The axle load distribution of automobile refers to the vertical load of each axle on the supporting plane when the automobile is in the static state of no-load or full load, and can also be expressed as the percentage of the total mass when it is empty or full load.

Axle load distribution affects tire life and many properties of automobile.

The driving mode, engine position, structural characteristics, head shape and use conditions of the car have significant effects on the axle load distribution. For example, the front axle load of a flat-headed truck driven by the front wheel of the engine is large, while the front axle load of a long-headed truck is small. Off-road vehicles that often drive on bad roads should have a small front axle load.

See Table 6-3 for the axle load distribution of freight cars.

Table 6-3 Distribution of Axle Load of Freight Cars

As can be seen from the table, the bearing capacity of the rear bearing is large when it is fully loaded. When designing, we must first estimate the mass of each component, calculate the center of gravity and front and rear bearing capacity of the drilling rig, and check with the values in Table 6-3. At this time, it is particularly important to check whether the front axle is safe, and the front axle cannot be overloaded. As long as it does not affect the passing performance of the car, individual components can be close to the rear of the car or extend out of the rear of the car, so that the center of gravity of the drilling rig is close to the rear axle.

2. approach angle and departure angle

When the tangent line is drawn from the front and rear protruding points of the car body, the included angle between the tangent line and the road surface is called approach angle and departure angle, as shown in Figure 6- 16. Represents the possibility that the chassis will not collide when approaching and leaving obstacles (such as hills, gullies, depressions, etc.). ). The greater the angle between α and β, the better the passability.

Figure 6- 16 approach angle and departure angle

The approach angle of a car reflects the maximum slope that the car can adapt to when going uphill. The departure angle reflects the maximum slope that can be adapted when going downhill. Reducing the departure angle has obvious influence on the passing performance. When going downhill, the rear of the car will be deformed by friction with the ground. Therefore, when installing hydraulic supports or other parts on the underbody, they should be above the front and rear wheel leads at the lowest position on the underbody.

3. Layout of parts on truck and selection of rig power

All parts of the drilling rig should be arranged in a plane, and the quality should be symmetrical as far as possible.

Vehicle-mounted rigs all have chassis composed of independent rig beams. In order not to raise the height of the center of gravity during transportation and facilitate the maintenance of parts, it is best not to arrange them in a three-dimensional cross.

When the mass on both sides of the main beam is transported asymmetrically, the plane of the rig chassis is obviously inclined when viewed from the back.

The overall dimensions of the vehicle-mounted drilling rig in the transportation state shall conform to the relevant regulations on vehicle loading and transportation.

Objects are generally not allowed to exceed the front of the car, and are allowed to exceed the rear of the car by 2 meters. Vehicle-mounted drilling rig is a special vehicle, and the mast can exceed the front of the vehicle, but it must be agreed with relevant departments through consultation. Therefore, it is necessary to limit the total length of the mast of the truck-mounted drilling rig.

The height of the whole machine shall not exceed 4m.

The width of the drilling rig refers to the horizontal distance between the outermost points on both sides of the cab. Consider the space for diesel engine maintenance.

Whether the power of drilling rig is integrated with the power of automobile should be separated as long as the conditions are met.

Shallow drilling, because domestic trucks have small wheelbase and short chassis, there is basically no room for independent power distribution. In addition, the power required by this kind of drilling rig is generally less than that of the automobile power machine, and the automobile power can be combined with the power of the drilling rig when drilling in short holes. It takes a long time to drill medium and deep holes, and it also takes a long time for the automobile power service drilling rig. Although the car has a short driving distance and drilled several holes, the power machine is close to the repair level, so the power of the car should only undertake the transportation task, and the drilling rig needs to be equipped with another power machine.