Lesson 1

Read the text: Axle

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. 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.Axles are an integral structural component of a 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, 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) exerts a rotational force on the axle, which is transferred to the wheel(s) to accelerate the vehicle.

Braking onversely 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.

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 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.

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

1. Match the left part with the right:

1 Axles are	a) part touching the ground, the axles must bear the weight of the vehicle plus any cargo, as well as acceleration and braking forces.
2. In addition to	b) wheels relative to each other and to the vehicle body.
3. Since for most vehicles the wheels are the only	c) an integral structural component of a wheeled vehicle.
4. The axles maintain the position of the	d) the structural purpose, axles may serve one or more of the following purposes depending on the design of the vehicle.

2. Complete the sentences with the suggested words: vehicles, wheels, axles, acceleration

The axles maintain the position of the _______ relative to each other and to the vehicle body. Since for most _______ the wheels are the only part touching the ground, the _______ must bear the weight of the vehicle plus any cargo, as well as _______ and braking forces.