DB3S

DB3S Description

In production: 1953—1956

Chassis numbers DB3S/101—DB3S/120 (except DB3S/109)

During the winter of 1952-1953, design proceeded on a shorter, generally smaller and lighter competition two-seater to replace the DB3. The use of large diameter tubes in the chassis and torsion bar suspension was continued, but in the DB3S, the tubes were 'cranked' to lower the central area and a spiral bevel replaced the hypoid bevel differential and the de Dion axle was located by a central slide, rather than by a Panhard rod. A four-speed David Brown gearbox replaced the five-speed box of the DB3. The 2,922 c.c. engine was further developed: with larger inlet valves and a new camshaft.

The rear inboard drum brakes, retained from the DB3, were subject to overheating and were moved outboard late in 1953. One car, DB3S/5, was built as a road car for David Brown, but was converted to a team car in 1954.

The success of the Works cars gave the type a good start when it was introduced for sale at the London Motor Show in October 1954. The specification, which was basically the same as the team cars, included the VB6K engine with a compression ratio of 8.68:1, single-plug cast iron head and three Weber 40 DCO carburettors, (though when reading the Motor Show pre-event guides in the motoring Press, the press release must have suggested three twin-choke Solex units), with an output of 180 b.h.p. at 5,500 r.p.m. according to the 1955 Works brochure but later shown as 182 b.h.p. at 5,500 r.p.m.

The hydraulically operated clutch was a 9” single-plate and the David Brown four-speed gearbox (5430/12) had synchromesh on 2nd, 3rd and top. The standard spiral bevel back axle

ratio was 3.73:1. Alternative ratios of 3.27, 3.54 and 3.91:1 were available. A Girling brake system, split front and rear, was used, with Al-fin drums all-round.

Very elegant two-seater bodywork, designed by Frank Feeley, clothed the chassis. While three different open two-seater bodies were used on DB3S during its Works life, the production cars featured the type as used in 1954-1956. However, over time, several have been changed in detail. The fixed head coupé as seen at the end of this section was also available

You can read of the Works development of the DB3S and the engine on pages 49 and 50 such that the power output was raised to 225 b.h.p. at 6,000 r.p.m.

However, such luxuries were not generally available to the private owners who had to content themselves with an iron head, which, nevertheless, was also ‘breathed upon’. The first use of disc brakes on an Aston Martin was also in 1954, when Lockheed discs were fitted to the front of DB3S/1 for the May meeting at Silverstone. Once again the private owner was not able to benefit from this development and had to be content with the ‘Alfin’ drum brake system.

In time, some of the above mentioned improvements found their way onto privately owned cars. Anybody who wanted to spend money was always welcome at Feltham!

Descriptions appeared in The Autocar (5th February, 1954 and 20th April, 1956).

A production DB3S was road tested by Autosport (10th February, 1956) and 0-60 m.p.h., 0-100 m.p.h. and standing quarter mile times of 6.6, 14.4 and 14.4 secs. and a maximum speed of 140.6 m.p.h. were recorded.

A total of 19 were made before production was discontinued in 1956; three (DB3S/113, 119 and 120) are Fixedhead Coupés (DP 179), based on the bodies fitted to DB3S/6 and 7 in 1954.

Two production cars, DB3S/117 and 118 are believed to have twin-plug heads now. Of the 31 cars made, there is evidence of only 4 or, perhaps 5 (/109 ?) having been written off and the present whereabouts of all but one of the remainder is known.

Alan Selby has pulled together research and records of the U.S.A. cars from Rod Carveth, Bob Tronolone, Dick Sherwin, Dick Green and Kean Rogers. Jim Sitz, Historian of Vintage Motorsport, has supplied race records, plus, of course, Chris Nixon’s input. My thanks to all of them.

DB3S Specification

Engine
VB6K/ 3 Litre engine
Twin overhead camshafts
Hemispherical combustion chambers
Bore 83 mm, stroke of 90 mm, capacity of 2,922 c.c.
Compression ratio 8.68:1.
Fuel System
Three, twin Weber 40 DCO3 carburettors.
Supplied by two SU electric pumps.
Ignition System
12 volt coil and engine driven Lucas distributor.
KLG 10mm T. 240/3 spark plugs.
Contact breaker gap 0.012"
Static ignition timing 10° before TDC.
Electrical System
12 volt system and dynamo.
Transmission
Borg and Beck 9" single dry plate clutch.
David Brown gearbox
Chassis mounted final drive
With 3.73:1 back axle ratio, overall ratios were:
Gearbox Overall
Top 1:1 3.73:1
Third 1.26:1 4.69:1
Second 1.87:1 6.97:1
First 2.92:1 10.88:1
With the 3.73 overall top gear ratio, 1,000 r.p.m. was equivalent to 23 m.p.h.
Alternative ratios of 3.27, 3.54 and 3.91:1 were available as an extra. 1,000 r.p.m. was equivalent to 21.4 m.p.h.
Alternative ratios of 3.31:1; 3.54:1; 4.09:1 and 4.27:1 were offered.
Steering
Rack and pinion with a divided track rod.
Brakes
Girling dual hydraulic, split front/rear. Wellworthy Ltd. light alloy 'Al-Fin' drums as used on the team cars.
Front: 13" x 2½" Al-fin drums. Total friction area, front and rear, 174 sq. in.
Rear: 12" x 2¼" (outboard)
Hand brake operated by a floor mounted lever.
Suspension
Front: Trailing link with transverse torsion bars and Armstrong lever dampers.
Rear: de Dion system with sliding block lateral location of the de Dion tube. Trailing links and Armstrong telescopic dampers
Body
A removable one-piece aluminium skin over a frame of steel tubes.
Interior
Leather covered bucket seats.
Wheels and Tyres
16" wire, splined knock-off Borani light alloy wheels with 600 x 16" Avon tyres.
Main dimensions
Length 12'10" (391cm)
Wheelbase 7'3" (221cm)
Width 4'11" (150cm)
Clearance 6" (15cm)
Track 4'1" (124.5cm)
Turning circle 30' (914cm)
Height (inc. screen) 3' 5" (104cm)
Weight 17½ cwt. (890 kg.)
Fuel system
Capacity 35 gallons. (159 litre; 42 U.S. galls.) with 3 gallons. (13.6 litre; 3.6 U.S. galls) in reserve.
Fuel Type Petrol 95 Ron, leaded.
Maximum power
VB6K. With compression ratio 8.68:1; 180 b.h.p. at 5,500 r.p.m.
Maximum torque
VB6K, 178 lbs/ft at 3100 RPM.
Acceleration
0 to 60mph; Autosport 6.6secs.
Maximum speed
Autosport 140.6 m.p.h
Price (Prices in brackets include U.K. purchase tax)
£2,600 (£3,684)
Fixedhead Coupé at £3,200 (£4,800).
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