When Mercedes Raced at Indy

Inside the factory's race at the Brickyard in 1923

by Karl Ludvigsen

Images courtesy of Ludvigsen Library and Mercedes-Benz Classic

Before Mercedes-Benz engines came to Indy with Penske in the 1990s, the three-pointed star's only previous official appearance at the hallowed Brickyard was in 1923. In that year, the white cars from Stuttgart made a powerful impression.

Both Mercedes and Benz were winners at the Indianapolis Motor Speedway - even before the first 500-mile race. In 1910, Spencer Wishart won a close race with his Mercedes 60, and Eddie Hearne dominated the Labor Day meeting with his 1908 Grand Prix Benz. In 1912, Ralph DePalma led all but the last five laps with his Mercedes, later making good his attack on the Speedway in 1915 with a superb victory driving one of the 1914 Grand Prix Mercedes cars.

None of these, however, was a factory-backed racing campaign. Private drivers, teams, and owners scored these successes, using machinery fashioned in Germany. Their activities mirrored the prominence of Mercedes cars in American society. Among imported cars, Mercedes was the most popular marque in the years before World War I. A short-lived attempt was made to build Mercedes cars in New York. But before the Great War, Daimler, unlike Benz, essayed no official race entries in the New World.

Conditions proved different after the war. Before Germany attacked its neighbors, 70 percent of Mercedes cars were exported. After the hostilities, the number fell to 20 percent. Nevertheless, with its domestic economy in an uproar, Germany desperately needed the stability that hard currencies like the dollar could provide. Thanks to the mark's depreciation, exports could be priced attractively, but winning back its prewar customers was no easy task for Daimler-Motoren-Gesellschaft (DMG). It needed a striking promotional initiative for its Mercedes cars.

DMG decided to tackle Indianapolis. The greatest race in the world's greatest car market, it was a fabulous showcase for motorcar makers. Peugeot and Delage had helped their causes with prewar victories. Looking ahead to the 1923 race, scuttlebutt was that such great marques as Bugatti and Packard would be taking part. This would be classy company for a Mercedes entry, pointed out Richard Schilling, president of the American Mercedes Company in New York.

In charge of designing a suitable racing car was Paul Daimler, son of DMG's founder. After joining the company in 1897, Daimler rose to technical chief in 1907. Although he had Grand Prix victories to his credit in 1908 and 1914, Daimler chose a technical dead-end for Mercedes with his sleeve-valve production models. Now, since 1919, he had pioneered the use of automobile supercharging. He built 1.5-liter twin-cam engines for road and racing cars fitted with Roots-type blowers.

Supercharging would be Stuttgart's speed secret for its 1923 Indianapolis campaign. Although others were pursuing the new technology, notably Fiat, in 1922 Mercedes was the first European company to race blown cars. Its technology embraced a part-time approach: The high-speed Roots-type compressor was engaged by a clutch that took hold when the driver pressed the accelerator pedal to the limit.

In the latter half of 1922, work began on an all-new car for the Indianapolis effort. Its engine would be 2.0 liters to suit new Grand Prix rules that required engines no larger than that, first imposed in 1922. The same size was also adopted by Indianapolis, a contest that was willing to accept the German entries, still barred from competing in France.

Otto Schilling was among those who prepared the new engine's design under Paul Daimler's direction. Its dimensions, 70 x 129mm for 1,989cc, figured in the engine's designation as the M7294, the last numeral recording its four cylinders. It had an integral-head steel cylinder block and quadruple valves in each cylinder. Symmetrically inclined at an included angle of 50 degrees, valves measured 34mm in diameter. A flat tappet, screwed into a bore in the valve stem to set clearance, was kept from rotating by a disc that wedged into it from below, secured in place by valve-spring pressure.

Gently domed pistons protruded well up into pent-roofed combustion chambers, made larger in diameter than the bore to provide room for the four valves and a central 18mm spark plug. Compression ratio was 7.5:1. Camshafts were driven by a vertical shaft at the back, next to the flywheel, topped by a single worm gear that turned worm wheels at the ends of the cams. Another worm-and-wheel pair drove a cross shaft to the magneto and the water pump. An extension of the bottom of the shaft drove the oil pumps.

During 1922, the M7294's planners began work on roller bearings for the bottom end as a means of extending its rev range safely to 4,500 and more. To avoid splitting the connecting rods, the crankshaft was made in five pieces, joined together at each rod journal by a massive tapered bolt and nut.

DMG took an amazing and costly precaution in the construction of the roller bearings for the connecting-rod big ends. Each of the rollers had a tiny gear machined on its end that engaged a gear all the way around the rod journal, at its side, to ensure that the rollers always rolled. At the bottom of each rod, a protruding scoop collected oil for the bearing rollers from a sheet-steel trough bolted into the finned cast-aluminum sump.

With steel rotors 130mm long, the supercharger was mounted vertically at the front of the engine, driven by bevel gears and a driver-engaged multiple-disc clutch. A special carburetor delivered pressure air to the engine. Driven from the top of one of the Roots-blower shafts was a four-bladed centrifugal fuel pump. When the compressor wasn't running, fuel flowed through the pump without obstruction. When the blower was engaged, the pump started spinning to supply fuel to the carburetor's float chamber at the increased pressure needed to deliver it to the venturi against the blower's higher air pressure.

A double-cone clutch took the drive to a 4-speed transmission. Its countershaft offset to the left, the gearbox was astonishingly compact. Less so was the rear axle, which contained two pinions and two ring gears, the latter bolted to their respective half-shafts. In the race, a 3.5:1 ratio was used. A peak engine speed of 4,400 rpm produced 119 mph with the 4.5 x 29 Dayton Racing tires fitted at the Speedway.

New chassis frames of channel-section steel were designed for the Indianapolis cars. Side members curved inward at the rear, following the tapering body in plan view, to a tubular crossmember for the rear spring shackles. Mounted firmly at four points, the engine's aluminum crankcase supplied virtually all the frame's front cross-bracing. Springing was on orthodox lines, with six-leaf semi-elliptics at all four corners. Enclosed friction dampers operated by a single arm were fitted at all four wheels, as were cable-operated drum brakes.

The front frame members and the forged I-section front axle were "streamlined" by strapped-on wood fairings in the time-honored DMG manner. Though shorter than other postwar Mercedes racers with a 107.5-inch wheelbase, the cars were larger and heavier by some 400 pounds than the 100-inch-wheelbase Indy Millers - not including the extra weight of a riding mechanic.

With a low outline and tapered tail, the two-seater racing body designed especially for the Indy Mercedes was fully up-to-date by the standards of 1922 - but not 1923. The Americans had dropped the requirement for a riding mechanic. Some of the new cars built by Harry Miller were pencil-slim. An information gap couldn't be blamed for the wider German cars, because the five Bugattis built for the 500-mile race the same year were snug single-seaters. Daimler kept the two-man configuration, because it felt that two heads were better than one in managing a racing car.

"The maximum power was satisfactory," reported DMG director Richard Lang during final tests in Germany, "about 95 bhp at the rear axle." Sorting last-minute problems with the engine's bearings wasn't made easier by an engineering interregnum at DMG in the early months of 1923. Paul Daimler resigned in the last days of 1922 to assume similar duties at Horch.

The new man in charge was Ferdinand Porsche. Although he wasn't officially installed at Untertürkheim until April 30, Porsche in fact arrived much earlier to find himself in the midst of final preparations for the most ambitious racing effort ever undertaken by Mercedes, a campaign that one of the participants said "cost our company an enormous amount of money."

Porsche participated in some of the last reviews of the optimum engine tune. Lang reported on an endurance test in which a leaner carburetor jet had been tried: "That showed that we can certainly save gasoline but that the danger of burning the piston draws closer. It will thus be necessary to run rather with a mixture too rich than too lean, to avoid too high a peak on the diagram [indicating combustion pressure]." Works director Lang, a member of the DMG management committee who had done some racing himself in 1921, was now gathering up the loose ends of the Indianapolis preparations.

Lang passed advice to team leader and driver Max Sailer: "The various exposed pipes, oil pipes, pressure pipes, etc., have broken several times. It is thus absolutely essential to brace everything." Lang said that he had, "in the presence of Dr. Porsche, expressed my feelings to sales director [Ernst] Berge and brought his attention to the many factors of uncertainty. Though he naturally places great weight on our running, in the last analysis he leaves to the technicians the decision to, or not to."

They did go. Four cars were sent to Indiana, one to serve as a spare and practice machine. During the last tests of the cars before they were shipped, an incident affecting Jakob Krauss validated Daimler's decision to keep a mechanic as well as a driver. "Krauss says that a team of horses coming toward him was spooked by the car your nephew was driving," Lang related to Sailer, "forcing him to swerve off the road, and at the same moment the accelerator stuck open and he couldn't switch off the engine. He flew into a telegraph pole and the front axle was bent, one wheel damaged and a few other items 'shivered.'"

"After the incident with Krauss," Lang continued, "we decided immediately that the cars would no longer be handled by only one man - something that had always appeared rather risky to me. Moreover Krauss has had a bellyful and now only wants to 'ride.' This accident wasn't really too bad. The car is all right again." Krauss had been seen as a possible relief driver for the 1923 race, but now he would be a riding mechanic, charged with shutting off the ignition if his driver got into trouble. He would ride with 1908 and 1914 Grand Prix winner Christian Lautenschlager.

At the Brickyard, Mercedes star Christian Werner was the fastest of the team in qualifying at 95.20 mph, ranking 15th. Two places down was Lautenschlager with 93.20 mph. Sailer was 20th at 90.55 mph. Tommy Milton's Miller-built HCS, the eventual winner, was the fastest at 108.17 mph of the five cars that qualified at 100 mph or better. Before the race, Sailer showed that the cars were better contenders than they looked in qualifying by lapping just on 100. And unlike many of the other entries, they were proving to be impressively reliable.

But there was a control problem. British driver Raymond Mays described his experience with a similar car four years later: "The blower only came into action when the accelerator pedal was fully depressed, which meant that the driver would have less sensitive control of the power available." This lack of control subtlety became embarrassingly obvious on the hard, oil-slicked Indy track.

When the white cars were waiting to qualify, a typical Midwestern rain squall hit the Speedway. On his way around the track to return to the "Gasoline Alley" garages, Sailer had a surprise: "In the last curve, actually already on the straight, when I began to apply the gas gently my car spun so rapidly that it was quite impossible to catch it, for the wet and oily pavement was worse than snow." His car hit the wall backwards, hurtling out both occupants. Sailer's veteran co-driver Hans Rieger was injured too badly to be of help on race day. Sailer and his nephew Karl shared the wheel of the spare car in the race, and Werner drove alone.

Control trouble struck again on lap 14 of the race. As Max Sailer described it, "Lautenschlager went into the south turn at about 100, engaged the compressor somewhat too early on the mirror-smooth oily track and with lightning speed spun around several times until the front of his car hit the wall." He was too seriously injured to be able to assist as a reserve driver in a race that saw only three of 24 starters go through without relief. His mechanic, the unlucky Krauss, was also injured.

"The Mercedes cars attracted full attention," Motor Age observed, "and there appeared to be no prejudice against them, even when they appeared to have a prospect of winning. The extraordinary noise made by these cars were [sic] the subject of much comment." There was not enough of it after some pit stops, when much pushing was needed to start the engines.

Valve blow-by slowed Werner, who at first challenged the winning Milton's HCS-Miller. Werner fell back to third, with Sailer fourth after 200 miles. Their final places were Max and Karl Sailer eighth, beating the best Bugatti, and Werner 11th. Although it was far from the result they'd hoped for, their performance was respectable after early promise. And the use of supercharging gave Harry Miller and the Duesenberg brothers something to think about.

After the fatiguing race at Indy, Max Sailer prepared suggestions for future improvements:

1. No oil should hinder the driver. After only a few laps we looked from head to toe like we'd been dragged through an oil bath. That made us unsafe, because we saw nothing more through our goggles and our hands could hardly hold the wheel.
2. Wider track.
3. If it's permitted to drive single-seated, then absolutely make a single-seater car.
4. Sprung steering wheel spokes, so the wrists and hands are not so insanely overloaded.
5. Great value is to be ascribed to a deep and comfortable seat for the driver, otherwise no man can stand to drive 500 miles. After the race we drivers were utterly exhausted.
6. Less weight.

All four of the team cars were sold in America, some making later appearances at the Speedway. Back in Europe, plans had been laid for an entry of similar cars in the Italian Grand Prix at Monza in September. Although a radically streamlined new rear-engined Benz appeared at Monza, no Mercedes arrived.

Mercedes cars of the Indy type competed in 1923 and 1924 in hill climbs at Solitude and Prague with success, driven by Otto Salzer and a burly newcomer to the ranks, Otto Merz. And they provided the raw material for the cars that competed in the 1924 Targa Florio after intense development by Ferdinand Porsche. In that Italian classic, one such Mercedes scored an epic victory. But never again would a fully fledged Mercedes team tackle the toughest racing challenge that America had to offer.