In automotive design, the front-engine, front-wheel-drive (FWD) front-engine, front-wheel-drive (b) layout incorporates internal combustion engine and steering wheel driven on the front of the vehicle.
Video Front-engine, front-wheel-drive layout
Usage implications
Historically, this designation is used regardless of whether the whole machine is behind the front axis. Recently, several car manufacturers have been added to the designation with a mid-term term that describes the car in which the engine is in front of the passenger compartment but behind the front axle. Most pre-World War II front-engine cars will qualify as front-center engines, using mid-front designation, or on the front axle.
This layout is the most traditional form, and remains a popular and practical design. Machines that take up a lot of space packed in passenger locations and luggage usually will not be used. The main deficit is weight distribution - the heaviest component is at one end of the vehicle. Car handling is not ideal, but usually predictable.
Unlike the front-engine layout, rear-wheel-drive (RWD), FWD layout eliminates the need for a central tunnel or higher chassis to accommodate the driveshaft that provides power to the rear wheels. Like the rear engine, rear-wheel-drive (RR) layout and rear-engine backdrop layout, rear-wheel-drive layout (RMR), placing the engine on the drive wheel, increasing traction in many applications. Because the steering wheel is also an actuated wheel, FWD cars are generally considered to be superior to RWD cars in conditions where there is low traction like snow, mud, gravel or wet tarmak. When climbing a hill in low traction conditions, the RR is regarded as the best two-wheel-drive layout, mainly because of the heavy shift to the rear wheels while climbing. The ability to corner a FWD vehicle is generally better, because the engine is placed on a steering wheel. However, since the driven wheels have additional steering demands, if the vehicle accelerates quickly, the grip is less available for cornering, which can lead to understeer. High-performance vehicles rarely use the FWD layout because the weights are transferred to the rear wheels under acceleration, while unloading the front wheel and reducing its grip sharply, effectively placing limits on the amount of power that can realistically be utilized; In addition, high horsepower from high performance cars can produce torque steer sensations. Electronic traction controls can avoid wheel spin but most negate the benefits of extra power. This is the reason to adopt the quattro four-wheel-drive system in high-performance Jensen FF and Audi Quattro road cars.
Maps Front-engine, front-wheel-drive layout
Historical settings
Early cars that used the FWD layout included 1929 Cable L-29, 1931 DKW F1, 1948 CitroÃÆ'¡n 2CV, 1949 Saab 92 and 1959 Mini. In the 1980s, traction advantages and layout packaging led many mid and compact size vehicle makers to adopt it in the US. Most European and Japanese manufacturers switched to front-wheel drive for the majority of their cars in the 1960s and 1970s, the latter being VW, Ford Europe and General Motors (Vauxhall - UK and Opel - Germany). Toyota was the last Japanese company to change in the early 1980s. BMW, focusing on luxury vehicles, but maintaining the rear wheel layout in their smaller cars though their MINI marque is FWD.
There are four different settings for this basic layout, depending on the location of the machine, which is the heaviest component of the drivetrain.
Mid-engine/Front-wheel drive
The earliest initial setup is not technically FWD, but rather a middle-engine layout, front-drive wheel (MF). The engine is mounted longitudinally (front and rear, or north-south) behind the wheel, with the transmission in front of the engine and the differential at the front of the car. With engines so far, the weight distribution of cars like the Cord L-29 is not ideal; driven wheels do not carry a sizeable weight proportion for traction and good handling. The 1934 CitroÃÆ' Â «Traction Avant solves the problem of weight distribution by placing a transmission on the front of the car with a differential between it and the engine. Combined with a low unibody design slung over the car, this generates tremendous handling for the era. Renault is the most recent user of this format - has used it on Renault 4, and Renault 5 first generation, but has since been disliked for disturbing interior space.
Front-engine engine and longitudinal front wheel drive mounted
The 1946 Panhard Dyna X, designed by Jean-Albert GrÃÆ' Â © goire, has a longitudinal engine in front of the front wheels, with a transmission behind the engine and a differential on the back of the assembly. This arrangement, used by Panhard until 1967, has the potential to have a weight distribution problem analogous to the above mentioned L29 Cord. However, Panhard's air-cooled flat twin engines are very light, and are mounted downward with a low center of gravity that reduces its effect. Air-cooled twin engine from CitroÃÆ'¡n 2CV is also mounted very low, in front of the front wheels, with the transmission behind the axle line and the differential between the two. It became very popular; cars using this layout include Ford Taunus 12M Germany and Lancia Flavia and Fulvia. This is the standard configuration of the Audi and Subaru front-wheel-drive vehicles. In 1979, Toyota introduced and launched their first front-wheel-drive car, Tercel, and the engine was installed longitudinally, unlike most other front-wheel drive cars on the market at that time. This arrangement continued also in the second generation Tercel, until 1987, the third generation received a new engine, mounted transversely. Other Toyota front-wheel models, such as the Camry, and Corolla, have installed the engine from scratch.
The 1966 Oldsmobile Toronado (along with his sister model Cadillac Eldorado and Buick Riviera) uses a novel arrangement that has engines and transmissions in a 'side-by-side' setting with the power transmitted between the two through heavy duty chains, and a specially designed medium driveshaft who passed under the engine. This family has the distinction of being the highest capacity engine (8.2 L) front wheel vehicle ever built. Saab 99 and Saab 900 "classics" also use similar arrangements. Eagle Premier uses a similar powertrain arrangement found on Renault 21 and 25 - later becoming the base for the Chrysler LH sedan that was produced up to the 2004 model year.
Currently, Audi is the most prominent user of this mechanical layout, has been using it since the 1950s in its predecessor DKW and Auto Union, and it can be found in larger models from A4 and above. The latest evolution of the format on the MLB platform Audi strives to overcome the unfair disadvantage of uneven weight distribution. This is done by packing the differential in front of the clutch, allowing the axle line further forward in relation to the rear face of the engine block.
Horizontally mounted front-engine drives/Front-wheel drive
The popular popular popular FWD car is the DKW 'Front' made from 1931, which features a two-cylinder two-cylinder engine. Saab copied this design on their first car, Saab 1910 92. Trabant in 1957 was also the only car with a transverse engine to become a precursor of the DKW. This is a new thing, especially for cars made in communist countries.
Mini Issigonis in 1959 and related cars such as Maxi, Austin 1100/1300 and Allegro have inline four-cylinder inline water engines mounted transversely. The transmission is located on the sump under the crankshaft, with the power transmitted by the transfer gear. Other models that use the "transmission-in-sump" layout include Datsun 100A (Cherry) and various applications from the PSA-Renault X-Type engine such as the Peugeot 104 and Renault 14. Suzuki Suzulight 1955 also introduced the front engine with two twin-cylinder engines transversely installed steps (using DKW technology) in car city car/ kei applications, based on Lloyd LP400 Germany.
Dante Giacosa's Autobianchi Primula in 1964, Fiat 128 and Fiat 127, put the transmission on one side of the transversely mounted engine, and doubled the drivetrain to place the differential just behind the transmission, but offset it to one side. Therefore the driveshafts to the wheels are longer on one side than the other. It lies just a little weight in front of the wheel. It is this system that dominates the world today.
Front-wheel drive vehicles tend to suffer from torque steer under heavy acceleration. This is due to the difference in drive shaft length which in turn results in different incidence angles at the driveshaft joint. The further along these joints are articulate, the less effective they are in giving the torque to the wheels.
Characteristics of front wheel design
Front wheel drive spindle
On the front-wheel drive vehicle, the drive shaft transferring the drive directly from the differential to the front wheels. A short stub on the inside is aligned with the differential side gear and the outer stub axle is aligned with the front wheel hub. Each stub axis has a yoke, or housing, to accommodate the universal connection, at each end of the connecting connecting shaft.
Universal joints let the shaft continue to spin while allowing changes due to suspension movements, such as the length of the shaft and horizontal angle, and the shaft angle as the wheel rotates. The universal speed constant jacks are commonly used to transfer power smoothly between components. The inside of the universal can be a plunge or tripod type connection. The tripod is placed on the intermediate shaft and held by the circle. A ball, supported on a needle roller bearing, is attached to each tripod post, and this slide is in the trunks inside the yoke. It serves the shaft length and horizontal angle changes. Drive is transferred through trunks and balls to rotate the shaft.
The universal outer joint allows for larger angular changes but does not change in the length of the shaft. This is usually a ball and type of enclosure with an inner race that extends into the middle axis. The outer races are formed on the yoke. The cage maintains the ball at a location in the groove in both races. The ball transfers the drive from the shaft to the hub and allows changes in the horizontal angle and for the wide steering angle to be achieved. Flexible rubber boots mounted on each connection hold the grease and prevent dirt and moisture.
Where the differential is not located in the centerline of the vehicle, the intermediate shaft can be mounted to maintain the drive shaft of equal length on each side. This keeps the drive shaft angle the same on both sides and helps prevent steering irregularities and vibrations. The outer end of the intermediate shaft is supported by the pads secured to the transaxle case and the universal connection support by alignment. In some cases, the longer drive shaft is used on one side. Dynamic rubber absorbers can be installed to absorb vibrations.
See also
- Front wheel drive
References
Further reading
- Sedgwick, Michael Cars of the 50s and 60s . Gothenburg, Sweden: A B Nordbok, 1983. (Includes engine layout images from Traction Avant and other designs.)
Source of the article : Wikipedia
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