Mercedes-Benz 300 SLR

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Mercedes-Benz 300 SLR

Mercedes-Benz 300 SLR preserved at the company museum
Category	World Sportscar Championship
Constructor	Daimler-Benz AG
Designer(s)	Rudolf Uhlenhaut
Technical specifications
Suspension (front)	double wishbone, torsion bar springs, telescopic shock absorbers
Suspension (rear)	single-joint swing axle, longitudinal torsion-bar springs, telescopic shock absorbers
Engine	Mercedes-Benz M 196 S 2,982 cm3 (182 in3) straight 8 naturally aspirated front mid
Transmission	Daimler-Benz 5-speed transaxle gearbox bevel-gear differential
Fuel	Super petrol (98 RON)
Tyres	Continental
Competition history
Notable entrants	Mercedes
Notable drivers	Juan Manuel Fangio Stirling Moss Pierre Levegh
Debut	1955 Mille Miglia

The Mercedes-Benz 300 SLR (W 196 S) was a 2-seat sports racer that took part in the 1955 World Sportscar Championship before a catastrophic crash and fire at Le Mans later that year ended its domination prematurely. The car was designated "SL-R" (for Sport Leicht-Rennen, eng: Sport Light-Racing), which was later condensed to "SLR". Technically, the W 196 S is based on the W 196 R, but has a slightly different engine, displacing 3 litres.

Just as the W 196 R Formula One racer's M 196 R engine, the W 196 S's M 196 S engine is a direct-injected 3-litre straight 8 engine (but with a 78 mm bore and stroke); its rated power is 276 PS (203 kW).

The W 196 S's monoposto driving position was modified to standard two-abreast seating, headlights were added, and a few other changes made to adapt a strictly track competitor to a 24-hour road/track sports racer.

Two of the nine 300 SLR rolling chassis produced were converted into 300 SLR/300 SL hybrids. Effectively road legal racers, they had coupé styling, gull-wing doors, and a footprint midway between the two models.

When Mercedes-Benz cancelled its racing programme after the Le Mans disaster, the hybrid project was shelved. Company design chief Rudolf Uhlenhaut, architect of both the 300 SLR racer and the hybrids, appropriated one of the leftover mules as his personal car. Capable of approaching 290 km/h (180 mph), the Uhlenhaut Coupé was by far the fastest road car in the world in its day.

History[]

Name[]

In spite of its name and strong resemblance to both the streamlined 1952 W194 Le Mans racer, and the iconic 1954 300SL Gullwing road car it spawned, 1955 300 SLR was not derived from either. Instead, it was based on the wildly successful 2.5-litre straight 8-powered 1954–1955 Mercedes-Benz W196 Formula One champion, with the engine, enlarged to 3.0 litres for the sports car racing circuit and designated "SL-R" for Sport Leicht-Rennen (eng: Sport Light-Racing). All were the work of Daimler-Benz's design chief Rudolf Uhlenhaut.

Racing record[]

Stirling Moss drives the Mercedes-Benz 300 SLR of former Mercedes racing teammate Juan Manuel Fangio at the Nürburgring in 1977

Mercedes team driver Stirling Moss won the 1955 Mille Miglia in a 300 SLR, setting the event record at an average of 157.650 km/h (97.96 mph) over 1,600 km (990 mi). He was assisted by co-driver Denis Jenkinson, a British motor-racing journalist, who informed him with previously taken notes, ancestors to the pacenotes used in modern rallying. Teammate Juan Manuel Fangio was second in a sister car.

After missing the first two races at Buenos Aires in Argentina and the 12 Hours of Sebring in the United States where Ferrari scored a victory and a second place respectively, the 300 SLRs later scored an additional 1-2-3 world championship win in the Tourist Trophy at Dundrod, Ireland, and a 1-2 at the Targa Florio in Sicily, earning Mercedes victory in the 1955 World Sportscar Championship. Further non-championship trophies were also scored at the Eifelrennen in Germany, and Swedish Grand Prix.^[1]

However, these impressive victories became overshadowed at Le Mans when the once again leading 300 SLRs were withdrawn after a horrific accident involving a team car driven by Pierre Levegh. Even with the innovative wind-brake, the car's drum brakes had been unable to prevent Levegh from rear-ending an Austin-Healey, causing his car to become airborne. Upon impact, the ultra-lightweight Elektron bodywork's high magnesium content caused it to ignite and burn in the ensuing fuel fire. Compounding it, an uninformed race fire crew initially tried to extinguish it with water, only making it burn hotter. Eighty-four spectators and Levegh lost their lives in what remains the highest-fatality accident in the history of motorsport. Mercedes withdrew from racing at the end of the 1955 season, and would remain withdrawn for three decades.

Uhlenhaut Coupé[]

Gull-wing doors were a signature feature of the Uhlenhaut Coupé

Daimler-Benz made two road-legal 300 SLR coupés, known today as Uhlenhaut Coupé. One of these two cars once served as the personal car of its designer, Daimler-Benz motorsport chief Rudolf Uhlenhaut, hence the name.

Prior to the Le Mans accident he had ordered two of the nine W196 chassis built to be set aside for modification into an SLR/SL hybrid. The resulting coupé featured a significantly more sculpted body than the 300 SL fitted over a slightly widened version of the SLR's chassis, with signature 'gull-wing' doors still needed to clear its spaceframe's high sill beams. These were intended to race in the Carrera Panamericana which was cancelled because of safety concerns following the Le Mans disaster

Before the project could be seen through, however, Mercedes announced a planned withdrawal from competitive motorsport at the end of 1955, in the works even before Le Mans. The hybrid program was abandoned, leaving Uhlenhaut to appropriate one of the leftover mules as a company car with only a large suitcase-sized muffler added to dampen its near-unsilenced exhaust pipes.

With a maximum speed approaching 290 km/h (180 mph),^[1] the 300 SLR Uhlenhaut Coupé easily earned the reputation of being the era's fastest road car. A story circulates that, running late for a meeting, Uhlenhaut roared up the autobahn from Munich to Stuttgart in just over an hour, a 137 mile/220 km journey that today takes two-and-a-half.^[2]

Uhlenhaut's 300 SLR coupé, in the Mercedes-Benz museum in Stuttgart

US auto enthusiast magazine Motor Trend road tested the car, as did two English journalists from Automobile Revue, who spent more than 2,000 miles (3,200 km) behind its wheel. After a high-speed session at four o'clock in the morning on an empty section of autobahn outside Munich the latter wrote: "We are driving a car which barely takes a second to overtake the rest of the traffic and for which 120 mph on a quiet motorway is little more than walking pace. With its unflappable handling through corners, it treats the laws of centrifugal force with apparent disdain."

Their only regret was that "we will never be able to buy [the car], which the average driver would never buy anyway.".^{[3][failed verification]}

The Uhlenhaut Coupé has been preserved by Mercedes-Benz and is displayed at its corporate museum in Bad Cannstatt. Its sibling is preserved in one of Mercedes-Benz's eleven car vaults.

Technical description[]

Design[]

The 300 SLR was front mid-engined, with its long longitudinally-mounted engine placed just behind the front axle to better balance front/rear weight distribution. A brazed steel tube spaceframe chassis carried ultra-light Elektron magnesium-alloy bodywork (having a relative density of 1.8 kg·dm⁻³, less than a quarter of iron's 7.8 kg·dm⁻³), which contributed substantially to the low vehicle mass of 901 kg (1,986 lb) (roadster),^[4] or 1,117 kg (2,463 lb) (coupé).^[5]

The SLR had a second seat for a co-driver, mechanic or navigator, depending on the race. As it turned out, it was only needed during the Mille Miglia, after which the 1955 Carrera Panamericana was cancelled due to the Le Mans accident. On some circuits such as the Targa Florio the extra seat was covered and passenger windshield removed to improve aerodynamics.

A total of nine W 196 S chassis were built: seven roadsters, and two coupés.

Engine[]

The M 196 S engine is a naturally aspirated straight 8 engine with a bore and stroke of 78.0 mm (3 in), resulting in a displacement of 2,982 cm³ (182 in³). The engine has a rated power output (DIN 70020) of 276 PS (203 kW) at 7000/min, and produces a peak power output of 310 PS (228 kW) at 7400/min. Its maximum torque is 31.7 kp⋅m (311 N⋅m) at 5950/min, which is gives the engine a very high BMEP of 1.31 MPa (190 lbf/in²). Like in the W 196 R, the engine was canted to the right at 53° to lower the car's profile, resulting in slicker aerodynamics and a distinctive bulge on the passenger side of the hood shared with the streamlined Type Monza Formula one car. To reduce crankshaft torsion, power takeoff was from the centre of the engine via a gear rather than at the end of the crankshaft. Daimler-Benz fitted the engine with a single desmodromic intake valve, and a single desmodromic exhaust valve per cylinder, actuated by two spur-gear driven overhead camshafts. The fuel system is a direct fuel injection system with a mechanically driven eight-plunger inline injection pump made by Bosch. In addition to that, the W 196 S's engine was fitted with a dry-sump lubrication system and chromium-coated aluminium cylinder sleeves. For ignition, the engine was equipped with conventional double magnetos.^[5] Unlike the M 196 R engine, the M 196 S engine is designed to run on standardised, commercially available Super 98 RON petrol (DIN 51600).^[6]

Suspension system[]

To enhance stopping power extra wide diameter drum brakes too large to fit inside 16" wheel rims were used, mounted inboard with short half shafts and two universal joints per wheel. Suspension was four-wheel independent. Torsion bars fitted inside the frame's tubes were used in the double wishbone front. To prevent cornering forces from raising the car, as occurs with short swing axles, the rear used a low-roll centre system featuring off-centred beams spanning from each hub to the opposite side of the chassis crossing one-another over the centreline. Nevertheless, snap-oversteer could be still a notable problem at speed.

At Le Mans in 1955, the 300 SLRs were also equipped with a large rear mounted "wind brake" that hinged up above the rear deck to slow the cars at the end of the fast straights. The idea came from director of motorsports Alfred Neubauer, who had been seeking to reduce wear on the huge drum brakes and tyres during long-distance endurance races where cars repeatedly had to decelerate from 180 mph (290 km/h) to as little as 25 mph.^{[3][failed verification]} In tests the 0.7m² (7.5 ft²) light-alloy spoiler slowed the car dramatically and improved cornering, helping to compensate for the superior new disc brakes of the SLR's main rival Jaguar D-type.

SLR McLaren[]

Mercedes-Benz SLR McLaren

Inspired by the 300 SLR Uhlenhaut Coupé, the Mercedes-Benz SLR McLaren grand tourer made its debut in 2003. Jointly developed by Mercedes-Benz and McLaren Automotive it featured a hand-built 5.4-litre, supercharged 626 PS (460 kW; 617 hp) all-aluminium V8 engine.

The SLR McLaren was available in both coupé and roadster versions, as well as a number of other specialized variants. Production ran through early 2010.

See also[]

• Mercedes-Benz W196
• Mercedes-Benz SLR McLaren
• Mercedes-Benz in motorsport
• List of Mercedes-Benz cars

References[]

Notes[]

Bibliography[]

External links[]

Media related to Mercedes-Benz 300 SLR at Wikimedia Commons

• Wolfgang Scheller, Thomas Pollak: Rudolf Uhlenhaut: Engineer and Gentleman - The Father of the Mercedes 300 SL, Dalton Watson 2016
• 1955 World Sportscar Championship