*What’s a Gearbox?*

A gearbox is a mechanical system of shafts and gears that serves the main purpose of slowing things down in a machine so that the energy from one place can be transferred and used in a different place. Gearboxes are most commonly seen in cars and trucks, and in these settings they adjust the high rotational speeds of the engine and convert them into more suitable slower speeds that the tires can safely use and interpret.

They’re also used in heavy machinery and other mechanical appliances, both small and large. Everything that uses high rotation speeds, but needs its energy reduced will make use of this system. When gears work properly, the rotational speed of the input shafts converts to a slower rotational speed on the output shaft. This results in output speeds helping the increasement of torque. The system looks slightly different in different situations, but the concept of work is usually the same.

*Composition*

The gear configurations more often than not occur within the inner workings of machines, motors and other mechanical components. In terms of basics and parts, they aren’t very complicated. The most simple models consist of two gears that have teeth of the same size but different diameter. The amount of teeth is proportional to the circumference – a smaller circumference gear will have less teeth than a larger one. For example, a gear with circumference of 8 inches will have twice as less teeth as a gear with a circumference of 16.

*Determining Gear Ratio*

The relationship expressed between the relative velocities of all involved gears is called a gear ratio. It’s almost always determined by the amount of teeth involved. The amount of teeth involved is calculated by the teeth involved in both larger and smaller gears. For instance, a single-stage gear reduction system comprised of two gears, one with 30 teeth and one with 10 teeth, would have a ratio of 3:1 or 30:10. The larger gear would turn at one third the time of the smaller, while having three times the torque.

Single-stage systems don’t allow as high gear ratios as multi-stage gear reduction gearboxes do. For example, a small gear added to the output shaft of the 1st set of gears will serve as the input driver for the 2nd set of gears. Every additional set of gears can be added if necessary. The end gear ratio is calculated by multiplying the ratio of each set of gears. For instance, a reduction gearbox ratios of 5:1, 4:1 and 3:1 would yield an end gear ratio of 60:1.

Reference: http://www.fcrmotion.com.au/reduction-gearboxes/