Mechanical Systems - Motion and Gears

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Types of Motion

There are 4 types of motion that could occur in a mechanism:

Linear - moving in one direction in a straight line.

Reciprocating - moving backwards and forwards in a straight line.

Oscillating - moving backwards and forwards in an arc.

Rotary - moving in a circle

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Gears

What is a gear?

A gear is a toothed wheel that can interlock with other gears.

What is a gear train?

Two or more gears linked together.

  • Every gear train has a driver and a driven gear. The driver gear can be turned by hand or by a motor. When the driver gear is turned it causes the driven gear to turn.
  • If the driver and driven gear are linked directly they will turn in opposite directions.
  • If the driver and driven gear are seperated by another gear (called an idler gear) they will turn in the same direction.
  • If the driven gear has half the number of teeth as the driver gear it will rotate twice as fast.

 

 A compound gear shaft is one that has more than one gear on its shaft. This makes is useful for changing the gear ratio easily.

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Rack and Pinion Gears

Rack and Pinion gears turn rotary motion into linear motion.

The Pinion is a round gear which turns the Rack which is a flat gear.

These can be found on railways when they have to go up a steep slope.

 

 

  

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Worm drive and worm wheel gears

Worm drive and worm wheel gears change the direction of rotation by 90 degrees.

The worm drive only has one 'tooth' so moves much faster than the worm wheel.

The worm drive acts very much like a screw.

This mechanism is found in a guitar for tightening the strings.

(http://t3.gstatic.com/images?q=tbn:ANd9GcS6fD3H5a7tCVGhiiqwY1Q6xwDNOgOuYYf36Cqpl3d90DRSfJTc) 

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Bevel Gears

Bevel gears also change the direction of rotation by 90 degrees.

The teeth are angled at 45 degrees so the two gears come together at right angles.

This type of mechanism is used in hand drills.

 

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Bevel Gears

Bevel gears also change the direction of rotation by 90 degrees.

The teeth are angled at 45 degrees so the two gears come together at right angles.

This type of mechanism is used in hand drills.

 

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