The DFP 12/40hp Speed Model has a highly significant place in motoring history as a car built to W.O. Bentley’s specification exclusively by DFP and incorporating aluminium pistons, a significant advance in automobile engineering technology which influenced in no small way future aeronautical engineering. The 12/40hp Speed Model was the stepping stone from W.O. Bentley’s involvement as a motor dealer to a manufacturer in his own right with the launch of the 3-litre Bentley in 1919.
In 1912 W.O. Bentley and his brother H.M., with their newly formed company Bentley & Bentley Ltd., had acquired the British and Commonwealth Agency for the French-built Doriot, Flandrin et Parant motor cars. The French cars were imported as rolling chassis and sent out to London coachbuilders for bespoke coachwork. W.O. successfully campaigned the 12/15hp model in competition however worked closely with his French mechanic Leroux to develop still more power from this engine. The result was the 12/40hp Speed Model, built exclusively by DFP for Bentley & Bentley. With this model they captured 12 of the Class B Speed Records at Brooklands in 1913 and 1914, achievements then described by W.O. “as representing the very highest point that motor car efficiency had ever reached”. W.O. raced the 12/40hp Speed Model in the Isle of Man Tourist Trophy Race in 1914, averaging 48mph and coming 6th out of 22 starters, all of which were of considerably greater horsepower. The Motor wrote, “The DFP covered itself in glory – hard, unmistakable glory of solid, sound running of a remarkably high order”.
As well as the aluminium pistons the monobloc 2-litre engine of the Speed Model featured twin spark ignition and for the 1914 season a highly efficient gilled tube V-radiator was featured. Drive was by a leather-faced cone clutch and through a four-speed and reverse gearbox.
Archives shows W.O. Bentley driving the TT car, bearing the registration number LL 2687. It is believed that this photograph was taken in practice for the TT as competitors were required to forego their national registrations for the race itself. W.O. continued to field a 12/40hp Speed Model during the summer of 1915, although the onset of war curtailed motor sport at that stage. Bentley’s introduction of aluminium pistons to the War Department resulted in recruitment to the Royal Naval Air Service where he designed his own version of the Clerget rotary engine in which he was able to resolve the reliability problems that had plagued the original French design. This work was a stepping stone between the development of the 12/40hp Speed Model DFP and the laying down of the first designs for the 3-litre Bentley of 1919.
This 12/40hp Speed Model was bought in 1986 from France, at that stage as a rolling chassis, although completely dismantled. Soon identified as the ultra-rare Speed Model, further research established that the Frenchman from whom the car was purchased had acquired the car from England, at that time bearing the registration number LL 2687, the registration number allocated to W.O.’s own car. No bodywork remained however the assemblage of the rolling chassis included chassis, engine, gearbox, torque tubes, both axles, springs, exhaust system, V-radiator, running gear, braking and gear change controls. These parts fully deserved restoration and, as many photographs survived of the streamlined and polished aluminium 1914 Isle of Man TT car, it was resolved to construct coachwork as closely as possible to that design. The sporting coachwork was constructed using traditional ash and aluminium methods by Martin Hull and the seats were fabricated and upholstered in antique claret buttoned hide. For reasons of safety and roadworthiness the badly rusted steel chassis was remanufactured in the same gauge and to the pattern of the original, likewise the steel saddle fuel tank. Every effort has been made to restore the authenticity of the car as closely as possible to that campaigned by W.O. Bentley, the electric starter motor representing the only minor indulgent concession.
LL 2687, although not conclusively proven to have been the car driven by W.O., is a unique and historic machine covering a significant period of W.O. Bentley’s life, which eventually led to the establishment of Bentley Motors Ltd and the 3-litre Bentley. It is registered as a historic vehicle and comes with a Vintage Sports-Car Club eligibility document, allowing it to compete in Edwardian events. It is offered with a Swansea registration document, current road fund licence and MoT certificate as well as a wealth of documentation regarding DFP, Bentley & Bentley and a copy of the definitive work ‘W.O. Bentley and the DFP’.