Lotus performs plastic surgery on its sports cars

An engineer’s teenage son has inspired Group Lotus to invest in plastic shells for its future models.

The sports car and engineering company has spent £30,000 on producing a transparent body shell for its vehicles, which is made of the same material as plastic bottles.

Robin Shute, 13, hopes to become an automotive engineer and his idea has reached the finals of the Engineering Council’s Young Engineers for Britain competition. The winners, who were to be announced yesterday, will share £75,000 in prize money.

His father Tony Shute, head of product development at Lotus, said: ‘Robin was racing one-tenth scale electric cars in a national race series and he wondered if the same plastic body technology could be used for full-scale vehicles. I took the idea to the research group and suggested we build a prototype to his design.’

In a vacuum

The plastic shell was produced using vacuum forming, not previously thought suitable for car bodies. Lotus, owned by Proton of Malaysia, will test the new plastic-covered vehicle over the next 18 months to refine the technology. The test car itself is a legacy of the development of the company’s 340R, the super-lightweight version of the Elise.

The moulding process is similar to blow-moulding, which is used to make plastic bottles. It involves taking a thermoplastic, in this case polycarbonate, which is heated to a pliable state and placed over a mould. The plastic is then drawn into the shape of the finished part by a vacuum, and the shell machined to remove flash and other nonconformities.

Vacuum forming is already used to manufacture car trim and interior components but not for vehicle body shells. This is because of difficulties with surface finish, which has a direct effect on the quality of the paint finish – an important factor in a customer’s perception of the build quality of a car. But Shute senior expects those problems to be overcome.

Polycarbonate is transparent and can be painted on the inside. This means the paint cannot be chipped and will not flake due to rust, as on a steel body. The paint could even be replaced altogether by simply colouring the plastic earlier in its production. Shute sees no problem with these colourings recreating the metallic and pearlescent finishes currently popular with customers. This could bring a major saving, as manufacturers would no longer need a paint shop and paint supplies.

Other advantages of a plastic shell, according to Shute, are that it is lightweight, which gives improved fuel efficiency, and can easily be recycled at the end of the car’s life. Design options include leaving sections transparent, such as the roof or areas where lights are normally placed.

The cheaper tooling costs of the vacuum forming process also enable small volumes to be made, suiting Lotus’s markets.

Crashing doubts

Despite these advantages, there are doubts about how good a polycarbonate shell would be at absorbing crash impacts – though Robin Shute points out that toy cars withstand impacts of 40mph.

Currently, full-sized shells cannot be made in one piece and have to be put together in a number of sections. Lotus plans to reinforce the shell with impact-resistant metal sections.

Meanwhile, what could be far more lucrative than any Young Engineers prize is the joint ownership of the intellectual property Robin has been granted. As such he will gain a share of any revenue from his invention.