Interview: Design on the Hills, translated by Mike Pilbeam
Looking at a top class hill-climb car, even with the most casual of glances, reveals that science has arrived in this formerly quiet backwater ot motor sport. The elongated cars immediately look ditterent from their circuit counterparts with their rearward extensions of the back aerofoils and bodywork devoted, through deep and graceful scallops, to developing the maximum possible downforce. The top runners and riders are propelled by an attractive variety of engines, but the sheer competitiveness of the sport is slowly but surely "bringing out the racers." Thus the lightened and aerodynamically modified machines snarl through the rounds of the top class championships to the note of a FordCosworth DFV (perhaps of 3.3 litres), or a thoroughbred Formula Two four cylinder from Brian Hart or BMW GMBH, rather than the base note of the 5-litre V8s so popular in previous years. Never has competition been fiercer on the hills, especially in the pursuance of vital hundredths of a second during a Top Ten RAC Championship run-oft at the close of a day's sport. Inevitably the top designers have been drawn Into the eye of the fiercest competition, so that the chassis match the phenomenal acceleration and braking forces available virtually "off the shelf " today. Pre-eminent at present are former Tyrrell and Ferguson designer Derek Gardner, and freelance racing car designer Michael Pilbeam, who has worked for many in circuit racing, including Lotus and BRM.
Pilbeam's name is the leading one in this branch of the sport. He has been converting cars for the hills, usually from a Brabham or March basis initially, since 1975. Now he has reached the stage of drawing complete hill-climb specials with their own type numbers and a wealth of Pilbeam experience behind them. the cars MP31-02 (Alister Douglas-Osborn's) and MP31-01 (awaiting delivery to Peter Kaye) are professional monocoque machines, drawn around the familiar Cosworth DFV Grand Prix V8, but carry an unusually high degree of fabrication by the manufacturer. This is partly out of idealism, and partially because, based in Bourne, Lincs, Pilbeam can capitalise on the obvious pool of skilled labour left over from BRM's heyday.
To see someone like Alister Douglas-Osborn, the current RAC Hill-climb Champion, charging such a shiny and sophisticated racing car through the unprotected trees and natural hazards is a subject worth returning to in itself, but what of Mr Pilbeam? What sort of man can bring effective thinking to the special problems posed by ascending hills at unnatural speeds?
A very experienced man. One who has worked at every stage of the game from putting together his own 1172 racing specials to the hothouse of Lotus Grand Prix car draughtsmanship. Mike Pilbeam was born in 1937 and lived tor many years in West London. Today he lives, as he has done since he left BRM in 1974, at Northorpe a few miles outside Bourne. Of his interest in competition cars Mike says it was unusual because, "I didn't know they existed until I was 21, or so. Then I got very keen indeed."
That enthusiasm led to the construction of a small sports car, which inevitably became the further modified base to go racing. Until he moved into the present single-storey workshops at Bourne his designs carried just the prefix R (yes, for racing) but from 1977 on his initials served in front of the type numbers. His first car, R1, "took about 18 months to build. I even had to go to evening classes to learn how to weld!"
The completion of the first car in 1959 soon led to others and an association with Tony Gould, then promoting the construction of an i.r.s. layout. Gould nearly won the 1172 title with one of their cars during the early 'sixties while Mike "enjoyed my couple of seasons racing, but never felt I was going anywhere. Perhaps if I had started earlier ..." this wistful note struck by the performances of contemporaries Brian Hart and Len Terry.
The competition bug had now insinuated itself firmly and Pilbeam proceeded to his first professional designing job. In 1963 he had been accepted by BRM as a stress engineer. After a year Tony Rudd moved him on to work on a 4WD version of the current 1 1/2-litre Formula One car. This was an intriguing project as Mike recalls today, "we found just the same problems' as all the major teams discovered when they tried 4-WD years afterwards. Lotus, McLaren, even Cosworth, nobody ever got over the problems of balancing the car and gaining the benefit of 4WD. If you could control the car easily, then it usually had the torque split so biased towards the rear wheels that it was not worth the weight penalty of 4-WD." Later the 4-WD BRM found a new lease of life in hill-climbing with Peter Westbury, who secured the RAC title with it under some supervision from Pilbeam. Mike says now. "It was the first car I had total responsibility for, but we used the 1920 c.c. enlarged version of the V8 Grand Prix motor rather than the usual 1 1/2-litre. The car was on loan to Peter initially, but I believe he bought it and eventually sold it to Peter Lawson. It's now in Tom Wheatcroft's museum at Donington." Obviously the lessons of 4-WD on the hills were not lost on Pilbeam, but agility and low overall weight appear to count for more today, mainly because of tyre improvements.
From BRM Pilbeam journeyed to Essex, working in the advanced planning side of Ford at Minton. "That was fine, until the planning was shifted to Germany," he remembers. However, he did meet a number of enthusiastic kindred spirits who were mainly Involved in saloon car racing, "But mainly I did it for the money," he admits rather more candidly than most ex-Ford employees.
By February 1969 Pilbeam was moved even further east, facing the challenge of Lotus. The 4-WD idea came up again while he was there; but even with Maurice Phillipe heading the department and Geoff Ferris working on the problems with Pilbeam as well, the Chapman equipe did not produce the effective 4-WD racing answer, though as we all know Lotus did achieve quite a lot With the 49B and 72 models, which also fell within Pilbeam's scope.
Early in 1972 Pilbeam left Lotus for a short period at Surtees (where he worked on the characteristic flat outlines of the TS9) before returning to Lincolnshire and BRM in 1973. When forty Southgate left, Pilbeam accepted a job managing their design office. At first they ran modified versions of the P160, but Mike did get the chance to do a complete Formula One machine, the BRM P201. "Like my first cars, it's still being used today," Mike commented with a wry grin! He is also proud of the fact that it was probably the only Grand Prix inboard front brake installation not to suffer any failures.
Pilbeam Racing Designs Ltd. was established at home when the Stanleys came into control at BRM late in 1974. Pilbeam says, "I always wanted to work on my own, and it turned out to be quite a lucky time at which to make the move. There was a long phone call about Formula Atlantic from Tom Wheatcroft. I was not quite sure where we were getting with the conversation, but Tom seemed very interested. He asked me if it was possible to build a car quicker than the opposition. 'Do you want me to?' I countered. 'Yes, that's it.' click and he was gone! I didn't see Tom for nearly two months after that, we just got on with R18," Pilbeam reports, smiling gently at the memories of a man who came to represent quite a part of Mike's freelance business life.
From the design viewpoint hill-climbing makes some special demands, not least of which is that the venues vary tar more than those of modern race circuits. Surfaces are especially variable and this, plus the narrow widths at many climbs, has forced physical changes in car specification.
Mike prefaced the technical priorities with a few general remarks. "The biggest problem is to test and develop a car. You cannot buzz round for 10 laps and have a consultation. Even it you go to Somewhere like Cadwell Park for a few shakedown miles, it must be said that the car does not feel the same on a circuit as it will on a hill. When he's competing, the hill-climb driver just has to go fiat out for 40-60 seconds. It is rarely that he'll be composed enough for the kind of detailed impressions that you use in circuit racing.
"These drivers are also very brave. We will make a change and then the driver will have to try it out at 100% effort. None of that ease-it-round the first lap or so business. Balls-out from the start, and then try to remember it the car felt any better!
"I think the standard of development in hillclimbing is quite high at present. It did not matter before if the car was not spot-on, you could still enjoy some success. Now that's totally out of the question."
Untortunately the truth of that statement was all too clearly demonstrated for me by the performance of Douglas-Osborn's Pilbeam at Wiscombe in April. The car wasn't as finely tuned as its rivals, being rather newer, and it was impossible even for this talented driver to get back on even terms, even though the original problem was only a minor braking one.
Another general problem is that of traction and tyre temperatures. In a typical RAC Championship round the cars can have two different characters. The first is on comparatively cold tyres (especially at the front) in the well-spaced runs that are part of the competition, but which can quality them for the top ten run-offs. If they do set a time that is in the top ten and there are plenty left outside today, so money and no talent is no substitute for less money and more talent then the car will be running far more frequently and the front tyres will benefit, along with the brake pad temperatures and so on. Thus you can easily have a car that behaves one way early on and develops from an oversteering Mr Jekyll into an understeering Mr Hyde.
Weight reduction is listed at the head of technical priorities to make a good car for the hills. When Mike is converting from an existing Brabham or March circuit racer he finds: "It is usually the weight we can make the biggest improvement on. Compared with a circuit racing car we could save 150 lb. through the use of new bodywork, wings and suspension, plus the more obvious savings in fuel (we carry about 2 1/2 gallons) and other things that are needed in racing, but not on the hills."
The desire for fresh bodywork is also prompted by the need for extra downforce. Mike explains, "We have a bit more freedom than on a racing car under today's regulations. The desire for extra big and deep wings is allied to the fact that the cars must run over bumpy surfaces at comparatively low speeds, therefore needing that extra push down into contact with the tarmac. The speeds are not as low as some people imagine, though: at Shelsley Walsh the cars certainly get up to 130 m.p.h., and there are other places where they are nearly as fast.
"So, we cannot completely ignore aerodynamic drag while creating this extra downforce. You can easily stick things onto the main body that create a turbulence that upsets wing performance.
"I have learned some interesting things about aerodynamics on the hills though. Their effect can be pronounced even on a 30-40 m.p.h. hairpin, and here I am thinking particularly of the shaping used for the body sides. Cars in hillclimbing have to run at bigger slip-angles than on a circuit you only have to look at them twitching up hill to realise that. The important point is that there should still be stability even when the car is sliding, and this is one of the things our cars have managed to achieve.
"Obviously the Lotus `side-wing' downtorce system is worth studying and may be helpful on the hills as well, but I generally find it's much better to stick with your own thoughts and carry them through. At least you know what you mean. Unless you copy other things quite literally, there is a danger of misinterpreting the original design."
"The other really important area is that of traction, and by that I mean in terms of two wheels off the line, and one wheel out of corners. Frankly I cannot say an awful lot about the detail of suspension mounting points and so on, as that is our business. As you can see we use conventional thinking, so it is a matter of detail improvement rather than sweeping principles."
The question of tyre temperature is basic to an effective start and the practice of warming-up the tyres with dummy starts before the cars are aligned tor the real "off" is an integral part of hill-climbing today, though it may serve only to warm the tyre companies' hearts in some cases.
Rigidity of the chassis is a part of traction and here Pilbeam feels, "If the basic monocoque provides a good mannered circuit car then we have the basis for conversion to a good hill-climb chassis. Because of the bumps, and the tar lighter all-up weights, we do use much softer springs than you would expect in a DFV-engined car. In tact the springs are softened right off to the poundage used in Formula Two, and the weight of the MP31 is close to that in Formula Two as well at approximately 1,100 lb. Generally we are aiming at a soft ride with long wheel travel.
"One feature that does help adapt the chassis to hill-climbing is the provision of a narrower track. Compared with the Lec Grand Prix car we did for Purley, our similarly powered hillclimb car would be 6" narrower at the front and 4" less at the back." Aside from the fact that it is easier to thread the 470 horsepower machine along the often claustrophobic courses, the slimmer track also allows tyre temperatures to rise. "This would be dangerous in longer events, of course," says Mike, "but for our minute sprints it is acceptable and helpful." The car sits on a 102" wheelbase, but measures nearly 180" total, the rear wing extends 50" to the back!
Sometimes the root of a car's poor performance is not to be found in the higher realms of science, or in Mike's University-trained aptitude for solving mathematical problems. In one case — the effective and mechanically interesting March Formula 2-3.4 V6 of Chris Cramer — the car just never really did seem to go quite as well as Pilbeam had hoped. "The chassis rivets were later found to be coming apart in the monocoque, so the solution could have been a lot simpler than we thought!"
Pilbeam has sincere, and dramatically proven, beliefs in chassis strength. The Lec Formula One car that he did for David Purley had its first monocoque destroyed in what was officially described in the accident report as the worst impact to have been inspected. Purley's Lee went straight on at Becketts when the throttles jammed in practice for the British Grand Prix at Silverstone. That Purley survived at all can be fairly attributed to Pilbeam's design, though it certainly was not this modest man's point to push that fact forward. What he did say was, "That was an unbelievable accident speed. We have had a good look at the tub and learned a great deal from it, so that knowledge is now in the hillclimb cars.
"A year on the hills, though less in miles than those of a circuit car, is about the same in terms of wear on a car's structure owing to the rougher surfaces. Basically it takes us ten times longer than a big racing car manufacturer to produce a monocoque; a kind of strength through effort." He forbears to mention that the same kind of effort does find them a weight reduction, compared with a proprietary car, probably in the order of' 30 lb.
Remembering how attractive the qualities of a rear-engine car can be in terms of traction I asked how the weight was split front to rear on his current hill-climb designs? "At one time I did, progress toward a 30% front and 70% rear bias in search of extra traction, but now (as in Grand Prix racing) we are settling more like 34-35% of the vehicle weight on the front wheels."
Talking about the engines used today Mike Pilbeam expresses the view that, "The DFV must be the way to go in the long run. The little Hart and BMW four-cylinder engines can put it over the DFV now, but I think that ultimately the DFV, probably at 3.3 litres, will be the answer. Torque is a big factor on the hills and with the 3.3 you gain an excellent torque curve allied to a power output almost exactly that of a Grand Prix car today.
"The current 3-litre DFVs usually have slightly softer camshaft profiles to emphasise torque, at the loss of to or so horsepower, as compared with using the normal F1 type of camshaft.
"Even if you have four cylinders, because it could be more agile, I would still favour one type more than another. I think the Hart saves about 30 lb. and can be overbored, so that is the four to have in my view. If someone asked us specifically to do a BMW-engined car we would, but I prefer working with the Hart.
"I think you can forget the days of the big American V8s now. There are not many really serious ones left and the cars tend to be a bit cumbersome." Keith Duckworth really cannot have known what he was starting with his Cosworth V8, can he? First Europe, then America (courtesy of the turbo) and now the heights of the English countryside. Tomorrow?... Well, Alister Douglas-Osborn has been heard to observe that they have bigger, faster hills in Europe.
A look at the first MP31 hill-climb chassis inside the unobtrusive premises at Bourne displays a couple of points at which hills are so very different to racing. Although mounted perfectly conventionally, outboard at the front and inboard nestling alongside the transaxle at the rear, the brakes differ to modern single-seater practice, the discs constructed in the solid sans the usual ventilation slots. "We definitely do not need extra cooling," says Pilbeam, "but it is worth having the two separate calipers, each with twin pistons at the front and rear of the front disc brake. I did think of having a similar arrangement at the back, but it would have involved a major redesign."
The monocoque itself is in an ordinary NS4 alloy with lightweight glasstibre panels providing the deep curves of this distinctive design. The monocoque accommodates both oil and petrol tanks, neatly hidden behind the driver and beneath both protective roll-over hoop and body. "Moving the oil tank from its old exposed position helped the flow of air to the rear wing, as well as fitting in with the current philosophy of moving all major masses towards the middle to help provide a responsive car," Pilbeam confirms.
The suspension components are predominantly Pilbeam, including deep magnesium alloy uprights at the rear with the abbreviated driveshafts passing through them. The light tubular wishbones and links are also made locally and now benefit from the argon arc gas-welding process, allowing neater fabrication with less effect on the intricate T45 aircraft steel tubing that is to be laced together. Triangulated suspension arms are used front and rear, but the rear arms do not appear to have such a wide base as one would expect to find in a formula car, especially the top arms which teed into a single link leading outboard.
Koni dampers are mounted front and rear with settings dictated by Pilbeam to match the locally-wound and tempered coil springs, all mounted in conventional manner and inclined front and rear. According to one well-known owner ot a Pilbeam-modified hill-climb car, the traction offered by the extended rear wing pylon arrangement (the sideplates and second section adding even more ettect to its deeply dished aluminium contours) is phenomenal. "People thought I was playing about at one round, not trying until the final runs. The truth was that we'd discovered the hard way that Mike's extra aerodynamic aids added so much extra rear-end grip that we could literally twist the driveshafts oil the line, it I wasn't careful." Thus that man's car steps turther and further into Pilbeam's territory. Next it will want, and has received, thicker shafts, but without putting any weight on!
So we have the outline recipe for getting from low-lying A to the top of B in the minimum time. Pilbeam, and any of the other designers who may develop in this increasingly challenging sport, will be providing cars with the following "star features" in my imaginary brochure: *Low weight *High aerodynamic downforce *Extremely high standards of traction *A torquey responsive engine of thoroughbred racing ancestry, probably overbored *Solid disc brakes *4-speed gearbox and revised change pattern to avoid dog-leg *Narrow track *Soft ride *Instantly competitive *Rolling chassis, from £12,000 in MP31 trim.*
Just building and modifying hill-climb cars is not enough to keep the Pilbeam business on its own. Mike's design capabilities are used by some leading names in the racing car industry as can be (partially) seen trom the accompanying notes on design projects he has undertaken. Just a couple of names have been changed to protect the tee-payers where necessary.
Of necessity and inclination Mike Pilbeam will be back at racing circuits. throughout Europe shortly, happy to be involved in cars at the front rank of International racing once more, and doing his best to back British expertise and drivers in an area where such actions are not "the norm." We wish him the best of luck and thank him tor his hospitality while initiating us into the mysteries of hill-climbing today. —J.W.
P.S. Thanks are also due for the assistance of the Aston Martin Owners Club in providing such a superb event at Wiscombe on April 15th/16th, enabling me to study how practice and theory were inter-related.