#1 Chassis Design and Construction 1950’s – 1970’s (article written by Jack Halford)

Hi everyone and welcome back to our technical column here. In this months article we shall be taking a look at the various ways in which designers/engineers have gone about the business of designing and manufacturing the chassis or monocoque as it is sometimes called. During my research on this topic I thought to myself I could write a book just on this one subject alone such is vast amount of information available, so what we are going to do is just have a brief look at the innovative chassis designs that made a difference in F1 over the years as it would be difficult to cover everything! We will break the subject down into two articles, the first will cover chassis design from the 1950’s through to the 1970’s and then the following month we shall take a look at chassis design from what I call the modern era of F1 the 1980’s through to the present day when Carbon Fibre becomes the material of choice for chassis construction.

You will have to excuse the fact that I will be referring to Colin Chapman and Team Lotus quiet a lot over the coming articles; the reason being is pure and simple, up until Chapman’s untimely death in December 1982 he was the most innovative designer of his generation and was responsible for most if not all of the major contributions in race car design.

Firstly, we shall jump back in time to an era when chassis design and construction was a little less complicated than it is today but it still remained the single most vital component in the race car’s design. From the middle to the end of the 1950’s we saw an array of cars on the Grand Prix circuit each with their own distinctive style of chassis and the two most popular were the Box Sectioned Frame which was used on standard family saloon cars right up until the early 1980’s and will still be found on today’s light/heavy goods vehicles. The second and more popular at the time was the more complex tubular style chassis commonly known as a space-frame, which consisted of steel tubes of varying lengths welded together.

Both types of chassis had their benefits; the box sectioned style had very good resistance to bending and also good torsional (twisting) resistance but was heavy. The space-frame chassis offered very good torsional resistance and to avoid bending in the areas of high stress more tubes were welded in and around those particular areas for added strength, it still remained a lot lighter than the box sectioned chassis. The most intricate space-frame of those times was used on the Maserati type 61, known as the ‘Birdcage’ this radical style of chassis was literally the backbone of Maserati’s sports racing cars and won them many victories.

By the 1960’s the space-frame was being used by designers throughout the F1 teams, the bodywork for the cars was formed using thin gauge sheets of steel or aluminium which was then screwed, riveted or welded to the chassis and thus added more rigidity to the chassis almost becoming semi permanent fixtures, what must also be remembered is that most F1 cars of the time still had their engines mounted in the front of the chassis. Race car designers were slow off the mark in following in the footsteps of John Cooper who designed and built 500cc race cars for hillclimbs in 1946. Moving into F2 and finally F1 with a rear engined Cooper using a 1,100cc Jap engine took part in an F1 world championship event at Monaco in 1950. In 1960 Lotus founder Colin Chapman built his first rear engined car, this was the Lotus Type 18 and still using the space-frame the car would be used in various formulae. We will be having a more in-depth look at engines/gearboxes in a later article.

Chapman moved away from convention in 1962 and came up with a completely new design of chassis (apparently drawn on the back of a napkin whilst having lunch). Moving away from the space-frame he designed the first ‘monocoque’ style chassis with its engine mounted at the rear, this was to be the Lotus Type 25, Chapman was a visionary; he revolutionized the design and manufacture of an F1 car. Always looking for ways to build the lightest and fastest car became an obsession for him; if he didn’t like it or was too heavy it would not find its way onto one of his cars. The new monocoque design nicknamed the ‘bathtub’ comprised of two fabricated bays that ran half the length of the car, these bays carried rubberized fuel tanks on either side from the back of the driver’s seat towards the front, a third fuel tank was located just behind the driver’s seat. The fabricated bays were linked by a series of fabricated steel bulkheads; one at the front, one in the middle (front of the cockpit) which the dashboard was mounted and a third behind the driver where the roll hoop was mounted. There were also another two tubular rails running along each side towards the back of the chassis and once again connected by a fourth bulkhead this was the sub-frame which would act as the compartment for the engine and gearbox to be mounted. The floor pan was formed around the two fabricated bays then riveted into place, this way the floor added to the overall strength of the chassis by becoming what is called a ‘stressed member’ It could be argued that Chapman’s design is only a semi monocoque and you would be correct in that argument but nevertheless this design of chassis would make the space-frame obsolete practically overnight!

Cockpit areas were also becoming much smaller and tighter, Chapman also started experimenting with different seating positions. In 1961 the Lotus Formula Junior 20 had a seat reclining angle of 50 degrees to the vertical; this was the start of what we see in today’s F1 cars, the laying down position of the driver. Chapman changed the position once again with the Lotus Type 25 to a 55 degree recline from the vertical and the drivers complained that they ‘could not see the road at the front of the car’ Chapman took a hard line with his drivers, he wasn’t interested in their complaints ‘the cars conform to the regulations and that’s good enough for me’ he quipped. The Type 25 chassis was used between 1962 and 1965 although a derivative of the Type 25 chassis was introduced in 1964 – the Type 33. This was a stronger and much simpler to build style of chassis due to the fabricated bays being straight and not kinked as in the Type 25; Chapman had now shown the way in F1 design and construction and everyone had to quickly follow his lead.

Safety was never of any real concern to the car designers of this era, if you ever come across any old photographs of the cars from the 1960’s look at the position of the driver’s crash helmet relative to the roll hoop, most of them sat higher than the roll hoop. Seatbelts or safety harnesses were not obligatory and only when Jackie Stewart took the initiative in 1968; the challenge of making F1 safer both with the cars and the circuits alike had begun but was not well received by his peers at the time. It wasn’t until 1972; a further five years later that the FIA introduced the ruling that the six point safety harness was now to be fitted as standard in F1.

By 1967-68 Chapman and co-designer Maurice Philippe had once again delivered another wondrous car; the iconic Type 49 together with the even more celebrated Ford Cosworth DFV V8 engine. This combination of chassis and engine had once again changed the way that F1 cars would now be designed and manufactured over the coming years. The ‘package’ as Chapman had called it; was the chassis, engine and gearbox fully integrated, with the engine becoming a ‘stressed member’ and mounted to the rear of the chassis at four points, this clever design kept the overall weight and height of the car down to the absolute minimum. The monocoque itself was now classed as full, with the aluminium construction coming over the driver’s legs and enclosing him completely and was made slightly shorter at the front; this was to enable a tubular sub-frame to be fitted to act as a mount for the front suspension, steering, brake master cylinders and the main oil tank.

In 1968-70 teams such as Lotus, Mclaren and Matra were experimenting with front and rear wings or aerofoils as they called them and the cars were now taking on the wedge shape that was seen in the late 1960’s and throughout the 1970’s. Single skin alloy monocoque’s were now being replaced by pre-fabricated panels that simply consisted of two sheets of thin gauge aluminium bonded on either side of an aluminium filling that looks just like bee’s honeycomb. The main problem that designers faced with this type of panel construction was that although far stronger in their stiffness and torsional rigidity they just could not be contoured in the way that a single skin panel could be, this would now be a majoring factor in the design and construction of the cars.

Through to the late 1970’s we saw no major changes in chassis design, although designers were still furiously trying to keep on top of their game with certain changes in materials used and other technical developments the distinctive wedge shape remained, with the lower half of the car’s bodywork being the actual monocoque itself whilst the upper bodywork was made from GRP (Glass Reinforced Plastic) molded panels. The underneath of the cars remained flat which gave Colin Chapman another ingenious idea to bolt skirts down each side of the car which immediately gave greater downforce by sucking the car onto the tarmac thus creating ‘Ground Effect’ We shall discuss bodywork, ground effect and aerodynamics in another article.

Phew! So there you have it, just a small insight into chassis design and construction from the 1950’s to the 1970’s. In next months article we shall take a look at the 1980’s to the present day, from the twin chassis of the Lotus Type 86 to the first full Carbon Fibre monocoque, the Mclaren MP4/1 designed by John Barnard, we shall also take a look at modern techniques in chassis design and construction together with the various materials used.

Until next month, enjoy your racing.

Jack

‘All views expressed in this column are those of the author and not Team Lotus’

Written by: Jack Halford

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