LESSON 3. LEARN TO MANEUVER
What you should know about the car?
Experts distinguish between active, passive, post-accident and environmental safety of the car and the environment movement. The last three types of security largely depend on constructive activities, while active safety, under which unde s measures for the prevention of accidents largely depends on human factor. For brevity we will focus only on those elements of active safety, which should include the driver in its activities. The forces acting on the car. When driving the car overcomes the force of rolling resistance, air lift, inera tion, and at movement on turn on it lateral force operates the Manifestation of the forces acting on the car when driving, can be confusing for an inexperienced driver and lead to a road traffic accident. To avoid this, you must learn to consider these forces and use them rationally, and you need to know under what conditions they arise and as abided, namely:
1) force of rolling resistance arises from friction Shino the road, their elastic deformation, friction in bearings of wheels, etc.;
2) the force of air resistance depends on the aerodynamics and frontal area of the car and sharply increases with increase in speed;
3) force of resistance to rise interferes with force of traction in th EME, and she the more, than more abruptly rise, and on descent, on the contrary, warehouses, as it is built with traction force and additionally speeds up the movement of the vehicle;
4) inertial forces arise at change of speed or direction of motion (lateral force), they prevent the acceleration and braking of the car, and in turn seek to shift it in opposite signs about the center of rotation. Troganie and movement of the car on the road is possible only under the condition that the thrust force developed by the motor and applied in contact with the road, exceeds the total force of resistance to tulene acting on the car. The obligatory conditions of a sufficient coupling wheels of the car, especially leading with the road surface, otherwise they will stall. The adhesive force depends on the mass per wheel, the state of the road surface, the air pressure in the tires and tread.If I stop the app force thrust, on a horizontal road a car under the influence of forces of resistance will gradually stop. The car can be stopped with the brake system. Efficiency of braking depends on the brake design, the magnitude of braking torque, condition of the tires and the road. The brakes of modern vehicles can produce far exceeds the next power of traction. Therefore, in practice, t is SW,when the wheels of the car are blocked and slide on road, not revolving. Thus from the intense heat deteriorates rubber traction of the road wheels and the braking distance is extended to 50%. In addition, the car may lose control. So we need to learn to brake without locking the wheels. On modern cars shall be defined regulators of braking forces that impede the development of wheel-lock.
To assess the impact of road conditions on the adhesion force is adhesion coefficient, which depends on the type of road surface and its condition. Wet, dirty road reduces size to the factor, and hence the force of adhesion of approximately half br well. Reducing the coefficient of traction is also observed when increasing speed. In case of low coefficients the case of coupling sharply increases the path taken by the vehicle to decelerate. Distinguish a brake and stopping way. The latter is determined from the moment of detection of danger up to a full stop Avto
mobile, and the brake way is counted from the moment of switching of the braking system to a full stop and depends mainly on the design of the brakes. The length of a stopping way in many respects depends on the driver, as it includes the path traveled by the vehicle during the driver's reaction time, which, depending on the complexity of the situation and features of the driver kolebletsja on the average from 0.2 to 1.2 s. thus a brake way only from for various time of reaction
can differ almost on 17 m at an initial speed of 60 km/h, and the path traveled by the vehicle during the driver's reaction time can be almost half the total stopping distance. Therefore, water tel, knowing places of probable occurrence of danger (a stop of public transport, the fare children's establishments, crossings, places with limited review, etc.), in advance transfers a leg on a pedal tor Mose. At real occurrence of danger he at once presses on the brake pedal, spending of 0.2–0.3 s. Stopping distance when the velocity is ti 60 km/h on the dry asphalted covering is about 37 m, on wet — 60, on ice-covered road — 152 m. It should take into account the driver when the safe driving speed in dependence of the status of the road. If operated wheels of the car turn, the car starts to act the lateral force tending to displace it from the prices of tra rotation. The driver usually at once feels it, the car is on the side of the roll, and it deflects in the opposite direction. If lateral force exceeds forces of lateral coupling with road, the car starts to slide sideways (RWD — log),increasing the turning radius. So it may not fit in povo mouth, to pull off the road and even to overturn. The action of lateral force depends on radius of turn and vehicle speed. Than the turning radius is, the less its effect. So an experienced driver is seeking to maximally increase the radius of the turn, using the whole width of the lane, but without going into oncoming traffic. The speed in turn changes lateral force in square-law dependence: if
speed to increase in 2 times, action of lateral force will increase in 4 times. Therefore, the reduction of speed before entering the turn is compulsory condition of its safe passage, except for up to the horn where speed is better to increase. Then the current stronger lateral force presses the car to the road. Steady (without drift) movement on turn depends also from with the standing tire and the road, the forces of lateral coupling of wheels with road, from
features drive on drive wheels (rear-drive, front-wheel drive, four-wheel drive) and on the location of the cargo. Drift and observed keyvani arise more likely on slippery roads in rear-wheel drive car with load, greatly in favour of the side boards. The most stable to drift AWD and FWD cars.
The phenomenon of withdrawal. When cornering due to the lateral elasticity of the tire there's sort of a drift car (without about skalyvanie) in the direction opposite to the steering kole sa. The phenomenon of withdrawal also can arise under action strong wind gusts. The higher the speed of movement on turn, the greater the slip. This phenomenon has, in certain circumstances of serious importance to traffic safety and the driver should be able
to take into account. If the driver fails to compensate for lateral avocatului turning the steering wheel when turning it right you set on a strip of oncoming traffic and the left turn — will drag along on the side of the road. Side pull due to the effects of wind usually are to compensate for a corresponding rotation of the steering wheel. Therefore, when entering de in a zone of calm it is necessary to reduce the angle of the steering wheel to avoid sudden changes of direction.
The handling and stability. Under the controllability understand the ability of a car to save or change the direction of movement accurately in accordance with applied effects. For conservation of rectilinear motion of the steered wheels of the vehicle and the suspension are established under some angles that ensures a stabilization of the front wheels (return to neutral)in case of accidental deviations after the exit of the turn.
Under the stability understand ability of the vehicle to counteract the drift (lateral sliding) and overturning. More than not turn the lateral stability violation arising selectivedelete lateral forces and lateral component of the force of gravity.The stability of a moving car depends on many factors include: vehicle weight, height of center of gravity, track width,a base the size of your tires, their construction and condition; radii of curvature of roads and the condition of its surface, speed and direction of motion of; ability to drive a car and others found that the higher the vehicle's centre of gravity and the narrower track and the base, the higher the probability of overturning on to sagore or climbing. It occurs when the force vector of gravity flows through the point of contact of the wheel with the road.The presence of cargo in the back, especially large, increases the height of the center of gravity, thereby reducing the resistance.On the turn a significant influence on stability renders so speed of turn of the guided wheels. A sharp turn more
total leads to overturning of the vehicle. Movement on a slope increases the chance of a rollover due to a possible displacement of cargo and passengers.
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