Cockpit Canopy Test – Full Story
There’s something sinister about the hard, black, angular and defiantly mechanistic object before us. Beauty has been slain on the altar of utility – function has vanquished form. No surprise, though.
It has been designed, after all, to fire things at things (within strictly controlled parameters, of course) and to discover what happens when scripted collisions occur. Read On..
WATCH THE VIDEO OF THE FIA INSTITUTE CANOPY TEST…[raw][/raw]
We’re talking about a cannon here, powered on this occasion by nitrogen gas compressed to 1200psi and built in a manner that scorns finesse. Stare at it long enough and you can work out not only what it does, but how it does it. A Swiss watch this is not.
But while its starkness of purpose is writ large against the big, blank, blue-sky backdrop of a Suffolk airfield, this unlovely creation is nonetheless a machine with a mission. It is, in fact, a vital component in an FIA Institute research programme into driver cockpit safety. And if, one day, exquisitely manufactured and elegantly formed components are added to Formula One cars, the better to protect a not-too-distant future generation of grand prix drivers, they may have this ugly construction to thank.
Here’s why: it has been brought here at the behest of FIA Institute Technical Advisor, Andy Mellor, who, along with Institute Research Consultants Peter Wright and Hubert Gramling, have for several months been investigating the possible benefits – and drawbacks – of adding some form of additional protection to the open-cockpit area of F1 cars.
Their research was prompted by the Formula One Technical Working Group (TWG) – a quorum of senior engineers from a number of F1 teams and bodies directly associated with the sport – which concluded that while driver safety provision continues to improve year on year, the open cockpit area of F1 cars merits further investigation.
In particular, the accident suffered by Felipe Massa at the 2009 Hungarian Grand Prix – when his helmet was struck by a spring that had fallen from the Brawn car of Rubens Barrichello, running slightly ahead on the track – raised questions about whether a driver’s head should be better protected. For 2011 a zylon strip has been developed for F1 helmets in the visor area where Massa’s helmet was hit (see IQ #1). Now the ongoing canopy research aims to establish if, and where, further improvements can be made.
“The work was instigated by the F1 TWG,” says Mellor, “and we have basically been looking into the science and engineering of protecting the cockpit from aggressive debris that can enter that space.”
The test to which IQ was granted exclusive access took place on 25-26 May this year, at the Bentwaters Airfield near Ipswich, England.
The aim was simple: to fire a Formula One wheel and tyre, together weighing 20kg, at 225km/h into, first, a polycarbonate windshield and, second, a jet fighter canopy made from aerospace-spec polycarbonate, and measure what happens (all close-up observations being recorded by strategically positioned high-speed film cameras).
The set-up of the cannon and – in the first test firing – the windshield, was meticulously calculated by Mellor and the team. They took as their base point known data from the effect of a bird-strike into a jet fighter canopy which assumed a 1.8kg bird impacting more than 1000km/h, creating energy of 73 kilojoules.
Today’s fighter canopies, such as that used in this study, are designed to resist this type of impact without discernable damage.
The F1 example is rather different, though. The flying object under investigation isn’t winged and feathery: it’s a wheel and tyre with some upright assembly attached, of an assumed overall mass of 20kg. The speed of impact, while still high at 225km/h, would be a great deal slower than any jet-fighter bird strike. But such a mass impacting at that speed still creates energy of almost 40 kilojoules.
“We needed to establish whether a bird-strike canopy could cope with a wheel at this speed,” says Mellor, “and our objective was to understand the science and engineering of violently deflecting a wheel and tyre away from the driver’s head.”
The equipment set-up for these tests called for extreme accuracy if they were to be fully valid. First, the cannon: it was supplied by the Bickers Action company – specialists in the provision of unusual vehicles and equipment to the movie industry, particularly for stunt scenes. For this test a 1200psi compressed-nitrogen cylinder was attached that would deliver the thrust needed to shoot a piston from its 2.5m barrel.
Viewed at real-time speed, the piston emerges from the barrel faster than the eye can register – an explosive blast of material that vanishes before you can comprehend its arrival, leaving behind nothing more than a trail of expended swooshing gases. A slo-mo version, though, supplemented by a detailed explanation from Mellor, provides a clue to the precision of what has occurred.
On firing, a huge compressed nitrogen build-up erupts behind the piston, allowing it to accelerate to 225km/h in just 2.0 metres. That’s a thrust average of 100g, in less than 1/10s which is why the eye can’t keep up.
Over this brief distance, the piston, with the wheel assembly still mounted on its tip, is sent flying. And it’s here that further extremely neat engineering comes into play. For the test to replicate the effect of a free-flying wheel assembly hitting a canopy – as it could in a real-world incident on-track – the wheel must be free of the piston by the time it hits the windshield. It’s at this point that yet another strand of already-proven F1 safety science comes into play. The piston, before it’s inserted into the barrel, is attached to four F1-spec wheel tethers, each designed to absorb more than 6kj of energy. They come into effect at exactly the two-metre mark from the point of exit from the cannon barrel.
“They’re designed to very quickly take some speed out of the piston,” says Mellor, “and they come into play at a very precise point, allowing the wheel to fly freely at the target object.” At the exact moment the tethers come into effect, the tail of the piston passes 20mm-diameter venting holes in the barrel, allowing the compressed nitrogen to escape, so reducing the thrust behind the barrel.
“It’s an extremely precisely calibrated set-up,” says Mellor. “Quite a lot of engineering has gone into it.”
There’s more. The wheel assembly at the end of the piston is aligned at 45 degrees – the angle deemed necessary to allow the lower part of the wheel rim itself (rather than just the rubber tyre surface) to come into contact with the target object. The leading edge of both canopy and windshield is 30 degrees, giving a 15deg misalignment. So, the steeper wheel/tyre will hit the shallower windshield and canopy with its trailing edge.
It maintains that approach angle thanks to its intricate positioning on the piston end. “It’s a sophisticated interface, designed so the centre of the barrel drives through the centre of gravity of the wheel,” says Mellor.
The result of all the science and engineering is to allow the 20kg wheel and tyre 500mm of free flight between leaving the piston as it’s slowed by tethers, and impacting the windshield or canopy.
“At this speed,” notes Mellor, “the wheel is a wing and it wants to take off, so this distance between release and impact has to be kept short.”
Almost all the test modelling in advance of the firing proper was done ‘theoretically’ – many hours of calculation being spent working out object mass, desired impact speed, and so on. The only dummy runs were to evaluate the speed calibration of the cannon and the correct piston mass.
There was a degree of trepidation before the live firings, but, Mellor reports: “The apparatus worked perfectly on the test day.”
There were three firings, two at the windshield and one into the canopy and the tests were carried out in the truest spirit of pure objective scientific research, says Mellor.
An executive summary reports that the firing into the 30mm-thick triple-layer (3x10mm) polycarbonate windshield resulted in it being shattered as it deflected the wheel and tyre assembly.
“But visually,” says Mellor, “it was possible to see that the windshield did manage to deflect the wheel over the space that would be occupied by the driver’s helmet, but in so doing it sustained significant damage.”
The canopy, however, deflected the wheel assembly suffering no permanent deformation. And viewing the canopy impact in slow motion shows it flexing to absorb impact energy, before ‘launching’ the wheel and tyre away.
“The full canopy manages to deflect it over the top, and very little damage, if any, was visible after the test,” says Mellor. “There were tyre transfer marks on both windshield and canopy, but on the canopy there was no apparent fracture. It shows that it’s quite an elastic material and that it’s very efficient at providing a load path to keep the wheel and tyre away.”
Full scientific results of the firings were recorded by six accelerometers and they have now been presented to the Formula One Technical Working Group.
It is reassuring to learn that the canopy is highly impact-resistant, but not entirely surprising: it’s manufactured by an aerospace firm and is exactly the same model as fitted to an F-16 Fighter jet.
What happens next has yet to be decided and will depend on the reaction of the FIA and the Formula One Technical Working Group to Mellor’s findings.
And that’s where the research rests right now. Any debate on implementation would have to take account of a number of known negatives, such as:
• Optical quality
• Emergency egress.
“We’re not looking at any of these things at the moment,” says Mellor. “This test was purely to look into the mechanical safety effect. Now that we have data on that, we can move towards a decision on what’s next.”
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