1. Principle
Off road, not only for military use, but also for mining. Many mining vehicles are all wheel drive vehicles. There are more three axle vehicles without front wheel drive. Load bearing is also a problem. It is difficult to pull tens of tons of ore and hundreds of tons of ore.
The principle of differential is that if one wheel loses enough friction, it will idle at twice the speed. Generally, full drive can solve the problem. To improve the performance, a differential lock is required to lock the differential function. This is not very useful and complicated. Tractors designed for southern paddy fields all have this device. The car has this, which is basically a meaningless "full configuration", just like the cigarette lighter, which is rarely used.
2. Comfort
Another basic common sense is comfort, which is directly related to the track width. It is easy to understand the geometric principle that the farther the wheel is, the smaller the body swing angle when the front and rear wheels pass through the obstacle in turn. If the two wheels are 100 meters apart and a brick is rolled over, then the position of the passengers will only change up and down, which may be eliminated by the spring, and the angle will almost not have the same "back and forth" change as the rocking chair. This is why the three door presidential car is designed to lengthen the track and improve comfort. The track width directly affects the passing radius. To have a satisfactory passing radius, it is impossible to have a long track width. Therefore, a real off-road vehicle like the 212 cannot be comfortable. The two are incompatible. You can't live without me. The fourth indicator is the climbing capacity. The highway design is expressed in percentage, the railway design is expressed in thousandth, and the automobile design is expressed in angle. This is an unreasonable contradiction and needs conversion. The climbing ability is mainly determined by the engine torque, and the diesel engine is superior to the gasoline engine. In fact, there are other factors. For example, when the oil level is inclined, the oil tank and oil pump should be able to absorb oil.
3. All wheel drive
With all wheel drive, you can leave the road for off-road driving, but the traffic capacity and different layout design will not be the same. First of all, the basic knowledge is that the chassis should be high, which depends on the tire diameter. In theory, layout is to obtain three indicators: approach angle, departure angle and passing radius. The approach angle is the angle at which the car can climb (not to the top, but to the top). It consists of the angle formed by the front wheel and bumper.
If the approach angle is small and the actual slope is large, the bumper will touch the road before the wheels go up the slope. Take the wall as an example. No car can have a 90 degree approach angle. If the wheels can't touch the wall at all, the bumper will stand against it, so it can't get on the wall. The car must have hit the wall.
If the front wheel trimming is outside the car body and can touch the wall first, then there will be 90% approach angle and you can climb the wall theoretically. The departure angle is opposite. The rear wheel is formed with the rear edge of the car, which determines how much the car can leave. If this angle is not enough, then when the car turns to the flat road after going downhill, the car body will scratch the road before the rear wheels reach the flat road, and the rear wheels will become "suspended". As if the car had been immobilized, it could not move. In the same way, if the rear wheel trimming is outside the body, theoretically there is also 90% departure angle, which may leave the wall.
4. Two rounds
Two wheels, and the lowest point (usually the transmission shaft) at the bottom of the car, draw an arc at three points, that is, through the radius. This decision can be too big a dike type obstacle. If the passing radius of the car is too large, when passing through an obstacle with a small radius, before the front wheel lands, the car body or transmission shaft will touch the obstacle, and in serious cases, it will be put up and become a "warping plate", which cannot be moved. The drive shaft of the rear drive will certainly be damaged.
