Mercedes-Benz 300 SL

The 300 SL (also called W 198) goes back to the racing sports car, Mercedes-Benz W194. In 1951, Daimler-Benz decided to take part in races and build a sports car for this purpose. Mercedes' largest engine, the M186 shared between the 300 "Adenauer" saloon (W186) and luxurious 300 S two-seat tourer (W188) was developed.[7]

The Mercedes-Benz W194 racing car

In 1952, the W194 took part in the most important races of the year. The new SL competed at the Mille Miglia at the beginning of May and achieved second place. It won the top three places at the Bern Sports Car Prize 131.04 kilometres (81.42 mi). At the 24-hour race at Le Mans the 300 SL won the top two places. First place went to Hermann Lang and Fritz Riess with an overall average 155.6 km/h (96.7 mph), they achieved a new record in Le Mans history. Second place went to Theo Helfrich and Helmut Niedermayr. A race at the Nürburgring ended with a four-fold success. At the Carrera Panamericana in Mexico, the 300 SL again won with Karl Kling and Hans Klenk – despite having a vulture flying through the windscreen.[8]

W194 at the Carrera Panamericana-Mexico 1952

These successes, especially those on the high-speed open road races, were rather surprising as the W194 engine was fitted only with carburetors, producing 175 hp (130 kW), which was not only less than the competing cars by Ferrari and Jaguar, but also less than the 300 SL road car developed from it and introduced in 1954. Low weight and low aerodynamic drag made the W194 fast enough to be competitive in endurance races.

1953 intermediate model at Pebble Beach in 2012

Mercedes-Benz developed a new version for the 1953 racing season by adding fuel injection and 16-inch wheels. The gearbox was installed on the rear axle. Its body was made of Elektron, a magnesium alloy, to reduce the weight by 85 kilograms (187 pounds). However, the car was not used because Mercedes-Benz decided to take part in Formula One from 1954 onward.[9] Later versions revised the body for lower air resistance and did not adopt the transmission arrangement.

New York Auto Show 1954

Mercedes-Benz 300 SL prototype

Mass production of the 300 SL was initially not planned. The idea of a toned-down Grand Prix car tailored to affluent performance enthusiasts in the booming post-war American market was suggested by Max Hoffman at a director's meeting in Stuttgart, in 1953.[10][3] Mercedes' new General Director Fritz Konecke agreed when Hoffman put an order in for 1000 cars[10] and the new 300 SL was introduced at the 1954 New York Auto Show rather than the Frankfurt or Geneva gatherings where company models made their usual debuts. In addition, the production of a smaller Roadster, the Mercedes-Benz 190 SL was announced[11] after Hoffman put another order in for 1000 of the 190SLs[10]

The two sports cars premiered at the "International Motor Sports Show" in New York, which took place in February 1954. Mercedes-Benz experienced a very positive visitor response to the 300 SL and the 190 SL at the Motor Show. Serial production began in August 1954 at the Sindelfingen plant.

The price for the Coupe in Germany was DM 29,000 and $6,820 in the US.[10] The Roadster was DM 32,500 in Germany and $10,950 in the US – a 10% jump in Europe but an over 60% increase in the US over the Coupe.[12]

[13]

Mercedes-Benz did not announce what the abbreviation "SL" meant when the car was introduced and various magazines and company officials have gone back and forth between Sport Leicht and Super Leicht (light).[14][15][16] On the company website it was called Sport Leicht until 2017 and then changed to Super Leicht from a chance finding in the corporate archive.[17][18]

The championship-winning 300 SLS was a 300 SL Roadster modified to comply with Sports Car Club of America class racing standards

A special 300 SLS (Super Light Special) version of the 300 SL Roadster was created for the Mercedes-Benz U.S. racing team to compete in the Sports Car Club of America (SCCA) national circuit in 1957. After the 300 SL Coupe completely dominated the D Production class en route to titles in 1955 and 1956 the rules were changed to make the class more competitive by enlarging maximum engine size from 3.0 to 3.5 litres. Rather than radically modify its engine size (on the cusp of releasing the company's new 300 SL Roadster to replace the Coupe), Mercedes-Benz instead created two specially modified Roadsters to campaign in the D Modified class on the SCAA circuit. These featured a solid cover over the passenger seat, a low profile racing screen in place of a full-width and height windscreen, a driver's seat roll bar, a custom cowl with engine air intake, and a lack of front and rear bumpers. These and other modifications lowered vehicle weight from 1,420 kilograms (3,130 pounds) to 1,040 kilograms (2,290 pounds). Engine output was increased 20 hp (15 kW) to 235 hp (175 kW). Team driver Paul O'Shea once again brought home the title for the company.[4]

Three checkered pattern seats fabrics were available as standard. The combinations of the basic colours were, grey/green, grey/blue and cream/red.[19] Most customers opted for leather upholstery, which became standard on the Roadster.

Even with the upward opening doors the Coupe has an unusually high sill, making entry and exit from the car's cockpit problematic. To further facilitate entry the steering wheel pivoted on its hub 90 degrees away from the dashboard.[20]

Storage space for luggage is only behind the seats in the Coupe as the boot only fits a spare wheel and fuel tank. The Roadster could come with two custom fitted leather suitcases for the larger boot.

The side windows in the Coupe are fixed, but roll down normally in the Roadster.

The body consists mainly of sheet steel, with the bonnet, boot lid, dashboard, sill and door skins made of aluminium. Silver grey was the standard colour; all others were options at an additional expense.[21]

The objective of the overall design was to make the vehicle as streamlined as possible. The exceptional width of the tubular frame along the cockpit allowed the cabin roofline to be inset considerably on both sides, dramatically reducing frontal area. The frame, however, was also quite high along the midline, prohibiting the attachment of normal doors. The only option – already used on the W194 race car – that would allow passengers up and over an exceptionally high and deep sill were the now iconic gull-wing doors. Rather than an aesthetic choice, they were a design necessity.

Eyebrows are a stylistic feature that also stretch the curvaceous body.[22][23] The front pair deflect road water from hitting the windscreen and the rear had to be added for visual symmetry.[24] These eyebrows give styling to an otherwise slab-sided body. Mercedes-Benz claimed they were aerodynamic additions and pushed airflow over the top of the car and kept the windows clean in bad weather.[25]

The Mercedes-Benz M198 engine is a water cooled 3.0 L; 182.8 cu in (2,996 cc) overhead cam straight-six. Like the racing Mercedes-Benz M194, the 300 SL borrowed the basic 2 valve per cylinder M186 engine from the regular four-door 300 (W186 "Adenauer") luxury tourer introduced in 1951.[3]

As such, it featured the M186's innovative aluminium head, which had a 30-degree diagonal base that allowed for larger intake and exhaust valves than a standard horizontal joint with the engine block. To improve performance, the M198 replaced the W194's triple two-barrel Solex carburetors with a Bosch mechanical direct fuel injection system.[3] Derived from the DB 601 V12 used on the Messerschmitt Bf 109E fighter of World War II, it boosted power almost 25% over the Gran Prix car's, raising output from 175 hp (130 kW; 177 PS) SAE gross to 240 hp (179 kW; 243 PS) SAE gross at 6100 rpm (215 hp (160 kW; 218 PS) DIN at 5800 rpm), over double that of the original Type 300 saloon's 115 hp (86 kW; 117 PS) SAE gross.[26] Compression was set at 8.55:1.[10]

Another high-performance feature was race-bred dry sump lubrication, which both ensured good oil distribution at high-speed cornering and reduced engine height by eliminating a traditional oil pan.

A free optional, even more powerful version of the M198, with radical Sports camshaft and 9.5:1 compression ratio,[10] could be ordered for the Coupe. The Roadster was delivered with this engine only on its debut in 1957.

The M198 engine, with its distinctive massive sand-cast aluminum intake manifold

In order for the M198 to be installed in the low profile car, it was tilted 50 degrees toward the driver's side.[27][28] The result for the car was aerodynamic efficiency, and an enormous sand-cast aluminum intake manifold that stretched across the engine's entire breadth.[29]

The engine was coupled by a single-disc dry clutch to a four-speed transmission, with gear ratios of 3.34:1, 1.97:1, 1.39:1, and 1:1, and a reverse of 2.73:1.[26] The stock rear axle ratio at the beginning of the construction period was 1:3.42; From the 41st vehicle, it was changed to 1:3.64 to give better acceleration. It allows a top speed of 235 km/h (146 mph) and acceleration from 0 to 100 km/h (62 mph) in 9.3 seconds. Faster acceleration was provided with ratios of 1:3.89 and 1:4.11. The lowest final gear ratio, of 1:3.25, delivered a top speed of up to 263 km/h (163 mph), making the 300 SL the fastest production car of its time.[3]

City drivers found the tall first gear a challenge.[11] Clutch pedal operation was initially very heavy, remedied by an improved clutch arm helper spring.

Adapting a race-bred mechanical direct fuel-injection system proved not without problems. Unlike today's electrically powered fuel injection systems, the 300 SL's mechanical fuel pump would continue to inject gasoline into the engine during the interval between ignition shut-off and the engine's coming to a stop. This both washed away the oil film critical to an engine during start-up and led to oil dilution, leading to excessive ring wear and scouring of the cylinder walls. Exacerbating the problem was the engine's racing-oriented dry sump lubrication system, with its large oil cooler and enormous 15 l (4.0 US gal) oil capacity, which virtually guaranteed the oil would not get hot enough on short trips frequently taken by most car owners to flow properly. In practice, many would block off airflow through the oil cooler and stick rigidly to the appropriately low 1,600 km (1,000 mi) recommended oil change interval. An auxiliary fuel pump provided additional fuel for extended high-speed operation or cold starts, but overuse could also lead to dilution of the oil.[30][31]

From March 1963 to the end of production later that year, a light alloy crankcase was installed in 209 vehicles.[32]

Explosion model without doors and roof

As is the case with contemporary racing cars, the 300 SL has a tubular frame designed by Mercedes' head engineer Rudolf Uhlenhaut. This ensured high stability with low vehicle mass. Thin straight chrome-molybdenum tubes were assembled as several triangles and the finished frame weighs 82 kilograms (181 pounds). The tubes make a deep side panel so gullwing doors are needed to enter the car.[33] The frame on the Coupe has two side rails with the top tube at the level of the driver's elbow.[10] The centre of gravity is almost exactly in the middle of the vehicle.

Tubular frame

The chassis was a regular Mercedes-Benz W186 but with a sportier tuning. Unlike many cars of the 1950s, recirculating ball steering was relatively precise and the four-wheel independent suspension allowed for a reasonably comfortable ride and markedly better overall handling. Front suspension was double wishbones, coil springs, stabilizing bar. However, the rear swing axle, jointed only at the differential, not at the wheels themselves, could be treacherous at high speeds or on imperfect roads due to extreme changes in camber. The Coupe has a high-pivot swing axle, radius arms, coil springs. This was replaced with a low-pivot swing axle in the Roadster.[10]

The front wheels are hung on double, unequal length wishbones with coil springs and hydraulic telescopic shock absorbers and a torsion bar stabilizer was installed. The Coupe's rear axle was of a two joint design with one joint at each side of the differential at its centre line.[19]

The Coupe's wheels were 5K × 15 inches while the Roadster was slightly larger at 5.5 x 15 inches. The wheels were steel bowl/aluminium rim rivet compound wheels. A valuable option was the Rudge rims 5J × 15 inches. The tires were 6.50-15 inches on the Coupe and 6.70–15 on the Roadster.

Rudge rims and eyebrow

The 300SL had the same 1,470 square centimetres (227.9 sq in) area, self cooled, turbo drum brakes as on the 300S Mercedes.[34] A brake booster was used to reduce the pedal force. The brake booster works by using the negative pressure in the intake manifold. Brake shoes were 90 millimetres (4 in) wide. The front drum brakes were 2 wheel brake cylinders/wheel, rear drum brakes were 1 wheel brake cylinder/wheel. The handbrake was a mechanical parking brake that acts on the rear wheels. The Roadster had the same drum brakes until March 1961 when Ø 290 millimetres (11.4 in) disc brakes were introduced front and rear.[20]

[37][10]

Numerous celebrities have owned 300 SLs. Among them, Mohammad Reza Pahlavi, Wernher von Braun[38] Rob Walker, Juan Manuel Fangio, Juan Peron, Tony Curtis, Pablo Picasso,[39] Sophia Loren, Romy Schneider, Clark Gable, Glenn Ford,[40] Briggs Cunningham, Luigi Chinetti, John von Neumann,[37] Pierre Trudeau, Justin Trudeau,[41] Paul Newman, Yul Brynner, Bernie Ecclestone, Ralph Lauren, Frank Lloyd Wright[42] and Adrian Conan Doyle.[43], King Abdullah II of Jordan