CAMPBELL’S “BLUE BIRD.”
Details of 1,450 hp. Challenaer Now Awaiting Trials.
N any attempt on the record for the highest speed in any element, experience can only be a guide up to the point reached in previous attempts. Such experience is, however, of vital importance in anticipating the difficulties likely to occur at
an increased speed, and it is Capt. Campbell’s unique experience of this particular work which must give everyone connected with the present attempt the greatest possible confidence.
The actual car, although virtually an entirely new vehicle as a whole, incorporates a large amount of the chassis of the previous cars used by him. Many people might consider this made the construction an easier matter, but anyone who has had any experience of re-designing or modifying the simplest contrivance, will realise that it is often far easier to start with a clean sheet than to adapt something which is already in existence.
To Mr. Railton, of Thomson and Taylors, fell the task of re-creating the present car, and whatever the result of the attempt, anyone who has had an opportunity of inspecting the Napier-Campbell, will agree that the greatest praise is due to him and to his firm for the ingenious and efficient manner in which the job has been done.
The chassis has been designed to enable the driver to sit as low as possible, and this has meant that both the seat and the transmission, have been offset. One of the difficulties of a vehicle of th’s type, is that the mechanical details are sd much governed by the shape of the body. This was decided on after exhaustive wind tunnel experiments with a Plasticine model, and possesses many unusual features, the chief of which is the fact that the body is not symmetrical. Owing to necessity of including the driver’s compartment in the streamlining scheme, it has made it impossible to have the car the same on each side, which gives it a peculiar appearance when viewed from above. The body was built by J. Gurney Nutting, of Chelsea in the remarkable time of only six weeks, and is one of
the finest examples of panel beating we have ever seen. The framework consists of steel tubes, and it is so constructed that the tail is the only fixed section. The rest is made in three sections, one covering the Napier engine, one the cockpit, and the third, the intermediate space. The top of the scuttle is less than 45 inches from the ground, while the clearance under the chassis is only 5 inches.
Campbell’s Own Views.
In discussing the prospects of the attempt with Capt. Campbell, prior to his departure for the States, we found him very modest in his statements, and while evidently confident, he adopted the very wise tone of refusing to make any rash statements as to possible speed, and pointed out that after the event was the only time for going into this !
Commenting on the increased power of the latest Napier engine he said, “This engine gives 1,450 h.p., as against 850 h.p. from the engine I used previously. There is no doubt that the power is sufficient to improve on the present speed, but the greatest factor is the stability of the car, which at the speed of a new record is bound to be somewhat of an unknown quantity.
“From my previous experience of such attempts I know some of the difficulties encountered, and though we have done all the experimenting we can, theory and practice are not always in agreement. However, we will hope for the best ! “
With this we wished him luck in his adventure and departed, feeling that if any man could drive that car at a speed in the region of 250 m.p.h., Malcolm Campbell would do so. The specification of the car is as follows :—
Chassis.—The chassis frame has been built at Messrs. Vickers’ River Don Works. The frame is underslung under the rear axle to provide a very low layout, the centre of gravity being considerably under the centre line of transmission.
Tubular cross members are used throughout, some of which are made out of solid forgings and machined.
The engine is supported on a sub-frame, made under a similar principle as the chassis, and providing a threepoint suspension by one spherical socket in the front and two at the rear.
The petrol tank is mounted at the rear end of the chassis and has a capacity of 23 gallons, and was made by the Gallay Radiator Co.
The oil tank is mounted inside the frame members alongside the engine and contains five gallons.
The wheelbase is 12ft. 2iins., the front track 5ft. 4ins. and the rear track 5ft. 2ins.
Wheels and Tyres.—Special wheels of the steel disc type have been designed and built by the Dunlop Rubber Co., with tyres by the Dunlop Company designed after a series of special tests to ensure their being capable of standing up to the high speeds anticipated.
Pairings to streamline the wheels and tyres leave only I ins. clearance between the tyre and the fairing, so a section 5ins. deep of the fairing near the tyre is made of very light sheet, so that in the event of a tyre deflating, this will he torn to pieces without locking the wheel.
Engine.—The engine is one of the latest type Napier racing engines, as fitted to the Gloster-Napier seaplane which set up a speed of 336 m.p.h. Special permission has had to be obtained from the Air Ministry for the use of the engine by Capt. Malcolm Campbell. Only certain information is allowed to be divulged, as it is still on the Air Ministry Part Publication List, and the following is the brief information available :—
Clutch.—The clutch is of the dry rnultiplate type, Perodo lined. Messrs. Perodo having greatly assisted in the design of the clutch.
Gearbox.—Three speed constant mesh, all dog clutches. The gear ratios are 1.58, 2.27, 4.01 and rereverse. Built by K.L.G. Sparking Plugs Ltd.
Rear Axle.—The central casing of the rear axle is offset 7ins., so as to enable the driver’s seat to be brought within 10ins, of the ground.
The final drive, which for the higher speed has a ratio of 1.58 to 1, is of the bevel gear type. Full floating axle shafts are provided, and the driving dogs at the hub end are formed solid with the axle shafts.
Front Axle.—The front axle is made in two pieces joined in the middle by substantial flanges and provision has been made for relieving the springs of torsional stresses.
Steering.—Both front wheels are directly controlled by the steering gear, while the track rod is retained. Two Manes steering gears are used in connection with the device, and although the lock of each wheel is directly controlled, the Ackerman action is maintained by the layout.
Suspension.—Half elliptic springs are provided in front and rear, the springs being of the Woodhead type with weldless solid eyes and solid lug plates and rebound clips. The dimensions of the springs are, at the front 3ft. lin., and 4ft. 4ins. at the rear. The spring blocks, which are made of manganese bronze, anchor the springs to the axles by a double set of clamping ” U ” bolts.
A feature of the springing is the fact that each rear spring has a different camber, so that when the car is at rest there is a slight list, but when engine torque comes into play it brings the car on an even keel. Hartford shock absorbers and Silentbloc bushes are utilised and fitted
Brakes.—Pour wheel brakes are provided, controlled by foot pedal, with an auxiliary control by vacuum servo of the Clayton Dewandre type.
The front wheel brake mechanism of the Atford & Alder system provides large logarithmic cams, mounted on special carriers which form the universal joint, and the whole of the arrangement is set well within the centre line of steering, a difficult thing to obtain in the ordinary way owing to the small width of the drums.
The brakes on the four wheels are all of the same size. The brake drums are made from solid forgings of special high carbon steel, and having an internal braking surface of 18ins. diameter and 1 tins. width. Thin fins for cooling purposes are machined on the outside. The shoes, made in ” Wilmil ” alloy, specially lined by Messrs. Ferodo, Ltd., are also identical, both for front and rear, and are operated by the same logarithmic type of cam as described above. The rotation plates for the front are formed by extension lugs made integral with the stub axle, and the rear reaction plates which are made also in steel are bolted to suitable flanges solid with the steel arms of the rear axle casing.
Radiator.—A special Serk honeycomb radiator has been designed, and the system has a specially large water capacity. The radiator is situated in the front of the car.
There is a gap between the radiator and the front of the actual body, the casing of the radiator being streamlined with that of the rest of the body.
This arrangement was decided on after considerable experiment, as providing the minimum of wind resistance, and also relieving the pressure inside the body, which is bound to occur with a normal radiator arrangement.
In instruments are installed throughout, including a rev, counter mounted on the front of the body, offset to the same extent as the driver, which can be used as a sight when driving.