SAFE AT ANY SPEED?
More than forty years ago, in 1959, in Stuttgart, for the first time, a serial Mercedes was smashed in a crash test and made sure: even at a speed of only 50 km / h, passengers have no chance to stay alive.
It was then that they recalled the patent DBP 845.157 (1951) by Bel Barenny “Automobiles, in particular, for the transport of people”, related to the construction of safe bodies. His main idea - kinetic energy should turn into work, deforming the front of the body and thereby save the riders. So, the crumpled front and a tough safety cell around passengers - this is the recipe that has survived to this day.
The first crash tests also showed: one of the most dangerous structural elements is the steering column, which pierces the driver’s chest during a collision. Something had to be done urgently. The same Barenny proposed back in 1954 a column with an element weakened at the break, but the idea could not break its way for a long time. The firm stubbornly tried to introduce a telescopic structure, although it proved to be effective only with a purely frontal impact.
Work in a new direction was conducted not only in Germany. The Swedes, for example, in 1959 serially equipped their P120 and P544 models with seat belts, which we still stubbornly do not want to fasten.
Fast forward, however, these days. The density of automobile flows on the roads has increased many times, there’s nothing to say about speed. But take a look at the chart. This shows the number of dead German residents compared to the country's car fleet. Since 1972, the sad curve has plummeted. Cause? Airbags began to appear on cars - they, along with the introduction of mandatory certification of new models for passive safety, turned the tide.
Today, such pillows have become almost an integral part of any modern model. Moreover, on some machines their number in the cabin exceeded ten, and the control of the squibs was brought to full perfection. In the few milliseconds that the blow itself lasts, the computer determines the starting position of each passenger, his age (adult - child), direction and strength of external influences … Accordingly, these or other safety elements are activated: belt pretensioners, pillows, active head restraints are activated.
Let's “open” a few of these very expensive devices and enjoy the original design solutions. Here, for example, the so-called green bag. (This is a sign of respect for the Green from Greenpeace). An impulse comes from the electronic “brains”, and a small squib with arsite explodes. (Arsit came into the car from tanks of solid rockets, it does not contain toxins and carcinogens and leaves only harmless calcium chloride after combustion). Do not think, however, that the gases from this microexplosion fill the pillow. No, the developers of Opel have acted much more cunningly: the task of the squib is only to destroy the chamber wall, which contains absolutely inert argon previously compressed under high pressure! Expanding, it cools the “powder” gases, and the surface temperature of the opened pillow does not exceed + 45 ° C - an excellent result. (Previously, when the pillows were filled with powder gases without quotes, there were cases of burns.) Other, not green, devices were also made difficult: in a couple of tens of milliseconds of the working process, the temperature of the gases drops from 1330 degrees to 150. In extreme cases, it will burn, but not strong. Here in the “exhaust” one can already find the usual CO and NOx, of course, in acceptable concentrations.
However, not only pyrotechnic tricks determine the cost of rescue devices. There are also a lot of electronics. For example, “Smart Airbag” from “Bosch”. (Do not confuse with a microcar.) This system was developed in three stages. At the first, depending on the signals of the accelerometer and sensors in the seat belt locks (that is, on the strength of the blow and the use of the belt by each particular rider), one or two squibs were set on fire or a response delay was introduced. On the second, in 1999, next to the rear-view mirror, ultrasonic and infrared sensors appeared, which determine the position of the passenger and driver immediately before the accident. For example, if the seat is free or the passenger is in an abnormal position (for example, he leaned forward), then the pillow should not be turned on. Finally, at the third stage, with the help of the radar, the whole picture of the future impact can be pre-calculated and, accordingly, the result will be turned on certain pillows, pretensioners and other things. How complicated this algorithm is can be seen from the graph of response thresholds.
But let's leave the pillows and see what else the modern arsenal of passive safety systems is rich in. We will only say about belt pretensioners that the meaning of this (also, by the way, pyrotechnic) device is the choice of the gap between the belt and the human body, which allows it to be protected from initial displacement with subsequent hard stop. The force limiter will not allow the belt to cut too far into the chest and slightly release forward towards the saving pillow.
Another “firearm” device is a safe starter terminal: as you can see in the photo, the positive output of the battery for three milliseconds is reliably disconnected from the aircraft network, which means that the likelihood of a fire and explosion is significantly reduced. And finally, the active head restraints, which we have already written about repeatedly. Usually it is a mechanical (ZR, 1999, No. 10) or pneumatic (ZR, 1999, No. 11) device that selects the gap between the back of the passenger’s neck and the headrest when hitting the rear.
In our time, there are all kinds of combinations. For example, inflatable … seat belts. Or a pedal assembly that breaks off on impact and saves the driver’s legs from fractures.
And yet, none of the most remarkable devices would have fulfilled its purpose, had not been fully realized the long-standing invention of Barenya: a rigid cell and a “soft” front. If there is not enough living space for people, there will simply be no one to save. Therefore, designers are trying to create new materials with predictable deformation - tricky profiles, sandwich panels, foam and honeycomb structures. And the more predictable their behavior, the cheaper the development of a new body. For it becomes possible to simulate crash tests … on a computer screen. Agree, this is much more effective than breaking unique prototypes. Only at the very end, when all the basic calculations and adjustments have already been made, some brand-new cars will nevertheless die at the stand so that we, their future owners, survive!
But they beat cars not only at manufacturing plants. The attention to the problems of passive safety today is so great that many automobile magazines, clubs and motor unions conduct their own crash tests of production models anonymously purchased at car dealerships. The test results are widely covered in the press, a comparative analysis is given. Here is a brief summary of the ADAC test - the General German Automobile Club. In this case, he was interested in small class cars - the most difficult for designers in this regard (see table).
As you can see, not all “kids” are equally safe.
Well, passengers in the cabin, we can say, were protected to the maximum. But there are other participants in the movement, for example pedestrians. You can hardly force them to put on a spacesuit, even for your own safety. Therefore, a standard is being developed for the special design of the front end and hood of a passenger car. It has long been no horned deer, easily ripping open the stomach of a gaping victim. If, for example, the Rolls-Royce cherishes the famous figure on the radiator too much, then you have to make it automatically retractable in the hatch, as soon as any object approaches it. But today, only the licked form of the front end and the hood is no longer enough. Experiment with installing pillows … outside along the top edge of the windshield. Together with the hood, which rises at the moment of collision with a pedestrian, this pillow, rolling on the windshield, will provide a soft "flight" through the sloping roof.
Of course, all these innovations make the car more expensive. But the standard of living in developed countries is gradually increasing, and its preservation takes first place in the scale of values. And probably, very soon about the car it will be possible to say with good reason: it is safe for everyone and at any speed!