Weight Distribution

Distribution of cargo has a definite bearing on the life of tires, axles, frame, and other parts of the vehicle. The fact that a truck or trailer is not loaded beyond its gross vehicle weight capacity does not mean that the individual tires and axles may not be overloaded by faulty distribution of the cargo. Additionally, states have maximums for GVW, GCW, and axle weights. Axle weights prevent the overloading of bridges and roadways. Some examples of proper and improper placement of the load are shown in figure 7-28.

To load a truck or tractor-trailer properly, you have to determine the center of the payload. In a truck, the position of the center of the payload is the center of the body or the point midway between the rear of the driver's cab and the tailgate. In a tractor-trailer unit, the position of the center of the payload is roughly the center of the trailer body, because the front wheels of the tractor seldom carry any of the payload. When you are loading, ensure that the maximum capacity of the vehicle is not

Figure 7-29.-Distribution of weight.

exceeded over any one axle and, if possible, that loads are distributed so there is less-than-maximum axle loading. Examples of approximate distribution of total weight are shown in figure 7-29.

The payload weight must be distributed over the body properly so the percentage of weight carried by the front axle and that carried by the rear axle equals the ratio for which the vehicle was designed, as shown in figure 7-29.

Loading Cargo

The tractor-trailer can be adapted to transport various types of materials, such as fragile, bulky, compact, dense, rough and high center-of-gravity items. To accommodate a variety of items, you must plan the load, properly prepare the tractor-trailer, and secure the load to the vehicle. Securing the load by restraining it with proper lines, cargo straps, chains, or fastened by tie-downs or binders should keep it from shifting or falling off the vehicle. Should a load fall from a vehicle, it could foul underpasses, culverts, bridge abutments, and create a hazard to pedestrians. Protect fragile items

Figure 7-30.-Permanent loading ramp.

from damage by chafing (rubbing together) with cardboard, paper, cloth, or other filler.