Equipment Specs

A gear is a toothed wheel that engages with a transmission to convert rotational force to another device. Gears can also transmit force to other gears of various sizes and diameters by the intermeshing of teeth of each gear or other compatible devices. This is referred to as a gear train and it produces a gear ratio, the rate at which the gears are turning in proportion to one another. Gears are used in many devices, mechanical or otherwise, such as vehicles, clocks, and VCRs.

Gears are useful for a variety of purposes. They allow the force of the rotation to be redirected; they can control the increase or decrease in the speed of the rotation; they can move the rotation to a different axis; and they can synchronize the rotation of two axes.[1]

Vehicle transmissions are rife with gear chains that enable them to fulfill a series of tasks through rotational force. The speed and rotation of the gear is dependent on the gear ratio, which can be measured by the diameter of the main gear in relation to each successive gear.

The teeth of the gears defines the ratio because the revolutions that a smaller gear can make while intermeshing with the teeth of a larger gear are normally higher in number, but exactly how much is determined by the diameter of both the main (and usually smaller) gear and that of the other gears. For example, if the main gear can achieve two revolutions for every single revolution of a larger one, the ratio would be defined as 2:1. The first number in a gear ratio is the main gear that is driving the other(s). Even if the exact diameters of the gears do not match up, they will consistently revolve because of the intermeshed teeth.[2]

Not only do the gear teeth enable the exact ratio to be determined, they also prevent the gears from slipping and synchronize the axles of the gears.[3]


[edit] Types

There are many different types of gears, including compound gears, spur gears, helical gears, sprockets and chains, bevel gears, rack and pinion, worm gears, and planetary gears.

[edit] Compound Gears

These gears consists of two gears revolving on the same shaft.

[edit] Spur Gears

These types of gears consist of the simple design of a cylinder or disc that rotates; they are the most common and provide the highest efficiency of any of the gear types.

[edit] Helical Gears

These are similar to spur gears but with much smoother operation due to their shape. They are more expensive than spur gears.

[edit] Spocket Gears with Chains

These gears are considered to be three separate gears and operate similarly to spur gears. They differ in that, due to the odd number of gears involved, they tend to rotate in the same direction. The operation of sprocket gears causes a lot of friction that requires heavy lubrication for efficiency. A chain breaker is required to adjust the length of the chains for these gears.

[edit] Bevel Gears

These are conical-shaped gears that rotate and intermesh at an angle while intersected on a shaft. They may consist of spur-like or spiked teeth or bevel spiraled teeth, which are curved and angled. They are considered ideal for changing the angle of the rotation but are less efficient than the other types, making them an undesirable type of gear.

[edit] Rack and Pinion

This type of gear consists of a toothed rod (known as a rack), which intermeshes with a toothed pinion, a wheel-shaped gear. The pinion turns while the rack projects in a straight line. This type of gear is normally found in steering systems and is prevalent in automobiles and other types of vehicles.

[edit] Worm Gears

The worm gear is similar to the helical gear with its helix angle, but resembles a screw. The worm intermeshes with a worm gear or wheel. In this variation, the worm always drives the gear but the gear cannot necessarily drive the worm.

[edit] Planetary Gears

These are also known as epicyclic gears. The gears to rotate while one or more of the axes rotate. This gear was invented by the same company that James Watt, the inventor of the measurement unit of electricity and the steam turbine, worked for. It is primarily used to move the wheels of automobiles and operates by having the axis of the central bevel pinion turned by the ring gear. When this occurs, the drive gears mesh with the bevel gears and the wheels are driven.[4]

[edit] References

  1. Gears. 2008-09-29.
  2. Gear Ratio. 2008-09-29.
  3. Gears. 2008-09-29.
  4. Mechanics Gears. Society of Robots. 2008-09-29.