X-ray spec -- McLaren M19

Ralph Bellamy designed this car when F1 was still a sideline for the team. He explains to Keith Howard the problems this caused.

In 1971 Bruce McLaren Racing began its first year without its founder. Bruce’s death in a Can-Am testing crash at Goodwood the previous June had been a body blow, but the company he had created was big enough and resilient enough to cope. International in more respects than the many nationalities involved in it, McLaren competed in Can-Am and Indycar racing in North America, as well as Formula One in Europe.

Australian Ralph Bellamy joined the team from Brabham at the beginning of 1971, and just a year later returned whence he came, for reasons he describes opposite. Recruited to the F1 project, he soon discovered where it ranked in the Colnbrook pecking order.

“Can-Am was the big deal at the time — that was top of its heap,” says Bellamy. “After that came Indycar racing. In terms of company policy, resources and kudos, F1 was bottom. So if any research money was going to be spent, it wasn’t on F1. It was the opposite set of priorities to most of our competitors.”

Bellamy found himself in sole charge of designing the new M19 and determined from the outset to equip it with an innovative rising-rate (progressive) suspension system front and rear. The car’s inboard springs were conventional linear types but Bellamy’s novel actuation system compressed the spring and damper by an increasingly greater factor the more the wheel rose in bump. At the front the top wishbone was extended inboard of its inner pivot, where it connected to one end of a short pullrod. At its other end the pullrod linked to the centre of a rocker arm, the inner end of which was pivoted to the chassis and the outer end to the top of the coil-over-damper unit. At the rear a different arrangement had to be contrived to fit the available space, but Bellamy spent many hours at the drawing board ensuring both ends of the car had the same rate curve.

As it turned out, the decision to use rising-rate suspension was only half right. McLaren wasted most of 1971 failing to get to grips with the car’s unfamiliar set-up requirements, leaving team leader Denny Hulme a lowly ninth equal in the drivers’ championship. Only in ’72, with the suspension problem sorted, did the car realise its full potential, with Hulme racking up three podiums and the team ending the year third overall…

Ralph Bellamy:

“Formula One cars were sprung very softly in those days. Typically we used springs of 300-350lb/in stiffness equivalent to wheel rates of about 200lb/in and we ran quite large ride heights. We had designed the car to run 3in ground clearance at the front and 3.5in at the rear, something like that. Even so, with a heavy fuel load under braking you were smacking the nose into the road unless you used bump rubbers in the suspension. When a rubber comes into action, it does so rather suddenly. Unless you have the opportunity to do lots and lots of testing and get the rubber lengths and stiffnesses just right, the balance of the car — the roll stiffness distribution front to rear — can vary as it rolls onto the rubbers in a corner. But if you have a progressive spring rate you have a smooth change in stiffness; there are none of the sudden notches in the rate curve you get with bump rubbers.”

“Throughout that year we had a tyre vibration problem that we tried to eliminate. But I came to understand that you only got tyre vibration when you were generating lots of grip. So I asked Denny. ‘What’s wrong with tyre vibration? Why is it such an issue for the driver?’ He said. ‘Mate, you can’t breathe!’ When you were strapped into the chassis with this high-amplitude, medium-frequency vibration coming through it, you really couldn’t. Eventually Goodyear fixed the problem when they realised that the relatively flat tread was distorting. They changed the construction to put more crown into the tread area: that cured it.”

“When I joined, McLaren was still run the way that had suited Bruce. He and his crew made decisions on the basis of what they could see and hold in their hands. I came from a different school where you designed things, produced drawings and the parts were made, assembled and used. With the M19, all the good old boys were flat out building Can-Am and Indycars, so we were able to work away quietly without interference. But later in the year, when everyone else left for North America, I was assigned to design an F2 car for Trojan. I was well aware what was needed because we had made very good F2 cars over at Brabham. I’d designed the car and we’d started to build it when I had a minor traffic accident and was off work for a few days. When I got back, the crew had returned from North America. Teddy (Mayer, team manager) told me, ‘We’ve made some changes on the F2. Fixed it up.’ It transpired that they’d all had a go at it and produced a real mess. That was the end for me: I was never going to work under those conditions.”

Although the M19’s Matra-like ‘Coke bottle’ shape was Jo Marquart’s concept, the rest of the car was Bellamy’s design…

“At the start of 1971 Jo was in charge of the F1 side and I went to work with him. I’d only been there a couple of weeks when I realised that he was busy on something that had nothing to do with McLaren — his Huron project. I told him that If he was going to leave I should design the F1 car as I’d rather be working on my own mistakes for the rest of the year. He was happy with that because he wanted to get on with the Huron.”

The principal reason for the bulbous side tanks was that they helped concentrate the fuel mass where it was wanted, but they also increased the chassis’ torsional stiffness…

“A car like the M19, which was physically big, was going to be stiffer than a car like the Lotus 72, which was slim. We were aware of this but I don’t remember ever measuring the car’s torsional stiffness to prove it.”

“The rear wing had two aerofoils a large and a small element. If you look in the textbooks, that’s how classic high-lift wings are supposed to be. The aerofoil sections would have been standard NACA ones, the 4412 or similar — that was a popular choice. We did not use the same section at the front because there you had to get a 1.5in steel tube through the wing as its main support and pivot. So you first chose the chord you wanted, then went looking for a section that had a large enough thickness:chord ratio to accommodate the tube. We weren’t able to do any aero testing on the M19 — that would have been the exception rather than the rule in those days. The first time l ever went to a wind tunnel was at Lotus.”

“The progressive springing worked very well at the front of the car but it didn’t work well at the back, although we only learnt that late in the year. It wasn’t really clear until we did a test with Mark Donohue at Silverstone, once Roger Penske had agreed a deal to get him a drive in the M19 at the Canadian GP. He said the car was oversteering a bit, so we put more rear wing on it. He then said it was oversteering more, so we put even more rear wing on and the same thing happened — more oversteer. We thought. ‘What’s going on? There must be a message here somewhere.’ We sat down and had a brainstorming session and decided maybe it was the rising-rate springing at the back. The more wing you put on the more it pushed the back of the car down into the stiffer part of the rate curve. Overnight they put an M14 rear end on the car and we went to test at Goodwood. That improved the car quite dramatically, and that’s the way they ran it, pretty much through 1972.”