AMONGST THE QUALITY
AMONGST THE QUALITY
THE NEW ATALANTA, WITH ALL-INDEPENDENT SUSPENSION, MAGNETIC GEARBOX, AND MANY INGENIOUS FEATURES
SPORTS-CA RS are not so numerous that the advent of a quality newcomer can be neglected. The new Atalanta was announced at the beginning of this year, and a certain number of models have already found their way into the hands of the general public. Now plans are ready for serious production in the spacious works at Staines, and the original design has been modified in detail, to present a specification of considerable appeal to the connoisseur.
First of all, the Atalanta is available in two forms, either li-litre or 2-litre, in each case with four cylinders, and either version may be supercharged or unsupercharged. A special feature of the supercharged models is that the blower may be brought into action, or not, at will.
The engine has three valves per cylinder —two inlet and one exhaust—a total magnetic gearbox is fitted, and, finally, all four wheels are independently sprung. In this last respect the car is, with the exception of one racing machine, unique amongst those produced by British manufacturers. To take the engine first, a single overhead camshaft operates all the valves, which are placed vertically in the cylinder head, and are made of KE 965 steel, according to the best racing practice. The two inlet valves for each cylinder are operated simultaneously by one cam, by means of a bridge piece which fits over the top of the valve stems. The stems are threaded to take the valve spring collars, and the tappet clearance is adjusted simply, by means of a hardened
steel hexagon which acts as a lock-nut on the end of the stem. Two 14 mm. sparking plugs are fitted for each cylinder, and these are placed on each side of the exhaust valve, with masked orifices. Each set of plugs is fed
by a separate magneto, of vertical type and driven off the crankshaft by gears and a double roller chain. The camshaft is also driven by chain, with a tensioning device. On the unsupercharged models two Arnott carburetters are fitted, one on each side of the cylinder head, and owing
to the paired arrangement of the two inlet ports for each cylinder, the effect is that each cylinder is fed by two carburetters, though the carburetters only number two in all. When a supercharger is fitted, this is mounted in front of the engine, and is driven via a clutch off the nose of the crankshaft. The single large carburetter is on the outside of the supercharger, not between the supercharger and the engine,
as in the other case of the famous car where the supercharger can be brought into action at will. On the Atalanta the supercharger clutch may be engaged or released by means of a lever under the dashboard. The induction system from the blower has two branches, one on each side of the
engine, and in each branch there is a valve, connecting to a passage direct to the carburetter. When the supercharger is not in action, these valves are held open against a light spring, and, though the blower is sucked gently round, the engine draws its fuel direct from the carburetter without passing through the supercharger vanes. When the blower is working, the valves close and allow pressure to be developed in the induction pipe. This system is simple yet extremely ingenious, and is designed to allow a driver to cruise easily without the blower, but to have a vast reserve of power available if desired. In order to help in accommodating the blower in front of the engine, on the supercharged models the wheelbase is increased by 6 in.
There is, however, no difference in wheelbase whether a 2-litre or a 1ilitre engine is fitted, since the external dimensions and appearance of both powerunits are identical. The bore and stroke of the 2-litre are 75x113 mm. (1,996 c.c.), while the 1 i-litre engine measures 69x100 mm. (1,496 c.c.). Practically, the bore and stroke dimensions are the only differences between the two engines, though the 2-litre has a longer throw crankshaft. The crankshaft has three main bearings, which really are of generous diameter, and all oil ways are cast in the side of the crankcase, which is of aluminium. The cylinder block, which is separate from the crankcase, is of grey iron, and has aluminium side-plates forming part of the water jacket, a device by vi hi:;..h much weight is saved. Water space is allowed all round each cylinder barrel. The sump is of electron, and holds nearly three gallons, and there is a large external Tecalemit
oil filter. The clutch bell housing is also of electron.
Specialloid pistons are used, and the connecting rods are of RR 53 alloy, running direct on the crankshaft, without white metal interposed, according to aero engine practice. The rods are thus extremely light but of substantial design. The Cotal magnetic gearbox has proved very satisfactory, and is actually lighter
than several other types of box. The gears are changed by a kind of switch working in a little gate. For reverse a separate lever is fitted. This has three positions—forward, neutral, and reverse. Thus one not only has four forward speeds, but also four reverse gears as well, while the neutral position can be obtained either by the lever or in the magnetic gearbox. The gear ratios are 12. 8.8, 5.6 and 4.25 to 1., giving 5,000 r.p.m. at 100 m.p.h. in top gear. Now one comes to the extremely inter esting chassis. There are three light gauge tubular cross-members, and a cruciform bracing, drilled for lightness, in the centre. The front suspension is by vertical coil springs, working in compression. The stub-axles are supported by parallel links of RR 53 alloy, cutting
down the unsprung weight, and the coil springs themselves are mounted on a tubular member carried high up and supported by triangular tubes. The whole of this rigid construction is so skilfully concealed by the radiator and wings that one would scarcely suspect a sus, pew:jot; out of the ordinary.
Similar RR 53 links are used at the rear, and coil springs are .again employed, but in this case are disposed horizontally, inside the side members of the frame. An adjustment is provided to vary the spring strength, according to the type of body fitted. Andre Telecontrol shock absorbers are used at front and rear.
In the 'steering gear a divided track rod is used, operating both wheels, and pivoted in the centre on the immensely strong front cross-tube.
The brakes are of Lockheed hydraulic pattern, and, as in racing practice, a double-barrelled master-cylinder is used, so that in the unlikely occurrence of either the front or rear brakes failing, the other set will continue to function. The drums are enormous, 16 inches in diameter, and are made of electron, with cast iron. liners. The wheels are, naturally, of knock-off pattern, and are provided with 5.25x18 inch tyres.
The petrol tank is at the rear, and holds fifteen gallons, and two separate petrol pumps are fitted. It is said that the petrol consumption on the unblown 2-litre is about 24 m.p.g., and on the blown if litre about 20 m.p.g.
At present the Atalanta is available either as a sports two-seater or with a drophead coupe body. The track is in all cases 4 ft. 5 in., and the wheelbase varies from 8 ft., for the unblo‘vn special two-seater, to 9 ft. 6 in. for the blown coupe. In between there are the blown two-seaters, with 8 ft. 6 in. wheelbase, and a 9 ft. chassis, either for the blown or unblown engines. Weights vary, according to body style, from l51 cwt. to 21/ cwt.
Altogether the Atalanta is a most interesting car, with many ingenious features, and it should certainly .make its mark among British sports-cars. It is hoped that a road test will appear in a forthcoming issue of MOTOR SPORT. when some excellent performance figures are expected. Prices are :
Supercharged 14-litre ; two-seater, £700; Coupe, £725: 2-litre ; two-seater, £760; Coupe £790.
Unsupercharged 14-litre ; two-seater, £540; Coupe £585: 2-litre ; two-seater, £580; Coupe L595.