Conditions for Drift
The conditions for Drift can be attributed to one thing: the rear wheel loses most (or all) of the grip, while the front wheel can maintain the grip (at most, only a small part can be lost, and it is best to gain extra grip); At this time, as long as the front wheel has a certain lateral force, the car will flick its tail and drift.
methods to make the rear wheel lose grip
1. make the rear wheel have a negative speed difference with the ground during driving (the rear wheel speed is relatively low)
2. make the rear wheel have a positive speed difference with the ground under any circumstances (the rear wheel speed is relatively high)
3. reduce the positive pressure between the rear wheel and the ground during driving.
it is enough to satisfy one of the three items. In fact, 1 and 2 are methods to reduce the friction coefficient, and they are separated because of different application methods.
methods to keep the grip of the front wheel
1. Do not make a big speed difference between the front wheel and the ground during driving
2. Do not reduce the positive pressure between the front wheel and the ground too much during driving, but it is best to increase the positive pressure. These two items must be met at the same time.
in actual operation, the hand brake must ensure that there is a negative speed difference between the rear wheel and the ground during driving (the speed of the rear wheel is relatively low) and that there is no big speed difference between the front wheel and the ground during driving.
there are ways to produce drift:
1. pull the handbrake and then hit the direction when driving in a straight road
2. pull the handbrake when turning
3. slam on the brake when driving in a straight road and then hit the direction
4. slam on the brake when turning
5. rear-wheel drive vehicles with sufficient power (or four-wheel drive vehicles with the driving force distribution ratio of front and rear wheels tending to rear-wheel drive) slam when the speed is not very high.
Among them, 3 and 4 use weight transfer (the weight of the rear wheel is transferred to the front wheel), which is the method to least hurt the car. One or two four-wheel drive vehicles are only used for front-wheel drive and rally racing, and they are free, unless you are not afraid of damaging the car. Note that 1 and 2, 3 and 4 are separated because the movement route of the car will be very different. Important note: drift cornering, like ordinary cornering, has a speed limit, and the speed limit of drift cornering can only be higher than ordinary cornering at most, and the speed limit of drift cornering on hard ground is lower than ordinary cornering!
whether the tail can be swung at last is related to many factors, such as the friction coefficient between the tire and the road surface, the speed of the car, the braking force, the size of the throttle, the angle of the front wheel, the weight distribution of the car, the wheel track wheelbase, the soft and hard suspension and so on. For example, it is easy to shake your tail when driving in rainy days and snow, but it is more difficult not to shake your tail; The higher the driving speed, the easier it is to flick the tail (so the first rule of safe driving is not to drive too fast); Hit the direction quickly, and it is easy to flick the tail (the master who taught me to drive told me not to hit the steering wheel too fast); The smaller the wheelbase, the higher the body, the more severe the weight transfer, and the easier it is to shake the tail (and it is easy to roll over! ）； The weaker the anti-tilting effect of the front suspension system, the easier it is to swing the tail.
Control in tail flick
If the car drifts with the handbrake, you should release the handbrake when the car rotates to your desired angle.
the task in the middle of drifting is to adjust the posture of the car body. Because the road surface is uneven, the degree of route bending, the cornering characteristics of cars and other factors will change frequently. Therefore, drivers often have to control the steering wheel, throttle, brake and even clutch (not recommended) so that the car can follow the driver's desired route.
first, explain the principle: to make the wheel slide long, we should try to reduce the friction between the wheel and the ground; To make the wheels slip less, we should increase the friction as much as possible. As mentioned before, the ways to reduce friction are to make the wheels rotate too fast or too slowly, and to reduce the positive pressure between the wheels and the ground. The way to increase friction is the opposite.
Among them, the way to make the wheels rotate too slowly is to step on the foot brake or hand brake (again: the foot brake acts on four wheels, and the hand brake acts on the rear wheels. No matter whether there is a handbrake on a car with other wheels, all the racing cars I know with handbrake are what I said.)
Pedal brake: all four wheels will slow down, and it cannot be generalized whether the front wheel loses more friction or the rear wheel loses more friction.
hand brake: the front wheel will not lose friction while the rear wheel will lose a lot of friction, so it is easy to oversteer. Because both the foot brake and the hand brake can slow down, the car will soon stop skidding.
real drift
and if you want the wheels to slip for a long distance, the only way is to let the driving wheels idle at high speed, and you must have a car with LSD and enough power to do this. Why is there LSD? Because the car body will tilt when it drifts, the pressure of the outer wheels on the ground is large, and the pressure of the inner wheels is small. Without LSD, the inner driving wheel will idle and the outer driving wheel will rotate slowly. The friction between the slow-moving wheel and the ground is large, and the side slip of the car will soon stop.
cars are divided into front drive, rear drive and four-wheel drive, and wheels without driving force cannot idle at high speed. Then the rear wheel of the front drive car can't do long-distance sideslip. If the driving wheel (that is, the front wheel) idles at high speed and sideslip is more than the rear wheel, the drift angle will be reduced, so the front drive car can't do long-distance drift. A four-wheel drive car is obviously possible. What about the rear drive? The front wheel of the rear-wheel drive has no driving force, but the front wheel can swing at an angle in the direction of the car body sliding, so the rear-wheel drive can also drift for a long distance.
The sideslip distance is related to the speed before the sideslip starts, which usually slows down and finally stops. However, if the site permits and is well controlled, it can theoretically do an infinite sideslip. Because the skidding wheels still have some acceleration, and the skidding tires are also resisted by the ground, when these two functions are balanced, the speed of the car will not decrease. For example, Doughnut is one of the infinite drift, but it can also make an infinite drift with a large turning radius.
all the above are methods to control the side slip length of the driving wheel.
methods used to adjust the body posture
1. control the angle of the front wheel, not too big or too small, especially for the rear-wheel drive
2. adjust the throttle and brake, so that the car tends to accelerate or decelerate, which will result in weight transfer, and control whether the front of the car slides more outward or the rear of the car slides more outward through weight transfer
3. use the hand brake to produce oversteer again.
Note: In 2, the effect of refueling with rear-wheel drive (or four-wheel drive with power distribution ratio tending to rear-wheel drive) is not necessarily acceleration. If refueling is too fierce, the friction may be reduced because the rear wheel speed is too high, and the rear of the car will slide more outwards.
Maximum drift angle
In the middle of drift, if the angle between the direction of the car head and the direction of the car body is greater than this angle, you must stop (if you don't stop, you will crash out). Note that it does not include when drift occurs.
for a rear-wheel drive vehicle, because the front wheel has no driving force, it can't produce high-speed idle steering and outward sliding, and only the lateral force facing the front wheel controls the movement of the front wheel. Therefore, the angle between the direction of the front of the car and the direction of the car body movement can only be equal to the maximum swing angle of the front wheel at most (the swing angle of the front wheel of different cars is different, and the swing angle of the front wheel of a general car can be about 3 degrees). If it is a little bigger, there is no way to restore the correct driving except to stop and start again. Note that the "large angle drift" mentioned by ordinary people does not refer to the angle between the direction of the car head and the direction of the car body movement, but the angle marked by the red in the attached figure. The steeper the bend, the greater the angle.
the rear-wheel drive also has insufficient front wheel grip and insufficient steering. In this case, the angle between the direction of the car head and the direction of the car body movement can not exceed the maximum drift angle, otherwise it must stop to resume normal driving.
the front drive can keep the grip of the rear wheel and increase the throttle to make the front wheel slide outward, so the maximum drift angle of the front drive is very large, which can be close to 9 degrees.
because the front and rear wheels of the four-wheel drive can idle at high speed, there is more possibility that the front wheel will slip outward when refueling (because the weight will be transferred to the rear wheel when refueling, and the friction between the front wheel and the ground is small), and the front wheel can swing outward, then the maximum drift angle of the four-wheel drive is larger than that of the rear-wheel drive.
comparing the three driving forms, the front drive is the easiest and safest to drive.
drifting out of the bend
the drift should be ended when the bend is made, and the ending method is the same as the method of reducing the drift angle in the drift process.
for the front-wheel drive,
1. refuel to make the front of the vehicle slide outward (because the front-wheel drive is basically understeer except when drifting occurs)
2. correct the front-wheel angle by swinging the front wheel outward
3. You can also put a little throttle after swinging the front wheel outward.
for four-wheel drive, 2 is usually necessary, 3 is also effective, and 1 is not necessarily effective.
for rear-wheel drive, the main 2. Depending on the specific situation, the weight distribution, driving force distribution, previous drift angle, road conditions and other factors have an impact.
pay attention to the fact that the car body is sliding outward during the whole drifting process (including the generation, midway and ending), so when preparing to turn, don't point the front of the car at the outside of the road, but point it inward, so that the lateral speed is just zero when the car slides to the outermost side of the road, which is the perfect turn.
Drifting in different cars requires a period of adaptation to understand the characteristics of cars; There should also be an adaptation process on different roads. In the rally, because the specific situation of each corner is unknown, even if you have run this stage last season, the road surface will not be the same as before. Therefore, the principle of "slow in and fast out" is advocated in the corner of rally-slow down before entering the corner, and then you can increase the throttle after seeing the corner clearly. Using this principle to turn a corner will not be much slower, and the safety will be greatly improved.
for the rear-wheel drive, if you want to float a long distance (that is, a long curve), you must step on the accelerator. Take the left curve you mentioned as an example, the center of gravity of the car is biased towards the right front wheel (the outer front wheel of the curve), and the pressure of the four wheels on the ground is: right (outer) front wheel >; Left (inner) front wheel >: Right (outer) rear wheel > Left (inner) rear wheel. In the process of drifting, the rear wheel slips and loses its adhesion to the ground, and the wheel speed ratio is low (due to the original concern of braking due to drifting). However, with drifting, the car stalls, and the vehicle speed slowly decreases. When the vehicle speed is as low as the rear wheel speed (because the rear wheel loses its adhesion, the resistance is small, so the rear wheel speed decreases more slowly than the vehicle speed), the rear wheel will resume its adhesion to the ground, and the drifting will end. In order to drift further, it is necessary to ensure the rear wheel speed. That is to say, to ensure that the difference between the rear wheel speed and the vehicle speed remains longer, the best way is to refuel so that the rear wheel speed is faster than the vehicle speed. In this way, no matter how much the vehicle speed drops, the rear wheel can be guaranteed to lose adhesion, thus ensuring the drifting time. This is the "dynamic tire sliding" in drifting, and the time and direction of sliding can be controlled by using the throttle and the direction of the front wheel. However, for the front-wheel drive with drifting brakes, refueling will accelerate the speed of the front wheel, but the front wheel is attached during drifting (except for four-wheel drift), so refueling will accelerate the car and cause the center of gravity to move backwards.