THE MARK II ASTON-MARTIN

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48

THE MARK II ASTON-MARTIN

A FAST SPORTS CAR WHICH INSPIRES CONFIDENCE.

ROME was not built in a day, we understand, and the thoroughbred attributes of the latest AstonMartin are likewise the result of consistent improvement on a sound foundation. For the past five years the cars have embodied a highly-efficient overhead camshaft engine, and the dry-sump system of lubrication, while the low-hung chassis passing under the rear axle has been a feature of the design for an equally long period. Regular participation in strenuous competitions, such as the 24-Hour Race at Le Mans, has each year given Mr. Bertelli invaluable technical data, and whenever a new model appears, one may be sure that it will include subtle alterations which make for better motoring.

Small but important changes have been made on the new Mark II series. A new type of cylinder-head is now used, and brings with it a further increase of horse-power, notably at the upper end of the range ; the fact that it is a fourcylinder already implies a good output at low speeds. The crank-shaft is fully balanced, and the full range of revs can be used without stressing the bearings, so that in point of the smoothness this four-cylinder power-unit compares favourably with many “sixes.” A slight alteration to the chassis has been made, an extending of the top webs where the front cross-member connects the side members has greatly increased the chassis rigidity at this point, and in conjunction with transversely mounted shockabsorbers makes a surprising difference to the road-holding on bumpy corners. It is the attention to small matters such as these which makes the Aston-Martin such an eminently satisfying vehicle and one which has a real fascination for the experienced driver. Extraordinary patches of local fog prevailed on the day we took over the car, and we arrived at Brooklands after a series of second gear crawls through the thick sectors alternating with sprightly bursts of speeds in places where visibility was normal. Conditions at the Track

were more favourable, but what with the ” breakers ” and various cars engaged in evolutions on the Railway Straight it was impossible to discover the Aston’s all-out speed. However, from a standing start on the Railway Straight the 80 m.p.h. mark was reached by the end of the Byfleet Banking, so one is safe at putting the maximum at about 85 m.p.h. The speedometer was 2 m.p.h. slow at

60 and fractionally so at 75, which is rather unusual, while the acceleration figures showed a material improvement at the upper end of the range over those put up by the forerunner of the Mark II.

Business matters compelled us to return to London, and gave a chance of trying the car in traffic. With the ignition half-retarded, an easy matter with the extended ignition control, the car ran smoothly down to 15 m.p.h. or less, on top gear. The exhaust note is a pleasant one and the gears can be used freely if required, while even in thick traffic there was no fear of oiling up the plugs.

Next morning the engine started easily, thanks to a Ki-gass primer, and we were soon on the way to the country. On a quite crowded by-pass road the car gathers speed in a most deceptive way, and the driver finds himself humming along at 65 m.p.h. quite without realising it. This speed we found to be the normal fast touring gait, since the engine runs inaudibly and almost forgotten, while the suspension and roadholding allows one to corner on fast bends without reduction in speed even with a full petrol tank. Top gear serves for a wide range of conditions, with the high third speed available for shooting up steep main road hills or negotiating the more winding roads.

Gaining at last the “great open spaces,” we decided to forget for a time our ideal of fast cruising and really give the car its head, secure in the knowledge that over two gallons of cool lubrication oil was circulating through the bearings. We explored fairly thoroughly the various straight stretches of Salisbury Plain and found that at 75 m.p.h. the car still gave no impression of speed. The maximum with the windscreen up is in the neighbourhood of 80 m.p.h., but on many occasions down the long slopes we passed the 90 mark without feeling that the car was being over-worked. Rain began to fall towards the end of our run, but we found that as long as the car was moving the windscreen deflected the drops over our head. The hood was easily erected and gave good protection and plenty of head-room.

The stability of the car was in no way affected by the wet roads, and the cycletype mudguards, which move with the wheels, were fully up to their work, and are firmly supported by stays fixed on to the back plates of the brakes. The brakes themselves behaved rather strangely, for at the commencement of our run when the sun was shining they were amply powerful and all four wheels could be locked if one exerted sufficient strength, yet when damp conditions set in this was no longer possible and from 40 m.p.h. 75 ft. was required to bring the car to a standstill. The drums are well protected from the entry of water, and the only explanation we could think of was that the linings absorbed moisture from the air. The exceptional range of engine speed makes the Aston-Martin almost as fast on winding roads as on straight ones. The engine runs smoothly and quietly up to 5,500 r.p.m., when the road speeds on second and third gears are respectively 53 and 75 m.p.h. At 4,500 r.p.m. on

third gear a useful 60 m.p.h. is reached, while on top gear at this speed the car is doing about 80 m.p.h. The increased power produced by the new head makes itself felt from about 3,000 r.p.m., and as the normal figure for changing up is around “3, 5,” a fine surge of power follows each movement Of the lever and road speed is very quickly regained after a check.

Straight pinions are used in the gear-box for all the ratios, and second and third gears are audible but not unpleasantly so. The gear-change is quite simple, but requires a day’s practise before one can guarantee a silent change every time. The change-down is remarkably quick, owing to the lively engine, while the upward movement is rather slower, and once these points are grasped, the driver is amply rewarded for his trouble by the finger-light and silent changes which may then be effected.

The Aston’s effortless attitude to allout speed is matched by its behaviour on corners. The car can be taken round fast bends or wrenched round tight ones in 4 Way which makes them all seem easy, and no doubt aided by the strengthened Cl) assis and the transversely-mounted shock-absorbers, the front wheels even on loose-surfaced eel-nets take the line desired without any conscious effort on the part of the driver. The steering is light, free from back-lash, and has a good caster-action. The seating position gives the driver. full control over the car and both front wings can be seen, while there is -a simple adjustment for altering the rake of the back rest. The windscreen is a large and sensible one, and has side screens which may be used as auxiliary ones when the

main one is folded down. An efficient two-blade electric wiper is now used. The pedals and the gear-lever are well Placed for easy operation, but the handbrake, which is on the driver’s right is difficult to reach when one is wearing a heavy overcoat. The racing ratchet, Operating’ only when a catch is raised, is a good feature, while those who specialise in racing changes will be glad to know that the pedals are so placed that foot

brake and accelerator may be operated simultaneously by swivelling round the right foot. Turning to the mechanical details, the engine is a four-cylinder overhead-camshaft unit, silentbloc mounted at four points. The detachable cylinder head and the block are both of cast iron, and the block is in one with the top half of the crankcase. The compression ratio is 7.5 to 1 and the fuel recommended for fast work is 50 per cent, straight petrol and 50 per cent. benzol. The camshaft is driven at its front end by a roller chain running at half crankshaft speed, and

the top chain and its sprocket remain undisturbed when the head is removed for decarbonising. The valves are actuated through rockers which have eccentric fulcrums for clearance adjustment, and each valve has three concentric springs secured by a threaded collar and a hardened lock-nut, Two S.U. carburetters are used, supplied by two S.U. electric pumps from a 13-gallon rear tank, the second pump being brought into action only when the 4-gallon reserve supply is required. The water pump and the Scintilla magneto are spigot-mounted on the near side of the engine, and the dynamo is driven off the front end of the crankshaft.

Dry-sump lubrication is used with a 2.9-gallon tank mounted between the front dumb-irons. A pressure pump draws oil from the tank and delivers it to the various points via a special pressure filter wnich can be cleaned by rotating a handle, and from the sump the oil is returned to the tank by a scavenge pump 50 per cent. larger than the pressure one. The oil temperature never rises above 75 degrees, and the use of large diameter flexible pipes provides for an easy passage for cold and thick oil, and avoids the possibility of fracture through road vibration.

Before leaving the engine one must not forget the stiff Nitralloy crankshaft, which is fully balanced and carried in three main bearings, and the aluminium pistons and the duralimin rods, which also have plain bearings. The gear-box is spigot mounted, and has a remote control gear-lever, a single dry-plate clutch is used, an open propeller shaft with two universal joints and a bevel driven back axle.

The chassis frame is particularly rigid, with six channel section cross-members, and is upswept over the front axle and passes under the rear axle. Friction shock absorbers are used back and front, those on the front axle being mounted transversely to increase the leverage. The front axle is typical of the fine workmanship which characterises the Aston-Martin chasus, and is of one section between the springs, and tubular at the extremities, where it has to withstand steering and braking reactions. The brakes are 14 inches in diameter, and operated by special cables which remain constant in length irrespective of the axle movement. The cables are lubricated from grouped nipples mounted on the chassis, and are adjusted by large wing nuts at their extremities.

The dash-board equipment is comprehensive, and we liked the largediameter Smith speedometer and revcounter. The lights give a field of view sufficient for comfortable driving at 60 m.p.h., and the dip-and switch mechanism is conveniently controlled by a lever in the centre of the steering wheel.

The front seats have pneumatic upholstery, afford good support, and are readily adjustable. The rear compartment is intended primary for luggage, and sufficient for a long tour can be carried comfortably and within the wheel-base, but the seat is fully upholstered and except that leg-room is limited a single passenger may be carried in reasonable comfort. For those who require a bigger car, a full four-seater body is of course now produced on the 10 ft. chassis.

Big-car enthusiasts are apt to think that effortless, fast touring is a quality exclusive to the vehicles of high horsepower rating, but their views will be considerably altered after they have taken the Aston-Martin over a 300-mile journey. The charm of handling of the smaller vehicle is undeniable and this the Aston has preserved, coupled with an allout speed and cruising speeds admirably suited to English conditions. Anyone who examines the components of engine and chassis cannot fail to be impressed by the quality and workmanship which are brought together in the production of the car, and the confidence of the makers in their product is reflected in the Guarantee, which runs indefinitely as long as the car remains in the same ownership.

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