Careful design and construction are necessary to stop the engine pulling the steering to one side when the car is accelerating, and special flexible joints, called constant velocity joints, are needed to allow the wheels to rotate evenly when turned to steer the car round a corner. Another variation of car layout, which also avoids the need for a propeller shaft, is the rear engine layout. This is, of course, rear wheel drive, the engine being mounted at the back of the car. Several problems became apparent in early rear-engine designs.
The engine usually overhung the back wheels, which made the car rather unstable since it had all the weight at the back (imagine throwing a dart flight first). In addition, the weight of the engine behind the rear wheels worked to lift the front, reducing weight on the steering. Front-wheel skids, which are the most dangerous kind of skid, and susceptibility to gusts of wind characterised most rear-engined cars of a couple of decades ago. Modern design has almost completely overcome the early deficiencies. A smaller, lighter engine is positioned more or less immediately above the rear wheels instead of behind them. Rear-engine cars with excellent handling characteristics are now made as can be seen in the very well engineered Ferrari 458 for sale.
For a long time, engines were invariably placed with the crankshaft – the main rotating part of the engine – pointing along the length of the car.
In more recent rear engine and front wheel drive designs, manufacturers have used the transverse engine position, in which the engine is mounted with the crankshaft pointing across the width of the car. This makes a valuable saving in space, although the engine is often less accessible for servicing. Most modern car designs begin with comfortable seating positions for each of the occupants. Visibility, accessibility of controls, and safety in the event of a crash are all given top priority. The designer then makes the most efficient use of the available space to fit in the engine, transmission and luggage space, subject to current ideas about styling.
European cars still contrast with many American designs, in which styling is given much greater relative importance; size, in particular, is often dictated by marketing conditions rather than engineering! There are a few obvious exceptions to this, for example, the latest models of Rolls Royce for sale and the new Bentley Mulsanne for sale, are still very large cars. However, there are signs that the average American motorist is becoming more mindful of economy. With a diminishing number of exceptions, cars are looking increasingly similar to each other. This is explained partly by the fact that continuous development by different manufacturers often leads them to the same optimum design. Thus all F.W.D. cars, all R.W.D. cars and all rear-engine cars of similar size and price are liable to be rather similar, be they from the United Kingdom, Italy, France, Germany or Japan.
