# Differential.

Mind Map by sarahrojas12, updated more than 1 year ago
 Created by sarahrojas12 about 4 years ago
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### Description

differential mental maps

## Resource summary

Differential.
1 What is a differential?
1.1 In automobiles and other wheeled vehicles, the differential allows the outer drive wheel to rotate faster than the inner drive wheel during a turn
1.2 A differential is a particular type of simple planetary gear train that has the property that the angular velocity of its carrier is the average of the angular velocities of its sun and annular gears.. In automobiles and other wheeled vehicles, the differential allows the outer drive wheel to rotate faster than the inner drive wheel during a turn
1.3 This is necessary when the vehicle turns, making the wheel that is traveling around the outside of the turning curve roll farther and faster than the other. The average of the rotational speed of the two driving wheels equals the input rotational speed of the drive shaft. An increase in the speed of one wheel is balanced by a decrease in the speed of the other.
2 Application to vehicles
2.1 A vehicle with two drive wheels has the problem that when it turns a uhuy corner the drive wheels must rotate at different speeds to maintain traction. The automotive differential is designed to drive a pair of wheels while allowing them to rotate at diferent speeds. In vehicles without a differential, such as karts, both driving wheels are forced to rotate at the same speed, usually on a common axle driven by a simple chain-drive mechanism.
3 Who invented it?
3.1 There are many claims to the invention of the differential gear. Some historical milestones of the differential include:
3.1.1 30 BC–20 BC: Differential gear systems possibly used in China
3.1.2 658, 666 AD: two Chinese Buddhist monks and engineers create south-pointing chariots for Emperor Tenji of Japan.
3.1.3 1810: Rudolph Ackermann of Germany invents a four-wheel steering system for carriages, which some later writers mistakenly report as a differential
3.1.4 1832: Richard Roberts of England patents 'gear of compensation', a differential for road locomotives.
3.1.5 1958: Vernon Gleasman patents the Torsen dual-drive differential, a type of limited slip differential that relies solely on the action of gearing instead of a combination of clutches and gears.
3.1.6 1720: Joseph Williamson uses a differential gear in a clock.
4 Epicyclic differential
4.1 An epicyclic differential can use epicyclic gearing to split and apportion torque asymmetrically between the front and rear axles. Epicyclic gears are also called planetary gears because the axes of the planet gears revolve around the common axis of the sun and ring gears that they mesh with and roll between.
5 Spur-gear differential
5.1 This is another type of differential that was used in some early automobiles, more recently the Oldsmobile Toronado, as well as other non-automotive applications. It consists of spur gears only. A spur-gear differential has two equal-sized spur gears, one for each half-shaft, with a space between them. Instead of the Bevel gear, also known as a miter gear, assembly (the "spider") at the centre of the differential, there is a rotating carrier on the same axis as the two shafts.
6 Non-automotive applications
6.1 The earliest definitely verified use of a differential was in a clock made by Joseph Williamson in 1720. It employed a differential to add the Equation of Time to local mean time, as determined by the clock mechanism, to produce solar time, which would have been the same as the reading of a sundial.

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