Chassis. Length: 11’ 6". Under slung at the rear. Tapering from the front to the second pressed cross member (at the rear of the engine bay) and then parallel to the rear. Tubular cross members at front and rear. Four pressed steel channel cross members and one fabricated channel cross member (just to the rear of the rear axle). A pressed steel bulkhead in three sections supports the firewall.
Engine. The Claude Hill designed 2 litre single overhead camshaft, 8 valve engine with dry sump. High compression pistons are fitted. The crank was made of nickel steel and was ‘Nitralloy’ hardened. The cylinder head had polished ports. Early Speed Model and some 15/98 cylinder blocks were cast with extra webbing to the inside of the crank case.
Twin SU side draught carburettors, 1⅝" HV3
Bore 78 mm, stroke 102 mm, 1949.57 cc.
Later Type ‘C’ had 4 branch extractor exhaust manifold.
Compression ratio: 8.2:1.
Power: approximately 110 bhp at 5250 rpm
Torque: approximately 110 lbft at 5500 rpm.
Magneto ignition by Scintilla ‘Vertex’.
Twin SU fuel pumps
Dynamo and starter by Scintilla.
Transmission. Aston Martin designed racing crash gearbox. Constant mesh main and layshaft with ¾" wide straight cut close ratio gears. The gearbox is mounted in unit with the engine and supported at the rear by a rubber block mounted on a steel strap tensioned by nuts at each side of the chassis. Ratios 11.38:1, 8.33:1, 6.11:1, 4.4:1. Clutch is dry plate Borg and Beck. A much heavier ENV differential is used. An alternative final drive ratio is 4.25:1.
Steering. Marles worm and peg with top thrust bearing.
Wheels and tyres. Rudge Whitworth 18" wires wellbase wheels, with 52mm hubs and 3 1/4" wide rims. Tyres 18 x 5.25.
Suspension. Semi elliptic leaf springs front and rear. ‘Hartford’ friction dampers are fitted at the front and the rear.
Brakes. Lockheed hydraulic, with 1¼" ‘Tandem’ master cylinder. 1 ¼" slave cylinders at the front and 1⅛" slave cylinders at the rear. Aston Martin designed 14" deeply ribbed drums in alluminium alloy with steel liners, with 2" wide brake shoes and linings. The brake back plates and all fittings were designed by Aston Martin. The back plates are fitted with twin air scoops, one to cool the hydraulic cylinder and one to pass air through the whole assembly. The centrally placed handbrake operates on the rear wheels only.
Wheelbase: 8’ 6".
Track: 4’ 6 ½".
Height: 4’ 3"
Weight: 20 cwt.
Fuel tank capacity: 13 gallons.
Price 1936, Chassis £695. Type ‘A’ and Type ‘C’ £775
Coachwork. The ‘Speed Model’ had a short production run of only twenty three cars to enable it to be homologated for International motor racing. As such there is not one single correct type of bodywork for the ‘Speed Model’ as had been the case for the previous 1½ litre models, for example the short chassis Le Mans or Mark II.
Many cars were built for racing and sported a variety of lightweight 2 seater racing bodies. Two early cars had racing bodywork very similar to the two works Le Mans team cars (but as two seaters). At least one car had a 1½litre ‘Ulster’ type body, suitably proportioned up to fit, and another car was said to have had a second hand ‘Ulster’ body fitted. However, because the 2 litre chassis is wider than a 1½ litre, and the wheelbase is different, a 1½ litre ‘Ulster’ body simply does not fit a ‘Speed Model’ chassis, and it would not have been worth modifying it to make it fit.
Abbey Coachworks built two rather heavy looking two seater road cars with very bulbous wings which are known as the Type ‘B’ two seater cars. Only one survives in its original form.
E. Bertelli Ltd. built five cars with 2/4 seater touring bodies (known as the Type ‘A’) with swept wings and a sloping tail at the rear. The slightly later ‘15/98’ short chassis had a very similar design, but the E.Bertelli Ltd. built body was more elegant in proportion, were coachbuilt to a very high standard and better equipped. They also built a one off full 4 seater (though still on a short chassis) for R. G. Barlow who had been a loyal customer to Aston Martin Ltd.
The two earliest Type ‘C’ cars had slightly heavy looking bodies with headlamps mounted on the wings and two lockers in the tail section, one for access to the spare wheel and the other for luggage. The prototype 1938 Motor Show car had a ‘V’ windscreen and painted in green and cream was known as the ’The Flying Banana’. Later cars had slightly better proportioned bodies, with the headlamps mounted behind the radiator stone guard and in front of the radiator core. Although this did give a very clean frontal appearance, it did not assist cooling.
All Speed Models were equipped with very high quality and expensive Scintilla ‘Vertex’ magneto, starter and dynamo, and had Scintilla switch gear, very similar to the contemporary Bugatti. All gauges were by Jeager with beveled glass as had been previously fitted to the ‘Le Mans Special 4 seater’ and the ‘Ulster’.
The ‘Speed Model’ is often thought of as the ‘Ulster’ version of the 15/98. Although it does have the same ‘U’ chassis number suffix as the 1½ litre ‘Ulster’ was is in fact developed and built before the works committed to building the short chassis 15/98, which is really a de-tuned and ‘productionized’ (by much outsourcing) version of the ‘Speed Model’.
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