The art of keeping your head...

Back in the 1920s, crash helmets were only ever worn by racing motorcyclists and, even though a few motor racing drivers made early adaptations, head protection was not widespread for many years - at Le Mans this year, crash helmets will add to the colour and spectacle of the annual 24 Hours.

It was not until the early 1950s that the flying cap finally gave way to mandatory protective helmets but, these days, the specification is high tech and the materials used by the leading manufacturers come from the aerospace industry, forming an integral part of a driver's safety equipment. Plain white helmets are also a thing of the past, most competitors - including the majority of those competing at Le Mans - taking the opportunity to sport personalised designs that not only reflect their nationality and personality, but also accommodate the all-important sponsors.

Essentially the crash helmet is worn to protect the brain from injury, offering little protection to facial bones and tissue or the neck, all of which come under the title of 'head'. When the head is banged, the brain is shaken up inside and, in the absence of a fracture of the skull, the damage is largely caused by the sharp internal edges of bone cutting into the brain surface. Apply a force to the skull and it deforms by about half an inch before cracking up. The force necessary to perform this is in the region of 5000lbs and, if the average head weighs approximately 10lbs, this force is equivalent to 500 times the force of gravity (G). If an unprotected skulls hits a solid, flat surface at only 12mph, the deceleration imparted to the brain is 500G - the critical level.

The construction of a crash helmet is a balance between safety and weight, and high-tech composites are used to yield the maximum strength and minimum weight. The majority of sportscar drivers now use top-of-the-range full-face helmets - each with a unique and eye-catching design, painstakingly applied by hand when it has left the factory - even though many of them will be driving closed-cockpit cars.

Complete with all its integral equipment, a race helmet can weigh as little as 1.3kgs - compared to a 1.5kg standard road helmet. The outer shell gives a large degree of the protection and is made of a mixture of glass fibre, carbon fibre and polyaramide. It is important that this outer surface is smooth and free from projections as, if the helmets 'sticks' to anything on impact, a violent angular movement can cause brain damage. The interior lining is made of the flame resistant Nomex(R) material, while the shock absorbing padding is made of polystyrene. Minimal distortion of this padding is vital and, in the past cork has been used, although it proved to be heavier than foamed polystyrene and less predictable. The helmet is also equipped with built-in hearing protection that reduces ambient noise up to 25dB.

Once the helmet has left the factory, specialist painters take over and this is an art form in itself. Adding paint to a helmet can increase its weight by up to 150g, depending on the number of layers of lacquer and the type of paint. However, as long as the BSI approved sticker is still visible, drivers can create the wildest and most eye-catching designs.

Helmets arrive at the paint studios in standard white, which has to be stripped back to basics before anything can begin. The design of the individual helmet is then pencilled on and areas masked off for painting. While the majority of the helmet is painted to millimetric precision, with fonts and logos matched exactly, the smaller logos are applied in sticker form to guarantee accuracy. When finished, the helmet is covered with five layers of lacquer to protect the design from wear and tear. All this takes no less than 16 hours, for just one helmet.

Among the most eye-catching designs at Le Mans this year will be the chromed examples sported by Japanese Chrysler drivers Seiji Ara and Masahiko Kondo, which require more hard work in their creation. More familiar colour schemes will be sported by former grand prix stars Johnny Herbert, Martin Brundle, Mark Blundell and Stefan Johansson, while the younger drivers in the field will be hoping that their designs become more familiar by taking the laurels on Sunday 17 June.