Good windscreen wipers wipe away your fears

By T. Uncle

IT is not always correct to assume that technology will always come up with better ways of doing things.

In fact, we are constantly surrounded by reminders showing us that, sometimes, there is only one way of getting things right.

Illustrations of this simple truth can be found in items like paper clips, safety pins, even bicycles.

In all these, there is one constant factor: despite man's ingenuity when it comes to improving, or radically changing things to make them work better, in these cases, the fundamental principles have never changed since the original, basic idea.

The same can be said of the windscreen wiping systems used on today's cars.

Look at the basic principles used on early motor vehicles, and you will see they are the same as a modern car.

A wiper arm supports a rubber blade, which sweeps in an arc across the glass to clear it of water.

By applying the right amount of pressure against the glass, the blade is able to efficiently squeegee the screen clear so the driver is able to maintain vision when driving in the rain.

Perhaps the best proof of the efficacy of the system is the fact that even high-tech jet aircraft use it when maneuvering on the ground (some aircraft have tried using alternative systems such as spinning perspex discs which throw the water off, but such ideas seem to have been discarded).

Early cars used unreliable and frustratingly ineffective systems for driving the blades.

One example was the engine manifold pressure-actuated system common 40 years ago.

This was one way of avoiding the reliability problems that affected some electric wiper motors, but there were shortcomings.

For example, if manifold pressure dropped while the engine was working hard, the wipers would virtually come to a standstill -- not all that helpful when driving up a steep hill on a dark, wet night.

As might be expected, electric motors were universally adopted by the 1960s.

Today, advances in wiper engineering -- which, after all, is a significant safety factor as it effects driver visibility -- seem to be largely concentrated on two fronts: ensuring that as large an area of the windscreen as possible is covered by the wipers, and finding better ways of controlling the function of the wipers in relation to driving conditions.

Mercedes-Benz, for example, developed a single-arm system for its compact 180E model in the 1980s that, through a complicated array of cams and connecting arms, actually managed to arc across the entire width of the windscreen in an irregular pattern that enabled the blade to reach right into the upper edges of the glass.

This helped minimize the "blind" spots that are the curse of all car designers.

The Mercedes design still stands out when compared to the simple, single-arm systems used by some other carmakers such as Jaguar.

Most carmakers, however, have stuck with conventional, twin- arm systems, often using a "pantograph" on one side that forces the blade to follow an irregular arc and therefore provide a greater wiped area.

Automatic wiper activation is something else carmakers have played around with.

Cadillac, for example, offered automatic wipers that switched on as rain began to fall as long ago as the 1950s, but it was not until recently that a reliable, effective system was developed.

Again, Mercedes-Benz can take much of the credit for perfecting what was basically a good idea that no one else could make work properly.

The German system operates via a sensor that detects how much water is hitting the glass, and regulates the intermittent mode accordingly -- more wiper action if the rain gets heavier, less when it eases off.

Those drivers accustomed to constantly fiddling with the wipers as the rain intensity increases and decreases will find such systems wonderfully easy to use.

A less sophisticated, but also welcome device is used on some BMW models.

While the car is being driven in the rain, the wipers operate normally, but when it comes to a stop, they switch automatically to intermittent mode which, again, is less irritating than having them slam back and forth at high speed across the dry windscreen.

BMW also came up with a way of increasing blade pressure as speeds increased, thus ensuring that the screen would be kept clear at Autobahn velocities.

Aerodynamic lift of the wiper blades is still something that effects some cheaper cars.

Of course not all carmakers think it worth the expense to develop much more than a basic three-speed wiper system with, perhaps, a variable intermittent control for adjusting to light rain.

Perhaps the day will come when an entirely new way of keeping the windscreen clear of water will be discovered. Although if the experience of using the one, unchanged, system virtually since the birth of the motorcar more than 100 years ago is anything to go by, the odds of this happening would not appear be particularly favorable.