Porsche 550A Spyder
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Automobilhersteller : |
Porsche |
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Modell: |
550A Spyder |
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Jahr: |
1957-1958 |
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Art: |
Roadster |
Engine Design: Four cylinder air cooled, horizontal opposed, 4 overhead camshafts. Power: Approximately 110 PS (81 kW) at 6200 rpm. Bore: 3.35 in (85 mm). Stroke: 2.59 in (66 mm). Piston Displacement: 1,498 cc (91.4 cu in) Compression ratio: 9.5:1. Crankcase: Aluminum. Cylinders: Aluminum hard chromed walls. Cylinder head: Aluminum. Valves per cylinder: 1 intake, 1 exhaust. Valve operation: 2 camshafts per head driven by vertical shafts. Crankshaft: Full roller bearing, built up. Pistons: Aluminum. Air blower drive: V-belt, crankshaft to generator shaft. Crankshaft-blower ratio: 1:1. Air volume: 1100 L/s at 6200 rpm. Engine lubrication: Dry sump, with oil cooler and oil filter in main current. Firing order: 1-4-3-2. Distributor drive: Camshaft. Spark plugs: Temperature valve 260 – 280. Carburetors: Solex 40 PJJ or Weber 40 DCM. Muffler: 2 mufflers leading into 1 exhaust pipe. Clutch: Fichtel & Sachs, K 12 Porsche Special. Transmission: 4 forward speeds, helical gears, synchronized, 1 reverse.
Gear ratios: 1st gear, 11:35 2nd gear, 17:30 – 16:31 – 18:29 3rd gear, 23:26 – 22:27 – 24:25 4th gear, 27:22 – 25:24 – 26:23 Reverse 1:3.56
Rear axle: Spiral bevel pinion, ZF lock type differential. Gear ratio: 8:35 – 7:31 – 7:34
Top speed: Approx 140 mph (220 km/h).
Chassis Frame: Tubular, seamless steel tubing Front springs: 2 transverse, 4-leaf adjustable torsion bars Rear springs: 1 round torsion bar on each side Shock absorbers: Fichtel & Sachs, telescopic hydraulic Front: 26 x 90 Rear: 36 x 140 Steering ratio: 1:14.15 Operating brakes: Oil hydraulic foot brakes to all four wheels Brake drums: 11.0236 in (280 mm) Rims: Aluminum Tires: Front: 5.00 – 16 Rear 5.25 – 16
Dimensions Wheel base: 83 in (2100 mm) Front tread: 50 in (1290 mm) Rear tread: 49 in (1250 mm) Length overall: 11 ft 9 in (3600 mm) Width overall: 5 ft 1 in (1550 mm) Height: (unloaded) 3 ft 4 in (1015 mm) Minimum ground clearance: Approx. 6 in (150 mm) Minimum turning circle: Approx. 36 ft (11 m)
Weight Dry weight: Approx. 1300 lb (590 kg) Empty weight: (DIN) Approx. 1510 lb (685 kg) Service weight: (FIA) Approx. 1410 lb (640 kg) Permissible total weight: Approx. 1984 lb (900 kg)
Axle weight: Front: 992 lb (450 kg) Rear: 992 lb (450 kg)
Inspired by the Porsche 356 which was created by Ferry Porsche, and some spyder prototypes built and raced by Walter Glöckler starting in 1951, the factory decided to build a car designed for use in auto racing. The model Porsche 550 Spyder was introduced at the 1953 Paris Auto Show. The 550 was very low to the ground, in order to be efficient for racing. In fact, former German Formula One racer Hans Herrmann drove it under closed railroad crossing gates during the 1954 Mille Miglia.
The 550 Spyder put Porsche firmly on the map as a serious competitor on the world’s racing tracks; indeed, the diminutive mid-engine roadster generated the nickname ‘Giant Killer’ for its ability to defeat much more powerful rivals. Introduced at the 1953 Paris Auto Show, the 550 and its second iteration, the 550A, remained in production through February of 1959, and a total of 130 chassis were constructed before the 718 RSK Spyders appeared. A large proportion of 550 production was destined for the United States.
Built on a frame of seamless mild steel tubing, the 550 utilised a front suspension of double trailing arms and transverse-leaf torsion bars. After the first few examples, the rear suspension was redesigned from leading control arms to trailing arms with swing axles and tubular transverse torsion bars. Porsche’s engineers had planned an all-new engine to power the Spyder at the gruelling Carrera Panamericana, but early testing determined that Dr Ernst Fuhrmann’s Type 547 advanced 1.5-litre air-cooled four-cylinder Boxer engine was not quite ready. Thus, the first few chassis were fitted with conventional pushrod Porsche engines. Soon, however, reliability was ensured and the new ‘Four-Cam’ would be installed in all the 550s, 550As, RSKs, 356 Carreras, and 904s that were to follow.
The 550a that came about in 1956 was not just a mere evolution of the preceding model, but more a revolution. Early Spyders employed a ladder frame for its proven design and rugged simplicity, but with Porsche opening its new dedicated competition shop, limited resources were no longer a concern. Leopold Schmidt brought the 550 to new levels of performance with his design of a space frame serving as the new core of the racer. The benefits from this upgrade permeated just about every metric of the vehicle. Chassis mass was down 95 pounds while 65 pounds were cut from the aluminum body, resulting in a feather-like 1170 pounds of weight in total. All the while rigidity was massively increased compared to the ladder frame of old. This in turn made the suspension, complete with a newly designed low pivot swing axle in back, work much more efficiently now that the mounting points were rock solid.
At first glance the body on the 550A appears identical to the older models, but a keen eye will pick up on several distinct clues demarcating it as the upgraded type. The most easily spotted of which is the rear engine cover, which lost its rear hinges and instead was simply lifted off the frame all in an attempt to save weight. The two grills were repositioned further rearward and small louvred hatches were also added in front of the rear haunches to maintain easy access to the motor for quick inspection. Additionally, the spare tire was stored up front for more ideal weight distribution. Smaller lighting treatments front and rear, again, make the 'a' model identifiable, while the subtlest change of all occurred up front with a reprofiled nose for better aerodynamics.
Porsche's Type 547 engine engaged in the all-important task of making the wheels rotate. Compact and intricate, this Dr. Ernest Fuhrman design featured dry sump lubrication, a roller bearing crankshaft and twin spark ignition. Most importantly, however, dual overhead cams sit atop both sides of the 4-cylinder boxer block. Unlike most motors that use pushrods or belts to run the valve train, the 547 relied on a series of shafts and bevel gears to keep things running smoothly. Piecing the whole unit together was said to have taken at least 120 hours with 8 of those spent just perfecting the timing. Despite the immense complexity, the motor proved to be reliable and served the car well in endurance racing across the world.
This marvelous but complex engine, called the ‘Drawer motor’ because its engineering drawings were quickly hidden in Fuhrmann’s desk whenever Dr Porsche walked into his office, was an all-alloy unit displacing 1,498 cubic centimeters. Its camshafts were driven off the Hirth-patent built-up roller-bearing crankshaft by a series of shafts and crown wheels. Cam timing took dozens of man-hours to properly establish, but once all the clearances were correctly set, the high-revving motor was very reliable. It featured dry-sump lubrication and two spark plugs per cylinder. With compression of 9.5:1 and breathing through a pair of Weber downdraft carburetors, this engine produced a strong 110 brake horsepower. In a chassis that weighed barely 590 kilograms, 550s were capable of top speeds approaching 210 km/h (140 mph), dependent on gearing. Because these little roadsters were ostensibly required to be street driven, they were fitted with a token canvas tonneau that met the letter of the rulebook but were otherwise better left folded away in the garage.
The first three hand built prototypes came in a coupé with a removable hardtop. The first (550-03) raced as a roadster at the Nurburgring Eifel Race in May 1953 winning its first race. Over the next couple of years, The Werks Porsche team evolved and raced the 550 with outstanding success and was recognized wherever it appeared. The Werks cars were provided with differently painted tail fins to aid recognition from the pits. Hans Herrmann’s particularly famous ‘red-tail’ car No 41 went from victory to victory. Porsche was the first car manufacturer to get race sponsorship which was through Fletcher Aviation, who Porsche was working with to design a light aircraft engine and then later adding Telefunken and Castrol.
