Rear wheel drive

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Rear-wheel drive schematic
Rear-wheel drive: Porsche 912

The rear-wheel drive is a version of the rear-wheel drive in motor vehicles in which the entire drive unit (consisting of the rear engine , transmission and drive axle) is combined on or directly behind the rear axle . This construction is also known as a rear drive block .

However, the term rear-wheel drive is often imprecisely equated with rear - wheel drive .

history

The widespread standard design among rear-wheel drive vehicles ( engine and transmission in front of the occupants, rear-wheel drive ) requires additional components and installation space due to the distance between the transmission and the axle differential . To transmit the power , a cardan shaft is required, which is usually hidden inside the car by a "tunnel". Due to the conflict of interests in costs, space and weight, the standard construction for small cars is not or only partially suitable.

One possible solution is to combine the motor, gearbox and drive axle into a compact drive unit. In the first half of the 20th century, this was mainly implemented as a rear-wheel drive in order to avoid the structural complexity of a driven and steered front axle . This design is also known as a rear drive block .

From the 1970s, front-wheel drive became the predominant type of drive, with rear-wheel drive becoming a niche solution for sports cars (e.g. Porsche ), small cars ( Smart ) and large buses. In America, there have been no rear-engined sedans since the Chevrolet Corvair was discontinued in 1969, which was notorious as a “rear-end spin”. In Europe, the Czech automobile manufacturers Škoda (with the Škoda Rapid until 1990) and Tatra (with the Tatra 700 until 1999) developed and manufactured sedans with rear-engined engines.

Hans Ledwinka and Ferdinand Porsche are considered the “fathers” of rear-wheel drive, even though the first patented motor car from Carl Benz had the engine in the rear.

Advantages and disadvantages

In addition to the advantages of rear-wheel drive, rear-wheel drive offers other advantages over drive concepts with a front engine :

  • Regardless of the load condition and the dynamic axle load distribution of the vehicle, the drive axle has a high proportion of axle load and therefore good traction on slippery roads or when accelerating heavily.
  • Compared to vehicles with a front-engine and rear-wheel drive, the passenger compartment is not restricted by a cardan tunnel. The vehicles with front-engined and front-wheel drive, which became more widespread from the 1980s and 1990s, also do not need a transmission tunnel, they only have comparable space for the exhaust and to stabilize the body's bottom section.

On the other hand, there are the following disadvantages compared to vehicles with a front or mid-engine :

  • The rear of the vehicle is partially or completely used by the drive unit and is therefore limited or not available for storage space.
  • If there is nevertheless a trunk in the rear of the vehicle, access to the trunk or to the engine is restricted, and the trunk close to the engine can be heated up considerably by the heat emitted by the engine.
  • The front of the vehicle cannot compensate for the disadvantages of storage space, because the available space is partially taken up by the wheel arches (which are larger than on the rear axle due to the steered front wheels), the steering mechanism and the footwell for the driver and front passenger.
  • The axle load of the rear axle is higher than that of the front (rear-heavy), which has a negative effect on driving stability and sensitivity to cross winds. Driving stability can be improved with wider tires on the rear axle and a more balanced axle load distribution, for example by placing the battery in the front of the vehicle.

Examples of rear-wheel drive cars

Example of a rear-wheel drive car: “ Cremeschnittchen ” (Renault 4CV) in action for the Paris police

The Hanomag 2/10 PS (Kommissbrot) does not have a rear-wheel drive, but a rear-wheel drive , since a transmission device (here: chain instead of cardan shaft) is installed between the central motor and the axle, so that the entire drive is not combined into one unit (rear-wheel drive).

Other drive variants

Differentiation according to motor position:

Differentiation according to drive axes:

Differentiation according to drive unit:

  • Front wheel drive (front engine and front wheel drive)
  • Standard drive (front engine and rear wheel drive)
  • Rear-wheel drive (rear-engine and rear-wheel drive)

See also

literature

  • Jan Drummans: The car and its technology. Motorbuchverlag, Stuttgart 1992, ISBN 3-613-01288-X .
  • Wilfried Staudt: Handbook Vehicle Technology Volume 1. Bildungsverlag EINS, Troisdorf 2005, ISBN 3-427-04520-X .
  • Hans Jörg Leyhausen: The master's examination in the automotive trade part 1. 12 edition, Vogel, Würzburg 1991, ISBN 3-8023-0857-3 .

Individual evidence

  1. ↑ Automotive Handbook of Bosch