|Porsche 718/2 RSK Spyder|
Porsche's first purpose built racing car, the 550, still shared many components with the road cars of the marque. Particularly the steel platform chassis prevented the small Spyder of living up to its potential. It was nevertheless a highly successful racing car, which could only get better as Porsche launched its replacement with a more sophisticated chassis and running gear early in 1956. Simply known as the 550A, in the hands of Umberto Maglioli the new racer lived up to its expectation by scoring an outright win in the Targa Florio, whereas its predecessor used to be in contention only for class wins.
Compared to the original 550, the biggest step forward was the new spaceframe chassis. Consisting of many small diameter tubes, the chassis was considerably lighter and as much as five times stiffer than that of its predecessor. To cope with the stiffer frame, the suspension was also reworked, although it still followed the traditional Porsche lines. At the rear the swing-axles were considerably lowered, eliminating many of the negative characteristics of this type of suspension. With the chassis so much stiffer, the body did not have to carry anymore load, so it could also be lightened considerably. Its design still followed that of the original, but the 550A can be easily distinguished by a louvered hatch on both sides behind the cockpit.
During the development of the 550 most of the time and resources were spent on developing the Type 547 engine. The small four cylinder boxer with four tiny camshafts had performed really well, but Porsche engineers felt there was more left. A major development was moving the drive for the distributor from the intake camshafts to the crankshaft. Other improvements were fitting two Weber Carburetors and raising the compression. The Type 547/2 as the engine was known produced 125 bhp early in the year and towards the end of the season a reliable 135 bhp could be attained. Torque was also increased considerably from 120 Nm to 145 Nm. The engine was mated to a five speed gearbox and mounted midships in the spaceframe chassis.
Still unpainted and virtually untested, the 550A was first raced during the 1956 Mille Miglia, understandably with little success. The German debut came during the 1000km race at the Nürburgring where two 550As were entered. They finished fourth and sixth overall, taking a one-two class win in the process. For the 24 Hours of Le Mans, two new cars were constructed, fitted with a fastback roof similar to the one fitted on the first 550s. One car retired, while the other finished fifth overall and first in class. After a successful debut season, Porsche commenced limited series production of the 550A for customers. In 1957 the factory continued development of the Type 547 engine and several versions with different displacements were constructed for use in hillclimbs. The largest was the Type 547/5 with a displaced of nearly 1.7 litre.
For the 1957 season all eyes were back on the chassis and body once more. Following the lines of the experimental low-drag 'Mickey Mouse' spyder a new body design was penned. It was both lower and smoother than that of its predecessors. Under the aluminium body there were several more detail changes. The front trailing arms were relocated to improve the suspension dynamics; the camber of the front wheels would now increase as the wheels moved upwards. The changes required the steering box to be mounted in the middle of the car. The much lower front frame resembled the letter K if looked at from the front and the new version was commonly referred to as the 'RSK'. The internal name for the new car was the Type 718.
The works team first entered the Type 718 RSK at the 1957 Nürburgring 1000 km race, but it only practiced. The car's first race was Le Mans, where it was forced to retire after 10 hours as the result of an accident. The car had not impressed at either events, so much time was spent improving the RSK for the 1958 season. First to go was the unusual front suspension and replaced by the original configuration. There were more dramatic changes at the rear, where for the first time in Porsche history, the traditional swing-axle design was discarded. A Watt-linkage of two radius rods replaced the single trailing arm, better controlling the angle of the wheel during travel. The 1.5 litre engine was modified and fitted with larger Carburetors, resulting in the 142 bhp Type 547/3. The larger 1.6 and 1.7 engines were also fitted to 718 RSK chassis for various races.
At least two of the RSKs used in 1957 were updated to the new specification and joined several new cars during the 1958 season. The modifications proved to be highly successful as the new Porsches were clearly the fastest cars in their class. Unfortunately the now heavily stressed engine and gearbox showed signs of weakness at several key moments, causing retirements at Sebring and the Nürburgring. At the Targa Florio Jean Behra impressed by finishing second overall in a 1.5 litre engined RSK. At Le Mans Jurgen Barth and Paul Frere placed a 1.5 litre RSK fourth overall and first in class. Jean Behra and Hans Herrmann did one better with a 1.6 litre engined example taking third and first in the 2 litre class. Now completely refined, the RSK was even more successful in 1959 with an overal win at the Targa Florio and a podium finish at the Sebring 12 Hours.
The Porsche 718 RSK did not only make its mark on sports car racing, it also proved to be a commendable Formula 2 racer. Thanks to the central location of the steering box, the RSK could easily be converted to single seater specification. Porsche already planned to race an RSK at Reims in 1957, but the Le Mans crash prevented that. At the 1957 Nürburgring Grand Prix, a modified 550A set the fastest F2 practice time and won the F2 race. In 1958 the RSK made its F2 debut with a victory at Reims and Avus as well as a second place finish at the Nürburgring against purpose built single seaters. In 1959 Porsche built four special RSKs for customers that could be easily converted to single seater specification. Encouraged by the success, Porsche built a dedicated single seater for the 1960 season. This Type 787 was still clearly related to the 718 and scored numerous wins.
For 1960 the rules for sports cars were modified, dictating a considerably wider cockpit and taller windshield. Reluctantly, Porsche adopted the RSK to the new regulations. The frame was widened and the wheelbase slightly lengthened. The rear suspension was modified once more and the swing axles were now gone completely, replaced by a more modern double wishbone layout. For the first time the 1.6 litre engine was also offered to customers, producing 160 bhp compared to the 150 of the Type 547/3. The new machine was known as the RS 60 Spyder and the subsequent 1961 cars were dubbed RS 61 Spyder, although they were identical. Porsche also developed a coupe version and a similar, but open car known as the W-RS. These cars had even larger two-litre engines and eventually fitted with an eight cylinder engine the W-RS was raced successfully well into 1964.
Despite being based on a car that debuted in 1956, the RS 60 Spyder again proved to be a giant slayer. The international racing debut came at the 1960 Sebring 12 Hours. Reminiscant of the 550A's early performance, the RS 60 took an amazing one-two victory in the 12 Hour event. Next up was a win at the Targa Florio and Porsche looked well on their way to winning the World Championship against the three-litre engined Ferraris. A second and fourth at the 'Ring must have felt like a disappointment. Le Mans certainly was disappointing with the highest placed RS 60 finished twelfth and second in class. Porsche and Ferrari had both scored 22 points, but Ferrari was awarded the title on the grounds that they had finished third more often than Porsche. In 1961, the Porsches had to make do with class wins as the Works concentrated on the Grand Prix program.
Although in heavily modified form, the first Porsche spaceframe chassis was raced successful for almost ten years, taking a Targa Florio win as late as 1963. These nimble racing cars lifted Porsche up from a class victory contender to a serious rival to racing greats. They were certainly instrumental in the company's long path to the much desired Le Mans win and all cars designed in the 1960s incorporated the lessons learned in the many years the 550A, RSK and RS Spyders were raced.
Article by Wouter Melissen, last updated on October 20, 2008
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