NOTES ON THE CARS AT JARAMA
THE 1970 season of GP racing continues to be full of mechanical interest, and brightest star on the scene is undoubtedly the Lows 72, two of which made their debut in Spain. The Lotus 72 is entirely new and also breaks new ground in current Grand Prix car design, at a time when a design-doldrum was perilously near. It is the result of knowledge gained from the Lotus 49, the Indianapolis cars and the 4-w-d Lotus 63, along with a lot of radical new thinking by Colin Chapman and his chief designer Maurice Phillipe. Fundamentally the car comprises a monocoque aluminium cockpit section, with the Cosworth V8 and Hewland gearbox forming the rear of the car, but there the similarity to any other GP car ends. The cooling of the engine is done by two radiators, one on each side of the cockpit rear-bulkhead, with 6-in, long water pipes from the front of the engine to the radiators, thus doing away with the many yards of piping and water that are normally employed when using a radiator in the nose. The two radiators are in ducts that catch the air flow along the cockpit sides, a system employed, on many Group 5 Sports cars and Group 6 Prototypes, where the all-enveloping bodies encourage this layout. By reason of this radiator positioning the nose of the car is formed in an accentuated chisel shape, as on the Indianapolis turbine Lotus cars, and apart from giving the driver a much better view forwards it also means he does not have to sit in the flow of hot air from the radiator, nor suffer the heat of hot water pipes on each side of the cockpit. This is particularly advantageous to Rindt, who suffers badly from cockpit heat and breathing hot air. On top of all this the body shape of the 72 follows certain aerodynamic theories of increasing cross-sectional area towards the centre of the length. Suspension front and rear breaks entirely new ground in today's GP racing, for coil-springs have been discarded and in their place torsion bats are used, these being of the compound type with a solid bar inside a thin-wall tube, the bar and tube being splined together at one end and free at the other end. The free end of the bar is splined to a link mechanism joined to the wheel supporting wishbones and the free end of the torsion tube is splined to a short lever anchored to the car, this lever having a screw adjustment for setting the suspension level. As the road wheel rises the link mechanism twists the torsion bar, which in turn twists the torsion tube, the load being absorbed in the anchor point on the small framework around the engine bell-housing that carries the rear suspension, and on the bulkhead at the front end, the fore and aft systems being similar. The advantages of the compound torsion bar and tube are that it halves the required length of a single bar, and all the loads are fed into the car at a single point, rather than applying a twist along the car. This compound system was used on the 1938 Vanwall Ten, on the independent front suspension on the Dubonnet system. Torsion bars give different springing characteristics to coil-springs, Which Lotus feel are more desirable with their new thinking on suspension geometry, which employs anti-dive characteristics under heavy braking, as on the Jaguar XJ6, and anti-squat characteristics at the rear under violent acceleration, all this aiming for a flat and level ride which will not affect wheel camber angles under suspension movement, and thus upset tyre characteristics. The front suspension, which is of the double wishbone type; is mounted on a light framework of square-section tubing attached to the front of the monocoque and a light tubular link mechanism runs inwards from the top wishbone to the torsion-bar linkage, the bars themselves projecting rearwards into the monocoque, among the petrol tanks and more or less parallel with the driver's legs. At the rear the hub carriers are supported on an upper wishbone, with its apex on a pivot on the bell-housing cross-member, with a single forward-facing radius rod. At the bottom there are very wide-base wishbones, the base pivoted on a framework on each side of the gearbox, with the apex on a ball-joint on the hub carrier. A link from the top wishbone runs down to the torsion-bar linkage, the bar on each side sticking out the back under the exhaust pipes.
Taking a leaf from the 4-w-d Lotus, all four brakes are mounted inboard, to save great lumps of unsprung weight, and have the rear calipers mounted on the gearbox. At the front the discs are carried on cast magnesium carrier plates on each side of the footwell in the nose of the monocoque, with the calipers hung underneath, and tubular shafts, similar to those at the rear; join the discs to the hubs. Ducts in the tapering nose scoop air on to the brakes and it is then centrifuged out of slots in the body above the discs. Battery, tire-extinguisher and brake and clutch fluid reservoirs are concealed in the nose of the car, which has no opening in its leading edge. Another Lotus innovation is the triple-bladed rear aerofoil, the lower one being attached to the car while the upper two are adjustable and exert their downthrust through the magnesium side-plates joining them to the lower blade. A major problem arose in testing in Spain when the front brakes overheated and melted the Tufnol distance-pieces between the discs and the inner universals on the front shafts. Replacing the very light solid brake discs by heavier ventilated ones cured this problem, by lowering the overall temperature, and metal distance pieces replaced the Tufnol.
Another brand new car was the McLaren-Alfa Romeo, built for de Adamich by McLaren Racing, this using a 1969 M7A monocoque, with the 3-litre V8 Alfa Romeo engine joined to a Hewland gearbox acting as the stressed rear part of the car, the suspension layout being as on the Cosworth-powered M7A cars. The four-overhead-camshaft Alfa Romeo engine is as used in the Group 6 Tipo 33-3, and fits very neatly into the layout, taking up no more space than a Cosworth V8. The exhaust system from each bank of cylinders runs under the suspension and ends in a megaphone, and an alternator is driven off the back of the Hewland gearbox, while Lucas fuel injection is used, mounted in the centre of the vee. The car is designated M7D/1.
Other new cars, rather than new designs, were a third Type 153 BRM, for Eaton, to replace the Type 139 he has been using, his car retaining BRM green with gold nose fins and rear aerofoil, and two new March 701 cars. The Tyrrell team had their third car, 701/6, and the STP-March had a third car, number 701/7. This last car was built of 20 s.w.g. aluminium, instead of the standard 18 s.w.g., a saving of 20 lb. on the monocoque, and was designed with revised rear suspension. In order to reduce unsprung weight at the rear the brakes are mounted inboard, on special Hewland side-plates for the gearbox, as on the McLaren M 4A, and this has entailed the use of a parallelogram tubular bottom suspension member, to clear the disc at the mounting points. The geometry of the suspension has been altered to try and overcome the rather twitchy rear-end steering of the first layout. The other STP-March team cars, 701/1 and 701/5, were also modified to this new rear end, as were the new Tyrrell car, 701/6, and the Stewart car 701/2, while 701/4 was left with the old layout. All the new rear ends use standard universally-joined, sliding ball-splined drive-shafts with no rubber "doughnut" drive joint. The STP-Oil Treatment Special, or 701/3 driven by Andretti, retained the old suspension and brake layout, but used a new type of American drive Shaft with enclosed universal joints and no "doughnut". The Tyrrell cars had modified nose fins which were adjustable, in direct opposition to the standard March arrangement of fixed fins and adjustable trim tabs.
The remaining cars in the entry list were those seen in South Africa, the de Tomaso having undergone some revision to its suspension geometry, with a wider rear track, the two BRM team cars having undergone the Yardley perfume treatment, as seen on Oliver's car at Brands Hatch, the 12-cylinder Matras being the same pair, as were the two Ferrari 312B models that Ickx had the use of. McLaren had to build another M14A after his Brands Hatch accident, though Hulme kept his same car, and Brabham and Stommelen had the two works BT33 cars. Soler-Roig was loaned the works Lotus 49B/R10 and R6 was a spare, which Miles used in practice while his 72 was being modified. The second Lotus 72 should have gone to Rob Walker for Hill to drive, but the factory did not consider it ready for release to a private team, so used it themselves. The STP-March team were using the new lightweight car as an experimental spare car for Amon to drive, and Tyrrell let Servoz-Gavin bed-in his new car, keeping 701/4 as a spare for Stewart.—D. S. J.