[By means of which the Continental Correspondent, while he is motoring abroad, keeps in touch with the Editor.]
Calling in at Stuttgart recently, just after the announcement of the Mercedes-Benz C111 with the three-rotor Wankel engine, I met Rudolf Uhlenhaut, who is head of Daimler-Benz Research and Development, as well as being a director of the firm. “Look here,” he said, “we are just going out in the C-one-eleven to try some modifications, why don’t you come along?” I didn’t need a second asking. We got into his 280 saloon to go round to the experimental shop and as we were turning round the low droop-snoot of the C111 appeared round a corner, followed by a white saloon Mercedes-Benz. After being introduced to Dr. Liebold, the engineer in charge of the development on the C111, he took Uhlenhaut’s 280 and I got into the passenger seat of the mid-engined coupé. You sit very low in a hammock-type seat that has adjusters on each side that pull the seat-back up and round each shoulder rather than merely change the angle of the seat. The scuttle seemed rather high, but Uhlenhaut pointed out that the car was very experimental and many things would be changed as development continued. We shot out of the main gate, and through the back streets of Stuttgart he took the three-rotor Wankel engine up to 7,000 r.p.m. in first and second gears, mentioning that the engine was giving 280 h.p. DIN and that this was early days and only the beginning development. Second and third gears were all that were needed to get us swiftly out of the town and up on the plateau to the south by the airport, where we waited for Liebold to catch us up. Discussing mid-engined coupés while we waited I enthused over the Rover BS6 that I drove a little while ago and Uhlenhaut asked about its suspension and ride characteristics, saying that it was easy to design a car for good road surfaces, and that the standard of English roads was very high. I assured him that one of my criteria of car design was high speed over bad roads and that the Rover mid-engined coupé had come out well. When the two white saloons had joined us we set off down a small lane and on to a long stretch of very bad road, with bumps, holes and undulations galore, over which the odd local vehicle was going carefully at 30-35 m.p.h. With a high-pitched whine from the Wankel engine, sounding not unlike a large DKW two-stroke, we pounded up and down this rough road at over 100 m.p.h., the suspension feeling very controllable but a bit hard, and Uhlenhaut said that if they produced the C111 it would be a sports car, that could be driven anywhere by anybody, not a touring car nor a racing car, and he agreed that since the 300SL gull-wing coupé they had not made a proper sports car. The suspension of the C111 follows classic racing lines and has all the desirable qualities built into the geometry, such as anti-squat at the rear when accelerating, minimal camber change, anti-dive at the front under braking, no castor-angle chance or toe-in under suspension travel; all things that the modern racing car has.
After this demonstration of suspension characteristics Uhlenhaut stopped and said: “Here, try it for yourself. First gear is rather high and the engine does not develop much torque under 2,500 r.p.m.” My E-type Jaguar has a high first gear, but produces torque at 600 r.p.m., so you can take off gently like a steam-engine, but the old six-cylinder engine lets you know when it is doing 5,000 r.p.m., and at 5,500 r.p.m. there is quite a bit of pandemonium. To get the C111 away from rest you need to use the tachometer and feed the clutch in steadily. It is not difficult, not does it produce any problems, but it comes in the small-car category, like a Lotus Elan or Europa. Acceleration is very smooth and deceptive, being a continuous push in the back that gets firmer and more persistent as the revs rise. Once past 5,000 r.p.m. it becomes very persistent, up to 7,000 r.p.m., which is the rev-limit at present and some quick snicking-about in the five-speed ZF gearbox produces performance that I put in the “high-performance” category. To get clear of the Stuttgart area we took to the Autobahn and headed east towards Munich, but it was mid-morning and holiday time so the traffic density prevented anything over 120 m.p.h. Fifth gear was unnecessary and fourth only just usable, for Uhlenhaut said: “If you want to enjoy the car keep the engine up around 7,000 r.p.m.,” I was very conscious all the time that there was a white Mercedes-Benz saloon in the mirror, which I assumed was Dr. Liebold, and I thought to myself that he must have been flogging Uhlenhaut’s 280 saloon to be keeping up with us! Down beyond Ulm we turned off the Autobahn and paused before heading for some mountains, and found it was Dr. Leibold who had been in my mirror, but shortly after leaving the factory he had changed cars, from Uhlenhaut’s 280 to a 300SEL 6.3-litre V8! It was the saloon that I had seen following the C111 out of the experimental department. “There is less traffic here,” said Uhlenhaut, “go off on your own and really try the car, we will follow in the six-point-three,” and as I zoomed off to the smooth hum of the Wankel engine I said to myself: “I bet you will.”
The driving characteristics of the Wankel engine are very much like a two-stroke engine, in as much as there is a very slight delay to throttle response, even in the high r.p.m. range, but this is very easy to become accustomed to. The smoothness and constant power output at peak speeds on the Mercedes-Benz Wankel engine is really impressive, like a turbine, and 7,000 r.p.m. was a good round figure at which to keep it spinning, The layout of the transmission is like most racing cars, with the gearbox sticking out the back, so that the central gearlever suffers from being a long way from the selector mechanism and the gear-change is nothing to rave about. However, the ZF unit is very much a temporary expedient, and later when I said I felt that the time was long overdue for infinitely-variable automatic transmission and torque-converters, so that the engine could run at constant speed, Uhlenhaut said: “Yes, of course, and the Wankel engine would make an ideal constant-speed unit, like a turbine.” The handling of the C111 was just as one would expect, having all the desirable characteristics of the mid-engine layout, with good balance, instant response, good straight-line running, negligible roll and nice steering that let you feel what the front wheels were doing. This particular C111 was running on special Michelin radial tyres, not because Daimler-Benz have fallen out with Continental or Dunlop, but because they are still experimenting, and part of the experimentation on this particular car was that it was running without a rear anti-roll bar. The Daimler-Benz engineers seem to have achieved a much higher standard of adhesion on the rear to that on the front, and the lack of anti-roll bar accentuated this, so that under provocation the front would slide outwards on a corner. Under normal fast motoring one never reached this limit, but a large-radius mountain hairpin offered provocation. Discussing this later Uhlenhaut said: “When you get back to the factory try the car on our test-track and then we will fit a thick rear anti-roll bar and you can try it again.” The point being that with fully-adjustable racing-type suspension a car’s characteristics can be altered to suit any driver or condition.
Having driven the car sufficiently to know that I would like one, for as you know I have been a mid-engined enthusiast as long as I have been a Wankel enthusiast, so the combination of the two must be right, I suggested to Uhlenhaut that he drove back, so that I could see how it really went. I have long been a great admirer of Uhlenhaut’s driving ability, especially in his own cars, and the return run to Stuttgart was no disappointment. Dr. Liebold sat behind us in the six-point-three for traffic kept Uhlenhaut down to 135 m.p.h. on the Autobahn. The reaction of people on the Autobahn was most interesting as we came up behind them; most of them swerved sharply into the slow lane and faces were pressed to the windows with eager interest, for though the C111 is still experimental and a research vehicle it proudly carries a three-pointed star on the nose. Those who were cruising their 250SE saloons along at 100 m.p.h., to be overtaken at 125-130 m.p.h. by a low, sleek, black and white projectile, closely followed by a V8 300SEL saloon, must have thought: “Oh, ho! The development lads from Stuttgart.” I wondered how many of them realised that the C111 was being driven by a Director off Daimler-Benz A.G. and the Chief Development engineer responsible for them being so content with their production Mercedes-Benz saloon. There were those who glared out of their cars and were obviously thinking: “Maniacs! Travelling at the speed on the public highway.” I wondered about them, too. In 1955 I travelled the German Autobahns at 130-150 m.p.h., on test with Stirling Moss in a sports/racing 300SLR Mercedes-Ben, closely followed by Engineer Kosteletsky on one of the Mexican road-race 300SL gull-wing coupés, and the same people in 200A Mercedes-Benz saloons cruising at 85 m.p.h. thought we were maniacs then. It is thanks to so-called maniacs that Mr Everyman now has a 280SE, which is so superior to his old 220A. I thought it was very significant that 14 years ago I had been in the latest Daimler-Benz racing car, being followed by an obsolete sports/racing coupé, and now I was in the latest sports coupé from Daimler-Benz, being followed by a production saloon car. I wondered how long it would be before its V8 power unit would be obsolete? Not long in terms of automobile engineering history is my guess.
Just before Stuttgart we turned off the Autobahn into a small village and stopped and Uhlenhaut said: “I’m leaving you now, I’ll see you later this afternoon on the test-track.” Just as I was wondering where he was going to walk off to, I saw this 280 saloon parked under a tree with a Daimler-Benz mechanic at the wheel. Uhlenhaut motored off, Dr. Liebold drove the C111 and the mechanic took the six-point-three and we returned to the factory. We were 1½ hours later than expected, but that is typical of Uhlenhaut, for if he is enjoying something and has no urgent appointments time becomes personal, which is as it should be. I tried the C111 on the circular test-course, which always exaggerates things, and it was impossible; a boot-full of throttle in second gear pushed the front wheels straight off at a tangent. After a very late lunch I tried again, this time with a thick anti-roll bar on the rear and the same situation in second gar proved controllable and stable, albeit on full lock. Round the normal part of the test-track it was quite impossible to make the front end break away and without the holiday traffic about I was able to really extend the C111 and it was impressive. I was very reluctant to stop playing games, but was forced to do so as Uhlenhaut was waiting to show me how the Wankel engine is built and one running on a test-bed, and, after all, it is the three-rotor Wankel engine which is the significant part of the C111 Mercedes-Benz.
Usually when I leave Stuttgart I find I have got three-pointed stars imprinted on my spectacles, but this time I found I had three-lobed rotors imprinted on them! It was only a few years ago, at Neckarsulm, not far from Stuttgart, that I first heard a Wankel engine run, and had the chance to play with one on a test-rig. That was at N.S.U., the first people to be convinced of the future that lies in the Wankel engine. I was as convinced then as I was when I saw the first jet-propelled aeroplane, and as much I was when I first rode in a mid-engined coupé. Next year is the start of the nineteen-seventies, and I feel sure that the next decade of automobile engineering is going to be a significant one.
Normally these letters to you cover my activities over three weeks or more, but this one has dealt with only one day, and only a small part of that day anyway, but it’s a significant part of a most interesting year.—D. S. J.