Axle

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Axle

An axle is a central shaft for a rotating

Rotation

A rotation is a movement of an object in a circular motion. A two-dimensional object rotates around a center of rotation. A Three-dimensional space object rotates around a line called an axis....
wheel

Wheel

A wheel is a circular device that is capable of rotating on its axis, facilitating movement or transportation whilst supporting a load , or performing labour in machines....
or gear

Gear

A gear is a component within a Transmission device that transmits rotational force to another gear or device. A gear is different from a pulley in that a gear is a round wheel that has linkages that mesh with other gear teeth, allowing force to be fully transferred without slippage....
. In some cases the axle may be fixed in position with a bearing

Bearing (mechanical)

A bearing is a device to allow constrained relative motion between two parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation as well as by the directions of applied loads they can handle....
or bushing

Bushing

A bushing is a cylindrical lining designed to reduce friction and wear inside a hole, or constrict and restrain motion of mechanical parts....
sitting inside the hole in the wheel or gear to allow the wheel or gear to rotate around the axle. In other cases the wheel or gear may be fixed to the axle, with bearings or bushings provided at the mounting points where the axle is supported. Sometimes, especially on bicycle

Bicycle

The bicycle, bike, or cycle is a pedal-driven, human-powered transport with two bicycle wheel attached to a bicycle frame, one behind the other....
s, the latter type is referred to as a spindle

Spindle

Originally, a spindle was a device to spin fibres into thread; see spindle . The term may refer also to:...
.

Vehicle axles
Axles are an integral structural component of a wheeled vehicle

Vehicle

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Encyclopedia

An axle is a central shaft for a rotating

Rotation

Wheel

A wheel is a circular device that is capable of rotating on its axis, facilitating movement or transportation whilst supporting a load , or performing labour in machines....
or gear

Gear

Bearing (mechanical)

Bushing

Bicycle

Spindle

Originally, a spindle was a device to spin fibres into thread; see spindle . The term may refer also to:...
.

Vehicle axles

Axles are an integral structural component of a wheeled vehicle

Vehicle

Vehicles, derived from the Latin word, vehiculum, are non-living means of transport. Most often they are manufactured , although some other means of transport which are not made by humans also may be called vehicles; examples include icebergs and floating tree trunks....
. The axles maintain the position of the wheels relative to each other and to the vehicle body. Since for most vehicles the wheels are the only part touching the ground, the axles must bear the weight of the vehicle plus any cargo

Cargo

Cargo refers to goods or produce transported, generally for Commerce gain, by Cargo ship, Cargo airline, Train#Freight trains, van or truck. In modern times, containers are used in most intermodal freight transport long-haul cargo transport....
, as well as acceleration and braking forces. In addition to the structural purpose, axles may serve one or more of the following purposes depending on the design of the vehicle.

Drive: One or more axles may be an integral part of the drivetrain. A mechanical system (typically a motor
Electric motor

An electric motor uses electrical energy to produce mechanical energy, nearly always by the interaction of magnetic fields and current-carrying conductors....
) exerts a rotational force on the axle, which is transferred to the wheel(s) to accelerate the vehicle.
Braking
Brake

A brake is a device for applying a force against the friction of the road, slowing or stopping the motion of a machine or vehicle, or alternatively a device to restrain it from starting to move again....
: Conversely a vehicle may be slowed by applying force to brake the rotation of the axle. Consumer vehicles' brakes are part of the wheel assembly and therefore exert friction on the wheels directly, but engine braking
Engine braking

Engine braking is the act of using the energy-requiring compression phase of a heat engine to dissipate energy and slow down a vehicle. Compression braking is a common legal term for the same mechanism....
may still be effected via the axle.
Steering
Steering

Steering is the term applied to the collection of components, linkages, etc. which will allow for a vessel or vehicle to follow the desired course....
: The front axle of most automobile
Automobile

An automobile or motor car is a wheeled motor vehicle for transportation passengers, which also carries its own car engine or motor. Most definitions of the term specify that automobiles are designed to run primarily on roads, to have seating for one to eight people, to typically have four wheels, and to be constructed principally f...
s is a steering axle. The vehicle is maneuvered by controlling the direction of the front wheels' rotational axis relative to the body and rear wheels.

Structural features

A straight axle is a single rigid shaft connecting a wheel on the left side of the vehicle to a wheel on the right side. The axis of rotation fixed by the axle is common to both wheels. Such a design can keep the wheel positions steady under heavy stress, and can therefore support heavy loads. Straight axles are used on train

Train

A train is a connected series of vehicles that move along a track to rail transport from one place to another. The track usually consists of two rail tracks, but might also be a monorail or magnetic levitation train guideway....
s, for the rear axles of commercial truck

Truck

File:Red truck USA.JPGA truck is a type of motor vehicle commonly used for carrying goods and materials. Some light trucks are relatively small, similar in size to a passenger automobile....
s, and on heavy duty off-road vehicles. The axle can be protected and further reinforced by enclosing the length of the axle in a housing.

In split-axle designs, the wheel on each side is attached to a separate shaft. Modern passenger cars have split drive axles. In some designs, this allows independent suspension

Independent suspension

Independent suspension is a broad term for any automobile suspension system that allows each wheel on the same axle to move vertically independently of each other....
of the left and right wheels, and therefore a smoother ride. Even when the suspension is not independent, split axles permit the use of a differential, allowing the left and right drive wheels to be driven at different speeds as the automobile turns, improving traction and extending tire life.

A tandem axle is a group of two or more axles situated close together. Trucks designs will use such a configuration to provide a greater weight capacity than a single axle. Semi trailers usually have a tandem axle at the rear.

Drive axles

An axle that is driven by the engine is called a drive axle.

Modern front wheel drive cars typically combine the transmission

Transmission (mechanics)

Using the principle of mechanical advantage, transmissions provide a speed-torque conversion from a higher speed motor to a slower but more forceful output or vice-versa....
and front axle into a single unit called a transaxle

Transaxle

A transaxle, in the automotive field, is a major mechanical component which combines the functionality of the transmission , the differential and associated components of the driven axle into one integrated assembly....
. The drive axle is a split axle with a differential

Differential (mechanics)

A differential is a device, usually but not necessarily employing gears, capable of transmitting torque and rotation through three shafts, almost always used in one of two ways....
and universal joint

Universal joint

A universal joint, U joint, Gerolamo Cardano joint, Hardy-Clarence W. Spicer joint, or Hooke's joint is a joint in a rigid rod that allows the rod to 'bend' in any direction, and is commonly used in shafts that transmit rotary motion....
s between the two half axles. Each half axle connects to the wheel by use of a constant velocity (CV) joint

Constant-velocity joint

Constant-velocity joints allow a rotating shaft to transmit power through a variable angle, at constant rotational speed, without an appreciable increase in friction or play....
which allows the wheel assembly to move freely vertically as well as to pivot when making turns.

In rear wheel drive cars and trucks, the engine turns a driveshaft

Driveshaft

A drive shaft, driving shaft, propeller shaft, or Universal joint#History shaft is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement between them....
which transmits rotational force to a drive axle at the rear of the vehicle. The drive axle may be a live axle

Live axle

A live axle, sometimes called a solid axle, is a type of beam axle suspension that uses the driveshafts that transmit power to the wheels to connect the wheels laterally so that they move together as a unit....
, but modern automobiles generally use a split axle with a differential.

Some simple vehicle designs, such as go-karts, may have a single drive wheel. The drive axle is a split axle with only one of the two shafts driven by the engine.

Dead axles/lazy axles

A dead axle, also called lazy axle, is not part of the drivetrain but is instead free-rotating. The rear axle of a front-wheel drive car may be considered a dead axle. Many trucks and trailers use dead axles for strictly load-bearing purposes. A dead axle located immediately in front of a drive axle is called a pusher axle. A tag axle is a dead axle situated behind a drive axle.

Some dump truck

Dump truck

A dump truck or production truck is a truck used for transporting loose material for construction. A typical dump truck is equipped with a Hydraulic machinery operated open-box bed hinged at the rear, the front of which can be lifted up to allow the contents to be deposited on the ground behind the truck at the site of delivery....
s and trailers are configured with airlift axles, which may be mechanically raised or lowered. The axle is lowered to increase the weight capacity, or to distribute the weight of the cargo over more wheels, for example to cross a weight restricted bridge

Bridge

A bridge is a structure built to span a gorge, valley, road, Rail tracks, river, body of water, or any other physical obstacle, for the purpose of providing passage over the obstacle....
. When not needed, the axle is lifted off the ground, to save wear on the tires and axle and increase traction in the remaining wheels. Lifting an axle also makes the vehicle perform better on tighter turns.

Several manufacturers offer computer-controlled airlift, so that the dead axles are automatically lowered when the main axle reaches its weight limit. The axles can still be lifted by the press of a button if needed.

Axle

Vehicle axles

Structural features

Drive axles

Dead axles/lazy axles

See also

Patents