Gears are everywhere, often hidden amongst the inner workings of highly advanced machinery or simple items whose use and operation we take for granted. A gear is a component that transmits force from a power source to a device. In a very simple design the power source turns the gear, which links to another gear or to a device through teeth, or "cogs", that mesh together, thereby transferring the power of the original source onward.
A well-known example of a gear in action would be a water wheel on a mill. The energy source in this instance is the water, which turns the gear (the water wheel), the water wheel has a shaft transferring that energy to another gear, on the opposite end, meshed to a second gear which drives the mill stone.
The most advantageous feature of the gear is that gears of unequal sizes can be combined to produce increased or decreased speed or torque, as the mechanical operation requires. This is what is known as creating a mechanical advantage. This change in the power of the original source of energy is known as the gear ratio and is determined by the change in size from one gear to another.
There are a number of different designs for gears. A spur gear is the most basic design. In this design the teeth of the connecting gears are straight and contact each other at the same time. While this can supply a great deal of force and energy transfer, it tends to great very loud operations and high amounts of stress on the gears.
Other types of gears have been developed to serve particular purposes. Helical gears employ a more gradual engagement of the teeth, which creates a smoother operation. Bevel gears are most useful for changing the direction of a shafts rotation. Hypoid gears are used in order to change the axes on which the opposing shafts operate. Worm gears are extremely efficient in creating large gear reductions.
The versatility of gears is nearly unlimited. Gears can be used to coordinate multiple shafts to run at equal speeds in the same or opposite directions or to run at varying speeds. Gear sizes can be manipulated to create high torque, or high speeds, beyond the direct power of the original energy source.
The use of gears can be seen in a variety of applications. Gears, of course, are used to convert the power from a car motor to the torque and force used to propel the vehicle. Rack and pinion gears are used in the steering systems of vehicles. Gears are used to operate conveyor belts and to turn the rotors of helicopters and can be found in simple items like a household scale.
Based off of one of man's earliest technological achievements, the wheel, gears are now used to harness the energy of any number of power sources. Continuous advances in the implementation and design of gears enable humankind to reach ever-higher levels of achievement, simplify work and create all manner of labor saving devices.