A 2-LITRE ASTON-MARTIN STRIKING NEW SUPER-SPORTS MODEL WHICH SHOULD GIVE SPEED OF 110 M.P.H. IN LE MANS TRIM
Persistent rumours of a larger AstonMartin took concrete form with the announcement in April of a 2-litre model. The first cars of the new type were prepared for the postponed Le Mans race last month) and should have given an excellent account of themselves. The new cars will be available either with an 8 ft. 6 in. chassis, intended only for two-seater or racing four-seater coachwork, or with a 10 ft. chassis, which will provide room for normal four-seater or closed bodies. The standard and the Ulster 11-litre models will he continued without alteration.
The engine is a four-cylinder, with bore and stroke 78 mm. and 102 mm., giving a capacity of 1,950 c.c. It follows the same general lines as that of the smaller power-unit, with the cylinder-block and crank-case cast as a single unit, and special ample water-spacing between the cylinders, very necessary with a 2-litre developing close on 100 b.h.p. The single overhead camshaft is chaindriven from the front end of the engine, the reduction being effected by a train of gears and a countershaft running on ball-bearings. The valves are operated by fingers with eccentrically mounted pivots, the rotation of these giving the adjustment for valve clearance. The inlet valves are larger than the exhaust valves, and the sparking plugs are fitted on the exhaust side of
the head. The carburetters are on the near side of the engine and the exhaust manifold on the off side, the opposite arrangement to that used on the 11-litre engine. Two horizontal S.U. carburetters are used as standard practice, but four could be fitted if required. They are fed by means of two S.U. petrol pumps, one of these operating on the main supply of 12 gallons, and the second being switched on to draw the last 3 gallons from the rear tank. A vertical Scintilla magneto is mounted at the front of the engine, and the dynamo is driven off the timing gears and carried in readily detachable metal straps. The starter motor is of the usual type, flange mounted in the
flywheel housing, and the battery is carried in front of the dash.
The crank-shaft is nitralloy hardened, fitted with balance weights and is safe up to 6,000 r.p.rn. Being hollow there is no risk of failure of the oil supply to the three main bearings and the crank-pins. The light alloy connecting rods run direct on these, while the gudgeon pins float in the pistons and the small ends, being retained by circlips. Needless to say, dry-sump lubrication is a feature of the 2-litre. Two oil pumps are mounted externally at the front of the engine, the larger one scavenging the sump, and returning it to a 2-gallon tank mounted between the front dumbirons. The smaller one forces cool oil through a disc-type pressure filter, which is kept constantly cleaned by being connected to the brake pedal. Thence the main supply passes to the bearings and a further supply under redueed pressure is led to the
56 m.p.h., and 41 m.p.h. With a high back-axle ratio and light coachwork a speed of 110 m.p.h. can be reached. A central gear-change is fitted, with a remote control operating in a gate.
An open propeller shaft with two universal joints takes the drive to the back-axle, which is of the banjo semi-floating type. Spiral bevel gears are used on the touring cars and straight bevels on those intended for racing.
New Front-Axle Layout
The chassis arrangement is the same as that used on the smaller cars, with the side-members upswept over the front axle and underslung at the rear. The front suspension is however, distinctly novel. At the front end the springs are carried outside the dumb-irons, giving an unusually wide spring base. At the rear end a normal type of shackle
is used, but instead of attaching the axle to the springs by the conventional U-bolts it is free to rock slightly in cradles. In this way the springs are relieved of most of the braking stresses, these being taken by wire braces running from the chassis to brackets carried above the axle-cradles. The front portions of the springs have also to withstand the stress of locating the axle, but being in tension are well suited to the job. The rear springs follow normal practice, and friction shock-absorbers are used fore and aft.
The other important change from previous Aston-Martin practice is the use of hydraulically-operated brakes, the reliability of which have by now been well proven on the majority of modern racing cars. The drums are almost as large as the wheel and are constructed of aluminium alloy, and have cast-iron liners.
The back-plates are also made of light metal. Air scoops serve to deflect air into the interior of the drum and on to the cylinders of the Lockheed operating gear. Separate master-cylinders coupled in tandem are used for the front and rear pairs of brakes, so that half the brakes will remain in operation even in the unlikely event of a pipe breaking.
The chassis is of channel-section throughout, with numerous cross-members of the same type. The short-chassis car has a wheelbase of 8 ft. 6 in. as compared with the 10 ft. of the touring car, the track in each case being 4 ft. 61 in. The short-chassis weighs 18 cwt.
The price of the long-chassis model has not yet been .fixed, but the short model will cost #300 for the chassis alone. With a light two or four-seater competition body the price is £875.
camshafts where drilled passages feed it to the cam-faces and other vital spots.
The engine temperature is controlled by means of a thermostat in the lower water connection. The cylinder-block is cooled by thermo-syphon, the full stream from the water-pump being directed into the cylinder-head. A carbon packing gland is used on the pump, ensuring notrouble service without any attention from the owner. The gear-box is mounted in unit with the engine, and the power is transmitted through a Borg and Beck single-plate clutch. The casing, the shafts, and the gears themselves are all exceptionally robust, and all bearings are either ball or roller. Straight pinions are employed for all gears, the overall ratio with the standard back-axle being 4.4, 6.11, 8.33 and 11.38 to 1. Speeds on the gears at 5,500 r.p.m. are 104 m.p.h., 76 m.p.h., Continued on page 863