The most efficient machine
The bicycle is one of the most efficient ways to travel. A person on a bicycle uses less energy per kilometre than walking, a car or almost any animal. There are more than a billion bicycles in the world.
The history of the bicycle
| Year | Development | Inventor or place |
|---|---|---|
| 1817 | Draisine ("running machine"): a wooden frame with two wheels and no pedals; riders pushed with their feet | Karl Drais (Germany) |
| 1860s | Velocipede ("boneshaker"): pedals attached to the front wheel; very bumpy iron-rimmed wheels | France |
| 1870s | Penny-farthing (high-wheeler): huge front wheel for more speed per pedal turn; riders sat high and often fell headfirst | England |
| 1885 | Safety bicycle: two wheels of similar size, rear-wheel chain drive | John Kemp Starley (England) |
| 1888 | Pneumatic tire (air-filled) | John Boyd Dunlop (Ireland) |
| 1890s | "Bicycle craze" across Europe and North America | |
| 1900s | Multi-speed gears | |
| 1970s | Mountain bikes developed in California | |
| 2000s–2020s | E-bikes with electric motors become popular |
Karl Drais invented his running machine partly because a volcanic eruption (Tambora, 1815) caused crop failures and horses were expensive to feed.
Parts of a bicycle
| Part | Job |
|---|---|
| Frame | Holds everything together; often a "diamond" of triangles for strength |
| Wheels and tires | Roll smoothly and cushion bumps |
| Pedals and cranks | Turn your leg power into rotation |
| Chainring (front gear) | Turns the chain |
| Chain | Transfers power to the rear wheel |
| Cassette (rear gears) | Different-sized gears for different speeds |
| Derailleurs | Move the chain between gears |
| Brakes | Use friction to slow down |
| Handlebars | Steer |
The science of bicycles
Gears
A gear ratio compares the size of the front gear to the rear gear.
| Combination | Effect | Best for |
|---|---|---|
| Large front, small rear | Each pedal turn spins the wheel many times; harder to pedal | High speed on flat roads |
| Small front, large rear | Each pedal turn spins the wheel fewer times; easier to pedal | Climbing hills |
Example: A 48-tooth front gear and a 16-tooth rear gear give a ratio of 48 ÷ 16 = 3. The rear wheel turns 3 times per pedal turn.
Simple machines
A bicycle combines several simple machines:
- Levers: pedal cranks, brake levers
- Wheels and axles: wheels, pedals, handlebars
- Pulleys and gears: chain and sprockets
Balance
Why doesn’t a moving bike fall over? When a bike starts to lean, the rider (and the bike’s front wheel geometry) steers slightly into the lean, bringing the wheels back under the centre of mass. Moving faster makes this easier, which is why it’s harder to balance at very slow speeds.
Friction and energy
- Rolling resistance and air resistance slow a cyclist. At high speeds, air resistance is the biggest force to overcome, which is why racers crouch low and wear tight clothing.
- Brakes use friction to turn kinetic energy into heat.
The bicycle and society
| Impact | Details |
|---|---|
| Freedom | Cheap personal transportation, long before cars |
| Women’s rights | Bicycles gave women independence and helped change clothing styles; American activist Susan B. Anthony said the bicycle had "done more to emancipate women than anything else in the world" |
| Roads | Cyclists campaigned for paved roads before cars were common |
| Inventions | The Wright brothers were bicycle makers; bike technology (ball bearings, chains, pneumatic tires) influenced cars and airplanes |
Cycling in Canada
- Montreal is considered one of North America’s most bike-friendly cities, with its BIXI bike-share system launched in 2009.
- Many Canadian cities are building protected bike lanes.
- Canadian cyclists have won Olympic and world championship medals in track, road and mountain biking.
Benefits of cycling
- Health: strengthens heart, lungs and muscles
- Environment: no emissions, little noise
- Cost: much cheaper than driving
- Traffic: takes up less space
Bike safety
- Always wear a properly fitted helmet.
- Use lights and reflectors at night.
- Follow traffic rules and signal turns.
- Check brakes, tires and chain regularly.
Common mistakes
- Thinking higher gears are easier. Lower gears are easier for climbing.
- Thinking bikes stay up only because of gyroscopic spinning. Steering into the lean is more important.
Try it yourself
- Count the teeth on the front and rear gears of a bike. Calculate the gear ratio for the easiest and hardest gears.
- Turn a bike upside down (with an adult). Turn the pedals once and count how many times the rear wheel turns.
- Design a poster about bike safety.
Quick recap
- The bicycle evolved from the 1817 draisine to the 1885 safety bicycle.
- Pneumatic tires and chain drives made bikes comfortable and efficient.
- Gears change how hard it is to pedal and how fast you go.
- Bicycles combine levers, wheels and axles, and gears.
- Cycling is healthy, cheap and clean.