What does a flywheel do and how does it work?



What does a flywheel do and how does it work?

In: Engineering

A flywheel is a weight added to an axle. It’s purpose is to create inertia so that the axle needs less energy to turn it at high speeds than it would without the flywheel.

Flywheels store rotational kinetic energy. You can store energy in or by increasing its speed and free energy from it by transferring or converting that energy – make something move, convert to electricity, etc.

How they’re implemented depends on their purpose. On a car with a manual transmission, they’re used to add rotational inertia to smooth the “impact” of releasing the clutch and putting a large load on the engine.

In power grids, they can be used to store over produced power, allowing that power to be drawn from at a later time.

A flywheel is just a wheel. Heavy wheels (relative to the application) take a lot of energy to get spinning, but once they do they really want to keep spinning. This means you can make an up front investment and then keep that mechanical energy stored in the rotation of that heavy object for some time.

The applications vAry, but usually they’re used to help balance out power fluctuations, the wheel can keep a system in motion when power cuts briefly or store up extra energy by accelerating when there is a surplus of power, or to temporarily power the whole system on their own after the initial power source cuts out.

A flywheel is a heavy round weight attached to the shaft of an engine. It maintains rotational inertia, meaning it takes energy to make it spin, but once it is spinning it wants to keep spinning. It is basically a top or a beyblade.

For engines with a few pistons, the flywheel helps keep things spinning smoothly. Engines with more cylinders tend to run smoother and have lighter flywheels.

Most cars add teeth to the outside edge of the flywheel, making it into a gear that can be turned by the electric starter motor when one turns the key.

A flywheel is used to keep a wheel rotating longer. By adding weight to a wheel, it’ll keep spinning longer once whatever is spinning it stops.

Think of a train rolling down a track compared to a [pump car](https://i.pinimg.com/originals/8f/ba/9f/8fba9faa91745b45277b2d3c79e6e4ee.jpg). If they’re both brought up to the same speed and then remove whatever is pushing them so that they just roll freely until they stop on their own, it’ll take the train a lot longer for friction/air resistance to slow it to a stop than the pump car. This is because the train has a lot more mass to it and thus momentum than a smaller pump car traveling the same speed.

Adding extra mass to a wheel will keep it spinning for longer once power is removed just like the extra mass on a train.

A flywheel is an energy storage device. It stores rotational kinetic energy according to

E = (I * omega^2 )/2

…where I is the rotational moment of inertia about the flywheel axis, and omega is the angular velocity of the flywheel.

This is analogous to the formula for linear kinetic energy, where

E = (m * v^2 )/2

…where the terms in the equation are mass and linear velocity.

So, large flywheels with high inertia store a lot of power, but you gain even more from higher rotational speeds, since that variable is squared. Power storage flywheels are often light weight but have operating speeds in the several tens of thousands of rpm for this reason.

Flywheels are used in car engines in order to smooth out the power delivery to the transmission. In the absence of a flywheel, the individual pulses from the detonations in each cylinder would lead to excessive vibration as the drivetrain responds.

Large power generation systems often use flywheels to ride through variances in delivered power. You can think of a flywheel like a battery or a hydraulic accumulator. It is a buffer of stored energy that can absorb peaks in power, or deliver power when there is a dropout.

Think of a flywheel as a battery for mechanical energy (well it’s more of a capacitor).
It’s a wheel with some weight.
To “charge it up” you spin it.
To “discharge it” you make the wheel spin something.
Which means you can do a lot of useful things. Say you got something that only causes a lot spinny force for as short then no spinny force for long while ( like an engine piston). If you just attached it to a regular wheel it’s all start stop start stop, which is not comfortable.
If instead you have a heavy fly wheel going, since there’s a lot of energy in a fast spinning heavy wheel, that big force makes it spin only a tiny amount faster. So it’s smoother.

Say you got something that needs an absurd amount of force and have only a weak motor. Well you can use the weak motor to slowly accelerate the fly wheel over a long time until there’s a lot of energy in it. Then abruptly ram a gear into that wheel and transfer all of the energy at once.

A flywheel is a heavy wheel attached to a shaft to help maintain momentum. Basically the more weight you can get moving (and the further that weight is from the axis) the harder it is to get it to stop spinning.

This is good in applications where you want smooth and continuous rotation, so motors and engines. You’ll see them on generators, cars, conveyors, etc.