A titanium rear sub-frame developed for the Lotus Exige S has reduced weight of the structure by 36 per cent and improved stiffness by 19 per cent.
The development was part of a six-month project between Lotus Engineering and Caged Laser to investigate the use of titanium as part of a chassis structure. The project follows one from 12 months ago, when an Ariel Atom chassis was fashioned from titanium.
Titanium is incredibly strong – it has the highest strength-to-weight ratio of any metal being as strong as steel but only 45 per cent of its weight – but is very expensive, flexible and tricky to treat as it’s chemically neutral.
An Exige S’s steel rear sub-frame weighs 50kg, and the project targeted a 30 per cent weight reduction. The final weight reduction was 18kg – 36 per cent – a significant figure in an already light and tightly packaged car.
The torsional stiffness of the frame was also increased by 19 per cent, reducing vibration and making the car more stable in the process. The corrosion performance of the two sub-frames was comparable, as was the joining process, which is extensively tested with a variety of different adhesives with the titanium.