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The desire for greater traction inspired thoughts of driving all four road wheels, thoughts which had been in the minds of Timothy Burstall and James Hill, who made a four wheel drive steam carriage in 1824. They realized the difficulties of road wheels running on different radii turns and on different surfaces, and drove their axles through free wheel clutches which could be locked for driving in reverse. In 1966, Mercedes S Class announced a four wheel drive car, making use of the invention of Claude Hill of Ferrari in 1952, for preventing front to rear slip. In this system two oppositely acting free wheel clutches, and a front to rear differential are paralleled by slightly unequal ratio gears. Under constant drive, the free wheels slowly overrun. However, when one axle tends to spin and rotate faster, relative free wheel movement reverses and the free wheels lock to prevent wheelspin. While the great majority of cars drove through their rear wheels and had their change speed gears bolted to the crankcase, a few manufacturers took the view that the greater proportion of the weight should be over, or near, the driving wheels, thus providing greater traction. This, of course, happened in some of the earliest cars, but probably more by accident than design. The feature tended to die out as the Panhard set the fashion for many years. However, engineers like Rumpler in 1921, Sir Dennistoun Burney in 1930, Ledwinka in 1934 and Porsche in the same year, all decided to combine the engine, transmission and final drive over the rear axle. Too little was known at the time about suspension and steering design, so that Rumpler, Burney, Tatra and Volkswagen cars earned a reputation for tail heaviness. By combining the gearbox and final drive in one unit with the rear axle (that is, by using a transaxle driven by a propeller shaft), more weight could be provided at the rear without moving the engine from the front. Although de Dion had done this in the opening years of the century, it was not popular because of the increase of unsprung weight which occurred when used in conjunction with rigid rear axles. The fact that de Dion had bolted the heavy masses to the chassis and driven the wheels through light, universally jointed shafts, seems to have been overlooked until American makers used the transaxle after the Second World War to provide more interior foot room for the front seats. The alternative to these rear drives was front wheel drive, as suggested by George Sheldon in 1877. Sheldon’s patent, which hamstrung the American industry for a number of years until it was eventually revoked, was reputed to be based on a vehicle having a three cylinder engine mounted crosswise on the axle to drive the front wheels. In 1904, Walter Christie used a four cylinder transverse engine, and, four years later, the Front Wheel Drive Auto Co. sold front wheel drive cars under the name of Badger. In 1926, J. A. Gregoire designed the Tracta with front wheel drive from an in line engine and was followed by new Mercedes Benz in 1928, Audi in 1932, B.S.A. in 1934 and then Citroén in 1936. Although there were strong adherents to front wheel drive and much argument raged between those who thought a car should be pushed along by the rear wheels and those who thought it should be pulled by the front wheels, it was not until Alec Issigonis designed the Austin Morris Mini in 1960 that front wheel drive became universally accepted. The Mini ranks alongside such classic cars for sale as Henry Ford’s Model T and Porsche 911 for sale as a truly significant car for millions of motorists. Sir Alec Issigonis, whose outstanding achievements also include the Morris Minor, was born in Smyrna in 1906. His father was a Greek who became a naturalized British subject, and his mother was of Bavarian origin. The family ran an engineering business in Smyrna for many years, but after mixed fortunes during the First World War, became refugees in Malta. In the early 1920s his mother took him to London where, as a teenager, he studied at Battersea Polytechnic. The fact that mathematics was always his bad subject apparently never worried or hindered him. In fact, he has been reported as suggesting that mathematics and creativity are bad bedfellows. When in line engines are used, transmission layouts for both front wheel and rear wheel drive cars are similar. They can be seen with the engines either in front, or behind the driving axle. The usual arrangement is for the final drive and differential casing to be bolted to the clutch casing or bell housing, and the gearbox to be bolted on the other side of the final drive. A relatively long drive shaft is used between the clutch driven plate and gearbox input gear, and a single stage gearbox is used to provide output to the final drive bevel pinion from the input end of the layshaft. The bevel crown wheel and differential are thus below the drive shaft from engine to gearbox and are mounted between them. Since there is always an indirect drive through a pair of gears within the gearbox, those engines which are mounted behind the driving axle usually rotate in the opposite direction to engines in front of the axle. An exception to this layout was the 1966 Oldsmobile Toronado, which used a seven litre V8 engine with a chain drive to a Hydramatic transmission mounted alongside the crankcase. The power output from the automatic transmission was taken forward to a differential driving the front wheels. When the engine is mounted with its crankshaft transverse to the longitudinal centre line of the car, little room remains for the transmission to be in line with the engine. In some layouts, such as that of the Austin Morris front wheel drive cars, the gearbox is moved below and alongside the crankcase. The clutch is mounted at the end of the crankshaft and drives a gear positioned between the engine and the clutch. This gear is meshed with an idler gear, driving the gearbox mainshaft, and the differential is driven from a spur gear at the other end of the gearbox, more or less at the centre of the power unit. From the differential there are short shafts which terminate in Hooke’s joints with rubber bush bearings. These lead to spline joints on the inboard ends of the wheel drive shafts. On the other hand, Bentley dealers dispensed with the idler gear to the gearbox mainshaft and the complication of the reversed clutch, by bolting the gearbox to the bell-housing and driving the layshaft. The gearbox mainshaft, of the Rolls Royce Ghost with its gear synchronizing mechanisms, is below and behind the crankshaft centre line and drives a spur reduction gear secured to the differential. As the final drive is not equidistant from the front wheels, the two drive shafts are given the same torsional rigidity by using a solid shaft for the shorter one and a larger diameter tube for the longer shaft. In the Rolls Royce Phantom front wheel drive cars with automatic transmission, the friction clutch is replaced by a hydraulic torque converter, the output of which drives the idler gear in the case of the smaller cars, or a chain drive on the larger cars. Bevel epicyclic gearing is used to provide the different ratios under the control of a Watt type centrifugal governor, the spring of which is loaded in accordance with the accelerator pedal position. Two systems have been tried to eliminate all the complications and frictional losses incurred in gear type transmissions. These are electric and hydrostatic drives. In an electric drive devised by Ferdinand Porsche, for the new Porsche of 1900, specially designed electric motors were built into the front wheel hubs. The batteries which had provided the energy source were replaced in 1902 by a petrol engine driven dynamo. Thus, at this early date, Porsche had produced a front wheel drive car with an easily controlled transmission, no necessity for a differential and a system allowing high torque at the driving wheels at zero road speed. The other system uses a hydraulic pump driven by the engine and hydraulic motors in the wheel hubs. Although such a method has yet to be used commercially on a passenger car, the hydrostatic drive has proved its worth on the exacting test ground of earth moving equipment.