GB/T 25988-2010Road vehicles -- Towing vehicle coupling device to tow caravans or light trailers -- Mechanical strength test (English PDF)

1 Scope

This standard specifies the test methods for the mechanical strength of coupling devices.

This standard applies to the coupling device, which is installed on the towing vehicle, for towing the category O1 and O2 caravans or light trailer (excluding semi-trailer).

2 Normative references

The provisions in following documents become the provisions of this Standard through reference in this Standard. For the dated references, the subsequent amendments (excluding corrections) or revisions do not apply to this Standard; however, parties who reach an agreement based on this Standard are encouraged to study if the latest versions of these documents are applicable. For undated references, the latest edition of the referenced document applies.

GB/T 3730.2 Road vehicle - Masses - Vocabulary and codes (GB/T 3730.2-1996, idt ISO 1176:1990)

GB/T 22552 Caravans - Masses and dimensions - Vocabulary (GB/T 22552-2008,

ISO 7237:1993, IDT)

GB/T 25980 Road vehicles - Coupling balls for caravans and light trailers -

Dimensions (GB/T 25980-2010, ISO 1103:2007, IDT)

3 Terms and definitions

The terms and definitions, as established in GB/T 22552, as well as the following terms and definitions, apply to this standard.

3.1

Coupling device

A device, which is equipped with towing bracket and coupling ball.

Note: Its common terms are as shown in Figure 1.

Fres - Test resultant force, in Newton (N);

alpha - Test angle, which is composed of the test resultant Fres and the reference line, indicating the degree of the angle;

Fstat - The maximum allowable static load of the trailer, on the coupling point of the towing vehicle, which is determined by the towing vehicle manufacturer;

h - The vertical distance, between the center of the coupling ball and the center of the support;

l - The horizontal distance, between the center of the coupling ball and the connection point of the ball support OR between the connection point of the ball attachment.

5 General conditions

5.1 The size of the coupling device shall comply with the provisions of GB/T 25980.

It shall provide the detailed design information of the coupling device, including information the data that may affect the strength of its components or assemblies (such as electrical connector socket plates, markings, etc.).

5.2 The test range is from the coupling ball to the fixed point or assembly point. The geometrical position of the coupling ball and the fixed point of the connection device, as corresponding to the reference line, shall be marked by the manufacturer AND quoted in the test report.

5.3 The strength test in Chapter 6 is a dynamic test, which is performed on a test rig (e.g., a vibration pulse test rig).

5.4 The test load does not take into account the lateral loads, which are generated by the front and rear axles of the trailer and their supporting devices.

5.5 The test angle is determined by the force distribution diagram, as shown in Figure

2, which is the result of road tests by various vehicle combinations.

To simplify the test procedure, two different test angles can be selected, for vertical static and dynamic loads.

If the center of the coupling ball is lower than the parallel line, which passes through the reference line closest to the highest point of the fixed point (see Figure 3), THEN, the test angle alpha = +15° ± 1° [see Figure 4a)].

If the center of the coupling ball is higher than the parallel line, which passes through the reference line closest to the highest point of the fixed point (see Figure 3), THEN, the test angle alpha = -15° ± 1° [see Figure 4b)].

it shall determine whether the test is appropriate or whether other tests are required, as necessary.

6 Strength test of coupling device

8 Evaluation criteria of strength

During the entire test period, the coupling device and its components (brackets, balls, supports, fixtures) shall not have permanent deformation, cracks or visible external quality degradation.

9 Welding of coupling device

Welding procedures for coupling devices (including welding machinery, welding conditions, welding consumables, welding consumption) shall be consistent with the approved manufacturing process.

10 Marks

The marks shall comply with the provisions of GB/T 25980. It shall be marked with the following contents:

a) The factory name and address of the coupling device manufacturer or the vehicle manufacturer (if the coupling device is produced by a vehicle manufacturer);

b) Approval number. However, if there is no approval number, mark the test number;

c) For the h and l values of the removable coupling ball, it is the determined h and l values;

d) The hmax, lmax, hmin, lmin values for different h and l.

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