Non-synchronous transmission

A non-synchronous transmission is a form of transmission based on gears that do not use synchronizing mechanisms. They are found primarily in various types of agricultural and commercial vehicles. Because the gear boxes are engineered without "cone and collar" synchronizing technology, the non-synchronous transmission type requires an understanding of gear range, torque, engine power, range selector, multi-functional clutch, and shifter functions. Engineered to pull tremendous loads, often equal to or exceeding 40 tons, some vehicles may also use a combination of transmissions for different mechanisms. An example would be a power take-off. History In 1890, Panhard used a chain-drive with a Daimler engine in a horseless carriage. Industrial marketing has since then coined spectacular names for various vehicle parts. Changing from the Locomobile, a 1906 race-car to what is now called the automobile, advertisers used design wording from the engineering departments to give new ideas a desirable appeal for sales promotions. From 1932, synchronizer mechanisms began to appear in automotive transmissions. The split-off of automotive transmission types that has prevailed in engineering designs uses three major categories: automatic, manual, and non-synchronous. Some of the differences are improvements, including the continuously variable transmission installed in hybrid vehicles that are powered partly by an internal combustion engine, and partly by an electric motor. The concepts of transmission continue to employ methods for transferring the most conceivably efficient use of power. How non-synchronization works Diagram of a non-synchronous transmission showing gear fork, gear box, and gears that would be used in a commercial motor vehicle Non-synchronous transmissions are engineered with the understanding that a trained operator will be shifting gears in a known coordination of timing. Commercial vehicle operators use a double-clutching technique that is taught in driver's trade schools. The most skillful drivers can shift these transmissions without using the clutch by bringing the engine to exactly the right rpm in neutral before attempting to complete a shift, a technique called "float-shifting." With payloads of cargo ranging in commercial freight of 80,000 lbs (40 tons (short) or 36.3 tonnes) or more, some heavy haulers have over 24 ″gears″ (i.e., combinations of gear ratios) that an operator will shift through before reaching a top cruising speed of 70 mph (113 km/h). Many low-low (creeper) gears are used in farm equipment to plow, till, or harvest. Also see Engineering vehicle. An inexperienced operator could suddenly find a piece of heavy equipment stuck in the wrong gear under full power, or even worse unable to shift a runaway vehicle from neutral into a gear for braking effect when headed down a steep slope, unless he or she possessed the synchronizing skill and understood torque issues in non-synchronous transmissions. Many...

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Manual transmission

A manual transmission, also known as a manual gearbox, a standard transmission or colloquially in some countries (e.g. the United States) as a stick shift is a type of transmission used in motor vehicle applications. It uses a driver-operated clutch engaged and disengaged by a foot pedal (automobile) or hand lever (motorcycle), for regulating torque transfer from the engine to the transmission; and a gear selector operated by hand (automobile) or by foot (motorcycle). A conventional 5-speed manual transmission is often the standard equipment in a base-model vehicle, while more expensive manual vehicles are usually equipped with a 6-speed transmission instead; other options include automatic transmissions such as a traditional automatic (hydraulic planetary) transmission (often a manumatic), a semi-automatic transmission, or a continuously variable transmission (CVT). The number of forward gear ratios is often expressed for automatic transmissions as well (e.g., 9-speed automatic). Overview Manual transmissions often feature a driver-operated clutch and a movable gear stick. Most automobile manual transmissions allow the driver to select any forward gear ratio ("gear") at any time, but some, such as those commonly mounted on motorcycles and some types of racing cars, only allow the driver to select the next-higher or next-lower gear. This type of transmission is sometimes called a sequential manual transmission. In a manual transmission, the flywheel is attached to the engine's crankshaft and spins along with it. The clutch disk is in between the pressure plate and the flywheel, and is held against the flywheel under pressure from the pressure plate. When the engine is running and the clutch is engaged (i.e., clutch pedal up), the flywheel spins the clutch plate and hence the transmission. As the clutch pedal is depressed, the throw out bearing is activated, which causes the pressure plate to stop applying pressure to the clutch disk. This makes the clutch plate stop receiving power from the engine, so that the gear can be shifted without damaging the transmission. When the clutch pedal is released, the throw out bearing is deactivated, and the clutch disk is again held against the flywheel, allowing it to start receiving power from the engine. Manual transmissions are characterized by gear ratios that are selectable by locking selected gear pairs to the output shaft inside the transmission. Conversely, most automatic transmissions feature epicyclic (planetary) gearing controlled by brake bands and/or clutch packs to select gear ratio. Automatic transmissions that allow the driver to manually select the current gear are called manumatics. A manual-style transmission operated by computer is often called an automated transmission rather than an automatic, even though no distinction between the two terms need be made. Contemporary automobile manual transmissions typically use four to six forward gear ratios and one reverse gear, although consumer...

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Direct-shift gearbox

A direct-shift gearbox (German: Direkt-Schalt-Getriebe), commonly abbreviated to DSG, is an electronically controlled dual-clutch multiple-shaft manual gearbox in a transaxle design, without a conventional clutch pedal and with fully automatic or semi-manual control. The first actual dual-clutch transmissions were derived from Porsche in-house development for their Model 962 racing cars in the 1980s. In simple terms, a DSG is two separate manual gearboxes (and clutches) contained within one housing and working as one unit.It was designed by BorgWarner and is licensed to the Volkswagen Group, with support by IAV GmbH.  By using two independent clutches, a DSG can achieve faster shift times and eliminates the torque converter of a conventional epicyclic automatic transmission. Part-cutaway view of the Volkswagen Group 6-speed direct-shift gearbox. The concentric multi-plate clutches have been sectioned, along with the mechatronics module. This also shows the additional power take-off for distributing torque to the rear axle for four-wheel drive applications. (View this image with annotations) Overview Transverse DSG At the time of launch in 2003, it became the world's first dual-clutch transmission in a series-production car, in the German-market Volkswagen Golf Mk4 R32, and shortly afterwards worldwide, in the original Audi TT 3.2. and the 2004+ New Beetle TDI. For the first few years of production, this original DSG transmission was only available in transversely oriented front-engine, front-wheel-drive and Haldex Traction-based four-wheel-drive vehicle layouts. The first DSG transaxle that went into production for the Volkswagen Group mainstream marques had six forward speeds (and one reverse) and used wet/submerged multi-plate clutch packs (Volkswagen Group internal code: DQ250, parts code prefix: 02E). It has been paired to engines with up to 350 N⋅m (260 lb⋅ft) of torque. The two-wheel-drive version weighs 93 kg (205 lb). It is manufactured at Volkswagen Group's Kassel plant, with a daily production output of 1,500 units. At the start of 2008, another world-first 70 kg (150 lb) seven-speed DSG transaxle (Volkswagen Group internal code: DQ200, parts code prefix: 0AM) became available. It differs from the six-speed DSG, in that it uses two single-plate dry clutches (of similar diameter). This clutch pack was designed by LuK Clutch Systems, Gmbh. This seven-speed DSG is used in smaller front-wheel-drive cars with smaller-displacement engines with lower torque outputs, such as the latest Volkswagen Golf, Volkswagen Polo Mk5, and the new SEAT Ibiza. It has been paired to engines with up to 250 N⋅m (180 lb⋅ft). It has considerably less oil capacity than the six-speed DQ250; this new DQ200 uses just 1.7 litres (0.37 imp gal; 0.45 US gal) of transmission fluid. In September 2010, VW launched a new seven-speed DSG built to support up to 600 N⋅m (440 lb⋅ft), the DQ500.  Audi longitudinal DSG In late 2008, an all-new seven-speed longitudinal S tronic version of the DSG transaxle went into series production (Volkswagen Group internal code: DL501, parts code prefix: 0B5). Initially, from early 2009, it is only used in certain Audi cars, and only with longitudinally mounted engines. Like the original six-speed DSG, it features a concentric dual wet multi-plate clutch. However, this particular variant uses notably more plates —...

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Differential (mechanical device)

A differential is a gear train with three shafts that has the property that the rotational speed of one shaft is the average of the speeds of the others, or a fixed multiple of that average. A spur gear differential constructed by engaging the planet gears of two co-axial epicyclic gear trains. The casing is the carrier for this planetary gear train. Overview Automotive differential: The drive gear 2 is mounted on the carrier 5 which supports the planetary bevel gears 4 which engage the driven bevel gears 3 attached to the axles 1. ZF Differential. The drive shaft enters from the front and the driven axles run left and right. Car differential of a Škoda 422 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 longitudinal input propellor shaft to the pinion, which in turn drives the transverse ring gear of the differential. This also 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 vehicles tend to have the engine crankshaft and the gearbox shafts transverse, and with the pinion on the end of the main-shaft of the gearbox and the differential enclosed in the same housing as the gearbox. There are individual drive-shafts to each wheel. A differential consists of one input, the drive shaft, and two outputs which are the two drive wheels, however the rotation of the drive wheels are coupled to each other by their connection to the roadway. Under normal conditions, with small tire slip, the ratio of the speeds of the two driving wheels is defined by the ratio of the radii of the paths around which the two wheels are rolling, which in turn is determined by the track-width of the vehicle (the distance between the driving wheels) and the radius of the turn. Non-automotive uses of differentials include performing analog arithmetic. Two of the differential's three shafts are made to rotate through angles that represent (are proportional to) two numbers,...

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Chain drive

Chain drive is a way of transmitting mechanical power from one place to another. It is often used to convey power to the wheels of a vehicle, particularly bicycles and motorcycles. It is also used in a wide variety of machines besides vehicles. Most often, the power is conveyed by a roller chain, known as the drive chain or transmission chain, passing over a sprocket gear, with the teeth of the gear meshing with the holes in the links of the chain. The gear is turned, and this pulls the chain putting mechanical force into the system. Another type of drive chain is the Morse chain, invented by the Morse Chain Company of Ithaca, New York, United States. This has inverted teeth. Sometimes the power is output by simply rotating the chain, which can be used to lift or drag objects. In other situations, a second gear is placed and the power is recovered by attaching shafts or hubs to this gear. Though drive chains are often simple oval loops, they can also go around corners by placing more than two gears along the chain; gears that do not put power into the system or transmit it out are generally known as idler-wheels. By varying the diameter of the input and output gears with respect to each other, the gear ratio can be altered. For example, when the bicycle pedals' gear rotate once, it causes the gear that drives the wheels to rotate more than one revolution. Roller chain and sprocket History Oldest known illustration of an endless power-transmitting chain drive, from Su Song's book of 1092 AD, describing his clock tower of Kaifeng Sketch of roller chain by Leonardo da Vinci The oldest known application of a chain drive appears in the Polybolos, a repeating crossbow described by the Greek engineer Philon of Byzantium (3rd century BC). Two flat-linked chains were connected to a windlass, which by winding back and forth would automatically fire the machine's arrows until its magazine was empty. Although the device did not transmit power continuously since the chains "did not transmit power from shaft to shaft, and hence they were not in the direct line of ancestry of the chain-drive proper", the Greek design marks the beginning of the history of the chain drive since "no earlier instance of such a cam is known, and none as complex is known until the 16th century." It is here that the flat-link chain, often attributed to Leonardo da Vinci, actually made its first appearance." The first continuous and endless power-transmitting chain was depicted in the written horological treatise of the Song Dynasty (960–1279) Chinese engineer Su Song (1020-1101 AD), who used it to operate the armillary sphere of his astronomical clock tower as well as the...

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Continuously variable transmission

continuously variable transmission (CVT), also known as a single-speed transmission, stepless transmission, pulley transmission, or, in case of motorcycles, a twist-and-go, 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 fixed number of gear ratios. The flexibility of a CVT with suitable control may allow the input shaft to maintain a constant angular velocity even as the output speed varies. A belt-driven design offers approximately 88% efficiency, which, while lower than that of a manual transmission, can be offset by lower production cost and by enabling the engine to run at its most efficient speed for a range of output speeds. 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. This is typically higher than the RPM that achieves peak efficiency. In low-mass low-torque applications (such as motor scooters) a belt-driven CVT also offers ease of use and mechanical simplicity. A CVT does not strictly require the presence of a clutch. Nevertheless, in some vehicles (e.g. motorcycles), a centrifugal clutch is added to facilitate a "neutral" stance, which is useful when idling or manually reversing into a parking space. Uses Chain-driven CVT Principle of variator Simple rubber belt (non-stretching fixed circumference manufactured using various highly durable and flexible materials) CVTs are commonly used in small motorized vehicles, where their mechanical simplicity and ease of use outweigh their comparative inefficiency. Nearly all snowmobiles, utility vehicles, golf carts and motor scooters use CVTs, typically the rubber belt or variable pulley variety. Many small tractors and self-propelled mowers for home and garden also use simple rubber belt CVT. Hydrostatic systems are more common on the larger units—the walk-behind self-propelled mowers are of the slipping belt variety. Hydrostatic CVTs are common in small to medium-sized agricultural and earthmoving equipment. As the engines in these machines are typically run at constant power settings to provide hydraulic power or to power machinery, losses in mechanical efficiency are offset by enhanced operational efficiency, such as reduced forward-reverse shuttle times in earthmoving operations. Transmission output is varied to control both travel speed and direction. This is particularly beneficial in equipment designed to pivot or skid steer through differential power application as the required differential steering action can easily be supplied by independent CVTs, allowing steering to be accomplished without braking losses or loss of tractive effort and allowing the machine to pivot in place. In mowing or harvesting operations a CVT allows the forward...

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Constant-velocity joint

Constant-velocity joints (also known as homokinetic or CV joints) allow a drive shaft to transmit power through a variable angle, at constant rotational speed, without an appreciable increase in friction or play. They are mainly used in front wheel drive vehicles, and many modern rear wheel drive cars with independent rear suspension typically use CV joints at the ends of the rear axle halfshafts and increasingly use them on the drive shafts. Constant-velocity joints are protected by a rubber boot, a CV gaiter, usually filled with molybdenum disulfide grease. Cracks and splits in the boot will allow contaminants in, which would cause the joint to wear quickly as grease leaks out. This way the friction parts don’t get proper lubrication and get damaged due to minor particles that get in, while water causes metal components to rust and corrode. Wear of the boot often takes the form of small cracks, which appear closer to the wheel,  because it is the wheel that produces vibration and up and down motions. Cracks and tears in the areas closer to the axle are usually caused by external factors, such as packed snow, stones or uneven rocky off-road paths. Animated representation of a six-ball Rzeppa-type constant-velocity joint History A universal joint, an earlier means of transmitting power between two angled shafts The universal joint, one of the earliest means of transmitting power between two angled shafts, was invented by Gerolamo Cardanoin the 16th century. The fact that it failed to maintain constant velocity during rotation was recognized by Robert Hooke in the 17th century, who proposed the first constant velocity joint, consisting of two Cardan joints offset by 90 degrees, so as to cancel out the velocity variations. This is the "double Cardan", shown below. Many different types of constant-velocity joints have been invented since then. Early automotive drive systems Early front wheel drive systems such as those used on the Citroën Traction Avant and the front axles of Land Rover and similar four wheel drive vehicles used universal joints, where a cross-shaped metal pivot sits between two forked carriers. These are not CV joints as, except for specific configurations, they result in a variation of the angular velocity. They are simple to make and can be tremendously strong and are still used to provide a flexible coupling in some propshafts, where there is not very much movement. However, they become "notchy" and difficult to turn when operated at extreme angles. The first CV joints As front wheel drive systems became more popular, with cars such as the BMC Mini using compact transverse engine layouts, the shortcomings of universal joints in front axles became more...

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