A Most Beautiful Brute
The 1938 Mercedes-Benz W154 Grand Prix racecar combined gorgeous looks with massive power that brought great victories
Article Karl Ludvigsen
Images Daimler Archives – Ludvigsen Partners
The 1938 season was the first year of a completely new Grand Prix formula; Mercedes-Benz won five of the sport’s seven major races. In these years, recalled Mercedes racing chief Alfred Neubauer, the Silberpfeil (Silver Arrow) nickname gained wider use because the new cars were lower and sleeker than ever, flashing by with a piercing howl in silvery glory.
Mercedes-Benz was decisively on top in the internecine German battle with Auto Union. Of the available 21 podium positions in 1938, its cars occupied 13. To be sure, the stuffing was knocked out of Auto Union by the tragic loss of Bernd Rosemeyer. The inimitable Bernd was killed attempting to break a speed record on the Frankfurt-Darmstadt Autobahn in October 1937 – a grievous loss to German motor sports.
Band of brothers
Mercedes on the other hand had the benefit of a talented new driver, Englishman John Richard Beattie Seaman, who took risks behind the wheel that had friends fearing for his life. Joining the team in 1937, Seaman won 1938’s German Grand Prix. Fellow driver Hermann Lang later wrote of tall, patrician Seaman, “I will always remember him: he was kind-hearted, cool and fair as a sportsman, just as I had pictured Englishmen to be.”
Seaman came back from the early-1938 tests at Monza saying that the new car was “the goods,” writing that “it is as low as the Delage and sounds like half-a-dozen ERAs. The roadholding appears to be even better than last year’s cars and is extremely soft, yet without causing a roll.” Seaman’s evaluation was of special worth because he and Hermann Lang were regarded by Rudolf Uhlenhaut, head of the Rennabteilung or Racing Department, as the only two drivers of the time whose technical opinions he didn’t have to double-check by trying the car himself.
Racing director Alfred Neubauer was still able to field the incomparable pilot Rudy Caracciola. Caracciola was a particular pet of Neubauer, not without good reason. “In his glory years,” said engineer Karl Kling, who followed the Mercedes team pre-war, “he was almost unbeatable. He was often the best, there’s no doubt.” To accommodate his game right leg, Caracciola’s cars had brake pedals with higher leverage. Neubauer also continued to employ the inveterate power-slider, Manfred von Brauchitsch of the red cloth helmet, nephew of the famous Wehrmacht Field Marshal of the same name.
The 1937 racing season saw the rise of a former Mercedes racing-team mechanic, Hermann Lang, to a fully-fledged position on the team. His upper-class team-mates, uncomfortable with the speed of a humble mechanic, pressed their case as high as Daimler-Benz chief Wilhelm Kissel that Neubauer should hold Lang back in the races. “In practice and the like, Lang was always faster than the others,” recalled Karl Kling, who raced the cars after the war. “And he didn’t always have the best material. With three cars there are always differences, in power, in everything!”
Noticing Hermann Lang’s obvious potential, not fully exploited at first by Daimler-Benz, Auto Union approached him secretly. Lang was of course devotedly loyal but no such constraints applied to his attractive brunette wife Lydia. She spoke with Max Sailer, the veteran of races before and after the Great War who oversaw Stuttgart’s Silver Arrows as engineering director. “If Hermann isn’t allowed to drive as he can,” she told the bespectacled engineer, “he’ll be going to Auto Union.” With the latter team’s Rosemeyer causing lots of problems for Mercedes, especially in 1936, Lang’s fetters were removed.
Hermännle or “Little Hermann” as he was known to the team, was the sensation of 1937, opening his account with a clear defeat of Rosemeyer at Tripoli in Libya and following with a win at the Avus at a record average over 96 miles of 162.62 mph. In 1938 Lang won again at Tripoli and at Livorno in the Coppa Ciano. Also winning for Mercedes were von Brauchitsch in the French G.P. at Reims and Rudi Caracciola in the Coppa Acerbo at Pescara and the Swiss Grand Prix at Bern.
A new engine
Lang’s detailed technical feedback was much in demand because the German cars of 1938-39 were the most exotic yet seen. The Formula to which they were constructed was the first to draw a distinction between supercharged and unsupercharged engines with the aim of allowing the latter a chance. The new rules enforced a 4.5-liter unblown limit but lowered the bar on blown engines to 3.0 liters, both with an 850-kilogram minimum weight.
This meant completely new engines for 1938, first making the choice between blown and unblown engines. The final choice for Mercedes-Benz was a supercharged 3.0-liter V-12 with two separate Roots blowers to improve efficiency. The Albert Heess design office created a 60-degree twelve with four valves per steel cylinder in a classic Daimler-Benz layout. Though originally planned with direct fuel injection it ultimately used carburetors instead.
Whenever possible, new engines were broken in on the dynamometer for four to five hours before power runs were made. And the output figures that were obtained were kept entirely secret, so much so that mechanics in the test cells couldn’t even tell their friends in the racing department how well the engines were doing. Although the best 1938 power was 474 bhp at 8,000 rpm, more typical during the season was 440 bhp at the same speed.
Chassis development
As schemed by Rudy Uhlenhaut, the new car carried over the essentials of its successful 1937 chassis. Welding a half-sleeve to the top of the tubular frame increased its torsional stiffness by 30 percent. An important innovation lowered the driver and reduced frontal area: Instead of passing the drive shaft below the driver as before, the W154 – as the new car was designated – angled its engine and propeller shaft from the right front to the left rear so the driver could sit alongside the shaft instead of on top of it. The drive shaft now connected to the left end of the transverse rear gearbox instead of at its center as previously.
Having made the decision to seat the driver alongside the propeller shaft, Daimler-Benz built a racing car that was strikingly, dramatically and beautifully low. Cowl height was a scant 34.25 inches above the ground. Main body lines, not including the headrest, were lower than the tops of the tires – something not achieved by the models that preceded and succeeded the 1938 W154. This slinky profile, accompanied by a low center of gravity, ideally complemented the trend toward softer springing that had begun with the arrival of Uhlenhaut as head of racing-car design in mid-1936.
On a wheelbase of 107.4 inches the designers at the Mercedes-Benz coachworks at Sindelfingen wrapped the new chassis in the slickest and most stylish aluminum bodywork yet seen in Grand Prix racing. Radius arms to the de Dion rear suspension were given bespoke slots just below the cockpit sides. Small when it was first constructed, the radiator air inlet was enlarged to improve cooling after tests at Monza.
In far-away Detroit, Michigan designers of the cars of General Motors often looked to racing for inspiration. They were struck by the novel shape of the W154’s radiator opening. At a time when grilles were transitioning from vertical to horizontal, it showed a way forward. The Mercedes look had a strong and clear influence on the frontal appearance of the Buicks of 1939–1942.
The angled drive line required an offset aperture in the grille for the starter shaft. For aesthetic reasons a mirror-image aperture was added. Fuel tanks were located in both the tail and the cowl, an innovation for 1938 designed to deliver more consistent weight distribution as fuel was consumed. The system was arranged to ensure that the cowl’s saddle tank was filled before topping up the rear tank was completed.
Originally Max Wagner's design group had suggested tanks amidships, alongside the frame, in an early layout for a fully enclosed low-drag car for fast tracks like Reims and Tripoli. The initial manufacturing order of 31 August 1937 called for the first car to have a rear tank and the second one side tanks – both with open-wheeled bodies. Cars number 3 through 9 were to have been open-wheeled and those numbering 10 through 15 were planned as fully enclosed.
Auto Union adopted side-mounted tanks in 1938 but the Daimler-Benz Rennabteilung was against them on the grounds that they blocked the driver's view, posed a safety hazard in crashes and looked unsightly. Thus they were not adopted. Nor were full-bodied versions of the W154 fielded. Streamlined individual wheel covers were built and tested for possible use at Tripoli but not committed to action.
A thirsty warrior
“Stepping up the power,” said Uhlenhaut, “meant that we had to cool the pistons with fuel, which is why the consumption was high. It was hard to get it all into the car.” Fuel mileage in competition was rarely better than 2.0 miles per U.S. gallon. The normal range was between 1.6 and 1.9 mpg with Caracciola almost invariably getting the best mileage.
Tank capacities varied from car to car but a typical value was 39 gallons for the saddle tank and 64 gallons for the rear tank, for a total of 103 gallons. During the season, different proportions of fuel in the two tanks were tested in private and in races. For the first time, on the 1938 cars, small round windows were let into the sides of the main tank so the mechanic filling the car from the pressurized supply could see how rapidly the level was approaching the top.
A question of weight
Aside from fuel tanks, the main preoccupation of those developing the chassis of the W154 was weight. It had much too much of it. At the Reims weigh-in required by the new Formula's minimum poundage provision of 1,870 pounds, with gearbox oil but otherwise dry, the W154 was equal-heaviest with the unblown Talbot at 2,150 pounds. Freed at last from the constraints of the previous Formula that required cars to weigh no more than 750 kilograms, 1,654 pounds, without tires and fluids, the designers had not kept a strict constraint on weights.
Checking weights under comparable conditions, the first W154 was found to be 262 pounds heavier than the W125 of 1937. Where had it all come from? Scaling 559 pounds, the engine was the largest single offender. The steel-cylinder construction that had been carried over from the previous straight eights to the new twelve showed its hand in this smaller engine, which was 73 pounds heavier than its in-line predecessor, whose swept volume was 87 percent greater.
During May an intensive lightening program was undertaken. It brought under scrutiny every part, nut and washer in the entire car. As they were developed, the fuel tanks were made to serve as the outer body skin. Exhaust pipes were removed from the grooves they had occupied in the belly pan in the first races at Pau and Tripoli, to allow the body to be simplified. They were first seen exposed at Reims. The hood and central-body belly pan were made experimentally of 1mm AM503 magnesium alloy sheet.
Adoption of a magnesium case dropped the gearbox weight from 197 to 182 pounds. Going through the transmission piece by piece and shaving metal off some 50 components reduced the weight a further five pounds – an index of the thoroughness of this effort.
The 1938 campaign to “add lightness” barely managed to keep pace with the need to install more equipment in the car, such as larger rear brakes and the supplementary oil tank. Checked before the last event of the season, one of the cars weighed at 2,160 pounds dry – almost 300 pounds above the minimum. With oil and coolant it weighed 2,252 pounds and with the driver 2,452 pounds. Laden with 99 gallons of Standard Oil fuel it grossed 3,140 pounds on the starting line.
A winning season
Overall the 1938 Grand Prix season had turned out to be a fine one for the Daimler-Benz racing team, bringing another European championship for Rudi Caracciola. But Auto Union had clawed its way back to competitiveness with the Stuttgart squad late in the year, with none other than the great Italian master Tazio Nuvolari standing in for the lost and lamented Rosemeyer.
Only those within the Daimler-Benz organization knew how much engineering creativity and resourcefulness had been needed to try to bring the 1938 W154 machine up to a consistent raceworthy standard. They also knew they had not yet reached that standard. They were reminded of this by Nuvolari himself in his remarks that followed the celebratory dinner after his Donington victory in an Auto Union. With a big smile Nuvolari said of Mercedes, “Perhaps if they build a better car, they will do better in future.” Neubauer led the applause.
At the Tripoli Grand Prix, May 15, 1938, W154s finished in 1-2-3 order headed by Hermann Lang (number 46), followed by Manfred von Brauchitsch (number 44) and Rudolf Caracciola (number 26).
German Grand Prix, Nürburgring, July 24, 1938 (from left), Manfred von Brauchitsch, winner Richard Seaman, Hermann Lang and Rudolf Caracciola.
Details from a September 1937 engineering drawing of the M154 V-12 engine created for the new 1938 racing formula. On both sides of the crankcase fuel injection pumps were shown, expected as they were for the new season. This plan was later given up.
A series of five studio views of the finished 1938 W154 racing car. Widened after the Monza trials to provide more cooling.
The grille of the W154 had great character. This was not overlooked by the stylists at General Motors, who patterned their 1939-1942 Buicks after the Mercedes-Benz racing designs.
The engine’s seemingly odd mounting angle was the result of engineering efforts to allow the driveshaft to pass alongside the driver, instead of beneath the seat as was typical at the time.
This permitted the the driver to sit lower, reducing frontal area and moving his weight lower in the car, inproving aerodynamics and handling.
At the Tripoli Grand Prix, May 15, 1938, Manfred von Brauchitsch, left, in red helmet, with Hermann Lang.
Meanwhile, the cars were being prepared for the circuit on which they could approach their top speed of 185 mph.
In front of the imposing grandstand at Tripoli, three Mercedes shared space in the front row with the fast new Maserati of Count Trossi. However none of the red Italian rivals was able to match the pace of the cars from Untertürkheim. For the heat of Tripoli, the three W154 entries had small air scoops placed to ventilate the area of the compressors and carburetors.
Before the French Grand Prix at Reims on July 3, 1938, the W154s were fitted with registration plates and driven to and from their garage in town.
Picked to head the new racing department in mid-1936 as a link between the drawing office and Alfred Neubauer’s on-track operation, Rudolf Uhlenhaut was able to drive the racing cars almost as fast as the team drivers, as here at Monza in the 1938 pre-season.