THE CONAN-DOYLES’ 12-CYLINDER 11-LITRE DELAGE 2
A MODIFIED 1925 GRAND PRIX CAR FOR 1937 EVENTS. L.M.B. FRONT INDEPENDENT SUSPENSION.
Richard Seaman’s remarkable successes with the ten-year-old 1j-litre Delage last season seem to have focused attention on. the revival of vintage racing-cars for the more serious races. At all events, ” Bira ” has had independent front suspension and other modifications applied to another of the 1925 straight-eight if-litre Delage cars, and Powys-Lybbe has rebuilt one of the 11-litre Talbots of the same period. There is no doubt that M. Lory, designer to M. Delage, produced the most outstanding of all racing-cars constructed under the limited capacity racing rules, and consequently great interest attaches to the twelve-cylinder 1925 Delage which Adrian and Denis Conan Doyle are modifying for this season’s events. Delage introduced the V12 on his return to racing in 1923, when 100 b.h.p. was developed at about 5,000
r.p.m. after hasty preparation. Rene Thomas drove it in the French Grand Prix, but retired with a punctured fuel tank. Delage then conducted comparative tests with this engine, a four-cylinder unit, and a blown eight-cylinder twostroke and as a result raced a team of three unblown V12 2-litre •cars in 1924. The b.h.p. was now about 130, and four-speed gearboxes were used. In the French Grand Prix at Lyons Divo was second behind the blown Alfa-Romeo, Benoist third and Thomas sixth. Five speeds were used in the San Sebastian G.P. in which More was third and Divo fourth, Benoist, who had led, and Thomas, both retiring.
For the 1925 season, five new 2-litre cars were built, now supercharged and developing about 200 b.h.p., while blowers were added to the four cars used the previous year. Divo drove one of the 1925 cars at Spa, retiring with misfiring, but in the French Grand Prix Benoist and Wagner finished first and second, and in the Spanish Grand Prix Divo, Benoist and Thomas were first, second, and third, Torchy striking a tree with the fourth car and sustaining fatal injuries. At the Targa Florio in 1926 Count Masetti overturned and was killed, and the other Delages were withdrawn in consequence. The 1926 G.P. ruling, of course, specified 1-litre cars, for which Delage built the famous straight-eight jobs that won him the championship of
Europe in 1927. Afterwards W. B. Scott acquired both a eight-cylinder and Divo’s 2-litre V12 and brought them to Brooklands. The 9-litre car was never seriously exploited in this country, but we understand that when tried against the LI-litre on one of its infrequent
jaunts on the concrete it proved to be the faster car by some eight m.p.h. The Conan Doyles acquired the V12 job, together with Masses of spares, some few years ago and last winter took the chassis to the Croydon works of Messrs. L.M.B. Motor Products, Ltd., for the incorporation of independent front suspension to the design of L. M. Ballamy.. The car has subsequently been reassembled at the L.M.B. works under the care of Jim Welsh, the Conan Doyles’ engineer. Before installation in the chassis the engine was bench tested at Heston. In spite of its age the Delage is of remarkably advanced design. The twelve cylinders are set in a V of two blocks of six. The blocks are of steel with integral heads, the crankcase, sump and unit
gearbox being of aluminium alloy. The crankshaft runs in nine bearings, of split roller type with alloy housings. The connecting rods are of H-section with roller bearing big-ends and the extremely tiny pistons are of aluminium alloy with domed crowns. The cylinder capacity has been brought down to put the car in the I Flitre class, the bore being 44.5 mut. and the stroke 80 m.m., giving a swept volume of 1,494 c.e. fiach cylinder has two tulip valves set at 90° in hemispherical heads. Operation, is by twin o.h. camshafts above each block, the camshafts being driven by no fewer than twenty-seven timing pinions in the form of a train from the forward end of the crankshaft. These pinions are quite small and display extremely fine craftsmanship. Each camshaft runs in seven split roller bearings with alloy housings, and. the cams operate via short side-pivoted rockers. There are three springs per valve, and each of the four narrow cam-cases is held down by twenty-two studs. There is a single sparking-plug in the centre of each head fed by two Bosch six-cylinder magnetos set side by side at the front of the engine and driven by the timing gears. Below the magnetos are located the twin Roots-type superchargers which sit side by side, have ribbed casings and are also driven from the timing train. They ‘draw from Zenith carburetters and feed directly into long unribbed steel induction pipes that run along beneath the outside of each cylinder-block, feeding into the six ports therein. Blow-off valves are fitted at the forward ends. Having originally to feed only a litre of engine each these superchargers are quite small. They blow at 12 to 15 lb. per sq. in. To compensate for the reduction in engine capacity the compression ratio has been increased to 7 to 1. The exhaust system
is quite imposing, the twelve off-take pipes rising vertically from the insides of the blocks, almost in a line, and dropping over to emerge horizontally on the near side. The bonnet is Specially cut away to receive them and there is a guidepiece to obviate binning of the rear bonnet-strap where it passes over them: Owing to the low set and compact engine this remarkable exhaust system does not entail an abnormally high bonnet ; indeed externally the car appears as low as the straight-eight jobs. Lubrication is of the full dry-sump type, with a threeunit gear-pattern oil pump set towards the forward end of the engine on the off side, driven from the timing train. One pump feeds the main-bearings, one supplies the valve-gear and auxiliaries and the third scavenges the sump. The large, square-shape oil tank is located beside the driver in the cockpit. It holds about eight gallons of lubricant and has a quick-action fillei cap. From the mainbearings lubricant is flung into channels cut in the crankshaft, from whence it reaches the roller big-ends under the influence of centrifugal force. The system operates at quite a modest pressure, now arranged to vary in union with engine-speed. There are two water pumps, one for each block, driven from
the timing gears. The water outlets, one per block, rise from towards the forward end of the heads to the neat honeycomb radiator, that on the near side being set further forward than its fellow to clear the exhaust system. The waterjackets are separate copper casings round the cylinders.
The rear fuel tank holds approximately thirty gallons and is accommodated in the streamlined tail, the filler cap being reached through a flap. Initial pressure is obtained by hand-pump and maintained by an automatic pump driven from the near-side camshaft. The rev. counter drive is taken from the rear of the offside camshaft. The forward engine mounting is in the form of a single bearer of circular section accommodated in a central sleeve member, thus allowing the engine a pivoting motion to combat frame whip. The rear mountings are conventional, side-placed trunnion members. The safe rev, limit is approximately 7,000 r.p.m.
The gearbox gives five forward speeds, the overdrive top not normally being engaged during a road race, so that fourth gear is the virtual top. The ratios will be varied to suit different circuits and as an outcome of experimentation, but at present the fourth ratio is 5.08 to 1. Control is by means of a short, central lever working in a bull-gate. The clutch is of multi-plate type and final drive is via an open propeller-shaft to a spiral-bevel rear axle. The frame has channel section side and cross-members. The rear suspension is by half-elliptic underslung springs. At the front the new L.M.B. independent layout is of great interest and displays considerable ingenuity. Each stub-axle assembly is carried on drilled, girder members which are attached to separate tubular half-axles. These halfaxles curve forward at their innermost ends, where they pivot on long silent bloc bushes set side by side, and held to the front cross-member by bolts miming parallel with the frame side-members. Thus each half-axle can rise and fall independently of its fellow, and at the same time brake-torque is taken by the silent bloc pivots. The steering tie-rod is pivoted in sympathy. A single transverse spring with five main leaves tied by clips is bolted to a cross-member before the radiator and engages with the girder axle-ends. Friction shock-absorbers
are set transversely behind each halfaxle. The braking system originally incorporated a mechanical servo-motor driven from the gearbox, but Ballamy has redesigned the layout and eliminated the servo. The pedal operates all four brakes and the central, typically Delage handlever the rear shoes only. Actuation is by cable, with link and chain compensators. The front brakes have Perrot pattern cam-rods supported by small brackets bolted to the chassis immediately behind the front spring, with wing-nut master adjustments where the cables engage the levers. The drums are ribbed and have cooling appertures around their faces,
gauze protected. The rear shoe cams are behind the axle. Four friction shockabsorbers damp the rear axle, set in pairs each side, one ahead and one behind the axle. They are attached by beautifully machined tubular brackets and the finish of the Whole axle assembly in particular inclines one in the belief that rumours that the car cost some C10,000 to build are by no means incorrect. The radiator is protected and streamlined with a neat cowl, carrying the blue badges of Delage and I,.M M. B. The driver sits to the off side of the cockpit, which is partially faired with a metal cover. The steering is of worm and nut type with the
steering-box bolted to the side-member of the frame. With fuel and tyres the Delage turns the scales at 1,948 lb. It is strikingly finished in dull gilt, with wheels to match. It is run on Shell racing fuel, Shell oil, and Bosch plugs, while, of course, Dunlop tyres are used and naturally the brakes are lined with Ferodo. A Ford truck is used for transport and Adrian Conan Doyle retains his big Mercales-Benz as a personal touring car. The Delage was not ready in time for the Coronation Trophy Race at the Crystal Palace, and was due to make its initial appearance at Avus on May 30th, but unfortunately owing to illness could
not go to Germany, and it is intended to give the Delage its first outing at Picardie. We understand that rumours to the effect that the engine internals of the V12 are unreliable are quite unfounded and that they probably arose as a result of troubles which occurred in the past solely on account of casual preparation. The Picardie race will be regarded merely as an experimental venture, and, right up to the time of sailing, tests will be conducted at Brooklands to ascertain the correct jet and choke combinations, correct gear-ratios, and to overcome initial bothers, including some trouble with the
superchargers. These tests have been generally satisfactory and we look forward to seeing this remarkably interesting car in effective action very soon. Certainly it makes one wonder how far racing-car design and technique have progressed since the abandonment of the limited capacity ruling. Some idea of the potency of the Delage can be gathered from Divo’s records established at Arpajon on September 11th, 1925. when the engine measured 51.15 x $0.6 tn.m. (1,989 c.c.). The flying kilo. was taken at 134.07 m.p.h., the flying mile at nearly 134 m.p.h., the standing kilo at 79,39 m.p.h. and the standing mile at 93.68 m.p.h.