Design Specifications for Semi Trailers (Part 2)

----Calculation specifications and technical requirements of common parts

1. Calculation specification of common parts of semi-trailer products

1.1. Suspension system

Semi trailer suspension systems mainly include American mechanical suspension, German mechanical suspension, Air suspension and Bogie suspension.

1.1.1 American mechanical suspension

The height H adopted by American mechanical suspension includes 130mm, 150mm, 180mm, 200mm, 225mm, etc. As shown in Figure 1 below.

Figure 1. Schematic diagram of American mechanical suspension

According to different vehicle design requirements, the common American mechanical suspension configurations are shown in Table 1 below:

Table 1. American mechanical suspension configuration

1.1.2 German mechanical suspension

The height H of German mechanical suspension is usually 155mm, as shown in Figure 2 below:

Figure 2. Schematic diagram of German mechanical suspension

According to different semi trailer design requirements, the common American mechanical suspension configurations are shown in Table 1 below:

Table 2. German mechanical suspension configuration

1.1.3 Air suspension

The height FH of air suspension is usually designed according to customer requirements, and the range is generally 340-470mm. The overall load capacity design of air suspension is 9-13 tons, as shown in Figure 3 below.

Table 3. Schematic diagram of air suspension

1.1.4 Bogie suspension

The bogie suspension is mainly used in the African market , Middle-east market and some Southeast Asian markets. Its loading capacity mainly includes 24 tons, 28 tons and 32 tons. As shown in Figure 4 below.

Table 4. Schematic diagram of bogie suspension

The common bogie suspension configurations are shown in Table 3 below:

Table 3. Bogie suspension configuration

1.2. Specifications of common tires and rims

According to the standard GB/T2700-2016 (Tyres’ specification, size, pressure and load of heavy duty vehicles), in the design of semi-trailers, the configuration of tyres and rims usually refers to the data in the following table, as shown in Table 4 below.

Table 4. Common tire and rim parameters

1.3 Leaf springs

A Leaf spring is an important part in mechanical suspension system. American and German mechanical suspension usually includes the following specifications of leaf springs, as shown in Table 5 below.

Table 5. Design Parameters of Leaf Spring

2. Design and calculation specifications of semi trailers

The height dimensions commonly used in semi-trailer design are shown in Figure 4 below.

Figure 4. Semi trailer height diagram

The dimensions are explained as follows:

1) H1: traction height, the height from the top surface of the fifth wheel of the tractor to the ground.

2) H2: Height of the front longitudinal beam

3) H3: Height of the rear longitudinal beam

4) H4: Suspension height

5) H5: Calculation height of the leaf spring

6) H6: Radius of tire.

7) H: Height of the rear cargo platform of the semi-trailer.

8) h: Height difference between heights of the front and the rear of the semi-trailer.

2.1 Height calculation of suspension

H4=H1+H2-h-H3-H5-H6

2.2 Height calculation of the rear cargo platform

H=H3+H4+H5+H6

The height design of semi-trailer is a comprehensive problem, which requires comprehensive consideration of vehicle use requirements and the parameter performance of each part to make a proper choice.

2.3 General technical requirements for semi trailers

The general technical requirements for semi-trailer design are shown in Table 6 below.

By  WONDEE Autoparts

2022-12-8