Friday, January 29, 2010

Driving the Beetle

Transaxle jacking and its effect on road/tyre grip. The car is going around a right hand bend. When the transaxle lifts, the heavily loaded outer wheel develops positive camber 'A', whereas the lightly loaded inner wheel develops negative camber 'B'. Grip is greatly reduced.

Driving a Beetle is very different from driving a more recent car. The seemingly lazy, slow revving engine which lacks straight bhp in fact delivers sufficient torque to get, and keep you, on the move without ever breaking into a sweat and, although the nought to sixty mph times are anything but impressive, the torque always seems to be there when you need it for overtaking. Ignore the speedometer reading at your peril; the slow engine revolutions are deceptive and can lull inexperienced Beetle drivers into driving far more quickly than they suspect.
The interiors of all Beetles are spartan in comparison with most modern cars. The seat bases are passably comfortable but the seat backs lack proper support, most noticeable when cornering. Instrumentation is kept to a bare minimum, displaying the speed and fuel tank contents but not the revs, oil pressure or engine temperature. Quite in keeping for a car which revels in being an anachronism in its own lifetime! Driver visibility is generally excellent, although all four wings are hidden from view, which perhaps explains the high numbers of town Beetles with dented wings!
The unnecessarily huge steering wheel coupled with the massive rear weight bias of the car makes the steering so light – even when manoeuvring at car park speed – that you could be forgiven for wondering whether Ferdinand Porsche cunningly hid a power steering pump within the steering box. Put a few too many psi in the front tyres, though, and the car feels as though the dampers at the front have failed; the eccentric bush-induced understeer is also increased which, coupled with the bouncing of the front end, can make cornering a little too exciting.

Correctly shod and with no weak points in the suspension and especially the dampers, Beetles can go around tight corners at considerable speed as sure-footedly as if they were Рexcuse the clich̩ Рrunning on a pair of rails. Push the car a fraction too hard, though, and the rear end can break away into massive oversteer or in extreme cases a spin so quick and vicious that even the most experienced drivers can have trouble gaining control of the car.
The problem is one of weight distribution. Having the weight of the transaxle and engine over the rear wheels gives plenty of traction to get you moving on slippery surfaces, but when centrifugal forces become great enough during hard cornering, this mass possesses great potential energy which makes its presence felt the moment the rear wheels lose traction. Few people, though, ever drive so close to the limit for this – the so-called 'dumbbell effect' – to be a problem.
Swing axle cars are more prone to snap into oversteer than more recent semi-trailing arm cars because their rear wheels suffer constantly variable camber. Unlike the later Beetles which had universal Joints at either end of their drive shafts, early 'swing axle' car drive shafts possessed only one UJ at the differential end. Because the transaxle which houses the differential rises and falls relative to the road (and thence the wheels) its angle alters that of the drive shafts and the hubs and wheels which were fixed to them. When the rear centre of gravity of these cars rises on a tight bend, the heavily loaded outside wheel develops a positive camber angle (which gives very poor grip). This rise in the centre of gravity is exacerbated if, for some reason, the driver lifts off the accelerator pedal – or worse, applies the brakes – part-way through the corner. When that happens at speed, the dumbbell effect is increased greatly.
Ixperienced Beetle drivers will be mindful of the potential dumbbell effect and will not rush headlong into blind corners which could conceal some obstacle which would force them to take avoiding action while the rear Suspension was loaded.
The fact that the engine and gearbox of the Beetle

re situated over the driving wheels brings one hugee benefit; their weight gives those wheels great traction
nd hence the car excels when used on slippery surfaces KtInd off-road. The Beetle will go where most other cars Imply sit still and spin their driving wheels, and even e Iron t-engined, front wheel drive car takes second lace to the Beetle because, although its engine and gearbox might place weight over the driving wheels, the rearwards transfer of static mass which occurs when torque is applied to the wheels lessens their tyres' grip.
15So, the Beetle is not especially rapid, comfortable nor well-behaved on the road when compared to modern cars; why then, do Beetle drivers gain more pleasure from driving their cars than those in more recent or more exotic machinery? The answer is simply that the Beetle driver can enjoy the Beetle experience. He or she wants to savour the sensations which only the Beetle can provide.

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