sprocket

Everyday

A sprocket is a wheel with teeth around its edge that fit into the links of a chain or the holes in a film or tape, so that it can turn it or be turned by it. On a bicycle, the toothed wheels the chain goes round are sprockets. tree →

In the lessons

In design and technology and science lessons sprockets and chains are a way to pass turning force from one wheel to another (like gears). On a bike, a big front sprocket and a small back sprocket make the back wheel turn faster. Old cinema film and camera film had sprocket holes. Phrases: "chain and sprocket", "sprocket holes", "rear sprocket".

Examples

• The bike chain slipped off the sprocket. tree →
• The front sprocket has more teeth than the back one. tree →
• Sprockets and chains are used in bicycles and motorbikes. tree →
• Old film had little sprocket holes along its edges. tree →
• We built a model with plastic sprockets in D and T. tree →
• Oil the chain so it runs smoothly over the sprockets. tree →
• If the front sprocket has 40 teeth and the back has 20, the back wheel turns twice for each turn of the pedals. tree →

Note

Countable. In maths problems, the number of teeth matters: turns of the small sprocket = teeth of big ÷ teeth of small × turns of the big one. A sprocket differs from a gear because a sprocket works with a chain, while gears touch each other.