AUTOMOBILE RUNNING SYSTEM AND POWER TRAIN 9. POWER TRANSMISSION SHAFT AND JOINT
The power from the engine is delivered to the wheels by the power train. In the conventional layout, power from the gearbox is transmitted to the wheels via the propeller shaft and the universal joints. There is also a slip joint, or the sliding joint as it is sometimes called, incorporated in between. In the front wheel drive car with transverse engine, drive shaft and constant velocity joints are used instead. The function of the universal joint is to transmit power at an angle. The slip joint serves to accommodate changes in length of the propeller shaft when the rear wheels go up and down over bumps and in potholes. The constant velocity joint serves the dual purpose of the universal joint and the slip joint.
9.0
Objectives After going through this lesson, you will be able to:
i. ii. iii. iv.
9.1
Explain the necessity of the universal joint and the slip joint. Explain the necessity of constant velocity joints Describe the construction and working of the constant velocity joint. Recognize failure symptoms of CV joints.
Introduction
In the conventional layout, the engine along with the clutch and the transmission gearbox is at the front while power is given to the rear wheels. This necessitates use of a long shaft called the propeller shaft to transmit power between the gearbox and the wheels. Further, the axis of the engine, clutch, and the gearbox is at a different level than that of the differential, which is the same as that of the wheels. This requires that the shaft be inclined while at the same time it is required to rotate at high speed. Hence universal joints are used which permit transmitting power at an angle. Now, when the rear wheels move up or down, due to a bump or a pothole, the length of the propeller shaft needs to change. If the connection between the gearbox and the differential were to be rigid, the propeller shaft would bend or extend. In order to overcome this challenge, we use a slip joint at the front end of the propeller shaft