CAR SIZES.

Press, Volume LXVIII, Issue 20499, 18 March 1932, Page 6

CAR SIZES.

CLASSIFYING THE WHEELBASE. GUIDE TO PURCHASERS. Owing to the British method of describing cars by their somewhat artificial horse-power rating, many motor' ists tend to lose sight of ths fact tliat the whcelbase is by far the most useful guide to the size, weight and body space of an automobile. It is a pity that this invaluable dimension should bo neglected, particularly in view of the fact that the modern tendency ia to provide a choice of engines in chassis which are well-nigh identical. For we may tako a number of niodiuni-sized cars, all with a wheelbase of between 9ft 6in and 10ft, the ratings of which may vary, according to engine size, between limits as far apart as 14 horse-power and 84 horsepower. The body and the general size of the car is practically the same in each case, yet people automatically tend to think of a 24 horse-power car as necessarily being' much bigger than a 14 horse-power car. Naturally the rating is useful as giving an idea of the siaw and power of the engine, but it should be limited to this purpose and should not be taken as a guide to car dimensions. Garage Accommodation. Another advantage of getting to know the wlieelbase is that it gives a good idea of the overall length of the car, wliieh is often very, important when garage accommodation is limited. Similarly, although to a lesser degree, the track is a useful dimension to Keep in mind, as it is a measure of the overall width and also gives an idea of the internal dimensions of the coachwork. The wheelbase and tracks are invariably stated in the'manufacturers' specifications, and the following average figures will show they vary in the car types which are most popular nowadays. Commencing with tho " baby" ears, which provide full scale seating for two people and emergency seating for additional passengers, it will be found that wheelbases vary between 6ft 3in and 7ft, while the track is usually or slightly less. These dimensions indicate the minimum size to which a motor car can usefully* be built. Next comes the new class of economy car in which full-scale four-seater coachwork is ingeniously fitted a chassis of small dimensions, the minimum wheelbase employed being 7ft 6in and the maximum nearly Bft. Here, again, the track is usually limited to 3|ft. Room Per Tour. Proceeding in order of size we come to a class which embraces the 10 horsepower four-cylinder models and small six-cylinder cars rated at about 12 horse : power. In each case the bodywork is of much the same size, pi'oviding adequate room for four people, but capable of carrying five at a pinch. The Wheelbases employed range from Bft to 9ft, and the track is usually about 4ft. Naturally, a six-cylinder engine is a few inches longer than the four-cylin-der type, so that for the same body space the wheelbase of t a " six" must be proportionately increased. Before going farther we may mention that the overall lengths of the cars we have described are usually found to be from 3ft to 4Jft longer than the wheelbase, while the overall'width may be takeiv as being nearly Ift greater than the track in almost all. cases.

We now come to a car class which provides somewhat roomier bodywork suitable for carrying three people in reasonable comfort on the rear seat. Here a great variety of engine powers is available ranging between limits of about 15 .horse-power and 25 horse-power. The nigh powered ex-, amples are naturally mostly of transatlantic origin, but there is a growing, number 0f British cars raited as high »■ 20 horse-power whieb .appeal to those who appreciate a power-weight ratio sufficiently to pay a heavier tax for this luxury. The wjieelbase of this class pf vehicle between 01ft and 10ft and the track is usually the standard dimensions of 4ft Sin; there are, however, examples of the use of slightly narrower tracks. * Overall length may be . anything from 4ft to s}ft longer than the wheelbase, according to the'space occupied by projections, such as bump-, era, luggage grids, and spare wheels.. The width, as in smaller ears, is usually about Ift greater than the track. ' The Big Models. Turning to larger cars usually rated at over 24 horse-power, we find that the wheelbases range from 10ft up to, something in the neighbourhood of 13ft for the very longest; and most costly types. Generally speaking, to carry seven' seater coach work with proper space for occasional seats a wheelbase not shorter than 10ft 6in is necCssarj;. In this class a 4ft Sin track was at ono time universal, but nowaday?, in order to provide still wider bodies, many makers are using tracks of sft, or even greater, dimensions. The overall lengths of these cars are usually between 4Jft and Sift; greater than the wheelbases, and widths are from lft to lift greater thai) the track. . In conclusion, it may be. mentioned that manufacturers try to use a moderate wheelbase and track for the reason that by *o doing weight and cost are reduced. HYDRAULIC BRAKES. In dealing with hyraulic brakes it is useful to understand , the law of fluid?, upon which principle the brakes work. Fluid pressure is measured by the force exerted per ',unit -area. Pressure applied to any area of an enclosed fluid js transmitted in all and without diminution to every part of the fluid and of the interior of the containing vessel. If you fill a bottfo with water, for instance, and force in an accurately fitting dense cork, sufficient pressure could be exerted to burst the bottle. Again, to show that the pressure exerted is equal at all points, you could take the form of syringe 4ised by glass blowers. This syringe is attached to a hollow sphere whieh has several openings over its surface: when the apparatus is filled with water and the piston forced into the cylinder the water escapes through the jets with equal force, though only one of .the jets is in direct line with the piston. A solid transmits pressure only in the direction in whieh tho force acts, but a fluid transmits pressure in every direction.

That is wliy wheVt you press the pedal of .tlie roaster cylinder in a hydraulic brake system the brake fluid pressure is the same at each wheel cylinder.

U' a wheel is always skidding when the brake is put on, it indicates that the linings are worn down. Do not speed in wet weather; it is hard on tyres, and skids may,occur. After a stop, start slowly; do not junip fprward. It jars the vehicle and'might damage any load the car may be tarrying,,. Do mot let the. tyres, stanti in puddles of oil; it de«troys. th@ni«