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VINTAGE: ‘Silver Arrows’ Ruled Grand Prix
Mercedes-Benz supercharged-V-12 race cars led the pack in 1938-39.
Wouter Melissen  | http://www.ultimatecarpage.com  |  Posted March 14, 2009   Charlotte, NC
The sleek lines of the Silver Bullets are still admired as an iconic example of race-car design. (Photo: UltimateCarPage.com)
Shortly after the first Grand Prix races were held, organizers created rules and regulations to create a somewhat level playing field and keep things relatively safe. In that light, the rules that were set up for Grand Prix racing from 1934 to 1936 made little sense.

The main element was a maximum weight of 750 kilograms (1,650 pounds), leaving the rest to the imaginations of the hugely talented designers. Not surprisingly, this lead to hugely powerful engines bolted on flimsy frames; very unsafe by any measure. To add insult to injury, the manufacturers could not agree on new regulations for 1937 so the madness continued for another season.

Mercedes-Benz dominated that year with the W125, which featured a 592 bhp engine and little to no crash protection for the driver. Some sanity finally returned in 1938 when a minimum weight linked to a maximum displacement (3-liter supercharged or 4.5-liter naturally aspirated) was agreed upon.

Fifteen W154s are believed to have been built by Mercedes-Benz, scoring 11 wins in 16 outings. (Photo: UltimateCarPage.com)
A quick calculation in the Mercedes-Benz design office revealed that a supercharged engine would be most competitive. In many ways, the new-for-1938 W154 was a development of the W125, which was originally created with the new regulations in mind. The unusually stiff nickel-chrome molybdenum tubular ladder frame was essentially carried over. The biggest difference was the shorter wheelbase of the new car made possible by the use of a smaller engine.

What also remained was the ground-breaking DeDion rear suspension. It combined the benefits of independent suspension without the dangerous side effects of the swing axles used by most competitors. Up front, the W154 was suspended by double wishbones, with longitudinal torsion bars. Although the maximum weight was discarded, reducing weight was still a top priority, so most chassis parts were drilled for lightness.

Carefully considering their options, the engineers at Mercedes-Benz eventually went with a brand new 3-liter V-12 engine. Each bank of the M154 engine was constructed from two blocks of three cylinders, with highly advanced heads featuring four valves per cylinder. At the nose of the engine, two Roots-type superchargers were fitted. Although a fuel-injection system was created, the engines were fitted with tried-and-trusted carburetors.

Reliability issues forced the team to fit “mild” cams on the first outings. In this tune, the M154 engine yielded a commendable 425 bhp and towards the end of the year an impressive 475 bhp was available. The engine was mounted off-set in the chassis so the prop-shaft could run alongside the driver. The whole package was tightly wrapped in an aluminum skin that was strongly reminiscent of the W125 body.

The Mercedes-Benz works team was to compete in just nine races in 1938, but they built no fewer than 14 new chassis and 19 engines. The W154 was raced by Rudolf Caracciola, Manfred von Brauchitsch and Hermann Lang. Halfway through the season, the three Germans were joined by British talent Richard Seaman.

There was a minor setback when a naturally aspirated Delahaye beat the new “Silver Arrows” at the season opening Grand Prix at Pau. After that it was business as usual with the W154 taking six victories in the following eight races. All four drivers shared in the honors and they ended the season in the top four positions on the table of the European Championship. Caracciola scored the most points of all and was crowned champion. The only blemish on the season was the cancellation of a trip to the Indy 500 due to technical problems; the 500 mile race was very early in the season.

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Wouter Melissen

UltimateCarPage.com

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