It was the dominant means for front-engine, rear-wheel drive layout cars in the 20th century. The name comes from the French automobile manufacturer Hotchkiss , although other makers, such as Peerless , used similar systems before Hotchkiss. During the early part of the 20th century chain-drive power transmission was the main direct drive competitor of the Hotchkiss system, with the torque tube also popular until the s. Torque reaction effects on a leaf spring in a Hotchkiss drive system Most shaft-drive systems consist of a drive shaft also called a "propeller shaft" or Cardan shaft extending from the transmission in front to the differential in the rear.
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Click here to read more about it. Many rear-drive cars and trucks use a live axle at the rear — that is, the rear axle incorporates the differential and halfshafts into a single rigid unit that moves up and down with the rear wheels. Live axles are cheap and rugged and ensure that the camber of both rear wheels remains constant as the wheels move through their suspension travel. The main drawback of live axles is that they are heavy. Drive forces from the wheels are transmitted through the rigid torque tube to the transmission mount.
Torque tubes were fairly common until the early s they were used by, among others, American Motors, Buick, and Chevrolet , but they fell out of favor because the torque tube adds significantly to unsprung weight. Open driveshaft: The second option is to leave the driveshaft open and use a universal joint on each end, allowing the axle to move relative to the driveshaft.
Since the linkage between the axle and the driveshaft is now flexible, the driveshaft itself cannot transmit acceleration or braking torque. When the engine applies torque to the axle, that force tends to cause windup — that is, causing the axle assembly to twist along with the drive wheels.
Severe axle windup can cause the entire axle to hop up and down on the rear springs, an effect known as axle tramp. Once the vehicle is actually accelerating, front-to-rear weight transfer also tends to cause the axle to squat. Similarly, when the brakes are applied, the rear axle tries to rise as weight shifts forward onto the front springs an effect called brake dive , sometimes causing the rear wheels to break traction with the ground and hop.
Meanwhile, in turns or on uneven pavement, lateral forces attempt to displace the axle assembly to one side. For the axle to do its job properly, it must be connected to the body with locating members — control arms or links — whose leverage resists all these forces. Simplified diagram of a five-link rear suspension. Lower links yellow transmit drive torque to the body; upper links orange stabilize the axle; a Panhard rod green locates the axle laterally.
Many GM and Ford cars of the sixties and seventies used a four-link version of this system, omitting the Panhard rod and angling the upper arms toward the centerline of the body so that they would provide lateral location. One approach, popular at GM for many years, uses four trailing arms, two above the axle and two below it, with the upper arms angled inward so that they resist lateral displacement of the axle.
A three-link variation of that approach, used by Alfa Romeo for many years, uses a single triangular or T-shaped upper arm attached to the differential housing to perform the same function. 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.
A simpler alternative is Hotchkiss drive. In a Hotchkiss layout, the axle is suspended by a pair of longitudinally mounted semi-elliptical leaf springs that serve to locate the axle as well as support the weight of the body. The trailing rear portion of each spring acts as a leading arm, resisting wheel hop under braking.
The springs also resist any lateral axle motions. By making the springs perform multiple duties in this way, Hotchkiss drive is very simple and thus very cheap. Diagram of a Hotchkiss drive layout. Making the springs stiffer makes them more effective in controlling axle movement, but it also makes the ride firmer, sometimes uncomfortably so. The more powerful the engine, the greater the problem.
The spring rate of a leaf spring is proportional to its length. If you move the axle forward toward the leading ends of the springs, the front section of the spring will be shorter and thus stiffer, allowing it to better control axle tramp without making the ride harsher.
The drawback is doing so effectively softens the rear portions of the springs the sections aft of the axle assembly , making them less able to resist brake dive or wheel hop on deceleration.
Powerful Chrysler cars of the sixties had good axle control on acceleration, but were prone to violent wheel hop on hard braking, occasionally with harrowing results. In this way, the shock absorbers are made to perform double duty, resisting axle tramp. Staggered shocks can be reasonably effective for street cars, but may not be adequate for really high-powered applications like drag racing.
Click here to read more about it. Many rear-drive cars and trucks use a live axle at the rear — that is, the rear axle incorporates the differential and halfshafts into a single rigid unit that moves up and down with the rear wheels. Live axles are cheap and rugged and ensure that the camber of both rear wheels remains constant as the wheels move through their suspension travel. The main drawback of live axles is that they are heavy. Drive forces from the wheels are transmitted through the rigid torque tube to the transmission mount. Torque tubes were fairly common until the early s they were used by, among others, American Motors, Buick, and Chevrolet , but they fell out of favor because the torque tube adds significantly to unsprung weight.
The Hotchkiss Drive | Torque Tube Drive
The diagonal radius arms are discretionary. A torque tube system is a power transmission and braking technology, that involves a stationary housing around the drive shaft , often used in automobiles with a front engine and rear drive, and rear brakes with or without front brakes, which play no part in it. The torque tube consists of a large diameter stationary housing between the transmission and rear end that fully encloses a rotating tubular steel or small-diameter solid drive shaft that transmits the power of the engine to a regular or limited-slip differential. Otherwise, the axle housing would suffer axle wrap, such that the front of the differential would lift up excessively during acceleration and sink down during braking.