Rear wheel drive
The drive of a motor vehicle via the (or a) rear axle is referred to as rear-wheel drive , regardless of the engine arrangement. The rear-wheel drive is therefore not to be confused with the rear-wheel drive , as this only describes the complete drive unit consisting of the rear engine , gearbox and drive axle.
Other types of wheel drives in vehicles are front-wheel or all-wheel drive .
history
The rear-wheel drive is the oldest type of driven axle in vehicle construction. This allowed the various functions to be distributed over the axles (steering via the front axle , drive and brakes via the rear axle) and thus implemented more easily in terms of design. Even after the successful establishment of front-wheel drive from the 1930s, rear-wheel drive remained the dominant drive in passenger cars for a long time because it was more robust and cheaper to produce. A survey in 1958 found that common car drivers appreciated the benefits of rear-wheel drive, while experts mainly advocated front-wheel drive. It was not until the 1970s that rear-wheel drive was increasingly displaced. In high-performance or comfortable cars on the one hand and trucks on the other, it has remained the usual drive to this day. The most common drive unit in rear-wheel drive vehicles is the so-called standard drive with a front engine.
Executions
The rear-wheel drive is used in various drive concepts:
- with standard drive with front engine
- with the transaxle arrangement
- with the mid-engine
- with rear-wheel drive
- with the rear engine (omnibuses)
In older designs and in the commercial vehicle segment, the rear-wheel drive is mainly designed as a rigid axle . Since rigid axles have a high unsprung mass, which has a negative effect on driving comfort, they have been replaced over time by pendulum axles , semi- trailing arms or multi-link axles . However, the design and cost advantages of rear-wheel drive were lost.
Comparison of standard drive and front-wheel drive
- advantages
The combination of a longitudinally installed engine at the front and rear-wheel drive offers favorable space conditions in the engine compartment and allows the use of large or long engines with six or more cylinders. The rear axle can apply more braking torque so that the front axle brakes are relieved. When braking, a higher proportion of the axle load remains on the rear axle. The separation of steering and drive means that there are no direct drive influences on the steering. The balanced axle load distribution offers good conditions for the coordination of driving dynamics and driving comfort. Rear-wheel drive is therefore preferred in vehicles from the upper middle class.
In contrast to the front-wheel drive, the driven axle is loaded when accelerating, which enables good power transmission on a non-slip road surface, especially when accelerating rapidly; quick start-up on inclines and with a trailer load. Since most rear-wheel drive vehicles carry the load on the rear axle, the load ensures even better conditions. For sports cars and other powerful cars, rear-wheel drive is the drive concept of choice, but often with a mid-engine or rear-engine arrangement, because the lower the power-to-weight ratio of a vehicle , the more pronounced the favorable distribution of the axle load is. Another advantage is the generally smaller possible turning circle - since there is no need to take the drive into account with the steered front axle, a larger maximum steering angle is possible.
- disadvantage
When using a front engine, a cardan shaft is also required for power transmission , which means higher costs and more weight. The cardan tunnel and the transmission bulge limit the space available in the passenger compartment, which is a significant disadvantage, especially in smaller cars. Particularly in older cars with rear-wheel drive, the axle load on the drive axle is low when unloaded, which leads to traction disadvantages on damp or loose surfaces and on slippery roads. Because of this disadvantage, sports car manufacturers tend to combine rear-wheel drive with a mid or rear engine. In modern cars with a front engine and rear-wheel drive, efforts are made to minimize the problem by moving the axles forward and moving heavy components to the rear.
Areas of application
There are the following areas of application for rear-wheel drive in passenger cars:
- Front engine: Medium and luxury class cars with powerful engines , especially those with high (“premium”) demands on comfort or sportiness
- Mid-engine: Very sporty vehicles, mostly with significant space restrictions.
- Rear engine: sports cars , microcars
Commercial vehicles mostly have rear-wheel drive:
- Front engine: trucks and vans weighing more than 3.5 tons
- Middle and rear engine: buses
Other drive variants
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Differentiation according to motor position: |
Differentiation according to drive axes:
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Differentiation according to drive unit:
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literature
- Max Bohner, Richard Fischer, Rolf Gscheidle: Expertise in automotive technology. 27th edition, Verlag Europa-Lehrmittel, Haan-Gruiten 2001, ISBN 3-8085-2067-1 .
- Jan Drummans: The car and its technology. 1st edition, Motorbuchverlag, Stuttgart 1992, ISBN 3-613-01288-X .
- Hans-Hermann Braess, Ulrich Seiffert: Vieweg manual automotive technology. 2nd edition, Friedrich Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig / Wiesbaden 2001, ISBN 3-528-13114-4 .
- Peter Gerigk, Detlev Bruhn, Dietmar Danner: Automotive engineering. 3rd edition, Westermann Schulbuchverlag GmbH, Braunschweig 2000, ISBN 3-14-221500-X .
Individual evidence
- ↑ a b front or rear drive set? In: Motor Vehicle Technology 2/1959, pp. 73–76 and 4/1959, pp. 162–163.
- ↑ Bernhard Heissing, Metin Ersoy, Stefan Gies (eds.): Chassis manual : Basics, driving dynamics, components, systems, mechatronics, perspectives . 3. Edition. Vieweg + Teubner, 2011, p. 11 ( limited preview in Google Book search).