The semi-trailer has a low bearing surface, and the center of gravity is low when the cargo is fully loaded, and the lateral stability is good in driving.
Under the premise of ensuring the passability of the semi-trailer, the bearing surface should be as low as possible, and the bearing surface is low. The main advantages are as follows: first, the semi-trailer has a low bearing surface, and the center of gravity is low when the cargo is fully loaded, and the lateral stability is good in the road. When it is not easy to roll over, the safety of the train is improved. Secondly, the bearing surface is low, the corresponding semi-trailer has a small shape, and the wind resistance is small, which can save fuel. In addition, the bearing surface is low, which can reduce the labor intensity of the loading and unloading personnel and improve the loading and unloading efficiency. Semi-trailer designers can design the cargo platform as a flat cargo platform (see Figure 3), a stepped cargo platform (see Figure 4), and a concave beam cargo platform (see Figure 5) depending on the type of cargo being transported. Some manufacturers have designed the frame as an overall load-bearing type, which reduces the height of the semi-trailer gooseneck and thus reduces the bearing surface. At the 62nd Hannover International Commercial Vehicle Show in Germany, the Phoenix series van semi-trailer changed the material of the gooseneck from the past steel plate and aluminum alloy plate to all carbon fiber. The thickness of the gooseneck is 90mm. It becomes 50mm, which reduces the height of the gooseneck of the semi-trailer, thus reducing the bearing surface [4]. However, it should be noted that when lowering the load-bearing surface of the semi-trailer, the distance between the tire and the side members such as the side sill, the bottom plate and the cable hook above the frame should be considered. If the size is too small, the semi-trailer is full or driving on rough roads. Due to the action of the dynamic load and the up and down swing of the balance beam in the suspension assembly, the tire is easily collided with the steel parts above it, causing the tire to be scratched. When designing, the tire should be kept at a gap of 100mm-150mm with the steel parts above it to ensure the beating of the tires in the driving.
