Axle Parts

An axle is a central shaft for a rotating wheel or gear. In some cases the axle may be fixed in position with a bearing or bushing sitting inside the hole in the wheel or gear to allow the wheel or gear to rotate around the axle. more...

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 bicycles, the latter type is referred to as a spindle.

Vehicle axles

Axles are an important structural component of an wheeled vehicle. 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, and also any acceleration forces between the vehicle and the ground.

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) exerts a rotational force on the axle, which is transferred to the wheel(s) to accelerate the vehicle.
• Braking
  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 may still be effected via the axle.
• Steering
  The front axle of most automobiles 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 (or live axle) is a single rigid shaft connecting a wheel on the left side of the vehicle to a wheel on the right side. The wheels rotate in unison, and about the same axis. Such a design can keep the wheel positions steady under heavy stress, and can therefore support heavy loads. Straight axles are used on trains, for the rear axles of commercial trucks, 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.

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