Gears

Gears

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These gears are all used in children's toys. The Worm gear could be used for making a mobile turn round and so could the bevel gear. They could also be connected to toy car wheels to change the direction of motion from the axle. The rack and pinion could be used to move a forklift up and down if a wheel was turned.

This is a bevel gear it changes rotary (round and round) motion through 90 degrees.

This is a worm gear it also changes motion through 90 degrees.

This is a Rack and Pinion gear. It changes linear (straight line) motion into rotary motion. (Or the other way round)

Try to think of other toys which use gears. Can you make gear calculation

When working with gears you have to remember that if the gear attached to the motor is little and the gear which is being driven is big then the speed is slowed down. If the gear attached to the motor is big and the gear it is driving is little then the speed increases. As an example if the little cog is 4cm diameter and it is driving a cog 16cm diameter then the speed is slowed down by 4 (4 divided by 16) in other words a quarter of the speed. So if the speed was 200 rpm (Revolutions Per Minute) then it would slow to 50 rpm. Doing it the other way round with the big cog driving the little cog the speed would increase by 4 making 200 rpm go to 800 rpm. Remember the cog size can be given in diameter, radius or number of teeth on the cogs. If it is an increase in speed its the big divided by the small and then multiplied by the motor speed. If its a decrease in speed it is the little divided by the big and then multiplied by the motor speed. Try working through a few examples of your own, they could well ask in the test !!!!