A New 2 1/2-Litre Alta-engined British G.P. Car, with All-Enveloping or Normal Bodywork, to be Built for Private Owners
At Goodwood during the afternoon of August. 12th a select assembly of Pressmen and enthusiasts who had taken the trouble to drive down to the Sussex circuit at the invitation of John Webb Press Services, saw Rodney Clarke drive a few sedate laps in the prototype 2 1/2-litre Alta-engined, all-enveloping F. 1 Connaught Grand Prix car.
No attempt was made to over-publicise this latest model from the courageous little factory at Send in Surrey, which modest Kenneth McAlpine sponsors from a warm desire to see Britain build an effective G.P. car and where Clarke has charge of a keen band of some forty engineers and draughtsmen.
The new F. 1 Connanght was designed over twelve months ago and made its debut before the Press just five years and one day after the first race victory was secured by this marque. The car is essentially a prototype and further development work will be done before any attempt is made seriously to race the car. Consequently it is the 1955 season to which we must look forward in respect of this Connaught entry into real G.P. racing, although it is just possible that the first car will be raced at the end of this season. In any case, Connaught will sensibly refrain from entering an official team of cars, realising that their financial resources will not stand the inevitable strain of so doing — it cannot be too strongly emphasised that Connaught Engineering is a non-profit-making concern which does not receive monetary support from publicity-seeking concerns or organisations.
Indeed, to offset expenses the new 2 1/2-litre F. 1 car will be sold to private owners and it is most satisfying to be able to state that a batch of seven is to be laid down, sufficient off-the-drawing-board orders having been obtained following the very good showing made by F. II Connaught racing cars since 1950.
The prototype car was, as has been said, demonstrated sensibly rather than sensationally at Goodwood on August 12th. It is doubtful if Clarke exceeded 100 m.p.h. on any part of the circuit, his intention being to humour the cameramen rather than provide false data for stop-watch clickers. The prototype is described as “Britain’s first streamlined racing car,” and while this may cause eyebrow raising amongst progenitors of low air-drag, it is certainly the first modern style all-enveloping F. 1 car to wear the green. Development work is estimated to have absorbed about £15,000 and £50,000 would be required to run a works team of three cars.
Apart from the prototype, which is a very purposeful, compact car, with big tail-fin, wide, tail and the rear wheels well clear of the cowling for wheel-changing, two further 2 1/2-litre chassis are complete and, indeed, were at the body-builders last month.
The second all-enveloping car will be Kenneth McAlpine’s. The third car will have an ordinary G.P. body and has been ordered by R. R. C. Walker for A. P. R. Rolt to drive. The fourth car will be of all-enveloping type, for Leslie Marr, the fifth is to be a normal G.P.-bodied car for Peter Whitehead. No. 6 could, it seems, be yours, and very nice too. A second production batch of these promising F. 1 Connaughts may be laid down. The cost will apparently be in the region of £5,000 each.
If the prototype is raced before Rob Walker receives his car Tony Rolt is likely to drive it and there could be no better choice, for a new car calls for a steady as well as a fast driver, while Rolt has had great experience of all-enveloping sports/racing cars, which should be useful when he drives the G.P. Connaught.
In common with earlier Connaught designs, large-section steel tubes are employed for the main chassis members of the new car. There are two parallel side-members of 3 3/4 in. diameter 16-gauge tubular steel, with four cross-members of the same dimensions welded into position at right angles. Welded to this is a basic superstructure of smaller steel tubes and square-section tubular members. This combines bracing for the chassis with mountings for the instrument panel and the body structure.
Built across the forward end of the main chassis frame just aft of the front cross-member is a rigid, welded box structure which provides the anchorage points for front suspension components. The front suspension is independent by two square-section, tubular wishbones of unequal length on each side, and Armstrong combined telescopic damper and helical spring units incorporating special modifications by Connaught Engineering.
These suspension units are located at their upper end at a mounting on the box structure. They pass through the top wishbone on each side and are attached to a bracket on the lower wishbones. Each of the lower wishbones is linked to a torsion-bar which runs transversely through the front cross-member of the chassis.
Steering is by rack-and-pinion, with the gear itself mounted transversely on a step on the forward face of the front chassis box structure. It is positioned forward of the hubs, and all the ball joints in the connecting-arms are in yokes. The gearing is arranged to give two turns from lock to lock and the geometry is such that there is almost no Ackerman.
The new Connaught employs a de Dion-type rear axle. In this layout, the de Dion tube is located by two radius arms, one on each side, running forward of the axle. They are mounted at their forward ends on an outrigger support, about mid-way between the two central chassis cross-members.
Braking torque is counteracted by a short torque-arm jointed at each end, which is anchored at a central point on the de Dion tube and a mounting on the top of the differential casing. Lateral location is provided by a short compound linkage on the near side which has the same effect as would have a full-length Panhard rod.
This layout is used in conjunction with a longitudinally-disposed torsion-bar on each side. A short shackle and a straightforward arm link the axle to the torsion-bars on each side. Damping is by Armstrong double-acting units.
Almost any available Grand Prix engine can be accepted by the readily-adaptable Connaught chassis. For the immediate future, however, a 2 1/2-litre four-cylinder Alta engine will be the standard unit, and we understand that only Connaught will have access to these engines. It is a twin overhead-camshaft engine with a bore and stroke of 93.5 min. and 90 mm., respectively (2,470 c.c.). The alloy block-casing and crankcase are all in one. Within the casing is positioned a single casting which forms four “wet” cylinder liners. There is a three-bearing crankshaft and Vandervall thin-wall bearings are employed for both the mains and the big-ends. Engine lubrication is on the dry-sump principle.
The cylinder head is detachable and is jointed by Wills rings. A compression ratio of 12 1/2 to 1 is employed. Carburation is by the latest S.U. fuel injection system with the pump being driven from the rear of the near-side camshaft. The timing gears are also at the rear of the block. Ignition is by a Lucas coil.
From the rear of the engine a prop.-shaft with Hardy Spicer joints connects to a four-speed Armstrong-Siddeley preselector gearbox which is positioned aft of the driver, close to the rear axle. The gearbox in turn is linked to the final drive unit through a Layrub joint. The final drive unit is a Connaught design with a magnesium alloy casing; it incorporates a double reduction gear which allows for up to a four per cent, variation in axle ratio to be speedily effected. The unit is rigidly positioned in strong mounting-plates which are welded to form an integral part of the main chassis frame. Universally-jointed shafts provide the final drive from the differential to the wheels. Two-leading-shoe Girling hydraulic brakes are employed utilising 9 in. by 1 3/4 in. Alfin drums at the rear and 12 in. by 2 in. units at the front. Specially-designed magnesium castings form the back plates. The brake master cylinder is a twin unit coupled by rod to the pedal and by cable to the handbrake: It is mounted inboard of the off-side main chassis member about mid-way along its length and is connected to a remote reservoir.
The Borrani-Rudge type wire wheels are equipped with 5.50 by 16 tyres at the front and 6.00 by 16 tyres at the rear.
Subect to satisfactory tests, later models may have Dunlop disc brakes used in conjunction with pin-drive wire wheels.
The Aluminium coachwork of the car is 14 ft. 4 in. long and 5 ft. 6 in. wide. It encloses the driver up to shoulder height and features a large combined head-fairing and fin. In the nose of the body are air intakes for the front brakes, the radiator (which is an ultra-light alloy unit) and the engine. Unobtrusive ducts, low down in the side of the car, direct air onto the rear brakes. The underside of the chassis is also fully faired in.
The complete body is divided at its waist line so that in a matter of minutes the complete top half can be removed. Fuel tanks housed in the tail of the car and on each side of the driver, provide a capacity of about 50 gallons. The driver sits well toward the forward end of the car. His feet are, in fact, on each side of the engine. This has been arranged so that in conjunction with the down-ward sloping bonnet line the driver can obtain the best possible forward and side visibility.
Every British enthusiast will wish Connaught Engineering the greatest success with these promising and modestly-announced Formula 1 cars. — W.B.
Cylinders: Four. Bore: 93.5 mm. Stroke 90 mm.
Cubic Capacity: 2,470 c.c.
Valves: Two per cylinder. Operated by twin o.h. camshafts.
Compression Ratio: 12 1/2 to 1.
Max. r.p.m.: 7,000, approximately.
Carburation: S.U. fuel injection.
Ignition: Lucas coil. Lubrication system: Dry-sump.
Prop.-shaft: Engine to gearbox, Hardy Spicer joints.
Gearbox: Armstrong-Siddley, preselector remote from engine, coupled to final drive unit by Layrub joint.
Final drive: Connaught double-reduction axle with magnesium alloy casing. Universally-jointed shafts to wheels.
General design: Tubular. Two parallel side-members and four cross-members each 3 3/4 inch diameter, 16 gauge.
Front suspension: Independent. Unequal length wish-bones with modified Armstrong suspension units (helical spring).
Rear suspension: De Dion with torsion bars. One radius-rod on each side forward of the axle.
Dampers: Armstrong units at front. Double-acting piston-type Armstrongs at rear
Wheels: Borrani-Rudge type, wire.
Tyres: Front: 5.50 by 16; rear: 6.00 by 16.
Brakes: 2LS Girling, 9 in. by 1 3/4 in. rear, 12 in. by 2 in. front. Alfin drums, magnesium back-plates. Note: Later models may have disc brakes in conjunction with pin-drive disc wheels.
Steering gear: Rack and pinion, two turns lock to lock.
Tank capacity: Fifty gallons.
Wheelbase: … 7 ft. 6 in.
Track, front and rear: … 4 ft. 2 in.
Overall length: … 14 ft. 4 in.
Overall width: … 5 ft. 6 in.
Ground clearance: … 4 in.