DRIVE SHAFT

Mechanical Drive Shaft



Measuring Mechanical Drive-Shaft

Introduction

As the power produced by the engine of a vehicle leaves the transmission, it still must go through a series of complex processes before the vehicle begins to move. The driveshaft is responsible for delivering the power from the transmission to the axle, or the wheel itself. In the rear, it connects to the differential, which takes the high rotational speed of the driveshaft, and slows it down before delivering the power to the axles. As the vehicle is moving, the tires, the axle and the differential will move up and down as the surface of the road changes. The rear driveshaft usually uses a pair of universal joints to keep the power to the wheels constant. With the universal joints, the driveshaft always is at the correct angles to the transmission and the rear differential to deliver the power consistently and without doing damage to any other parts. In the front, the process is more complex. (Dudley, 2009: 45) The wheels not only react to the movement of the suspension, but they also must be allowed to steer. In vehicles with driven front wheels, the driveshaft uses constant velocity joints in the place of universal joints. This type of joint is more flexible and can allow for the lateral movement of the steering tires, especially when it is combined with a slip joint. The constant velocity joint also produces less vibration than the universal joint, making it much more suitable in the very short front driveshaft. In any driveshaft, the joints will begin to suffer from the effects of corrosion and foreign substances, often producing an audible grinding noise just before the joints, and thus the driveshaft, need to be replaced. (Wu, 2005: 56)

Drive shafts are carriers of torque: they are subject to torsion and shear stress, equivalent to the difference between the input torque and the load. They must therefore be strong enough to bear the stress, whilst avoiding too much additional weight as that would in turn increase their inertia. In front-engined, rear-drive vehicles, a longer drive shaft is also required to send power the length of the vehicle. (Dudley, 2009: 171) Two forms dominate: The torque tube with a single universal joint and the more common Hotchkiss drive with two or more joints. This system became known as Système Panhard after the automobile company Panhard et Levassor patented it.

Most of these vehicles have a clutch and gearbox (or transmission) mounted directly on the engine with a drive shaft leading to a final drive in the rear axle. When the vehicle is stationary, the drive shaft does not rotate. A few, mostly sports, cars seeking improved weight balance between front and rear, and most commonly Alfa Romeos or Porsche 924s, have instead used a rear-mounted transaxle. This places the clutch and transmission at the rear of the car and the drive shaft between them and the engine. In this case the drive shaft rotates continuously as long as the engine does, even ...