How does a bicycle work?

The bicycle is the most efficient way of transport ever invented. It transforms your energy into movement. But how does it work?

In order to maintain balance, the cyclist has to continuously adjust the front wheel's direction which, this way, has a waved trajectory.

In order to turn right or left, all you have to do is turn the handlebar to the desired side, isn't it? Wrong! Cyclists turn using their body weight, the handlebar is just for counterbalancing. In fact, in order to run left, you turn a little to the right at first, which will push your weight to the left. This is called countersteering and takes places instinctively. Do it on purpose, and you will fall !

The back wheel's spokes do not descend straight from the wheel's log, that's why they intersect. The fact that they're a bit decentred helps them tolerate the torsion force that spins the wheel.

The gearing
It controls the back wheel's speed and force. A big gearing report transforms one pedals' rotation into several back wheel's rotations, ideal to accelerate. A small gearing report slows the wheel's speed, but increases the force, ideal for climbing slopes.

The wheels have a double role. On one hand, the back wheel transmits the pushing force of your legs to the ground. On the other, both wheels reduce friction to the ground by spinning on small contact areas. The thinner the tire, the smaller the friction.

The handlebar is made out of two levers which easily control the front wheel. The bigger it is, the easier controlling the front wheel is. Racing bicycles have curved handlebars to ensure a lower position to the cyclist. This helps the aerodynamics.

The breaks squeeze the wheels' frame in order to create friction and this way, they slow down the bike. The bike's energy doesn't vanish instantaneous - it transforms into heat and sound. Try to touch that frame after breaking and you'll see it's hot.
If you suddenly squeeze the breaks the inertia can make you fly over the handlebar. The secret of a safe breaking is to gradually break and maintain a balance between the front and the back break. On wet roads, break longer and slower.

Did you know?
A bicycle transforms 90% of your energy into movement, this way making it the most efficient way of transportation. A car transforms only 25% from the energy it receives, due to its big weight. The energy you use to go 1 km with a bike would move your car for only 20 meters. A bike uses less energy to travel 1 km than the car, the train, horse riding, and even walking !