Sobering Races for Silver Arrows

The saga of the Mercedes-Benz legends continues

The W25K’s failure led to Rudy Uhlenhaut’s arrival, abandoned races, and a major overhaul of racing-car design at Untertürkheim. When they arrived at the fast, hot Tripoli circuit in May 1936 the Mercedes-Benz drivers finally had a chance to extend fully their new and gorgeous W25K with its upgraded ME25 engine.

Comparing it with the same engine in the 1935 chassis and body, albeit with slightly different gear ratios, both had the same 175-mph maximum speed.

At Barcelona for the June 7 Gran Premio de Penya Rhin, Caracciola’s W25K was decanted from its truck. He finished second, 3.4 seconds behind Nuvolari’s Alfa.

Rudi Caracciola complained of understeer, which was reduced by replacing the locked differential with a ZF limited-slip unit. The drivers were not yet fully satisfied with the roadholding and steering, which still mustered a strong steering-wheel kick-back.

Technically the Tripoli race was as inconclusive as Monaco. One of the longer 255 mm blowers failed in practice so all the cars were switched to the 240 mm unit for the race. One car, that of new man Louis Chiron—a close friend of Caracciola—suffered minor troubles that retired it.

The Mercedes-Benz team set up shop at the Nürburgring for the 142-mile Eifelrennen on June 14. Chiron’s car in the foreground was one of four new W25K models.

Manfred von Brauchitsch stopped on the circuit when his tank failed to feed all its fuel, a problem noted in the Monza trials but not rectified. And both Luigi Fagioli and Caracciola lost their front brakes after a pipe failure caused by the new mounting of the front-circuit master cylinder on the right-rear engine bearer.

The drivers found their cars very sensitive to the windy conditions at Tripoli on race day. Observing out on the course, chief mechanic Jakob Krauss thought they looked less steady on the turns than the Auto Unions. “Perhaps,” mused team manager Alfred Neubauer afterward, “the longer chassis is better for fast courses.”

Two W25K Mercedes took part in the Eifelrennen, this one pictured in the ’Ring paddock. At its wheel was Hermann Lang, mechanic cutting his teeth as driver.

A victory was achieved in another race in North Africa, at Tunis, when the leading Auto Unions crashed and burned. Moving to Spain, at Barcelona Tazio Nuvolari’s Alfa beat the new cars in a straight fight. Here the sharp pitching tendency of the shorter chassis was especially bothersome. Pitching was also a problem at the subsequent Eifelrennen on the Nürburgring, which saw all but two of the cars retiring and those finishing well back. Engine trouble struck there and in the subsequent race at Budapest, where all the Mercedes-Benzes failed.

Pushed hard at last, the new engine showed a critical frailty. Cylinders in the forward block were too weak to handle the high specific output and had begun to fail. First the existing parts were strengthened, then completely new cylinders and blocks were made for the all-important German Grand Prix in late July. Before that race several of the engines were switched from 240 mm to 255 mm superchargers, two of which subsequently broke. Louis Chiron crashed and one car limped home sixth.

During practice for the 1936 Eifelrennen all four new W25K models were in the pits. Of the two entered in the race only Chiron’s survived and that in a lowly sixth place.

After such a run of disasters any sporting team determined to be victorious would call a rapid halt and make some changes. So too it was with Daimler-Benz. The organization that had served it so well since automobile racing began was apparently no longer equal to the pace and intensity of Grand Prix racing in the 1930s.

The liaison between Alfred Neubauer’s sports department and the engineers in the central design office had always been direct. This changed with the creation of a new technical body that was specifically concerned with the racing cars. An offshoot of the experimental department, it was called the Rennabteilung, the racing department.

The 155-mile Hungarian G.P. took place on June 21, with three W25Ks. In his von Brauchitsch had a tender touch from Tazio [not clear what this sentence is saying. In his car von Brauchitsch…?] that caused a spin and bent steering arm.

Placed in charge of it was a handsome young man who had been with the company only five years. Born of a German father and British mother, he had joined Daimler-Benz directly from engineering school as a carburetion specialist in the experimental department. The young man, whose arrival on the scene can only be described as marking a turning point in the racing history of Daimler-Benz, was Rudolf Uhlenhaut.

Uhlenhaut’s new group was made fully responsible for designing, assembling, preparing, and testing the cars, then turning them over to Neubauer’s sporting department for racing. Reporting directly to Fritz Nallinger, who headed the main experimental department, he was assigned the services of Jakob Krauss in charge of car construction and Georg Scheerer as head of testing and inspection.

On the Budapest circuit von Brauchitsch recovered but retired with steering-arm breakage. The other two W25K starters retired with engine trouble. Not a good day.

“Naturally we had a good design office,” Uhlenhaut said, “but the people there were cautious and our opinions often differed. However, if I wanted something I said so and they would generally let me have it.” He and his colleagues said what they wanted in their recommendations and requirements, expressed from mid-1936 onward in a blizzard of reports, memos, and analyses generated by the new Rennabteilung.

It was too late to do much about the W25K, which Uhlenhaut tested extensively at the Nürburgring. Race entries at Montenero and Pescara were abandoned to try to get the cars ready for the Swiss G.P. at Bern on August 23. There Fagioli broke a connecting rod, Caracciola broke the right side of his rear-axle tube, and von Brauchitsch had cooling failure initiated by a piece of newspaper caught in the front of the grille. Newcomer Hermann Lang eked out a finish in fourth place.

The Forsthaus Sankt Hubertus at Nürburg was home for the Mercedes-Benz team. Five of the new low model were prepared there for the German G.P. on July 26, 1936.

Caracciola had taken and held the lead at Bern—until Rosemeyer motored past him. “The drivers declared themselves as by and large satisfied with the roadholding, with empty as well as with full tanks,” Uhlenhaut reported. “In this race it was clearly evident that the power of the Auto Union in the middle and upper speed ranges is far superior. To be able to hold the pace to some extent our drivers must constantly strain the engine to the limit and moreover attempt to gain back in the turns what they lose on the straights.

“A further participation in racing with the E motor seems to be useless,” Uhlenhaut concluded. Auto Union had more power and torque with its bigger V-16. Daimler-Benz management agreed with him. Entries for the Italian Grand Prix, the European season’s final event, were withdrawn. It was a heavy decision for the proud company. But the light shined on the technology of racing by Uhlenhaut’s new Rennabteilung would bring brilliant results in coming years.