TAKING time off in Stuttgart recently, I called at the Porsche factory and visited the racing department to have a closer look at the RSK Spyder models, for when you see these cars at race meetings they are seldom without their all-enveloping bodywork and it is difficult to study the mechanical details. Before going into details let me recall briefly the Spyder lineage, these being the open two-seater racing Porsches with four-camshaft engines, in all models the engine being ahead of the rear axle line. The early Porsche Spyders had a chassis frame based on two large-diameter tubes and swing-axle rear suspension identical to the production Porsche coupes, as was the front suspension. As racing and development went hand in hand the power output and reliability of the Spyder engine improved, the chassis was strengthened by a superstructure of small-diameter tubing and larger brakes were designed. On all these early Spyder models the complete rear of the body hinged upwards front the back of the chassis and the spare wheel was mounted inside the tail on top of the gearbox. The next edition of the Spyder had a different chassis frame that was almost, but not quite, a pure space frame, the bottom frame rails still being of larger diameter than the rest of the chassis tubing. This model, known as the 1500 RS (Renn-sport) had a new rear axle layout, with a low centre pivot and exposed sliding-spline half-shafts, a pair of fabricated swinging-arms being pivoted under the gearbox with their outer ends located by forward running radius-arm plates coupled to the ends of transverse torsion-bars, as on the production Porsches. The RS model did not have a hinged tail, it being bolted in place with a hinged flap on each side to provide access to carburetter and plugs, while the spare wheel was moved to a position in the nose of the car, ahead of the fuel tank. The gearbox was still of normal Porsche construction, made in two halves split longitudinally into a right-and left-hand part, and it had an extension on the rear which contained a fifth speed, or extra bottom gear, to assist starting from rest when a high top gear was being used. For the Le Mans race in 1957 the RSK (or 718 as it was also named) was produced, and this car incorporated a great many design changes. The front suspension was still by transverse torsion-bars and trailing-arms but the vertical distance between the trailing-arms was greatly increased and the geometry was such that when the wheels were turned they leant in towards the corner a matter of 1½ degrees. Instead of the cross-tubes containing the torsion-bars being parallel the top one was in two pieces, each containing a short torsion-bar, and these sloped down to the centre of the car forming a vet, an that with the bottom cross tube they formed a K lying on its side, hence the nomenclature of RSK. The steering-box was mounted in the centre of this vee, thus providing equal-length track-rods instead of the RS arrangement where the steering-box was mounted on the left. The rear suspension was unchanged from the RS model, though the chassis frame was now a pure space frame of small-diameter tubing. On the Spyder and the RS models an oil cooler was mounted in the nose of the body and air entered through a slot very low down in the bodywork. On the RSK this oil cooler was abandoned and the front body lid covering the fuel tank incorporated rows of tubes in a double skin providing a surface-type oil cooler In consequence of this the spare wheel now took the old position of the oil cooler, lying horizontal in the nose of the car rather as the spare wheel used to lie in the tail of the old Silverstone Healey, and was covered by a detachable lid, so that this new car had no openings in the front of the body, which greatly assisted air-flow. Also the RSK was considerably lower in overall height than the RS and had small fins on the extremities of the rear wheel arches. This car was involved in a crash during the race and was a virtual write-off, and it was not until this year that new RSK models appeared.
In the meantime, Porsche racing, development and production were continuing to work hand in hand and the 1500 GS engine was in full-scale production, this being the flat-four air-cooled 1½-litre unit with four shaft-driven overhead camshafts, identical apart from compression-ratio to the engines used in Spyders and RS models. Other racing items transferred to the production cars were steering-gear, brakes, carburetters, shock-absorbers, front suspension geometry advances, and ignition arrangements.
For 1958 the RSK remained unchanged as far back as the cockpit but from there rearwards the chassis frame was redesigned, and the main reason for this was alterations to the rear suspension. On the RS and original RSK rear suspension the wheel hub did not rise vertically but rotated about the radius of the locating radius-arm plate and on the latest RSK this has all been redesigned and the wheel hub is now located by a Watt-link layout, the bottom tubular link running forwards and the top one backwards exactly as used on the W196 and 300SLR Mercedes-Benz in 1955. Also, the swinging-arms have been redesigned and are now rather like two large tuning forks, the ends of the prongs being pivoted on a shaft under the differential housing. No longer having the radius-arm plates to join to the transverse torsion-bars, a complete change of suspension was incorporated in the new layout and long coil-springs are used, surrounding telescopic shock-absorbers. In addition, on this new RSK a new gearbox/final-drive housing is used which follows production-car practice. The split casing is no longer used, the new casting being in the form of a tube with end plates, the gear clusters and shafts being fed in from one end. Also the exposed half-shafts no longer have sliding spline joints but have a sliding pot-joint on the inner universal joint.
It can readily be appreciated that production Porsches benefit very directly from the factory racing activities, and the Carrera model, named after the Mexican road race in which the four-camshaft engine Underwent a lot of its initial testing, continues to be modified in accordance with knowledge gained on the Spyder, RS and RSK models, though as yet there are no production low-pivot swing axles, nor have any production cars been built with the engine ahead of the rear axle line, but perhaps time will tell. The name Carrera was given essentially to the race-bred four-camshaft engine and it could be fitted into the normal coupe, the drophead or the open Speedster model, and was intended primarily for competition purposes. So successful have the Porsche Carreras proved that many are used as purely road transport and never see a competition number. For 1958 the Carrera coupe was offered from production in a special competition form known as the Carrera G.T., and this was simply a production Carrera coupe without any frills. The main body-shell is still of steel but the doors, front cover over the fuel tank and cover over the engine compartment are of aluminium, there is no rear-seat squab, no heating system, and all the side windows are of Plexiglass, while Koni shock-absorbers are fitted. Wider front brakes are available, as used on the RS model and the fuel tank can be extra large, filling most of the front of the car and having a quick-filler protruding through the front cover, while racing-type bucket seats are fitted and sound-proofing of the interior of the body is skimped. An RS exhaust system can be fitted and the result is that the Carrera G.T. is a very potent competition cur, looking front a distance like any other Porsche coupe. All these G.T. modifications are also available on the Speedster open two-seater, the one with the hunchback tail.
After looking at the RSK models in preparation for the 1,000-kilometre race at Nurburgring, I mentioned to von Hanstein, Porsches’ competition manager, and Ing. Hilt, the head of the racing department, that it would be interesting for me to try an RSK or even a simple ordinary RS, but it was not possible as they were all in an incomplete state. However, in one corner of the racing shop stood a Carrera G.T., rather grubby and dirty and bearing the racing number 26, and thereby hung a tale. This car was to normal G.T. specification with all the optional extras fitted, such as the Spyder front brakes, separate oil cooler underneath the car with its own air scoop, twin-choke Weber carburetters, oversize fuel tank, etc., and was devoid of floor coverings and had the plastic steering wheel covered with sweat-absorbing tape. It had been used in the factory team at Sebring back in March, and just recently it had been driven to Athens for the Greek hill-climb and then to the Targa Florio in Sicily, as reported in last month’s MOTOR SPORT, where it was illustrated in the centre-spread. After the Targa Florio it was loaded with luggage and Hilt drove it back to Stuttgart, into the racing department, having covered some 7,000 kilometres, including two racing events. As the Porsche factory believe in using competitions to test their cars, the aluminium doors and the aluminium engine compartment cover bad been removed and were in the experimental department being measured for distortion, as they felt that the roads of Greece, Yugoslavia. Italy and Sicily had provided a good test. In addition, the Continental Raring tyres had been sent back to the factory for inspection on wear, so a set of old Michelin ” X ” had been fitted and the car had been pushed in a corner until it was needed again. As there was no RSK available, I suggested borrowing a Carrera G.T. and Milstein said, “Well, there is the old Targa Florio car, take that; it is just as it arrived back from Sicily.” It had been sitting there for a number of days but started instantly and was driven out into the yard behind the experimental shop. “You don’t want the doors, do you?” they said, and after warming it up away I went. The only thing that was wrong with the car was that the rev-counter was not working, but there were marks on the speedometer to indicate 6,500 r.p.m. in each gear. As it had been used for the Targa Florio it had the low axle ratio of 6 by 31 fitted, so that its acceleration was violent to say the least, While it had a maximum of just under 120 m.p.h., which it reached with ease as soon as the autobahn was clear, and at that speed ran as steady as one could wish, while there was surprisingly little turbulence in the car in spite of the absence of doors. They had said, “Bring it back for lunch,” so, heading for the wonderful Solitude circuit to the south-west of Stuttgart, I really had fun in this really quick little coupe. With its nicely shaped bucket seat the driving position was of the outstretched-arm type, and the gear-lever on these G.T. models, as on all 1958 Porsches, has been moved backwards some six inches. It was noticeable that with the higher r.p.m. of the Carrera engine and subsequent higher rotational speeds in the gearbox it was possible to heat the synchromesh between third and top when wound up to close on 7,000 r.p.m. On the push-rod engines even at 5,500 r.p.m., it is absolutely impossible to beat the synchro., but that extra 1,500 r.p.m. meant fractionally slower changes had to be made. Mind you, they were still jolly fast changes by normal standards, but slow by Porsche standards. One of the joys of the normal Carrera Porsche is the way it charges forward when you change from peak in third into top, making a glorious hard growling noise from behind. On this light G.T. model, with over 125 b.h.p. available as against 110 b.h.p. for the standard car, the growl was really something, and the noise from the Spyder exhaust system really echoed through the trees. The ride on this G.T. car, with comparatively soft suspension and Koni shock-absorbers, was really excellent and, after the rather American-like ride of the 1956 and 1957 Porsches, the latest type is a reversion to real Porsches, for Porsche motoring and the performance of the G.T. was as much as anyone would want-on the open road. After spending the morning in this “fun machine,” I realised that what it represented was in reality a production version of the original Spyder Porsche, and though the chassis/body-shell was the same as a standard 1600 model, the mechanical components on the G.T. model were all descended directly front racing, so that of Porsche we can truly say that ” racing improves the breed.”
After putting the car back in its corner in the racing department, I joined von Hanstein for lunch and he said : “You could buy one exactly like that, if you like, except that it would not be worn out and it would have doors” !
Continuing on their theme of development through racing, an experimental Carrera G.T. was run in the 1,000-kilometre race at Nurburgring using an engine with the bore enlarged to 87.5 mm., giving 1,600 c.c., and having a plain bearing crankshaft instead of the normal Hirth roller-bearing one. As the roller-bearing crankshafts have now been dropped completely from the production 1600 and 1600 Super engines, this step with Carrera engines was obvious, but as yet it is not ready for production; perhaps by the end of the year. The interesting thought is—when will the low-pivot rear axle be available in production, for all good things on the works cars come to the public in the end. It was not many years ago that Porsche won the Liege-Rome-Liege with a special car having a four-camshaft engine; now you can buy that engine over the counter. Before that the early Porsches had crash-type gearboxes and at one race a factory car appeared with a synchromesh box, and now all Porsches have the-all-synchromesh box, and so it goes on—design, racing, development and production. It is not surprising that the end product is an exceptional car for those people who like fast motoring and can drive.—D. S. J.
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