How Cars and Engines Work

What Is a Car?

A car is a machine that carries people from place to place. It rolls on wheels, it can turn left or right, and it can stop when you want it to.

A car may look like one big object, but it is really made of thousands of parts all working together. In this book we will look at the most important parts: the engine that makes the power, the wheels that roll, the steering that points you the right way, and the brakes that stop you safely.

Let's open the hood and find out how it all works!

The Engine: The Heart of the Car

The engine is the part that makes a car move. Most cars use an engine that burns fuel, usually petrol or diesel. The engine turns that fuel into movement.

Here is the clever trick. Inside the engine are metal tubes called cylinders. In each cylinder, a small splash of fuel mixes with air and is set alight by a spark. This makes a tiny, fast explosion — a little bang. The bang pushes a part called a piston down very hard.

The pistons go up and down, over and over, hundreds of times every second. A bent rod called a crankshaft changes that up-and-down motion into a round, spinning motion. That spinning is the power that will turn the wheels.

So an engine really does just one job: it turns burning fuel into spinning.

From Engine to Wheels

The spinning power from the engine has to travel to the wheels. It does this through parts called the gearbox and the driveshaft.

The gearbox holds different sized gears — round wheels with teeth around the edge. Small gears and big gears work together to make the wheels turn at the right speed. When a car starts moving slowly, it uses a low gear for lots of pushing power. When it goes fast on a road, it switches to a high gear.

You can read more about gears and other clever parts in How Machines Work.

Wheels and Tyres

A car rolls on four wheels. Around each wheel is a rubber tyre filled with air.

Tyres do two important jobs. First, the air inside makes the ride soft and bouncy, so you do not feel every bump in the road. Second, the rubber grips the road so the car does not slip and slide. The pattern of grooves on a tyre, called the tread, pushes water away when it rains so the car can still grip.

Without good tyres, a fast car would skid all over the place. That is why tyres are so important for keeping everyone safe.

Steering: Pointing the Car

To choose where the car goes, the driver turns the steering wheel. This is connected to the two front wheels.

When the driver turns the steering wheel left, a set of rods and gears pushes the front wheels to point left, and the car curves to the left. Turn the wheel right, and the front wheels point right. The back wheels just follow along behind.

It is a bit like steering a shopping cart, but much smoother and more powerful, thanks to a helper called power steering that makes turning easy.

Brakes: Stopping Safely

Going is only half of driving. The car also needs to stop. That is the job of the brakes.

When the driver presses the brake pedal, a strong pad squeezes against a metal disc that spins with each wheel. The squeezing creates friction — a rubbing force that slows things down. The faster the car was going, the more the brakes have to work.

All that movement does not just vanish. It turns into heat. After a hard stop, the brakes can become very hot! Brakes are one of the most important safety parts of any car.

Electric Cars

Not all cars burn fuel. Electric cars work in a different way.

Instead of an engine with tiny explosions, an electric car has an electric motor. Instead of a fuel tank, it has a large battery that stores electricity. The driver plugs the car in to charge the battery, a bit like charging a phone.

When you press the pedal, electricity flows from the battery to the motor, and the motor spins the wheels. Electric cars are very quiet and do not puff out smoke from a tailpipe. Many people think they are the cars of the future. To learn how electricity itself works, try The Story of Electricity.

Staying Safe

A modern car is full of clever safety parts. Seatbelts hold you in place if the car stops suddenly. Airbags puff out like soft balloons in a crash to protect you. Lights help the driver see at night and let other people see the car.

Cars are amazing machines, but they are heavy and fast, so they must always be driven carefully.

What We Learned

A car turns fuel (or electricity) into movement. The engine or motor makes spinning power, the gearbox sends it to the wheels, the steering points the car, and the brakes stop it with friction.

Next time you ride in a car, listen to the engine and watch the wheels turn. Now you know the busy, hidden machine that is carrying you along!