Some regions and industries need to use off-road transport vehicles, that is, heavy vehicles with off-road capabilities. Although the road logistics vehicle has a certain ability to cope with complex road conditions, the vehicle structure is still quite different from the multi-function off-road vehicle. So what are the requirements for vehicles that can cross mountains?
We usually talk about 'chassis height', which actually refers to the passing ability of the vehicle. It has several commonly used evaluation indicators: minimum ground clearance, approach angle, departure angle, and longitudinal passing angle (or longitudinal passing radius).
I believe that many old drivers have some knowledge of these parameter terms, so there is no text analysis here, just look at the illustration. The larger the minimum ground clearance, approach angle, departure angle, and passing angle, the better the vehicle's passing performance.
Highway dump truck with high chassis can cope with general rotten
The overall height of road vehicles is low. Not only is the poor passability, but some key components such as engine oil pans and gearboxes are also prone to damage in complex road conditions. Therefore, off-highway vehicles must first increase the overall height including the cab. The common practice is to use large-diameter tires to increase the suspension height.
Gate axles for off-road use
The height of the body from the ground is large enough to cope with many non-paved roads, but there is a technical difficulty in dealing with extreme road conditions, that is, the height of the axle-the tooth wrap is often the lowest off the ground. This has a portal axle.
The wheel-side reduction mechanism of the portal axle can increase the axle height
The gate axle for off-road vehicles, the axle axis is higher than the wheel axis, it is achieved by the gear reduction mechanism on the wheel side, so it is also a type of wheel reduction bridge. The use of a portal axle not only improves the passability, but also amplifies the torque output on the wheels. The light and medium-sized Unimog and the heavy-duty tow trucks all use gantry axles.
Power, driving form and tires:
Strong engine power is also necessary. On the one hand, due to the complex structure of the multi-axis drive, it will bring more transmission losses, on the other hand, in complex road conditions, it is necessary to cope with the situation of high-angle climbing and multiple tire slipping.
Multi-wheel drive or even all-wheel drive is the iconic configuration of off-road vehicles. It can play an effective power output in extreme road conditions and help to get out of the trap.
4x4 transport vehicle
It should be noted that the multi-wheel drive mentioned here should include front and rear axles. The double rear drive of a road truck is not considered for off-road use. When driving on mountain roads, front and rear axle load transfer, such as reversing and climbing, the front axle functions like the rear axle, so the front axle can drive and steer, and the load capacity is also very important. same.
Block pattern off-road tires
For any type of vehicle, tires are critical. Off-road tires are thicker and more wear-resistant, usually using a block tread. Off-road tires are also divided into types, suitable for different environments. For example, the special tire for mud (MT tire) has wide and deep tread grooves, which can play more power on the dirt road and it is easier to throw the mud away, but the adhesion on the paved road is lower. In addition, when off-road driving, the tire pressure should also be set to a lower value, but it should not be too low, depending on the use.
The output torque is related to the outer diameter of the tire
In addition to the gearbox, axle deceleration, and wheel deceleration, the tire size also changes the power output. The larger the outer diameter of the tire, the less the driving force of the wheel. Therefore, the selection of tire size is also very important for small, four-wheel-drive vehicles without wheel reduction bridges and limited power.
Suspension and axle:
The off-road performance of road bikes is low. In addition to the passability and driving form, suspension and axles are also restricted. The balance axle suspension of the double rear drive makes the axle have a certain swing amplitude, but it is not enough for off-road. Sometimes 4X2 may be better than 6X4, because the suspension of the two-axle car is more flexible and the wheels are more likely to contact the road.
Too much dragging the iconic chassis structure
Setting a larger suspension stroke is to solve this problem. Light vehicles can use long coil springs, long shock absorbers and other components to increase the suspension travel. Compared with heavy-duty vehicles, the leaf springs are inferior, but the balance between load-bearing capacity and flexibility is a difficulty in setting the suspension.
Tow axles, disconnectable swingable axles
Some off-road vehicles make a fuss on the axle. The most representative technology of too dragging is the chassis structure of the central spine tube frame and the disconnected swinging half shaft. Because the axle housing is not integrated, the middle part adopts a soft connection, and the two half shafts can swing, so it is the same as the independently suspended vehicle. The wheels on both sides do not interfere with each other while driving, which greatly improves off-road performance. However, the structure that is too procrastinating has certain specialities, so there are many shortcomings, and the integrated bridge that is simple and more reliable is widely used.