Plastic helps create safe cycle helmet

An ultra-safe cycle helmet has been developed with a built-in rear view mirror system that means the cyclist does not have to turn or look over his or her shoulder to gauge what is happening behind and so there is no loss of vision of the road in front. And the lightweight plastic used to develop the product enabled the design team to reduce the thickness of the helmet by 50%, from 24mm to 12mm, making the design more streamlined and lightweight. Launched in September last year, the periscope-like mirror system was developed by Durham-based design firm Reevu in collaboration with global plastics manufacturer DuPont and French manufacturer Pactuco International. The helmet's central peak and crest (ie. the raised cap section of the helmet) is manufactured from a tough, impact-resistant, lightweight nylon resin – DuPont's Zytel ST, super-strength plastic. This area of the helmet houses a periscope-like system of three mirrors which bend the image over the wearer's head. This system gives the wearer complete rear views without the person having to take their eye from the traffic in front. General manager at Pactuco, Antoine Monville, explained: "Because it [the rear view mirror system] is on top of the helmet, its impact strength is critical to the overall safety of the helmet. During the development phase, we subjected the helmet to flat surface and kerbstone impact [sharp edge] tests under a variety of conditions – hot, cold and wet. The impressive impact resistance of Zytel ST means that the helmet can easily withstand international drop tests of 5kg from 1.5 metres under these conditions. "It's ideal for the critical cap part because although it is flexible to a degree, it does not become overly flexible in hot weather, nor does it become brittle in the cold… The excellent overall performance of the material enabled us to reduce the thickness of the original helmet design by 50 per cent, from 24mm to 12mm, meaning the helmet could be even more streamlined and lightweight than we originally envisaged," he added. He went on to say that because it is a thermoplastic, it was possible for Pactuco to injection mould the Zytel ST, which gave them more freedom to make the cap and the overall helmet more stylish and attractive to the eye. The moulding work was carried out by Paris-based moulding firm, Joy Plastics, which designs and manufactures helmets for mining and building applications. CEO of Reevu, Bill Morgan, said there were three main specifications for the helmet. "It had to meet all international safety standards in order to afford the wearer as much head protection as possible. So the mirror system had to be tough, lightweight, highly reflective and crack-resistant, but require minimum maintenance. And it needed to be light and comfortable to wear with high levels of airflow." He added: "The rear view system was designed to address a failing in the heart of cycle design and operation. It is against the law not to have a rear view mirror system in a car or motorcycle, but on a pedal cycle no such rules apply. We took the view that that accident prevention is just as important as the protection of the user. Our design goal, therefore, was that wearers of our helmet would continually glance at what is going on behind them in much the same way as car drivers do – but will continue to face ahead." Morgan said that the idea for the system came about when a colleague's son fell of his bicycle while glancing over his shoulder before turning right. The boy wobbled, clipped the kerb and fell off. Several solutions were put forward, including mirrors on handlebars, "but these tended to vibrate and distort, and they're easily broken," he claimed. "And when you turn the handlebars, the mirror points in the wrong direction. That's why we came up with the idea of putting a mirror inside the helmet." Morgan also explained that the optical mirrors, made from ABS, had a metallic surface which needed to be lacquered to prevent the mirrors from oxidising. "The optical, reflective surface had to have a very high quality polished finish and be rigid enough to withstand the specified impact forces on the helmet." There was another design problem to solve though. As Morgan explained: "We couldn't just use flat mirrors because we had to achieve an optical field of vision for the wearer. The cyclist needs to see an object two metres in height from a distance of 10 metres with an average eye height of 1.75 metres from the road. That was our specification." According to Morgan, the finished helmet design has other advantages, apart from protection against accidents. "80% of cycle accidents are caused by the cyclist looking over his or her shoulder. 40% of these result in facial injuries. Therefore, we decided to design a structural peak which would give protection to the person's face. But while designing the aperture from the front to the back of the helmet for the mirror system, we realised that we could also use this aperture as a vent system to cool the wearer's head. The cavity produced by the rear view mirror system creates a chimney effect that pulls cool air through and over the top of the wearer's head. And it also prevents the reflective optical surfaces from steaming up." It certainly appears Reevu and its partners have developed a 'bullet proof' design. The helmet conforms to all international impact standards for protective cycle helmets but also withstands all of the dirt and rain that nature can produce. Morgan told Eureka that the helmet's fitting system also allows maximum adjustment to ensure that the helmet maintains an optimal angle on the wearer's head and stays comfortable in the process. Reevu and Pactuco have now sold more than 30,000 of the patented helmets across 12 different countries. DuPont Reevu