MAKE YOUR EASY ARROW
THE DRIVER HAS A SECURITY BELT, A PILLOW, A STRONG SEAT … AND A PEDESTRIAN?
TEXT / ALEXEY SPARROW-SHOES
Designers have been thinking about the danger of a car to pedestrians for a very long time. Here, for example, a cheerful drawing for the patent … 1911. The sloping hood throws up the gapeous revelers up, and they fly over the car, apparently getting only bruises upon landing (see also ZR, 1997, No. 6).
Tests in our days have confirmed the idea: the most severe injuries to the pedestrian are caused by protruding parts: a windshield frame, a kangarin … a deer above the radiator of the old Volga. By the way, the latter disappeared along with the Yaroslavl bears and Zisov’s banners precisely because of the exceptional “hostility” to the pedestrian. Today, only a few firms install traditional figures on the hood. And even then, the Mercedes-Benz star easily bends backward, and the “Spirit of Ecstasy” at the Rolls-Royce is generally automatically sunk into a special hatch at the slightest pressure.
What else can be done to protect a pedestrian from serious injuries when a car hits? The recipe has long been known: to create artificial deformation zones that would extinguish part of the impact energy. From the point of view of physics, it makes no difference whether to put a person in a suit 10 cm thick or to create an easily deformable barrier on a car. As you guessed, we took the second path.
Race statistics suggested that at the time of impact the speed in 80% of cases does not exceed 50 km / h - it is already easier. Further, in the same proportion of cases, pedestrians fell under the car, and this is also a great success (for designers, of course): to “soften” the vertical “face” of the truck would be much more difficult. Finally, numerous experiments with mannequins imitating both adults of different complexions and children showed in front of the lenses of high-speed movie cameras which parts of the car come into contact with the head and other parts of the body of the pedestrian. There, it is necessary to take priority measures to mitigate the blow.
The main attention was focused on protecting the head: no matter how painful the injured by fractures of the limbs, in most cases, they are still non-lethal. Red bar graphs show conditional HIC scores measured by impact of a mannequin head with different areas of the hood. The critical mark of 1000 HIC is significantly exceeded in most cases. The reader, of course, has already noticed much more optimistic green bars. This is a pedestrian protection rating developed by Autoliv, a Swedish company. The hood rises 100 mm in the first 60 ms after collision, and as a result, a rescue gap is formed between its fairly “soft” panel and rigid elements of the power unit. Slipping, the hood provides the necessary slowdown in the movement of the victim’s head, which does not lead to fatal consequences. The command to trigger the system is given by special shock sensors, and pyrotechnic devices fill with gas a kind of steel bellows hidden near the wipers.
A similar solution was applied by the German company EDAG, only it has a double-layer hood, like a sandwich, where instead of oil there is a flat 10-liter airbag. In the normal state, the upper and lower hoods are glued at several points. When a pedestrian hits a pedestrian, an inflated (again at the command of the sensors) pillow breaks the adhesive connection and raises the upper plastic layer, creating a deformation zone.
The drawback of both designs is, first of all, the extreme complexity of recognizing pedestrian collisions from other collisions. False triggering may not be dangerous, but … the hood will have to be thrown out with all its expensive stuffing.
The designers of Ford followed a different path and forced … a pedestrian to save himself. In their system, the hood rises mechanically under the influence of a previous blow to the bumper (approximately the way active head restraints are arranged). The ingenious lever design is called PEHKS (Pedestrian Protection Hood Kinematic System - a hood with kinematic protection of pedestrians). If it works, for example, with inaccurate parking, it will be enough just … to "close" the hood.
There are other interesting developments. When hitting a pedestrian at a faster speed, the head hits the windshield. A rising hood will not help here, but … an external airbag rolling along the glass is what you need. (At the same time, maybe the glass will survive - the new one is also not cheap!).
All of these devices have not yet gone into production today. Moreover, carmakers, preparing for the inevitable … actively resist the intention of the European Commission to legitimize pedestrian protection systems. But! Instead, they are willingly willing to commit themselves not to install “abnormal” grilles in front of off-road radiators weighing up to 2.5 tons (and rightly so - we are not a kangaroo!). The Association of European Manufacturers of ASEA also promises to equip all cars with an ABS system from July 2004. And since October 2002, to produce 90% of cars with constantly switched on daylight headlights - if only they would not be forced to implement the protection systems described above. The reason is simple: marketers are not sure that the consumer is willing to pay for very expensive devices that do not directly affect the preservation of him, the driver, life and health.
We have yet to educate and educate. For example, using publications of the results of the next crash tests EuroNCAP (European program for testing new cars), where the “stars” earned by running on mannequins on a separate line are given. Look, they say, gentlemen, the prestigious BMW 3 Series and Audi A4 received only one star and, therefore, are extremely dangerous for pedestrians. A little more (two stars) received the Citroen C5, Ford Mondeo, Hyundai Elantra, Peugeot 406 and 307, Skoda Octavia, Opel Vectra, Volvo S60, Alfa Romeo-147 ", " Rover 25 ". But still - bad. Against this background, the most safe "Honda Stream" and "Honda Civic" - they have three stars. Now it’s clear to you who should be afraid first of all when crossing the street into a red light? Low ratings in this nomination are not yet considered a crime that spoils the image of the company, but they push to think in the future about a new approach to design.
Obsessed with the car, Europeans, especially Germans, carefully read such reports and form their preferences on their basis. So, the research that is being conducted today is not completely wasted money. You look useful in the not so distant future.
So they offered to save pedestrians at the beginning of the last century.
The hood of the Otoliv company was raised by steel pneumatic bellows, providing a more “profitable” tilt angle and clearance to the power unit. The speed is about 25 km / h.
The rescue gap between the hood and engine parts is formed by the command of special sensors (“Casting”, EDAG) or lever system (“Ford”).
At a collision speed of 40 km / h, the head hits the windshield - cover it with a pillow.
The degree of damage to the head during its impact on different areas of the hood (HIC criterion, EuroNCAP technique).
Glued hood EDAG.