Sweetness and light
All the best ideas start as a sketch on a napkin. In the summer of 1961, Lotus founder Colin Chapman held a meeting at a pub called the Maple Leaf Inn. The company was developing the Elan, due to be launched the following year. The new sports car was based around a backbone chassis – a strong steel box-tube running down the middle of the car, with an engine attached to one end. Over a pie and pint Chapman’s purchasing director, John Standen, made a simple but startling suggestion: imagine an F1 car with two box-tubes, one each side of the driver, connected by bulkheads. Chapman immediately leapt on the idea and started sketching.
A few months later, in May 1962, Team Lotus arrived at the Dutch Grand Prix with one of the most pivotal cars in F1 history: the Lotus 25. All Formula 1 cars at that time were built around spaceframe chassis, a complex latticework of welded pipes. And that includes Chapman’s other new car for the 1962 season, the Lotus 24. To the dismay of Chapman’s customers – who thought they’d bought the very latest technology – the new 25 turned up in Zandvoort and immediately made everything else obsolete.
Chapman had taken Standen’s basic idea and created a hollow, alloy sled that formed the lower half of the car, with fibreglass upper panels. A box ran down each side of the reclined driver, doubling as fuel tanks and extending rearwards to create a cradle for the 1.5-litre Climax V8. Three bulkheads and an alloy floor connected these pontoons, creating a single, fully-stressed structure. It became known as F1’s first monocoque single-seater, though Chapman called it – more precisely – a ‘twin-tube ladder-frame’. It was quickly nicknamed ‘the bathtub’.
Incredibly, Chapman’s tub was almost 14kg lighter than the 24’s spaceframe, and much stiffer. This torsional rigidity allowed Chapman to soften the car’s suspension, improving grip in slower corners. That other great innovator, John Cooper, wandered over to see Chapman’s new car in the Zandvoort paddock and asked laconically, ‘Where did you hide the chassis?’ He knew the game had changed.
The Lotus 25’s internal dimensions were all measured precisely around Jim Clark. At the start of 1962 Chapman’s rising star had yet to win a Grand Prix, though he soon put that right in the Lotus 25. That season Clark won three races, finishing second in the championship; the following year he won seven more to take his first world title. The 25 was then modified for wider tyres, and – renamed the 33 – continued winning in 1964, taking Clark to a second world title in 1965.
No other driver won in the 25 or the 33, and the car and the man will be forever linked; but the 25’s impact went well beyond Clark’s two world titles. Although the other teams took a season or two to catch up, eventually everyone developed bathtubs for their cars; and when McLaren replaced alloy with carbon in 1981, the modern F1 car was born.
John Cooper asked laconically, ‘Where did you hide the chassis?’