Motion transmission – belt, chain and gear drives
Design & TechnologyMechanical EngineeringAges 13–14
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Mechanical Engineering
Two wheels are coupled by a belt, chain or meshing teeth: the driver wheel turns at a set speed, and the driven wheel follows at a speed found from the transmission ratio i = n₁/n₂ = Z₂/Z₁. Students change the number of teeth (or diameter) of the two wheels, change the driver's speed, choose an open or crossed belt, click Run to watch the wheels turn at the correct ratio and direction, or drag on the driver wheel to turn it by hand bit by bit. The simulation shows the formula, the transmission ratio, the driven wheel's speed, and whether the drive is speeding up or slowing down.
Lesson: Transmitting and converting motion: belt drives, chain drives, gear drives and the transmission ratio
What it shows
Belt, chain and gear drives pass rotation from a driver wheel, connected to the motor, to a driven wheel. Because the belt, chain or meshing teeth move the same distance at the rim of both wheels, rotational speed is inversely proportional to wheel size: i = n₁/n₂ = Z₂/Z₁. A ratio above 1 reduces speed and increases torque; a ratio below 1 increases speed. Direction depends on the drive: an open belt or a chain turns both wheels the same way, while a crossed belt or two meshing gears reverse the driven wheel. Bicycles, machine tools and conveyors use these mechanisms.
How to use
Start with the gear drive and click Run, comparing the red marks on the two wheels to see which turns faster. Change the number of teeth Z₁ and Z₂, predict the driven wheel's speed n₂, then check it against the formula under the wheels. Switch Drive type to Belt drive, tick Crossed belt and watch the driven wheel reverse. Use Reverse direction, or drag the driver wheel by hand, to follow the motion slowly.
Parameters you can change
- Drive type Belt drive, Chain drive, Gear drive
- Driver wheel: number of teeth Z₁ (belt: diameter D₁) 10–60 teeth
- Driven wheel: number of teeth Z₂ (belt: diameter D₂) 10–60 teeth
- Driver wheel rotational speed n₁ 10–300 rpm
- Crossed belt (belt drive only)
Questions to explore
- If Z₁ = 20, Z₂ = 40 and n₁ = 60 rpm, what is n₂, and does the drive speed up or slow down?
- Which drive types make the driven wheel turn in the opposite direction to the driver wheel?
- For fast riding on a flat road, should a bicycle's front chainring have more or fewer teeth than the rear sprocket?
