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14/06/2011
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Paul Fanning talks to a man who is at the cutting edge of ensuring that low carbon vehicles are also safe and crashworthy.
 The rapid advances in alternative fuel vehicles are not only affecting the way in which cars are powered, but are having a significant impact on the way in which they are designed for safety as well.
Phil Glyn-Davies is manager of Crashworthiness & CTL Engineering at leading automotive proving ground Millbrook and has had to learn the hard way that every change to the motive technology of a vehicle has major significance for its crashworthiness.
"We've got these business units here at Millbrook – Powertrain and crash," he says. "But as we move forward, we're finding that everything that has an impact on fuel consumption or range also has an impact on the crashworthiness of the vehicle. And the Powertrain guys do have this really annoying habit of putting big, stiff lumps in the middle of cars that don't improve crashworthiness at all."
The speed with which the alternative fuel vehicle market has progressed has meant that crashworthiness issues have often taken a back seat in the development process. Says Glyn-Davies: "I think it took a while for people to realise you couldn't just swap from one power source to another and everything else would be basically the same. Possibly more in a crash environment than in any other environment, in fact – because, by its nature, it tends to come at the end of the process."
One of the major issues to have been revealed is that new powertrain systems tend to mean increased weight for the vehicle and, because of the increased number and size of components needed within the car, a reduction in 'crush space' to absorb impacts. Says Glyn-Davies: ". Packaging with hybrid electric vehicles or fuel cell electric vehicles is a real challenge – it's hard to fit everything in.
"There are things you can do from a crash point of view. One is to put more investment into your restraint system. You have to have a much cleverer restraint system if you've got a stiffer car because you're trying to manage the occupants' loads against a much stiffer crash. So you need to have better pre-tensioning, better load limiters and better airbags.
"So, for instance, you might use two-stage airbags to change the bag's response depending on the size of the occupants and different positions of the occupants and – to an extent – the severity of the crash. So it's possible to manage these things but you have to put more investment into the safety."
This 'packaging' issue also affects the car when it comes to pedestrian protection. "Pedestrian protection is impacted by packaging," says Glyn-Davies. "Pedestrian protection relies on free space behind impact points and it's quite hard to find that free space if you significantly change the packaging. Hi-tech deployable bumpers or bonnets that give you that crush distance back are one solution."
Of course, regulation and legislation are crucial when it comes to car safety issues, but here again the speed with which the technology is moving causes significant difficulties, as Glyn-Davies acknowledges. "Legislation is a real challenge," he says. "You typically have to give legislation a long period of notice for its implementation and the problem is that those implementation periods are starting to exceed the time being taken to develop new technologies that will render that legislation obsolete.
"There are a lot of challenges in that sense. And it's hard for legislators because they are a barrier to market if you don't meet the legislation. So if you do introduce it too early you can cause havoc. There is a higher level of agreement and co-operation with legislative bodies now, though. Because there basically has to be!"
Clearly, then, there are huge challenges to be addressed when it comes to safety and crashworthiness in alternative fuel vehicles, but Glyn-Davies is keen to reassure that this is not the same as saying that such vehicles are unsafe. He says: "The thing I want to do is to dispel any impression that alternative fuel vehicles are inherently unsafe.
"It does present new challenges and there's quite a lot of engineering that has to go into ensuring that they don't present a hazard. If you took people who'd never driven a petrol car and told them that you were going to put a plastic tank full of highly-flammable fuel under the back of your car that's going to be providing your motive power, then they would probably express some concern. Ultimately, good engineering can overcome most of the challenges."
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Author
Paul Fanning
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