Mercedes had pulled out of grand prix motor racing in the late 1920’s due to the depression and the financial complexities of the time. Rudi Caracciola soldiered on with his own SSKL and the combination won every race they entered in 1931.
Mindful of the costs of motor racing the AIACR (motor sports international governing body) set new regulations to come into effect from 1934. This would be the famous 750kg Formula devised to slow the cars down and make racing safer and cheaper. A maximum dry-weight (that’s minus fluids and tyres) of just 750 kg was imposed. The idea was to reduce the engine sizes but the manufacturers simply lightened everything else to keep their big powerful engines in place. Safety, it seems, was of minor concern to the designers, or the drivers!
Mercedes M25 engine, (a Roots-type supercharged, twin-cam, 4 valves per cyl, 8 cyl engine) was traditional Daimler-Benz design thinking. The engine being built from two groups of 4 separately forged steel cylinders to which sheet-steel water jackets and valve-ports were welded. It had an Initial power output of 302bhp at 5,800rpm. Using a “Standard Oil” provided fuel mixture, of gasoline/benzol with methyl alcohol, horsepower increased to 354 bhp. The M25 engine alone weighed just over 200 kg so weight saving over the rest of the car was now paramount. The box-section longitudinal chassis beams were reinforced by cross-members and a cross-tube at the front. Then it was all drilled for lightness.
All-round independent suspension was by means of very short double wishbones at the front and swing-axles at the rear. Bell-cranks fitted inside the cross-tube operated the front coil springs while transversely mounted quarter-elliptic leaf springs were used at the rear. Friction dampers controlled the suspension front and rear. All the smaller parts were drilled for lightness and in the same spirit the four-speed gearbox was combined with the final drive. This rolling-chassis was covered in a thin alloy skin aimed at giving a very aerodynamic appearance to the car.
When in comes to racing, legends surround Mercedes. That Gordon Bennett Trophy win in 1903 using borrowed cars, the epic 1914 French grand prix victory, and the name “Silver Arrows”. Said to have arisen, by both Alfred Neubauer and Manfred von Brauchitsch, when the cars weighed in at 751 kg and were rejected by the scrutineers of the 1934 Eifelrennen. The team then spent the night scraping all the white paint from the bodywork and presented shining silver aluminium cars at scrutineering the next morning. Duly passed legal von Brauchitsch went out and won the race. In fact the race was run to Formula Libra regulations so the weight issue was fictitious, and the Auto Unions were already painted Silver.
1/43rd scale model.
Restored by Ian.
Ian found this model in a very poor condition but fell in love with it as soon as he saw it. A "well loved" Dinky toy it was in need of restoration. Ian stripped off all the original paint, primed it with Halfords paints and Mercedes Silver metallic paint. All the details were painted with Humbrol enamels and Citadel acrylic paints. The wheels were replaced with some spares from an old Airfix E type kit and the screen and mirror were scratchbuilt..
A very simple model but quite effective really.
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