Automotive Design
The three companies are investigating the feasibility of producing a titanium roll cage for lightweight niche vehicles. Because titanium must be welded under oxygen-free conditions, this means using a barometric chamber to contain the parts under argon gas.
The main challenge was building the chamber itself: for a complete chassis, the chamber has to be 3.5 x 2 x 2m – is larger than any chamber currently in existence.
The challenge was to evacuate the chamber of all traces of oxygen (and nitrogen). This is not easy when you consider that many materials – rubber, steel, ceramics – actually have oxygen
A titanium-based Atom car has now been built, and is being tested. A limited edition will be launched in the near future. If successful, it will be added to the options list, says Squance.
He says that the project was instigated because of the ongoing need to reduce the weight of cars in the face of emissions legislation.
And, he says, learning how to work with titanium could eventually see it competing with the industry’s lightweight material of choice: aluminium.
“So many large companies are into aluminium: it’s lightweight, and quite strong, but it corrodes badly unless it’s pre-treated correctly,” he says.
A simple scratch can destroy this corrosion protection, he says. At the same time aluminium is expensive to process, and not as strong as steel – meaning that parts must be designed thicker.
Fig. 3. A titanium roll cage could cut the weight of Ariel’s Atom car by up to 10 per cent.
embedded within them. This meant that items like hosing had to be redesigned. Out went rubber, in came high spec 216 stainless steel. The whole chamber was shrouded in special glass that contained no oxygen.
Even after all this, the tolerance for oxygen was very low. Anything over 100ppm was too much: it would lead to brittleness, and the likelihood of a catastrophic failure of the part. The aim was to weld in an atmosphere of 20-70ppm.
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The titanium project was part-funded by the Technology Strategy Board, through its Niche Vehicle Network programme.
“These projects are about innovation, and thinking outside the box,” he says. “They’re ideal for small companies, who have the will and the know-how to do things that larger companies don’t want to consider.”
And Caged Laser is already involved in another titanium-related NVN project. In partnership with Lotus Engineering and S&D Metals, it is investigating whether titanium sheets might be bonded together with adhesives. ●
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