Back when cars had heavy-duty, stiff springs and solid axles at the front and rear, the chassis was relatively unimportant - serving as a point of attachment for the suspension and other car components. The axles themselves were what kept the wheels parallel, and in contact with the road. However, the dynamics of this system was bad when used on race cars in competition. There was a lot of axle mass moving around and this proved to be unwieldy at racing conditions. When the first independent suspensions came to be used, a flimsy, bending chassis caused the wheels to take on rather odd angles with respect to the road surface, resulting in poor handling. To win races the wheel angles and therefore the suspension geometry had to be maintained dynamically at optimal values. This meant that chassis stiffness became the determining factor for cornering ability.

Chapman had to deal with this problem in the Austin 7 specials he built. To improve chassis stiffness he first tried using metal body panels, which would take some of the stress load. Soon Chapman tried metal tubes fixed together in the form of a triangle - a geometry that would not flex. He stiffened the forward part of the chassis of the (Austin 7 modified) Lotus Mark III this way, as seen in the photo.

In 1951 the Mark III, with its chassis stiffened at critical points by triangulation, showed superior handling characteristics and was the car to beat at the track. The next logical step would be to stiffen the entire chassis by triangulating every part of the chassis. Instead of re-doing a bad design Chapman abandoned the cars he was using as a starting point and decided to build his own chassis. A chassis composed only of tubes would be light and quite inflexible, if triangulated properly. Thus, the so-called multi-tube space frame became the chassis that was the basis of his first production car - the 1952 Mark VI.

The space frame is a box-like system of welded metal tubes forming a series of bays. The structure is rendered inflexible by tubes welded diagonally across the rectangular, exterior sides of each bay. To allow the driver access to the car, there are no tubes across the top of the driver's bay. Instead bulkheads are used for strength.

From 1955 to 1958 Lotus developed the space frame in a number of aerodynamic sports racers, the Marks VIII, IX, X and finally the XI which was invincible on the race track during its production. The space frame, and eternal, Lotus 7 kit car was introduced for club racing in 1957 and still can be obtained today in various versions by Caterham and other re-manufacturers. The 7 had an off-beat but appealing shape and offered race car handling at a production car price. Lotus entered Formula I competition in 1958, the first five cars being space frames.

Although having been superceded in the '60s by more advanced chassis technology, the space frame is still, at this late date, the chassis of choice in some European high-end, low-production sports cars. Assembled essentially by hand at a high cost, the multi-tube space frame production car is not capable of the torsional rigidity exhibited by more advanced and less costly designs.

Lotus Mark VI Space Frame Chassis: 1952	Lotus 21 Formula I Space Frame Chassis: 1961