No. 6 The Auto Union

EARLY last year the four well-known German motor firms of Audi, D.K.W., Horsch and Wanderer were linked up in a great combine known as the Auto Union, and though the indi

vidual companies continued to produce many of the models which had previously been made, their technical and financial resources were pooled. About this time the Chancellor was making a great effort to revive the German motor industry, and there could be no more convincing proof of its healthy state than to take part in international motor races. Almost at the same time as the Mercedes started to take shape therefore, an Auto Union racing car was being evolved.

The chief engineer of the Auto Union was Doctor Ferdinand Porsche, a designer who had already shown that he had original ideas about racing cars. As far back as 1926 he had produced the Benz ” Drop” racing car, a single seater blunt in front and tapering off to the rear, with the engine carried behind the driver. It was not a great success at the time, but the lessons learnt from it came in useful later on.

The new car was built with the utmost secrecy, and not even Stuck and his fellow drivers saw it until last December, when it was given a short run on the Niirburg track. Surprisingly low and following the lines of the” crop” car already designed, it was a complete break-away from current racing practise. The car was taken to Italy for its preliminary road tests and. after some ten days high speed work on Monza reached a speed of 155 m.p.h. on the Milan-Varese Autostrada. A final proof of its qu:ilities was given by Stuck’s successful attack on the World Hour Record on the Avus road in March, where it put up the terrific speed of 134.9 m.p.h.

Unfortunately, like the Bugatti and the Mercedes, the details of the Auto Union are still very much “on the secret list,” but we have received from the makers information revealing some of the problems to be faced and the solutions evolved by the designer of a modern racing car. The last International Racing Formula lays down the following requirements :

1. The maximum weight of the car without fuel and tyres shall not exceed 750 kg.

2. The cross section of the body at the driver’s seat must be at least 850 by 250 mm. Comparing the weight limit with that of two-seater racing cars of the present day, e.g., Mercedes S.S.K. 1,400 kg., Bugatti and Maserati 1,100 kg., it is clear how great the difficulty would be in

order to reduce it by 30%. Present day constructional methods were deemed out of the question, and the solution was found in the shape of a new lay-out and a careful saving of weight on each single item. Much weight was saved in the transmission, not to speak of the ease with which the driver’s seat could be kept low, by mounting the engine at the rear. The fuel tank was placed in front of the driver on a level with the centre of gravity, so that the amount of fuel remaining should not affect the handling of the car, making

the best use of a space otherwise unused. The driving seat is well placed for good visibility, ease of handling and good streamlining in front of the petrol tank, while the radiator occupies its usual place in the front of the machine. Large ports in the sides of the scuttle allow the air to escape.

The frame is tubular and is braced by tubular cross bracings, and this construction, and particularly the rigidity of the joints provides very great bending and torsional stiffness. This is particularly necessary on the Porsche Wagen, since the light metal streamlined coachwork plays no part in stiffening the vehicle.

In order to obtain good road-holding, directional stability and certainty of steering it was considered essential to have independently sprung and driven wheels. The front wheels swing in planes parallel to the side members of the chassis and are therefore free from tramp or shimmy. The actual suspension is carried out on the Porsche torsion rod principle. There are two hollow tubes one above the other which serve as the front axle. The wheel pivots are carried on swinging arms pivoted on the ends of the hollow tubes and the movement of the arms are controlled by a steel rod which passes through them and which twist or untwist as the wheels encounter road-shocks. The position and design of the steering pivots, the

makers claim, makes the steering unaffected by the movement of the wheels. Hydraulic operation is used for the brakes.

The back wheels swing vertically on axle tubes operating through slots in the differential casing. Engine and braking reactions are transferred from the wheels via the axle tubes to the differential casing, and so to the chassis. Vertical movement is controlled by a single leaf spring which is carried above the axles.

The advantages of a rear-engined car were manifest, but brought with them limitations of length and breadth. The power of the modern racing engine makes even its mounting a matter of some difficulty, and the makers therefore decided to use 16 cylinders in order to get as smooth a torque as possible. The two blocks of eight are set at 45 degrees and have a total capacity of 3,080 c.c.

This unusual construction brought with It other advantages. Being compact, it was easily built into the space at the back of the body, which was unusually narrow on account of the streamlined body. In addition the designer acchieved a short crankshaft which was free from the usual periods. The engine is carried in front of the axle, but is started by a handle which goes in at the rear end of the tail. In the construction of the engine light alloys were extensively used. Engine gearbox and back axle are built in one

unit, and a five-speed gear-box is used.

The lines of the coachwork have een determined as the basis of extensive research in a wind tunnel and follows the most efficient shape discovered in this way, as far as practical considerations of racing will allow.

The equipe consists of Stuck, Prince zu Lehaingen and Sebastian or Burggaler, with Willi Walb, who at one time used to drive the Benz streamline car, as team manager. Momberger was also mentioned at one time as a likely member of the team. Stuck’s successes on the Austro-Daimler in 1928-29-30 are too well-known to need further comment, and it will be remembered that he visited Sheisley Walsh in 1930 and gained one more victory towards the European Hill-climbing Championship. He was equally successful in the following years on Mercedes.

Sebastian has generally been spare driver, and in 1931 was with Caracciola in the Mille Miglia and various other races and hill-climbs. Leiningen gained most of his experience on Bugattis.

Unfortunately the Auto Union cars were not ready in time for the Monaco Grand Prix, but will be closely watched at the French Grand Prix, while there is a possibility of their being ready for the Avus Race in the middle of June. These rearengined machines may well be the pioneers of a new racing car era.