CARS FOR THE R.A.C. GRAND PRIX. Short Notes on the Probable Starters in this Important Event.
THE S.T.D. concern having raced the three Darracq cars for over three years with such remarkable success have at last produced a team of three new racers with which they hope to repeat or improve upon their previous performance. The new cars, although called Talbots, actually emanated from the French factory, and have already been entered in several important continental events. However, the teething troubles so often associated with a new design have prevented the Talbots from giving a really good account of themselves, though it is confidently expected that these will have been overcome before August 7th. The engine, of 1,500 c.c., is of the now popular 8-cylinderin-line type, which has practically become the recognised standard for the modern medium-sized racing car. The cylinders are of steel with water jackets welded to them and are arranged in four blocks of two. The valves, two per cylinder, working in the usual hemispherical combustion chamber are operated by twin overhead camshafts driven by a train of gears at the rearmost end of the engine. A supercharger of the Roots blower type draws the mixture through a single solex carburettor, the whole apparatus being arranged low down at the forward end of the chassis. As will be seen from the illustration a sloping radiator is fitted for cooling purposes, supplemented by a centrifugal pump. An interesting point is the oil radiator, fitted
below the water radiator and through which the oil is circulated by two mechanical pumps.
Four speeds forward and reverse are provided by the gearbox and a multiple metal plate clutch running in oil comprises the first step in the transmission. Ignition is provided by two 4-cylinder Bosch magnetos running at engine speed and one sparking plug per cylinder is employed. The chassis is of extremely deep channel section and being liberally cut away is very light. The whole is slung very low, both front and rear axles passing through the side members. The petrol tank, which is easily removable, is carried at the extreme
rear end of the chassis immediately above the rear axle, while in order to seat the driver more comfortably the engine is slightly offset, enabling a low and reasonably central position to be obtained. In all probability these interesting cars will be handled by Segrave, Divo and Moriceau, who now comprise the S.T.D. team.
Previous racing Delages have lately been of the 12cylinder type, but on the introduction of the 1,500 c.c. limit the “straight eight” model was produced and this type will be used for all the 1926 classics. The cylinders have a bore and stroke of 55.8 mm. by 76 mm. respectively, and two overhead valves inclined at 50 degrees are arranged in the hemispherical cylinder
head. A single sparking plug is situated centrally between the valves and ignition is performed by a single magneto at the front of the motor. Two carburettors and two superchargers supply the mixture, the latter being situated between the engine and the carburettors. The water pump and radiator are both at the forward end of the chassis and the lubrication is effected by three pumps, one to lubricate the crankshaft, one the camshaft, and the third drawing the oil from the sump and delivering it to the oil tank where it is cooled.
A dry plate clutch and four speed gearbox are built up in one unit with the engine while the normal racing speed of the engine is 7,500 r.p.m.
The chassis and body are extraordinary low, the highest point of the whole car being less than 3 feet from the ground, a feature which should ensure great steadiness and speed on corners. It has been found necessary in order to utilise a sufficiently large radiator, to mount the latter in front of the front axle and pierce it to allow for the starting handle.
Hartford Shock-absorbers and the new Silentblocs are fitted to all four Rudge-Whitworth wheels, and as on the Talbot a large petrol tank is carried at the rear of the chassis.
THE THOMAS SPECIAL.
These cars are also of the straight eight type, with aluminium cylinder blocks and steel liners ; the conventional detachable head is used hal, ing two overhead valves per cylinder, operated by a single oN,erhead camshaft, which is driven by spur gears. The valve gear is very similar to that employed on the big Leyland Thomas, leaf springs being employed to return the valves to their seatings. The supercharger is watercooled from the engine water jackets. The chassis is considerably underslung and the radiator slopes back at a sharp angle, thus necessitating an extra water tank under the scuttle, in order to maintain the supply in the engine which is high relative to the radiator. A fabric multi-plate clutch of Thomas design is
used and only one universal joint in the transmission. Dry sump lubrication is employed and the main bearings of the engine are plain white metal bushes. Both hand and foot brake levers operate on all four wheels and the seat position is remarkably low.
Two of these cars are entered and will be driven by the designer and T. Thistlethwayte.
This-verybusiness-like car is to some extent a development of the last year’s 200 mile racer, in that the unconventional but nevertheless successful front wheel drive principle is adhered to. The whole chassis, however, has been tidied up considerably and has lost that “down by the stern” appearance which distinguished the earlier cars. The most notable breakaway from normal Alvis design, however, concerns the engine which is a supercharged straight eight, built on distinctly unconventional lines. In the first place the whole cylinder block complete with cylinder heads and top half of the crankcase is cast in one, the valves being operated by two camshafts running from end to end of the engine on a level with the heads, the two magnetos being driven off their forward ends, while the rear ends are connected to water and oil pumps. The valves themselves are arranged horizontally in the sides of the cylinder heads, the inlets on one side and the exhausts
on the opposite ; this unconventional arrangement has been adopted in accordance with the designer’s views on the special conditions engendered by the use of a supercharger, and enables a compact combustion chamber to be used yet with the sparking plug well removed from the piston crown.
The supercharger is situated at the rear of the engine and a multiple disc clutch transmits the power via gearbox and universal joints to the front wheels. The body is in accordance with modern streamlining ideas, having a flat undershield to prevent “squeezing,” with a turtle back. In the hands of C. M. Harvey this car may be expected to give a good account of itself, and in any case is bound to cause
considerable interest by reason of its unconventional design.
THE ASTON-MARTIN, HALFORD SPECIAL, AND BUGATTI CARS.
The Aston-Martin entered by G. E. T. Eyston is his usual standard 4-seater chassis, well known at B rooklands, but now fitted with a supercharged Anzani engine and a new body. This type of engine, designed by Mr. Hagens and successfully used by Eldridge, should perform well if sufficient time has been allowed for its installation., The Halford Special is too well known to Brooklands habitués to need description, but since its recent mishap
at the Essex club meeting, a new radiator has been fitted of a different shape, thus minimising the chance of another similar occurence. The car has, of course, a 6-cylinder supercharged engine of good design and has already proved itself capable of good speeds on the track. A Bugatti was entered at the last minute by Capt. Malcolm Campbell and will be of the 1,500 c.c. straight
eight type that has already won several continental classics this year at Miramas and San Sebastian. The only other entries are two Eldridge Specials which are at present in America and are therefore not likely to compete. With fourteen starters the race should at least create as much interest as the premier continental races for which no larger number of entries are usually received.