Chapman.27s design Chapman strut

lotus twelve. strut spring, driveshaft below , radius rod can seen

in 1956 chapman using de dion rear axles lotus racing cars , vanwall. these had used transverse leaf springs, later changed coilover shock absorbers. chapman had identified of de dion s disadvantages including high unsprung weight, need sliding splines in rear driveshafts, , (a typical chapman fixation) insensitivity changes in weight fuel consumed. first lotus twelve formula 2 cars used same system, although de dion s mass drawback lightweight single-seater racing car.

at 750 motor club meeting in 1957, chapman saw goggomobil system , impressed lotus-like simplicity , light weight. use of drive shafts both drive , suspension component appealed chapman, favoured solutions make 1 component double duty.

chapman struts introduced in lotus first single-seater car, lotus twelve. developed 1.5-litre formula 2 in 1957, re-engined in 1958 competed in formula 1. same car introduced lotus wobbly-web wheel.

there 2 differences these precursors chapman strut. lotus twelve had inboard disk brakes, there no need pass braking torque through radius rods. chapman avoided swing axle , camber changes suspension travel, in favour of drive shaft 2 universal joints. connection between hub carrier , shock absorber base made rigid, making spring unit strut , controlling camber angle. using drive shaft control rear track meant shaft of fixed length, avoiding need sliding spline joint , stiction problems.

chapman applied patent on strut design on 13 june 1957.

the chapman strut appeared on lotus sixteen of 1958. in 1959 design revised use lower wishbone. in turn required return sliding joint in drive shaft.