The rim is the outer edge of a wheel, holding the tire. It makes up the circular design of the wheel on which the inside edge of the tire is mounted on vehicles such as automobiles. For example, on a wheel the rim is a large hoop attached to the outer ends of the spokes of the wheel that holds the tire. The term rim is used non-technically to refer to the entire wheel, in the 1st millennium BC an iron rim was introduced around the wooden wheels of chariots. Diameter, distance between the seats, as measured in the plane of the rim and through the axis of the hub which is or will be attached. Width, separation distance between opposed rim flanges, the flange-to-flange width of a rim should be a minimum of three-quarters of the tire section width. And the maximum rim width should be equal to the width of the tire tread, Depends on the type of vehicle and tire. There are various rim profiles, as well as the number of rim components, modern passenger vehicles and tubeless tires typically use one-piece rims with a safety rim profile.
Heavy vehicles and some trucks may have a removable multi-piece rim assembly consisting of a base that mounts to the wheel and they have either a side ring or a side and lock ring combination. These parts are removable from one side for tire mounting, while the opposite side attached to the base has a fixed flange, oversized rims may cause the tire to rub on the body or suspension components while turning. Overly narrow rims in relation to the width may cause poor handling as the tire may distort sideways under fast cornering. On motorcycles, a narrow rim will alter the tire profile, concentrating tire wear in a small area during cornering. On bicycles, the tire width is approximately twice the rims internal width or one-and-a-half times the rims external width. A standard automotive steel wheel rim is made from a sheet metal. The metal plate is bent to produce a cylindrical sleeve with the two edges of the sleeve welded together. To support the rim structure, a disc is made by stamping a metal plate.
It has to have holes for the center hub and lug nuts. The radial outer surface of the disk has a cylindrical geometry to fit inside the rim
The Mazda MPV is a minivan manufactured by Mazda. Introduced in 1988 as a model with optional selectable four-wheel drive. Over one million MPV models were produced since its introduction, the MPV was designed from the ground-up as a minivan specifically for the American market, and was introduced in 1988 for the 1989 model year. It was based on the large rear-wheel-drive Luces HC and it would be called the LV platform, and this larger platform allowed such options as a V6 engine, and optional four-wheel drive. However this large platform created some liabilities in other markets and it was available at Mazdas Japanese luxury dealership network ɛ̃fini starting in 1991. Its selectable 4WD system is not to be confused with all road conditions all-wheel-drive systems, a dash mounted switch controlled the center differential, creating a locked power distributions on the front and rear axles. The 4WD is not for use on dry roads, but can be engaged and disengaged while moving. Like the Honda Odyssey introduced in North America in early 1995, it featured traditional hinged doors instead of sliding rear doors and this was the only Mazda MPV generation with a manual transmission, offered in the 89 through 91 model years.
The middle row was available as a 3-person bench, allowing seating for eight, because of the MPVs optional 4WD, the Mazda Navajo version of the Ford Explorer was only offered as a two-door, so as to minimize internal competition. The van was named to Car and Driver magazines Ten Best list for 1990 and 1991, initial sales were strong as well, but rapidly fell off once other makers introduced all-wheel drive and V6 engines. In the years to come, Toyotas 1991 Previa, Nissans 1993 Quest, in 1992 for the 1993 model year, a new Mazda emblem and a remote keyless entry system were introduced. A standard drivers airbag was introduced in early 1993. The van was face-lifted in 1995 for the 1996 model year, adding drivers side door, passenger side airbag. While the four-cylinder engine was retired for the American and Canadian markets, it was replaced with a similar, a mild refresh was introduced in 1997 for the 1998 model year with all-sport body cladding and wheel arches, and polished alloy wheels. Mazda discontinued the original MPV after the 1998 model year for North America, the MPV was replaced in June 1999, using the short-wheelbase, front-wheel-drive LW platform.
It now featured sliding rear doors equipped with roll-down power windows. In the North American markets, the MPV was set apart from other minivans by its comparatively sporty chassis, at introduction, the MPV used the same 170 hp DOHC2.5 L Ford Duratec V6 unit that powered the Ford Contour and Mercury Mystique and Cougar. DX models featured a two-place middle bench seat, the LX model featured two middle buckets with a feature whereby the passenger side seat could slide sideways, power windows and locks, heated power mirrors, privacy glass, and antilock brakes
As torque carriers, drive shafts are subject to torsion and shear stress, equivalent to the difference between the input torque and the load. They must therefore be enough to bear the stress, whilst avoiding too much additional weight as that would in turn increase their inertia. The term drive shaft first appeared during the mid 19th century, in Stovers 1861 patent reissue for a planing and matching machine, the term is used to refer to the belt-driven shaft by which the machine is driven. The term is not used in his original patent, another early use of the term occurs in the 1861 patent reissue for the Watkins and Bryson horse-drawn mowing machine. Here, the term refers to the transmitting power from the machines wheels to the gear train that works the cutting mechanism. In the 1890s, the term began to be used in a closer to the modern sense. In 1899, Bukey used the term to describe the shaft transmitting power from the wheel to the machinery by a universal joint in his Horse-Power. In the same year, Clark described his Marine Velocipede using the term to refer to the shaft transmitting power through a universal joint to the propeller shaft.
Crompton used the term to refer to the shaft between the transmission of his steam-powered Motor Vehicle of 1903 and the driven axle, an automobile may use a longitudinal shaft to deliver power from an engine/transmission to the other end of the vehicle before it goes to the wheels. A pair of short drive shafts is commonly used to power from a central differential, transmission. In front-engined, rear-drive vehicles, a drive shaft is required to send power the length of the vehicle. Two forms dominate, The torque tube with a universal joint. This system became known as Système Panhard after the automobile company Panhard et Levassor patented it, most of these vehicles have a clutch and gearbox mounted directly on the engine, with a drive shaft leading to a final drive in the rear axle. When the vehicle is stationary, the drive shaft does not rotate, some vehicles, seeking improved weight balance between front and rear, use a rear-mounted transaxle. This places the clutch and transmission at the rear of the car, in this case the drive shaft rotates continuously with the engine, even when the car is stationary and out of gear. A drive shaft connecting a rear differential to a wheel may be called a half-shaft.
The name derives from the fact that two such shafts are required to one rear axle. Early automobiles often used chain drive or belt drive mechanisms rather than a drive shaft, some used electrical generators and motors to transmit power to the wheels
A drive wheel is a wheel of a motor vehicle that transmits force, transforming torque into tractive force from the tires to the road, causing the vehicle to move. The powertrain delivers torque to the wheel to overcome stationary forces. A two-wheel drive vehicle has two wheels, typically both at the front or back, while a four-wheel drive has four. A steering wheel is a wheel turns to change the direction of a vehicle. A trailer wheel is one that is neither a drive wheel, front-wheel drive vehicles typically have the rear wheels as trailer wheels. For four-wheeled vehicles, two-wheel drive describes vehicles that transmit torque to at most two road wheels, referred to as either front- or rear-wheel drive, the term 4x2 is used, to indicate four total road-wheels with two being driven. For vehicles that have partial four-wheel drive, the term two-wheel drive refers to the mode when four-wheel drive is deactivated and this configuration allows all four road wheels to receive torque from the power plant simultaneously.
It is often used in racing on mostly paved roads. Four-wheel drive is common in vehicles because powering all four wheels provides better control on loose. Four-wheel drive manufacturers have different systems such as High Range 4WD and these systems may provide added features such as varying of torque distribution between axles or varying gear ratios. Common terms for this configuration include four-wheel drive, 4WD, 4x4, front-wheel drive vehicles engines drive the front wheels. Using the front wheels for delivery of power as well as steering allows the force to act in the same direction as the wheel is pointing. This layout is used in modern passenger cars. A rare example of front wheel drive was the Opperman Motocart and this slow-speed agricultural and light freight vehicle was a tricycle with the front wheel carrying a large tractor tyre. The wheel was powered by a single cylinder Douglas engine carried on the front mono fork that formed the steering gear. See Front-engine, front-wheel drive layout, rear-wheel drive typically places the engine in the front of the vehicle, with a driveshaft running the length of the vehicle to the differential transmission.
However, mid engine and rear engine layouts can used and it was a common layout used in automobiles throughout the 20th century. At this time, FWD designs were not practical due to complexity, drive sprocket, the powered sprocket on a tracked vehicle
A wheel is a circular component that is intended to rotate on an axle bearing. The wheel is one of the components of the wheel. Wheels, in conjunction with axles, allow heavy objects to be moved easily facilitating movement or transportation while supporting a load, wheels are used for other purposes, such as a ships wheel, steering wheel, potters wheel and flywheel. Common examples are found in transport applications, a wheel greatly reduces friction by facilitating motion by rolling together with the use of axles. In order for wheels to rotate, a moment needs to be applied to the wheel about its axis, cognates within Indo-European include Icelandic hjól wheel, Greek κύκλος kúklos, and Sanskrit chakra, the latter both meaning circle or wheel. The invention of the falls into the late Neolithic. Note that this implies the passage of several wheel-less millennia even after the invention of agriculture and of pottery, precursors of wheels, known as tournettes or slow wheels, were known in the Middle East by the 5th millennium BCE.
These were made of stone or clay and secured to the ground with a peg in the center, but required effort to turn. True potters wheels were apparently in use in Mesopotamia by 3500 BCE and possibly as early as 4000 BCE, and the oldest surviving example, which was found in Ur, dates to approximately 3100 BCE. The earliest well-dated depiction of a vehicle is on the Bronocice pot. The oldest securely dated real wheel-axle combination, that from Stare Gmajne near Ljubljana in Slovenia is now dated in 2σ-limits to 3340–3030 BCE, the axle to 3360–3045 BCE. Two types of early Neolithic European wheel and axle are known, a type of wagon construction. They both are dated to c, in China, the wheel was certainly present with the adoption of the chariot in c.1200 BCE, although Barbieri-Low argues for earlier Chinese wheeled vehicles, c.2000 BC. In Britain, a wooden wheel, measuring about 1 m in diameter, was uncovered at the Must Farm site in East Anglia in 2016. The specimen, dating from 1, 100–800 years BCE, represents the most complete, the wheels hub is present. A horses spine found nearby suggests the wheel may have part of a horse-drawn cart.
The wheel was found in a settlement built on stilts over wetland and it is thought that the primary obstacle to large-scale development of the wheel in the Americas was the absence of domesticated large animals which could be used to pull wheeled carriages. The only large animal that was domesticated in the Western hemisphere, Nubians from after about 400 BCE used wheels for spinning pottery and as water wheels
Continuously variable transmission
A continuously variable transmission is an automatic transmission that can change seamlessly through a continuous range of effective gear ratios. This contrasts with other mechanical transmissions that offer a number of gear ratios. The flexibility of a CVT allows the shaft to maintain a constant angular velocity. When power is more important than economy, the ratio of the CVT can be changed to allow the engine to turn at the RPM at which it produces greatest power and this is typically higher than the RPM that achieves peak efficiency. In low-mass low-torque applications a belt-driven CVT offers ease of use, a CVT does not strictly require the presence of a clutch. Nevertheless, in vehicles, a centrifugal clutch is added to facilitate a neutral stance. Simple rubber belt CVTs are commonly used in motorized vehicles. Nearly all snowmobiles, utility vehicles, golf carts and motor scooters use CVTs, many small tractors and self-propelled mowers for home and garden use simple rubber belt CVT, though hydrostatic systems are more common.
Hydrostatic CVTs are common in small to medium-sized agricultural and earthmoving equipment, Transmission output is varied to control both travel speed and direction. In mowing or harvesting operations a CVT allows the speed of the tractor or combine harvester to be adjusted independently of the engine speed. This allows the operator to slow or accelerate as needed to accommodate variations in thickness of the crop, CVTs have been used in aircraft electrical power generating systems since the 1950s and in Sports Car Club of America Formula 500 race cars since the early 1970s. CVTs were banned from Formula 1 in 1994 because of concerns that the teams would dominate if they managed to create a viable F1 CVT. More recently, CVT systems have developed for go-karts and have proven to increase performance. The Tomcar range of vehicles utilizes the CVT system. Some drill presses and milling machines contain a pulley-based CVT where the shaft has a pair of manually adjustable conical pulley halves through which a wide drive belt from the motor loops.
The pulley on the motor, however, is fixed in diameter. This gap width thus adjusts the gearing ratio between the motors fixed pulley and the output shafts variable pulley, changing speed of the chuck, a tensioner pulley is implemented in the belt transmission to take up or release the slack in the belt as the speed is altered. In most cases, the speed must be changed with the motor running, in this most common CVT system, there are two V-belt pulleys that are split perpendicular to their axes of rotation, with a V-belt running between them
A coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power. Couplings do not normally allow disconnection of shafts during operation, however there are torque limiting couplings which can slip or disconnect when some torque limit is exceeded. The primary purpose of couplings is to two pieces of rotating equipment while permitting some degree of misalignment or end movement or both. By careful selection and maintenance of couplings, substantial savings can be made in reduced maintenance costs, shaft couplings are used in machinery for several purposes. The most common of which are the following, to transfer power from one end to another end. To provide for the connection of shafts of units that are manufactured separately such as a motor and generator, to provide for misalignment of the shafts or to introduce mechanical flexibility. To reduce the transmission of shock loads from one shaft to another, to alter the vibration characteristics of rotating units.
To connect driving and the driven part slips when overload occurs Clamped or compression rigid couplings come in two parts and fit together around the shafts to form a sleeve and they offer more flexibility than sleeved models, and can be used on shafts that are fixed in place. They consist of short sleeves surrounded by a perpendicular flange, one coupling is placed on each shaft so the two flanges line up face to face. A series of screws or bolts can be installed in the flanges to hold them together, because of their size and durability, flanged units can be used to bring shafts into alignment before they are joined together. Rigid couplings are used when precise shaft alignment is required, shaft misalignment will affect the performance as well as its life. Examples, A sleeve coupling consists of a pipe whose bore is finished to the required tolerance based on the shaft size, based on the usage of the coupling a keyway is made in the bore in order to transmit the torque by means of the key.
Two threaded holes are provided in order to lock the coupling in position, sleeve couplings are known as Box Couplings. In this case shaft ends are coupled together and abutted against each other which are enveloped by muff or sleeve, a gib head sunk keys hold the two shafts and sleeve together. In other words, this is the simplest type of the coupling and it is made from the cast iron and very simple to design and manufacture. It consists of a pipe whose inner diameter is same as diameter of the shafts. The hollow pipe is fitted over a two or more ends of the shafts with the help of the taper sunk key. a key and sleeve are useful to transmit power from one shaft to another shaft. In this coupling, the muff or sleeve is made into two parts of the cast iron and they are joined together by means of mild steel studs or bolts
The number of forward gear ratios is often expressed for manual transmissions as well. The most popular form found in automobiles is the automatic transmission. Similar but larger devices are used for heavy-duty commercial and industrial vehicles. This system uses a coupling in place of a friction clutch. These systems have a set of gear ranges, often with a parking pawl that locks the output shaft of the transmission to keep the vehicle from rolling either forward or backward. Some machines with limited speed ranges or fixed engine speeds, such as forklifts and lawn mowers. Despite superficial similarity to other transmissions, traditional automatic transmissions differ significantly in internal operation and drivers feel from semi-automatics and CVTs. In contrast to conventional automatic transmissions, a CVT uses a belt or other torque transmission scheme to allow a number of gear ratios instead of a fixed number of gear ratios. A semi-automatic retains a clutch like a transmission, but controls the clutch through electrohydraulic means.
The ability to shift gears manually, often via paddle shifters, can be found on certain automated transmissions, semi-automatics, the obvious advantage of an automatic transmission to the driver is the lack of a clutch pedal and manual shift pattern in normal driving. This allows the driver to operate the car with as few as two limbs, allowing amputees and other disabled individuals to drive, the automatic transmission was invented in 1921 by Alfred Horner Munro of Regina, Saskatchewan and patented under Canadian patent CA235757 in 1923. Being a steam engineer, Munro designed his device to use compressed air rather than hydraulic fluid and they were incorporated into GM-built tanks during World War II and, after the war, GM marketed them as being battle-tested. However, a Wall Street Journal article credits ZF Friedrichshafen with the invention, zFs origins were in manufacturing gears for airship engines beginning in 1915, the company was founded by Ferdinand von Zeppelin. Modern automatic transmissions can trace their origins to an early horseless carriage gearbox that was developed in 1904 by the Sturtevant brothers of Boston and this unit had two forward speeds, the ratio change being brought about by flyweights that were driven by the engine.
At higher engine speeds, high gear was engaged, as the vehicle slowed down and engine RPM decreased, the gearbox would shift back to low. Unfortunately, the metallurgy of the time wasnt up to the task, and owing to the abruptness of the gear change, the next significant phase in the automatic transmissions development occurred in 1908 with the introduction of Henry Fords remarkable Model T. The pedals actuated the transmissions friction elements to select the desired gear, in 1934, both REO and General Motors developed semi-automatic transmissions that were less difficult to operate than a fully manual unit. These designs, continued to use a clutch to engage the engine with the transmission, parallel to the development in the 1930s of an automatically shifting gearbox was Chryslers work on adapting the fluid coupling to automotive use
History of steam road vehicles
The first half of the 19th century saw great progress in steam vehicle design, and by the 1850s it was viable to produce them on a commercial basis. This progress was dampened by legislation which limited or prohibited the use of powered vehicles on roads. Nevertheless, the 1880s to the 1920s saw continuing improvements in technology and manufacturing techniques. Many of these vehicles were acquired by enthusiasts for preservation, in the 1960s the air pollution problems in California gave rise to a brief period of interest in developing and studying steam powered vehicles as a possible means of reducing the pollution. Apart from interest by steam enthusiasts, the occasional replica vehicle, the size reduction necessary for road transport meant an increase in steam pressure with all the attendant dangers, due to the inadequate boiler technology of the period. Ferdinand Verbiest is suggested to have built what may have been the first steam powered car in about 1672, during the latter part of the 18th century, there were numerous attempts to produce self-propelled steerable vehicles.
Many remained in the form of models, the extreme complexity of these issues can be said to have hampered progress over more than a hundred years, as much as hostile legislation. Nicolas-Joseph Cugnots machine à feu pour le transport de wagons et surtout de lartillerie was built from 1769 in two versions for use by the French Army and this was the first steam wagon that was not a toy, and that was known to exist. Cugnots fardier, a term applied to a massive two-wheeled cart for exceptionally heavy loads, was intended to be capable of transporting 4 tonnes. The vehicle was of tricycle layout, with two wheels and a steerable front wheel controlled by a tiller. It was reported as weighing 1520 kg fully loaded, with a speed of 14.5 km/h on the flat, during its first trip it was left unattended and self-destructed. Trevithick soon built the London Steam Carriage that ran successfully in London in 1803, in 1805 Oliver Evans built the Oruktor Amphibolos, a steam-powered, flat-bottomed dredger that he modified to be self-propelled on both land and water.
It is widely believed to be the first amphibious vehicle, however, no designs for the machine survive, and the only accounts of its achievements come from Evans himself. The dredger was not a success, and after a few years lying idle, was dismantled for parts, at the same time, the act gave local authorities the power to specify the hours during which any such vehicle might use the roads. The sole exceptions were street trams which from 1879 onwards were authorised under licence from the Board of Trade, in France the situation was radically different from the extent of the 1861 ministerial ruling formally authorising the circulation of steam vehicles on ordinary roads. Whilst this led to technological advances throughout the 1870s and 80s. To an extent competition from the railway network reduced the need for steam vehicles. Steam trucks were developed but their use was generally confined to the local distribution of heavy materials such as coal and building materials from railway stations
A transmission is a machine in a power transmission system, which provides controlled application of the power. Often the term refers simply to the gearbox that uses gears and gear trains to provide speed. In British English, the term refers to the whole drivetrain, including clutch, prop shaft, differential. In American English, the term more specifically to the gearbox alone. The most common use is in vehicles, where the transmission adapts the output of the internal combustion engine to the drive wheels. Such engines need to operate at a high rotational speed, which is inappropriate for starting, stopping. The transmission reduces the engine speed to the slower wheel speed. Transmissions are used on bicycles, fixed machines. Often, a transmission has multiple gear ratios with the ability to switch between them as speed varies and this switching may be done manually or automatically. Directional control may be provided, single-ratio transmissions exist, which simply change the speed and torque of motor output.
The output of the transmission is transmitted via the driveshaft to one or more differentials, while a differential may provide gear reduction, its primary purpose is to permit the wheels at either end of an axle to rotate at different speeds as it changes the direction of rotation. Conventional gear/belt transmissions are not the mechanism for speed/torque adaptation. Alternative mechanisms include torque converters and power transformation, automatic transmissions use a valve body to shift gears using fluid pressures in conjunction with an ecm. Early transmissions included the right-angle drives and other gearing in windmills, horse-powered devices, and steam engines, in support of pumping, most modern gearboxes are used to increase torque while reducing the speed of a prime mover output shaft. This means that the shaft of a gearbox rotates at a slower rate than the input shaft. A gearbox can be set up to do the opposite and provide an increase in speed with a reduction of torque. Some of the simplest gearboxes merely change the rotational direction of power transmission.
Many typical automobile transmissions include the ability to select one of several gear ratios, in this case, most of the gear ratios are used to slow down the output speed of the engine and increase torque
A preselector or self-changing gearbox is a type of manual gearbox used on a variety of vehicles, most commonly in the 1930s. Most pre-selector transmissions avoid a driver-controlled clutch entirely, some use one solely for starting off. Preselector gearboxes are not automatic gearboxes, although they may have internal similarities, a fully automatic gearbox is able to select the ratio used, with a preselector gearbox this remains the drivers decision. There are several radically different mechanical designs of preselector gearbox, the best known is the Wilson design. Some gearboxes, such as the Cotal, shift gear immediately the control is moved and these are termed self-changing gearboxes, but were considered under the same overall heading. In recent years, a role is carried out by the increasing number of Tiptronic or paddle shift gearboxes, using manual selection. For the driver, there are two advantages, Fast shifting, with only a single operation and this requires less skill to learn than techniques like double declutching and it offers faster shifts when racing.
Ability to handle far more power, with a lighter mechanism. In engineering terms, some designs of pre-selector gearbox may offer particular advantages, the Wilson gearbox offers these, although theyre shared by some of the other designs, even though the designs are quite different, Their friction components are brakes, rather than clutches. These are simpler to engineer, as the components can be arranged to not be rotating parts. The friction wear components can be mounted on the outside of the mechanism and this makes maintenance and regular adjustment easier. They were common on Daimler cars and commercial vehicles, Alvis, Talbot-Lago, Lagonda Rapier and they have been used in racing cars, such as the 1935 ERA R4D, and hillclimbing cars such as Auto Union Silver Arrows. Military applications began in 1929 and included tanks such as the German Tiger I and Tiger II in World War II, many pre-selector designs made use of a series of epicyclic gearboxes. The Wilson pre-selector gearbox is the best known design and is the archetype generally meant when the term pre-selector gearbox is used without further qualification, major W. G.
Wilson was rewarded as one of the major co-inventors of the tank after World War I. He had mainly been involved with the development of transmissions for tanks and he had become an advocate for the benefits of the epicyclic gearbox, which allowed large torques to be transmitted whilst still being controllable through a small input force. In 1917, Wilson designed the Mark V tank, which incorporated his epicyclic steering gear and this was the first of the heavy tanks that could be driven by a single driver, without requiring him to signal orders inside to others working the secondary gear levers. Since 1900, the Lanchester Motor Company had built cars with manually controlled epicyclic gearboxes, first with a cone clutch and these formed the ratio-changing gearbox of the transmission. In 1918, an experimental tank Lanchester Gearbox Machine or Experimental Machine K was tested, fitted with an epicyclic gearbox built by Lanchester, after the War, Wilson had a considerable reputation as an engineer of genius, particularly for gearbox design
Differential (mechanical device)
In automobiles and other wheeled vehicles, the differential allows the outer drive wheel to rotate faster than the inner drive wheel during a turn. 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, when used in this way, a differential couples the input shaft to the pinion, which in turn runs on the ring gear of the differential. This works as reduction gearing, on rear wheel drive vehicles the differential may connect to half-shafts inside an axle housing, or drive shafts that connect to the rear driving wheels. Front wheel drive tend to have the pinion on the end of the main-shaft of the gearbox. There are individual drive-shafts to each wheel, non-automotive uses of differentials include performing analog arithmetic.
The ball was painted black and white in hemispheres, and graphically showed the phase of the moon at a point in time. See the Chinese South-pointing chariot, an equation clock that used a differential for addition was made in 1720. In the 20th Century, large assemblies of many differentials were used as analog computers, for example, the development of electronic digital computers has made these uses of differentials obsolete. Practically all the differentials that are now made are used in automobiles, there are many claims to the invention of the differential gear, but it is possible that it was known, at least in some places, in ancient times. Some historical milestones of the include,100 BC–70 BC. Some such chariots may have used differential gears,658,666 AD, two Chinese Buddhist monks and engineers create south-pointing chariots for Emperor Tenji of Japan. 1720, Joseph Williamson uses a gear in a clock. 1810, Rudolph Ackermann of Germany invents a four-wheel steering system for carriages,1827, modern automotive differential patented by watchmaker Onésiphore Pecqueur of the Conservatoire National des Arts et Métiers in France for use on a steam wagon.
1832, Richard Roberts of England patents gear of compensation, a differential for road locomotives,1874, Aveling and Porter of Rochester, Kent list a crane locomotive in their catalogue fitted with their patent differential gear on the rear axle. 1876, James Starley of Coventry invents chain-drive differential for use on bicycles,1897, first use of differential on an Australian steam car by David Shearer. 1958, Vernon Gleasman patents the Torsen dual-drive differential, a type of differential that relies solely on the action of gearing, instead of a combination of clutches. An epicyclic differential can use epicyclic gearing to split and apportion torque asymmetrically between the front and rear axles, an epicyclic differential is at the heart of the Toyota Prius automotive drive train, where it interconnects the engine, motor-generators, and the drive wheels