Gears

Spur Gears Most common type of gear Straight teeth Mounted on parallel shafts Very cost effective Noisy because of the sound caused by the teeth of one gear engaging with those of another gear, which also puts stress on them Internal spur gears (teeth on the inside diameter) and external spur gears (teeth on the outside diameter) are used in conjunction to allow rotation in the same direction and in the opposite direction. Used in objects such as electrical screwdrivers, dancing monsters, oscillating sprinklers, windup alarm clocks, washing machines, and clothes dryers because they can rotate in two directions (which each of these devices requires) while minimizing work and remaining durable.

Worm Gears Used when large gear reductions are needed (common reduction of 20:1, can be 300:1 or greater) Most common gear system (worm and worm wheel) Smoothest and quietest form of gearing Transmit motion and power between right angle shafts Worm able to turn the gear but not vise-versa because the worm is held in place by the friction between them Worm gears can act as conveyor brakes when a motor is not running because of this friction; for this reason, they are used in musical instruments (tuning pegs), mechanical gates, and conveyors to

Crown Gears Teeth project at right angles to the face of the wheel, allowing them to join with the crown wheels Used with a pinion, or a cogwheel Considered a bevel gear Mesh with other bevel gears as well as spur gears Used in junction cars because of their equal distribution of torque between two drive shafts, noise reduction ,and efficiency

Rotary to Linear Motion Uses the turning of a rolling device to move an apparatus Converts rotational energy to forward energy All energy is conserved, so the motor transfer the same amount of power to the apparatus. Often uses crown or spur gear conjunctions with an axel attached to a base or using gear teeth turning a row of compatible teeth Drive mechanism often used in machine tools such as shapers or a cam and follower device

Sources http://science.howstuffworks.com/transport/engines-equipment/gear2.htm- Spur http://science.howstuffworks.com/transport/engines-equipment/gear5.htm- Worm http://www.wmberg.com/products/Gears.aspx- General http://www.wisegeek.com/what-is-a-differential-gear.htm- Crown