Gears A gear is a wheel with teeth. The gears interlock (mesh) to create movement. K Walstra St Stithians

What is a gear? A gear is a wheel with teeth that mesh together with other gears. Gears change the speed torque (rot. force) direction of rotating axles. Robotics Academy 2002. All Rights Reserved.

Spur Gears Most “common” type of gear, a wheel with teeth.

Adjacent gears on a gear train rotate in opposite directions Adjacent gears on a gear train rotate in opposite directions. Notice how the driver rotates clockwise while the follower rotates anticlockwise.

Idler Gears An idler gear is a gear that is inserted between 2 other gears. The addition of a third gear makes the follower and driver rotate in the same direction.

The gear ratio of the gear train above is 8/18. or 4/9 The gear ratio of the gear train above is 8/18.or 4/9. Notice the direction of the follower in each gear train.

The gear train above is connected to an internal combustion engine The gear train above is connected to an internal combustion engine. The gear ratio is 1:1 there is no mechanical or rotational advantage. The gear in the middle allows the driver and the follower to rotate clockwise.

The gear train below is a speed multiplier The gear train below is a speed multiplier. The gear ratio is 8/18 or 4/9. For every 4 turns of the driver the follower makes 9 complete revolutions.

The gear train above is a force multiplier The gear train above is a force multiplier. The gear ratio is 18/8 or 9/4. For every 9 turns of the driver the follower makes 4 complete revolutions. This is an example of a force multiplier.

GEARS

GEARS

BEVEL GEARS Bevel gears are spur gears that mesh at a 90 degree angle. The gear ratio rules remain the same, but the axles are perpendicular to one another.

BEVEL GEARS

BEVEL GEARS

WORM GEAR The worm gear acts like a gear with 1 tooth! This gives very large gear ratios.

WORM GEAR You can turn the worm gear’s axle, but you can’t turn the spur gear’s axle. This property is used as a locking mechanism.

Rack & pinion gear The gear moves along the rack http://www.osha.gov/SLTC/etools/machineguarding/images/rack1.gif K Walstra St Stithians

The above gearing system is called a rack and pinion The above gearing system is called a rack and pinion. Circular motion is changed into linear motion. If the pinion rotates in a fixed position the rack moves in a linear motion.

If the rack remains stationary the rotating pinion moves along the rack in a linear motion as shown on the diagram.

RACK AND PINION The rack and pinion gear system allows rotary motion of the steering wheel to be converted to linear motion. As the steering wheel is turned, the pinion gear also turns, driving the rack in the right or left direction, pointing the wheels in the desired direction.

RACK AND PINION STEERING

RACK AND PINION

RACK AND PINION

RACK AND PINION

RACK AND PINION

A car jack is used to lift a heavy load.

CHAIN GEARS

CHAIN GEARS

CHAIN GEARS

CHAIN GEARS

(POSSIBLE ANSWERS)

GEARS

GEAR RATIO

GEARS

Gear Ratios The gear ratio tells you the change in speed and torque of the rotating axles. If it takes 5 turns of the 8 tooth gear for every 1 turn of the 40 tooth gear, that means the 40 tooth gear will rotate 5 times slower than the 8 tooth gear. BUT, it also means the 40 tooth gear’s axle has 5 times the torque (rotational force) as the 8 tooth gear’s axle. Robotics Academy 2002. All Rights Reserved.

GEAR RATIO

GEARS

GEAR RATIO

Notice in the compound gear train on the left that four gears are used and that gears "B" and "C" are fixed together on the same shaft. When the driver gear "A" makes one complete turn gear "B" turns 1/4 of a full rotation. This also means that gear "C" also turns 1/4 of a full rotation. Gear "D" will turn through 1/16(1/4 X1/4) of a turn. The gear ratio for this compound gear train is 16:1