Compound gear and pulley systems: Belts
Transfers movement from one rotating pulley to another rotating pulley. transfer movement from one rotating pulley to another, each held on a A circular rod that mechanical parts such as pulleys sit on.. Shafts and pulley wheels can be made out of any material, whereas pulley belts are generally made from a soft, flexible material such as rubber. Grooves on the A wheel with a grooved edge that a cord passes around. and belts help them to grip and turn.
A machine that lifts heavy loads by turning a rope or chain around a circular drum., treadmills and washing machines are examples of belt-driven Parts that work together in a machine..
Belts can be attached around different-sized pulleys to drive shafts to change speed. As with A wheel with teeth that can change the speed of a mechanism., the bigger the wheel, the slower the speed. The Distance moved by effort over the distance moved by load. between two pulleys can be calculated.
This can then be used to calculate the output speed:
Example
A driven pulley has a diameter of 120 mm and a driver pulley has a diameter of 40 mm.
Velocity ratio = diameter of the driven pulley ÷ diameter of the driver pulley
= 120 ÷ 40 = 3 or 3:1
The smaller driver pulley turns three times to make the driven pulley turn once.
The output speed of the larger driven pulley can then be calculated using the information available - the input speed is 100 revolutions per minute (rpm) and the velocity ratio has been calculated as 3.
Output speed = input speed ÷ velocity ratio
= 100 ÷ 3 = 33 rpm
Question
Calculate the velocity ratio and the output speed of the driven pulley on this lawnmower belt and pulley:
Velocity ratio = diameter of the driven pulley ÷ diameter of the driver pulley
= 15 ÷ 150 = 0.1 or 1:10
The smaller driver pulley turns ten times for every one turn of the driven pulley.
Output speed = input speed ÷ velocity ratio
= 300 ÷ 0.1 = 3,000 rpm
The smaller driven pulley will turn at 3,000 rpm. This is the speed that the lawnmower blade will spin at on the lawnmower, ten times faster than the speed of the motor.
