The four wheel drive was born at the beginning of the last century, developed by a succession of visionaries, that started with a Wisconsin blacksmith and continued with such men as Harry Armenius Miller and Harry Ferguson. They never would have believed their development would prove to be the most popular "school" transport a century later.
The first four wheel drive car was built in 1903, but it wasn't until the early 1980's that the concept again found favour in series production, and even then only one major manufacturer had enough faith in the concept to make it an integral part of the range, other than for off-road use. That company was Audi
, which offered two Quattro
It is strange that the same enthusiasm that greeted the Quattro on its first appearance at Geneva in 1980 was also shown towards other 4 x 4 designs that had preceded it. Road cars like the Jensen FF
, racing designs such as the Cisitalia
47, and the various Formula 1 prototypes of the seventies together with sophisticated off-road models like the Range Rover
, were all acclaimed on their introduction, but only the cross-country vehicles prospered. In many cases, the problem had been technical (the lack of an effective constant velocity joint prior to 1930 being a major consideration), or financial.
Prior to the Quattro, most of the vehicles lacked proper development and marketing back-up, and many of them featured four-wheel drive in combination with other advanced techniques, such as turbine engines or anti-lock braking systems for example, which made the vehicle package too complicated for commercial success. Others, like the AMC Eagle and the Subaru Leone
, aimed their designs more at the off-road user than the road driver (although things would change at Subaru over the years, with their stellar All-Wheel-Drive system). Fortunately, military users had been constant four-wheel drive devotees since the Second World War, and it is to the military that we must give thanks indirectly - for the development of the Audi Quattro range and all that followed Audi's lead.
The Military Heritage Of The Four Wheel Drive
The American army made the first move in 1912, when it began to swap some of its horse-drawn carts for trucks made by the FWD
Auto company, which featured four wheel drive - as the initials implied. In June 1940, the army asked its suppliers for proposals for a "General Purpose 4 x 4 Truck" that would have a maximum speed of 50 mph and cross-country capability. The American Bantam Car Company, formed to build the Austin 7 under license, called on a freelance designer from Detroit, Karl Probst, who came up with a set of plans in only five days. The prototype
was completed in 49 days, and Bantam won a contract to supply 3000 examples of the vehicle, which was already known as the "Jeep" from its "General Purpose" title. Later, Ford and Willys Overland were to take over the contract because of their more competitive prices, and between 1941 and 1945 more than 600,000 Jeeps, all following Probst's original concept, were to spread the 4 x 4 message throughout the world.
Before and during the war, only the Americans had espoused the Jeep concept. Sure, there was the German amphibious Schwimmwagen designed by Dr. Porsche which featured all-wheel drive, as did a total of 564 special VW Beetles built between 1942 and 1944, but the best-known German military vehicle, the Kubelwagen, had rear-wheel drive only. After the war, however, every general in every country was on the lookout for a Jeep of his own. In 1946, just as the US Government demobilized its GI's, so did Willys Overland
demobilize the Jeep, turning it into a relatively comfortable closed vehicle while retaining its military forbear's off-road abilities. The Universal, as it was known, created a new class of vehicle that was to enjoy an ever-increasing popularity, particularly in the USA. The age of the off road leisure vehicle had arrived - however unlike the luxury 4x4's that command the roads today, in their infancy it was the dirtier and more un kemp off-road vehicles that better expressed the macho appeal of the 4 wheel drive.
Austro-Daimler armoured car with four powered wheels. It was first demonstrated during manreuvres of the Austrian army in 1906. It was turned down because Emperor Franz-Josef said it was unsuitable for military use since "it would frighten the horses".
The 2CV "Sahara" was designed to meet the 1950's passion for African roads.
The Peugeot 205 Turbo 16, purpose built brilliance.
, following this train of military thought, the German army approached a number of constructors and asked them to submit prototypes for evaluation. The model chosen was that from Auto Union, the DKW Munga. It was notable for the fact that most of the major suspension units were interchangeable front and rear. Twenty-two years later the same construtor, which had changed its name to Audi in the interim, was successful in winning another contract, this giving birth to the VW lItis, the direct descendant of the Munga. It was during winter trials one day - or so the story we have been told - that engineer Jorg Bensinger watched the lItis performing alongside some Audi prototypes and had the idea of adapting the lItis running gear to a road car.
To the credit of the Audi management, they accepted the idea and sold it to corporate headquarters at Wolsfburg. The investment in the Quattro was made, and development carried through tiII the car was a saleable commodity. The final investment, an important one, was in a strong promotional campaign designed to overcome the ignorance and general malaise which surrounded the 4 x 4 concept for road cars. The Quattro's success in rallies was an important part of that campaign.
Ferguson the Pioneer
The story of Harry Ferguson, a man who was probably ahead of his times, is interesting. Starting in 1950
, the wealthy tractor manufacturer undertook the task of convincing the motor industry of the advantages of all-wheel drive for road cars, in terms of both safety and efficiency. However, if any manufacturer was impressed by his arguments they did nothing to show it in terms of action.
Harry Ferguson Research built prototypes of a sedan with four-wheel drive and all-independent suspension - the engine was mounted in a sub-frame at the front, the transmission was semi-automatic, and the brakes
were equipped with Dunlop's Maxaret anti-skid system.
A Mustang fitted with Ferguson "All Wheel Control" and a Capri that followed it almost convinced Ford. Chrysler took out a licence for production in the USA, and a transverse-engined Austin 1800
impressed BMC. The Ferguson system could have won at Indianapolis, but was banned by USAC
before it could have a chance to make its mark.
went into production with the Interceptor FF
, a car relying heavily on Ferguson technology, using an uneven torque split of 63 percent rear and 37 percent front. However, of the 5000 or so Interceptors sold between 1966
, less than 400 were FF versions. The vehicle's downfall was its high price, lack of forceful marketing and promotion, and the failing of its Maxaret brakes.
With its name changed to FF
) Developments, in 1972
the small British firm built two prototypes for Fiat on the base of a 130 and a 128. There was no immediate reaction from the Italian giant, but ten years later they used the principal of the epicyclic differential for both the Lancia Delta Turbo 4 x 4
and the Panda
4 x 4.
, AMC adopted the Ferguson system for use in its Eagle for the American market. In the meantime, Ferguson had perfected its Viscous Control system, which used a viscous coupling to achieve a progressive self-locking effect, and which was used in the rear-wheel drive Sunbeam
Lotus Rally cars as a self-locking differential.
decided to revert to the less-sophisticated Quadra-Trac for its Jeeps and part-time 4 x 4 road cars, but then along came Peugeot. In the 205 Turbo the differentials operated normally and had no effect on steering
or road-holding. In the event of a lack of traction, the silicone-faced discs of the Ferguson coupling automatically locked almost completely, although there was a degree of slip similar to that which takes place in a hydraulic torque-convertor. In order to cover all eventualities, Peugeot also used a conventional ZF limited-slip differential in the rear and made provision for a similar fitting at the front.
All this mechanical complexity was designed to extract the maximum from a car weighing around 2000 pounds and propelled by an engine that developed more than 300 horsepower in competition trim. It served to show that there was almost no limit to the search for perfection in a four-wheel drive configuration, and consequently almost no limit to the costs involved.
The Advantages Of A 4 Wheel Drive System On A Road Car Not So Obvious At First
It took three years from the announcement of the Quattro before a serious motoring magazine - Germany's Auto Motor und Sport
- carried out comparative tests that showed that four-wheel drive gave no advantage in terms of road-holding - on wet, dry, or snow-covered surfaces - no protection against aquaplaning or loss of control on black ice, and no reduction in braking distances. But four-wheel drive did improve grip - the ability to move away from rest and accelerate - phenomenally, because the engine's torque is split into four smaller units rather than two big ones and is fed through four tyres
rather than just two. The advantage is most noticeable on snow or wet surfaces, and even more so with a powerful engine.
An additional advantage is that under certain conditions, a 4 x 4 car also enjoys advantages in braking. The conditions are obtained when the two axles are locked. Ideally, the rear differential should also be locked, and in this configuration no one wheel can lock before any of the others, a situation which compromises the stability of the car and its decelerative qualities. Until more recent advances in four wheel drive systems, it was still possible that all four wheels would lock at the same time. This was a state of affairs that could arise only too easily when descending a snow-covered slope - exactly the occasion many people saw as the justification for purchase of a four-wheel drive car.
Again we turn to the design of the Quattro to discover just how the Audi engineers developed such a brilliant system. With their design, the two driven axles shared the burdens of propelling and controlling the car, instead of having one overworked while the other had nothing to do, and this facility was coupled to great powers of acceleration. The driver could put the power on in the middle of a corner, well over the limit and much earlier than any other type of car previously built, and experience neither sliding nor unbalance.
Beyond the Road
It was during the early 1980s that the 4WD again became popular, signifying a lifestyle that could take the owner almost anywhere, even if the opportunities were limited in the world of concrete and freeways. They became popular in America, Europe and Australia, and it seemed as if all the major manufacturers wanted to have one in their lineup. At first this allowed a niche for the smaller Japanese players, such as Suzuki with their popular LJ80 and Daihatsu with their F20 and subsequent Rocky. Along with the Land Rover, the true off-road vehicle was found to be lacking in such qualities as comfort, performance, road holding in the wet, and fuel consumptin when it was primarily used on the roadhowever.
But things were about to change - the AMC Eagle and the Subaru Leone combined a light 4 x 4 chassis with family car comfort, the Subaru even featuring a liquid crystal display instrument panel. Interested by the possibilities of the class, Toyota joined in with the Tercel 4 x 4 and they were followed by Renault, Fiat, and Alfa Romeo. These experiments in taking the family car off the beaten track had only two characteristics - they had four-wheel drive and they were looking for a market that nobody had defined.
With their modestly increased ground clearance, off-road tyres, simple rigid-axle suspension, and family car power output levels, the first crop of off-road sedans used the advantage of four-wheel drive to enable them to stray from the paved road when necessary. But there was a fundamental difference with the Quattro, which used its sophisticated suspension and tyres, low ground clearance and high-powered engines to keep them on the road under hard driving.
Nearly all the early 4WD sedans used a four-wheel drive system that was only used when it was required. This "in or out" system was the simplest and the cheapest, but it limited the occasions on which four-wheel drive could be used because of the absence of a central differential. The centre differential - or the disengagement of the four-wheel drive system - was needed for road use because the front and rear wheels of any vehicle describe different arcs while cornering and must therefore rotate at different speeds. The "in and out" system was therefore of less interest for high-performance road cars of the 1980's.
The problem of the speed difference between the two axles led to some unusual solutions among the many proposed, including the use of four-wheel steering. This gave the two axles a similar cornering radius and had been used most often on commercial vehicles, starting with the FWD wagon of 1904. In Porsche's experimental 911 Turbo 4 x 4, another method was chosen: the drive shaft to the front wheels incorporated a free-wheel mechanism allowing the front wheels to rotate at a higher speed than those at the rear during cornering. However, when this happened they were not transmitting the engine's torque.
Audi chose to use permanent four-wheel drive, with a central differential and a rear differential that could be locked by the driver at will. Locking the centre differential is recommended on slippery surfaces, and in order to extract the maximum from the car on difficult terrain the rear axle could also be locked. This action had its effect on the car's handling
however, causing understeer characteristics that were almost impossible to overcome in the case of an error by the driver. In the case of the competition model, it Michele Mouton and her colleagues had to resort to a fair degree of acrobatic agility to get the car sideways when it was necessary. It is for this reason that Audi tried a limited-slip rear differential instead of the manually operated 100 percent lock-up device.
In Search of the Ultimate - The Peugeot 205 Turbo 16
The majority of early 4WD cars, including the Quattro, used a 50/50 split, which was about right when you consider the weight transfer that takes place during heavy acceleration. The Lancia Delta Turbo 4 x 4
had a 58 percent front and 42 percent rear torque split, which reflected the vehicle's weight distribution. A purist however would probably prefer 40 percent of the torque to the front, in order to avoid overloading the steering
wheels, and 60 percent to the rear, where weight is transferred during acceleration. To balance this split, he would mount the engine in a centre/rear position to give the right weight distribution. The result of his work would be the Peugeot 205 Turbo 16
Of course, Peugeot sacrificed all to efficiency, with no concessions to passenger space or economy in construction or operation. The 205 Turbo 16 was a two-seater built purely and simply to win rallies, while Audi were using rallies to prove the efficiency of a system that was applicable to its entire range. In order to homologate the 205 Turbo 16 for international competition, Peugeot will had to build at least 200 of the 200- horsepower bolides. The Peugeot's engine was mounted transversely, ahead of the rear axle, and the torque split could be varied from 25/75 to 45/ 55 by changing the pinions in an epicyclic differential.
This worked in the same fashion as a normal differential, but all its pinions revolved in the same plane. Engine torque was transmitted to the planetary gear carrier, and the planet gears engaged on a central sun gear and an internally toothed crownwheel. The difference in torque output was dependent upon the difference in diameter between the central sun gear and the crownwheel. The differential was developed for Peugeot by FF Developments Ltd, formerly Harry Ferguson Research.
The Inconveniences of Four-Wheel Drive
The increased weight of a 4 x 4 system inflicts a penalty in terms of fuel economy; on the highway, where the influence of the extra weight is less noticeable, thanks to the reduced need for acceleration and deceleration, a four-wheel drive car can show a marginal improvement in consumption unless it is driven at maximum speed. The reason for the improvement is that driven wheels exert a lower rolling resistance than those which are being pulled or pushed. At maximum speed however, the mechanical losses inherent in the more complicated drive-line make themselves felt in terms of fuel consumption.
The disengagement of one set of driving wheels, a standard feature of most of the off-road sedans of the 1980's, gave little to no saving in fuel because the weight still had to be moved and the disconnected differential and drive shafts still continued to turn, being driven by the cars forward motion rather than directly by the engine. To counter this latter problem, early off-road designs usually incorporated a freewheel mechanism in the front hubs that worked when the drive was disconnected - but the weight, however, was still present.
Things changed rapidly over the next 20 years, and one manufacturer was to claim the high ground in 4WD technology, applying this to all models in their lineup (albiet re-branding it as All Wheel Drive). Performance manufacturers soon realised the benefits of being able to put the power down on the road outweighed the weight penalty, and of course the large true off road vehicle evolved into an entirely different beast, the vast majority never venturing outside the city, and mainly spotted picking up the kids from school.
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A short history of four-wheel drive - cars referred to in this article include...
Lancia Delta S4
Land Rover, Series 1
Mercedes-Benz 300GD Gelandewagen
Peugeot 205 Turbo 16
Range Rover Mark 1
Subaru Leone (also see Subaru Brumby)
Toyota Tercel 4x4