TO : UDAY RAJ SIR BY NAWAL KISHORE BABUL 100109034 NEELESH MAHESHWARI 100109035 PRAYAS NAVAL 100109040
Forces on rear axle Wt. of the body Driving trust Torque reaction Side thrust
Automakers have developed a number of common methods oflocating a live axle First approach uses four trailing arms, two above the axle, two below it, angled inward so that they resist lateral motion of the axle.
Another approach, used by Buick in the 1960 . uses two lower control arms and a single upper arm, mounted next to the differential, with a lateral track bar (a Panhard rod) or parallelogram linkage (Watts linkage) to limit lateral motion. Both the three-link and four-link layouts are reasonably effective, but the control arms and track bars make the rear suspension more complex, and thus more expensive to build .
The Hotchkiss drive is a system of power transmission . It was the dominant form of power transmission for front-engine, rear-wheel drive layout cars in the 20th century
Simplest and most widely used type of rear axle drive . The spring besides taking weight of the body also take the torque reaction , driving thrust and side thrust . propellar shaft is provied with two universal joints also a sliding joint . The front end of the spring is fixed rigidly on the frame while the rear end and is supported in the shackle .
In a Hotchkiss layout, the axle is suspended by a pair of longitudinally mounted semi-elliptical leaf springs, which serve to locate the axle, as well as supporting the weight of the body. The front portion of each spring functions like a trailing arm, transmitting drive torque to the body and resisting squat and axle tramp .
The rear portion of the spring acts as a leading arm, resisting wheel hop under braking. The stiffness of the springs also serves to resist lateral motions. By making the springs perform multiple duties, Hotchkiss drive is very simple, and thus very cheap. Since it has few parts, its also very sturdy, which is useful for heavy-duty vehicles like trucks.
The HOTCHKISS drive requires that the springs be rigidenough to withstand the twisting action (torque) of therear axle and the driving and braking forces that thesprings transmit to the frame. This type of drive iscommon to the equipment you will encounter in theNavy .
The differentiating characteristic of the Hotchkiss drive is the fact that it uses universal joints at both ends of the driveshaft, which is not enclosed . The use of two universal joints, properly phased and with parallel alignment of the drive and driven shafts, allows the use of simple cross-type universals .
Used in pick-up trucks and sport utility vehicles .
The design problem that the torque tube solves is how to get the traction forces generated by the wheels to the car frame . The "torque tube" transmits this force by directly coupling the axle differential to the transmission and therefore propels the car forward by pushing on the engine and then through the engine mounts to the car frame .
In contrast, the Hotchkiss drive has the traction forces transmitted to the car frame by using other suspension components such as leaf springs or trailing arms . A ball and socket type of joint called a "torque ball" is used at one end of the torque tube to allow relative motion between the axle and transmission due to suspension travel
Since the torque tube does not constrain the axle in the lateral (side-to-side) direction a panhard rod is often used for this purpose. The combination of the panhard rod and the torque tube allows the easy implementation of soft coil springs in the rear to give good ride quality .
Torque tubes differ from the Hotchkiss design inthat a soliddrive shaft is enclosed in a hollow torque tube and rotates within a support bearing to preventwhipping
In both types of drive shafts the side thrust is taken the leaf springs . A separate member is employed to overcome this situation : Panhard Rod it si fixed parallel to wheel axis with one end pivoted to the axle and other to chassis frame
EXAMPLES OF THE TORQUETUBE American cars of the Ford brand up through 1948, which used the less expensive transverse springs that could not take the thrust. The C5 and C6 Chevrolet Corvette , Mercedes-Benz SLS AMG
Loads on rear axle shafts Shearing force due to wt. of vehicle . Bending moment on account of load applied through spring seats . End thrust caused by side forces on account of cornering , side wind Bending moment by end thrust and its reation offered by tyres on ground Driving torque
Types of rear axle shaft Semi floating axle . Full floating axle . Three quarter floating type.
SEMI FLOATING AXLE With a semi-float axle, the axle shaft both carries the weight and transmits torque. The wheel is often bolted directly to the flange on the axle. Semi-float axles are seen on cars and light duty trucks. Semi floats are more limited in capacity, but lighter and cheaper to manufacture.
FULL FLOATING AXLE the weight of the vehicle is supported by the axle housing- more specifically, a bearing spindle attached to the axle housing , and a set of bearings in a separate wheel hub. Torque is transmitted by a separate axle shaft that carries no weight. As commonly built, full-floaters are considerably heavier, but also much stronger
THREE QUARTER FLOATINGTYPE A three-quarter floating axle is the same as semi-floating, with one difference. The outer bearing is moved to the outside of the outer end of the axle tube, supporting a hub assembly via the bearings outer circumference edge. The splined or keyed shaft drives this hub, to which the wheel is attached. The shaft now supports minimal vehicle weight (so has much reduced radial load), but still locates the wheel axially, and transfers axial cornering loads (side thrust) to the axle inner bearing.