Total Production: 7 1962 - 1963 Formula One racing is all about technical innovation and pushing back the boundaries of the standard norms. And while there would be many cars throughout the history of Formula One that would provide revolutions in car design and innovation, perhaps none would be as influential and long-lasting as what the Lotus 25 Coventry Climax represented to the world of motor racing.
The fact that Colin Chapman constantly pushed back the boundaries of car design and innovation was a given. Always in search of lighter, stronger and more aerodynamic concepts, Chapman and his team of engineers at Lotus would manage to create some truly remarkable designs over the years, despite not being one of the bigger manufacturers in the world.
And it was, perhaps, the size of Lotus that enabled it to try some truly futuristic and radical ideas when it came to car design. But none would revolutionize motor racing on every level as what the Lotus 25 would.
The standard for years in Formula One, and in just about every other discipline of motor racing for that matter, was some kind of space-frame/ladder chassis construction. Therefore, it would be the space-frame, or ladder, construction that would provide the strength and rigidity for a car. Pieces of aluminum would then be bent to create something of an aerodynamic shape. This kind of construction would be used in such revolutionary cars as the Ferrari 500, the Maserati 250F and others in Formula One. This form of construction would also be widely used in sportscar design as well as it would open up the inside of the car and would allow more space for fuel tanks and other components. This would become a standard in car production and continues to be used to this very day.
However, such chassis would make the ideas Chapman had in his mind impossible to build. Having a chassis and then bodywork over top of it all seemed like excess and unnecessary weight to Chapman. He would set out to devise something different. This pursuit would become an obsession when the advancements in technology were beginning to take their toll on the chassis of the day and when the governing-body would make the decision to reduce the maximum engine displacement from 2.5 to 1.5-liters. Chapman needed a stronger car, and yet, a lighter one as well. It seemed impossible. But it would be in the land of the impossible where Chapman would usually shine.
Chapman would first try to address the issue of the smaller engine displacement by building the Lotus 24. Sporting a very low profile and very sleek, the Lotus 24 would require the driver to lie down in the car nearly flat. Amazingly, the driving positioning would be something of an issue given the fuel tank needing to be moved from the sides of the car in order for the car to be as compact as possible with the space frame chassis.
While the car would be very tight and compact, the handling would not be as good as what the car looked. Although it was low to the ground, the rather high positioning of the fuel tank would negatively impact the handling of the car.
Combined with Girling disc brakes, ZF 5 speed gearbox and the new 1.5-liter Coventry Climax V8, the Lotus 24 would still be a good car. Jim Clark would score two victories with the car and a handful of pole positions. However, the Lotus 24 would not be Chapman's car of the future. He had developed a concept for a wholly-new car that would likely be the answer to all of the challenges he currently faced.
The answer would be found when folding metal and then riveting pieces together. It would be a very simple idea, but then, often it is the simple ideas that are the most far reaching and profound.
The monocoque structure was, by far, not a new idea. It had been used in aviation for decades. It would also be used at different moments throughout motor racing history. However, what Chapman and his team would manage to achieve with the Lotus 25 would be absolutely astounding and ground-breaking.
Instead of a whole series of space-framing, the crew at Lotus would bend and rivet together boxes of the chassis that would be joined together. For extra rigidity, the engine would be mounted in a semi-stressed configuration between the driver's tub and a mounting plate at the rear of the car. The radiator in the nose of the car would simply mount to the front of the tub with the radiator line running along the left side of the car back to the engine.
The ultimate in space-saving chassis design, the riveted aluminum chassis boxes would allow for the fuel bladders to be placed inside the chassis and lower to the ground. It would also allow for the coil sprung suspension to hide many of its components within the inside of the chassis. Especially on the front suspension, all that would be exposed out of the side of the car would be the double wishbone/rocker arm assembly and the rack and pinion steering arm. At the rear of the car, it would be a slightly different issue. Because of the presence of the engine and other mechanical components, the angles coil spring would be exposed at the rear of the car, as would the anti-roll bar and the twin-trailing links.
Since the strength of the folded sheets of aluminum proved so strong (about three times as strong as a regular space frame chassis) the amount of metal used to make the body of the car would be minimal, hence the idea of the driver's tub. In many ways, the driver sat on top of the chassis of the car, but would be surrounded by the fiberglass bodywork. This was due to the fact the chassis was so strong that it needed very little metal to do its job. When combined with the fiberglass body, the Lotus 25 would be a very light and sleek car with a low center of gravity and a very low profile.
This low profile would take a little bit of getting used to as it would require the driver to literally lay down inside the chassis. Being this low to the ground took a special kind of driver to not only drive the car, but also, to be brave enough to push it as hard as it could go. But when combined with the single-piece wraparound windscreen would make for one incredibly stylish and aerodynamic machine.
Without the fiberglass body, the driver was totally exposed lying down on top of the car. The only thing that crossed over the body of the driver would be the cut piece of sheetmetal that housed the instrument cluster and served as an attachment and rigidity point for the steering column. One feature of the steering column would be drilled holes that would allow the crews to adjust the length of the steering column to fit the desire of the driver. This instrument panel would be attached to the chassis of the car, as well as, a series of tubing to provide a roll-over crash structure over the top of the driver's legs and waist.
Chapman was all about compact size and reduced weight while increasing the rigidity of the car. This created some issues when it came to the cockpit itself. The driver's cockpit was already quite tight, especially when the fiberglass body was placed overtop of the car. However, Chapman wanted it even tighter, if it was possible. Therefore, one of the interesting features Lotus looked into was mounting the manual gear lever somewhere on or near the steering wheel instead of in the more familiar location just to the right of the instrument panel. Unfortunately, this would prove too difficult and a much more conventional layout for the ZF gearbox gear lever would be used.
Directly behind the driver's head, and behind the roll-over bar, sat the 90 degree Coventry Climax 1.5-liter V8. Utilizing Lucas fuel injection and normal aspiration, the Climax engine would produce 195 bhp at 9500 rpm. Out of the top of the engine, between the two banks of cylinder heads, would be the eight trumpet inlets feeding the necessary air into the engine. The exhaust pipes would all blend together behind the mounting plate at the rear of the car. The four exhaust pipes on either side of the car would blend into two larger pipes that would extend and protrude well out the back of the engine. All but the two exhaust pipes and the air inlet pipes would be exposed.
With all of the bodywork in place, the Lotus 25 weighed just 995 pounds but would have incredible rigidity. When combined with the low center of gravity afforded by the chassis and the position of the fuel tanks, the handling of the Lotus 25 vastly improved. In addition, the light weight of the car, combined with the Climax V8, would allow the Lotus to claw back a good deal of the performance lost through the decision to run small displacement engines.
Chapman would be involved in a bit of slight of hand as he would campaign the Lotus 24 publicly while the Lotus 25 was developed secretly. It would seem incredibly when Chapman was not all that disturbed when the 24 didn't do much better. But when the 25 made its debut at the Dutch Grand Prix in 1962, all would be understood.
The Lotus 25 would take Formula One by storm as Jim Clark would take the pole in its very first race. However, teething problems would cause the car to only come away with a 9th place result. Still, Chapman and Clark knew they had the car they needed. By the end of the season, the brand new car would earn no less than three victories and would help Clark just miss out on a World Championship title.
One year later, the car would still be the class of the field. And when combined with better reliability, Clark would go on to win seven out of ten races and would easily win the Drivers' and Constructors' Championships for Clark and Lotus.
The Lotus 25 would be such a ground-breaking design that it would not die easily. Although Lotus would only produce the car for a couple of years, the Lotus 25 would continue to be used and updated by teams well into the late 1960s, a true testament to Chapman's genius design.
Although not the first to make use of a monocoque structure, when combined with a low-profile design and a mid-engine Climax V8, the monocoque chassis would make for one incredibly beautiful and landmark design that would change the course of motor racing as even the modern grand prix cars of today follow the same basic idea of which Chapman drew on a napkin during a meeting with Frank Costin. Therefore, the Lotus 25 isn't just a special grand prix car in the history of Formula One, it is one of those very few that belongs in a special category all its own where success isn't just the determiner of greatness. The truly great designs are successful and ground-breaking at the same time, and the Lotus 25 would be that in spades.
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'Lotus 24 Climax', (http://www.ultimatecarpage.com/car/697/Lotus-24-Climax.html). Ultimatecarpage.com: Powered by Knowledge, Driven by Passion. http://www.ultimatecarpage.com/car/697/Lotus-24-Climax.html. Retrieved 11 July 2012.
'Lotus 25 Formula 1—Car Profile', (http://www.sportscardigest.com/lotus-25-formula-1-race-car-profile/). Sports Car Digest: The Sports, Racing and Vintage Car Journal. http://www.sportscardigest.com/lotus-25-formula-1-race-car-profile/. Retrieved 11 July 2012.By Jeremy McMullen