TYPE OF GEAR
INFORMATION
APPLICATIONS
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Spur gears are the most commonly used gears for transmitting motion between 2 shafts that lie parallel to one another. The teeth in each gear mesh with the other during rotation. The teeth are cut out from a cylinderical blank.
The input is at the driver gear and the other gear is called the driven gear.
In such a combination, the gear with the larger number of teeth always moves more slowly than the one with less teeth. Furthermore the two gears move in opposite directions.
Well made meshing gears give smooth balanced motion without any rattle or chatter
Piv by
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Bevel gears are used to power intersecting shafts. The motion of the driver gear is transmitted through 90 degrees.
These gears are called bevel gears because each of the meshing edges have a 45 degree bevel on them. (the teeth are cut on a cone with sides sloping upwards at 45 degrees)
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A rack and pinion is used to convert linear motion into rotary motion and vice versa.
The round spur gear is called the pinion and it meshes with another spur gear, the rack which has its teeth set in a straight line.
If the Pinion is the driver and is on a fixed shaft, rotation will cause the Rack to move in a straight line.
If the Rack is the driver, movement of the rack will cause the Pinion to rotate
If the Rack is fixed, rotation of the Pinion will cause the pinion itself to move along the rack.
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In this combination of gears, the worm is the gear which looks like a screw thread. The worm wheel has teeth that are at an angle (helical ) so that they can mesh with the thread like teeth of the worm. The worm is always the driver in this mechanism . This mechanism will lock if the worm wheel tries to drive the worm.
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In this gear train the Drive gear is rotating clockwise and the Driven gear is being rotated anticlockwise.
If however we need the driven gear to rotate in the same direction as the driver gear we need another gear between the driver and driven gear called an Idler.
Now the driver is rotating clockwise, the idler is rotating anticlockwise but it causes the driven gear to rotate clockwise. Hence both the driver and driven gear are rotating in the same direction.
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The purpose of the spring is to push the pawl onto the teeth. This causes a clicking noise when the ratchet is turning in its allowed direction.
Often gravity alone is sufficient to hold the pawl against the ratchet. Lifting the pawl off the wheel allows the wheel motion to be reversed.
