, May 11 2016

 //In an engine, you need the mass at low RPM, if you could find a way to reverse the effect... //

I haven't looked at the mechanics of it, but a gut feeling for the physics tells me that you can't do it automatically using simple levers and whatnot. However, in a car you can afford to have a lot of mechanicky stuff to dynamically adjust the flywheel's moment of inertia.
 — MaxwellBuchanan, May 11 2016

 // I'm now confused and want a BMW //

 More deserving of pity than condemnation (probably).

Or maybe both.
 — 8th of 7, May 11 2016

With the right spring tension, once spun up, the flywheel will continue to spin at a constant rate, despite losing energy, which sounds useful.
 — FlyingToaster, May 11 2016

 // constant rate //

 Constant angular velocity ? Until the masses return to their rest positions, at which point it will commence deceleration.

 The device will either need to be enclosed, or spin in a vacuum chamber. The structure sounds prone to aerodynamic drag if left exposed.

It might be an interesting and useful adjunct to an autogyro rotor.
 — 8th of 7, May 11 2016

 //With the right spring tension, once spun up, the flywheel will continue to spin at a constant rate, despite losing energy, which sounds useful//

 V.V.V useful for, say, maintaining exactly 50 Hz* during power generation. In fact, put a viscous coupling on the front end and within a given range the speed OR torque of your mechanical power source aren't important.

* other mains frequencies are available
 — bs0u0155, May 12 2016

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