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Front-wheel Drive (longitudinal engine)



Function

The front-wheel drive with straight-mounted engine always has a good amount of weight on the driving wheels. This brings good traction and a low sensitivity to crosswinds. Even driving uphill, the front axle is not as strongly lightened as it is with a transverse-mounted front-wheel drive. It is well suited for upgrading to an all-wheel-drive. The most important reason however, for car manufacturers, could possibly be the freedom of engine choice. The possible length of straight-mounted engines is, as a rule, unlimited, this of course, is not the case with the transverse-mounted engine. For this reason, this construction method is interesting, particularly for vehicles of the upper middle class and for top-of-the-range models.A further advantage, compared with the transverse engine is, less effort and complexity in the insulation against noise.

How it works

The front-wheel drive with straight-mounted engine is the oldest front wheel-drive design (1931). The engine lies in front of the front axle, the gearbox behind it. From the clutch, the torque is first transfered through a long differential shaft to the non-coaxial gearbox. The gearbox driven shaft at the output carries the bevel wheel for the transmission of the torque to the final drive. The axle drive shafts are of equal length.

Disadvantages

This drive chain configuration makes the vehicle very top-heavy. A well-balanced chassis is more difficult to realise with this axle load distribution. The larger and heavier the vehicle is, the closer this design gets to the ideal distribution, however, it cannot really reach this goal. An interesting solution of this problem at the longitudinally mounted front wheel drive unit can be found here.

The large overhang, particularly with engines with a greater construction length, reduces the wheelbase. From a construction point of view, the problem can be reduced, if the cooling system is mounted beside the engine.Generally speaking, the disadvantage of this construction - the drive being coupled to the steering - as in all front-wheel drive vehicles, remains. Nowadays, the power-chain forces are hardly perceptible in the steering, but still, they do slightly diminish the feeling for the road.

In vehicles with a manual gearbox, a four-wheel drive can be more easily realised. Invehicles with fully automatic gearboxes it's more difficult. With some automatic four-wheel drives, an additional, external shaft can be seen in the final drive, for the return of the torque. 06/09

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