The crash helmet, skid lid, bone dome, whatever you want to call it, it’s been part of any rider’s wardrobe in this country since 1973. But it wasn’t always like that. And it wasn’t always pretty.
Since the introduction of Bell’s open face helmet in 1954, little has changed in basic construction techniques over the past fifty years. Look inside any modern crash helmet and you’ll still find a polystyrene, energy-absorbing inner shell and a hard, fibre-glass laminate or ABS outer shell to resist hard impacts and abrasion.
From leather or sheepskin helmet caps at the turn of the last century helmet technology slowly progressed to cork covered in leather. Using tree bark as head protection might seem slightly nonsensical in today’s day and age but, back then, man made materials like epoxy resins and fibreglass just weren’t available. Commercially produced glass fibre didn’t appear until 1936.
Th e first fibreglass helmets adopted the rigid outer shell approach. Put simply, you can either build a helmet with a deformable outer shell or inner shell. The helmet’s end purpose is to defer the energy of an impact away from the head, much in the same way as a crumple zone in a car. So some part of a helmet’s construction needs to be deformable.
Enter the polystyrene inner shell. It’s designed to do its job once and once only. In an impact incident the polystyrene cells compress to spread the loadings and reduce the forces acting on the skull and brain. It’s for this very reason that a helmet is really a one-crash item. Once the inner shell has absorbed the impact it’s toast. Time to buy a new one.
Some helmets use just a single density of foam to form the inner shell but most high-end helmets will use multiple layers of different density polystyrenes, particularly in different areas of the helmet where loadings vary according to the shape of the shell and the shape of the head.
Polycarbonate lids take the opposite approach. The flexible nature of the material allows the outer shell to act as the energy absorbing part of the helmet’s construction. This technique lets the helmet’s designers specify a much harder inner shell.
Various methods of fastening have been tried over the years. Chin cups, press studs, belt and buckle, seat belt type buckles, strapless (GPA in the eighties) and the D-ring.
The D-ring has prevailed as the ubiquitous helmet fastener for two principle reasons, one: it’s cheap and strong and two: nearly everyone knows how to fasten it (apart from the very young). But more importantly, everyone knows how to unfasten it. This is most important when emergency workers and doctors are on the scene.
Yes, T.E. Lawrence, or Lawrence of Arabia.
Lawrence crashed his beloved Brough Superior on a country lane near his cottage in Dorset. He lost control of the V-twin SS100 after swerving to avoid two boys on push-bikes who were obscured by a dip in the road. After spending six days in a coma, Lawrence died.
One of the doctors trying to save him was neurosurgeon Hugh Cairns. Profoundly affected by the experience, Cairns began research that would eventually lead to the use of crash helmets by both military and civilian motorcyclists.
Before this epiphany, helmets had only been worn to protect riders against wind and rain, much like those worn by early open cockpit biplane pilots. The military link probably goes back further. Helmets have been worn in warfare as early as Egyptian times and the link is patently obvious. When you need to protect your head, you wear a helmet.
Since the early leather skull caps, motorcycle helmets progressed using military technology. Cork helmets aside, the first lids to offer serious protection drew their style and construction from the first jet fighter pilot’s headgear. ‘Jet’ helmets were made from fibreglass, trimmed with flame-retardant leather and shaped to allow goggle and face mask use (not that oxygen starvation was much of an issue for bikers). The first jet-age helmet was Bell’s much copied 500 in 1954. It’s probably more famous for being worn by Steve McQueen than the technological advances it pioneered.
It wasn’t until 1967 that the full-face helmet made an appearance and the basic design has changed little since. Bell-Toptex inc launched their ‘Star’ model to an initially sceptical world audience but the idea quickly caught on, particularly in racing circles. Despite unfounded fears of decapitation the full-face helmet caught on a and stuck around.
Click here for Things that changed our lives: Helmets page 2 of 2
Posted: 01/12/2010 at 15:21
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