Flywheel

a manual transmission might seem like a basic mechanical design.

you do all the work to shift gears, don’t you?

but what you don’t see are all the parts that are constantly in motion to keep your car under your control.

One of those parts is the flywheel. In a vehicle with a manual transmission, the flywheel serves a crucial purpose.

Let’s take a closer look at what a flywheel is, what it does, and what could go wrong.

A flywheel’s construction

In a manual transmission, the flywheel is a thick metal disc.

It’s typically made of cast iron, steel or, in some cases, aluminum.

It’s extremely rigid to prevent flexing or warpage during use.

The edge of the flywheel has a row of gear teeth that engage with the engine’s starter motor.

The flywheel is firmly bolted to a flange on the transmission side of the crankshaft inside the bell housing.

On the side facing the manual transmission, the surface is machined flat for the clutch disc to grab onto.

what the flywheel does

But what does the flywheel do? it actually has a few different purposes:

The flywheel provides mass for rotational inertia to keep your car’s engine running. otherwise, the engine will stall when you let your foot off the accelerator.

It balances the engine. a flywheel is specifically weighted to the car’s crankshaft to smooth out the rough feeling caused by even a slight imbalance.

It allows for an electric starter. the starter motor engages the starter ring on the edge of the flywheel to begin engine rotation.

Most importantly for drivers, the flywheel connects the engine with the transmission via a clutch to transfer power to the wheels.

when your foot is on the clutch pedal, the clutch disc is disengaged from the flywheel.

This is how a car can sit still at idle with the shifter in gear, or how a car can coast to a stop.

But when the pedal is released, the clutch disc will press firmly against the flywheel.

When this happens, the transmission input shaft rotates at the same speed as the engine’s crankshaft.