Production of the 1956, 1957, 1958 Lotus Eleven
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The 1098-cc Coventry-Climax engine is easily accessible with the front bodywork removed.
Multi-tube space frames had originally been developed as the basic structure for military aircraft, with the principle gradually being adopted for use in postwar racing cars.
Although most people assume that the original automotive space frame had been designed by Mercedes-Benz (for the 300SL of 1952), one shouldn't forget the complex tubular frame utilized by Jaguar for the 1951 C-Type.
For use in Lotus sports cars, Chapman took the principle even further. Early Lotus space frames were not as delicate as those found in the 300SL, but the Eleven's frame was a delicate, even flimsy-looking, masterpiece.
As was already well-known, the correct way to design a true space frame was to link stress points by straight tubes that were only ever in tension or compression; incorrectly located tubes were subject to bending loads, which they could not easily withstand.
As far as motor cars were concerned, the need to get passengers in and out of the cockpit, and to allow for engine removal, meant that the Eleven's frame wasn't an ideal design. Within limits, however, Chapman and the Costin brothers had worked ruthlessly to provide an immensely strong frame, even though it looked flimsy.
Most of the tubes were 1.0-inch or 0.75-inch round -- or square -- section pieces. Depending on the loads they had to carry, they were either of 18 -- or (even thinner) 20 -- gauge thickness.
Stripped of all its aluminum bodywork, the bare frame weighed a mere 56 pounds, and there was no difference between the de Dion or live rear axle type suspensions in terms of weight. To add to the rigidity in key areas, Lotus arranged to rivet some of the inner body panels to the chassis frame.
Although the chassis layout was fascinating enough, it was the body style, and the fine detailing, which had gone into it, that caused most discussion. Compared with the Mark IX, which it replaced, the Eleven was even lower and smaller, the height at the scuttle, immediately ahead of the windscreen, being an astonishingly low 27 inches.
Given the basic dimensions already settled upon -- including an 85-inch wheel-base and the use of a Coventry-Climax engine -- Costin then designed a pure aerodynamic shape for front and rear wheelarch fairings.
As a perfectionist whose sensibilities were irritated by lots of joints, flaps, and badly fitting contours, he was delighted to know that Lotus proposed to build the entire front and rear body sections in one piece, and to hinge them at the extreme ends of the chassis frame.
Go on to the next page to read about feedback for the Lotus Eleven.
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