Drive wheel

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 enough torque to the wheel to overcome stationary forces, resulting in the vehicle moving forwards or backwards.[1][2]

A two-wheel drive vehicle has two driven wheels, typically both at the front or back, while a four-wheel drive has four.

A steering wheel is a wheel that turns to change the direction of a vehicle. A trailer wheel is one that is neither a drive wheel, nor a steer wheel. Front-wheel drive vehicles typically have the rear wheels as trailer wheels.

The rear driven wheels of a racing car throwing gravel

Differentials and drive shafts deliver torque to the front and rear wheels of a four-wheel drive truck

Drive wheel configurations

Front-wheel drive

Front-wheel drive (FWD) vehicles’ engines drive the front wheels. Using the front wheels for delivery of power as well as steering allows the driving force to act in the same direction as the wheel is pointing.[3] This layout is commonly used in modern passenger cars.

Opperman Motocart

A rare example of front wheel drive was the Opperman Motocart. 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 small single cylinder Douglas engine carried on the front mono fork that formed the steering gear.

Rear-wheel drive

Rear-wheel drive (RWD) 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 also used.

It was a common layout used in automobiles throughout the 20th century. At this time, FWD designs were not practical due to complexity (in FWD, engine power and steering must both be combined in the front axle).

Rear-wheel Two-wheel Four-wheel Six-wheel Eight-wheel Twelve-wheel

Two-wheel drive

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 4×2 is also 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 torque is applied to only two wheels.

All-wheel drive

Four-wheel drive

This configuration allows all four road wheels to receive torque from the power plant simultaneously. It is often used in rally racing on mostly paved roads.

Four-wheel drive is common in off-road vehicles because powering all four wheels provides better control on loose and slippery surfaces. Four-wheel drive manufacturers have different systems such as “High Range 4WD” and “Low Range 4WD”. These systems may provide added features such as a varying of torque distribution between axles or varying gear ratios.[4]

Common terms for this configuration include four-wheel drive, 4WD, 4×4 (pronounced “four-by-four”), and all-wheel drive (AWD).

Six-wheel drive

Eight-wheel drive

Twelve-wheel drive

Notes

  1. “Driving wheel”. thefreedictionary.com. Retrieved 13 July 2013any wheel of a vehicle that transforms torque into a tractive force.
  2. Russ, Carey. “Driving Wheels: Introduction and Rear-Wheel Drive”. The Auto Channel. Retrieved 13 July 2013.
  3. Hillier, V.A.W.; Coombes, Peter (2004). Hilliers Fundamentals of Motor Vehicle Technology (Fifth ed.). Nelson Thornes. p. 263. ISBN 9780748780822. Retrieved 13 June2013.
  4. “Jeep.ca”. www.jeep.ca. Retrieved 2016-07-25.
Torque converter A torque converter is a type of fluid coupling which transfers rotating power from a prime mover, like an internal combustion engine, to a rotating driven load. In a vehicle with an automatic transmission, the torque converter connects the power source to the load. It is usually located between the engine's flexplate and the transmission. The equivalent location in a manual transmission would be the mechanical clutch. The key characteristic of a torque converter is its ability to multiply torque when the output rotational speed is so low that it allows the fluid coming off the curved vanes of the turbine to be deflected off the stator while it is locked against its one-way clutch, thus providing the equivalent of a reduction gear. This is a feature beyond that of the simple fluid coupling, which can match rotational speed but does not multiply torque, thus reduces power. Some of these devices are also equipped with a "lockup" mechanism which rigidly binds the engine to th...
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 ...
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 ta...
Transmission (mechanics) A transmission is a machine in a power transmission system, which provides controlled application of the power. Often the term transmission refers simply to the gearbox that uses gears and gear trains to provide speed and torque conversions from a rotating power source to another device. In British English, the term transmission refers to the whole drivetrain, including clutch, gearbox, prop shaft (for rear-wheel drive), differential, and final drive shafts. In AmericanEnglish, however, the term refers more specifically to the gearbox alone, and detailed usage differs. The most common use is in motor vehicles, where the transmission adapts the output of the internal combustion engine to the drive wheels. Such engines need to operate at a relatively high rotational speed, which is inappropriate for starting, stopping, and slower travel. The transmission reduces the higher engine speed to the slower wheel speed, increasing torque in the process. Transmissions are also used on pedal...
Suspension A clutch is a mechanical device which engages and disengages power transmission especially from driving shaft to driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). In these devices, one shaft is typically attached to an engine or other power unit (the driving member) while the other shaft (the driven member) provides output power for work. While typically the motions involved are rotary, linear clutches are also possible. In a torque-controlled drill, for instance, one shaft is driven by a motor and the other drives a drill chuck. The clutch connects the two shafts so they may be locked together and spin at the same speed (engaged), locked together but spinning at different speeds (slipping), or unlocked and spinning at different speeds (disengaged).   Single dry-clutch friction disc. The splined hub is attached to the disc with springs to damp chatter. Friction clutches ...