GB/T 44126.2-2024Road vehicles - Test of braking systems on vehicles with a maximum authorized total mass of over 3.5 t using a roller brake tester - Part 2: Air over hydraulic and purely hydraulic braking systems (English PDF)

Foreword

This document was drafted in accordance with the provisions of GB/T 1.1-2020

Directives for standardization - Part 1.Rules for the structure and drafting of

standardizing documents.

This document is part 2 of GB/T 44126 Road vehicles - Test of braking systems on

vehicles with a maximum authorized total mass of over 3.5 t using a roller brake tester.

GB/T 44126 has been published in the following parts.

-- Part 2.Air over hydraulic and purely hydraulic braking systems.

This document is modified in relation to ISO 21069-2.2008 Road vehicles - Test of

braking systems on vehicles with a maximum authorized total mass of over 3.5 t using

a roller brake tester - Part 2.Air over hydraulic and purely hydraulic braking systems.

This document has made the following structural adjustments compared to ISO 21069-

2.2008.

-- Chapter 2 is added;

-- Chapter 3 corresponds to Chapter 2 of ISO 21069-2.2008;

-- Chapter 4 corresponds to Chapter 3 of ISO 21069-2.2008;

-- Chapter 5 corresponds to Chapter 4 of ISO21069-2.2008.

The technical differences between this document and ISO 21069-2.2008 and their

reasons are as follows.

-- The scope of application of the standard is changed to clarify the content of the

standard (see Chapter 1);

-- The normative reference GB/T 15089 is added to clarify the specific vehicle

models to which it is applicable (see Chapter 1).

The following editorial changes were made to this document.

-- Appendix B of ISO 21069-2.2008 has been deleted because it does not contain

specific technical content;

-- Note 2 of 4.4.2 in ISO 21069-2.2008 has been deleted because this part does not

contain specific technical content.

1 Scope

This document specifies the terms and definitions, test methods, test conditions, test

equipment, and data processing for the test of brake systems using a roller brake tester.

This document is applicable to tests on vehicles of categories M2, M3, N2, N3, O3 and

O4 as specified in GB/T 15089, with a maximum authorized total mass of more than

2 Normative references

The provisions of the following documents constitute the essential clauses of this

document through normative references in this text. Among them, for referenced

documents with dates, only the versions corresponding to the dates are applicable to

this document; for referenced documents without dates, the latest versions (including

all amendments) are applicable to this document.

GB/T 15089 Classification of power-driven vehicles and trailers

3 Terms and definitions

The following terms and definitions apply to this document.

4 Symbols

See Table 1 for general symbols and definitions, and Table 2 for special symbols and

definitions for air-over-hydraulic braking systems.

5 Test conditions and measurement methods

530 mm~1300 mm can be tested.

A.1.5 In order to obtain the locking point of the tested axle under greater braking

force/wheel end pressure, the height of the upper surface of the roller can be raised to

40 mm, but not higher than the front roller by 100 mm.

In order to inspect the multi-axle group (bogie), some rollers shall be raised. The upper

surface of the rear roller and the front roller can be raised by 40 mm, but the height

from the ground shall not be greater than 100 mm.

A.1.6 When the tires normally used on commercial vehicles are used for testing, the

surface adhesion coefficient of the driving roller shall be above 0.7 in dry state and

above 0.5 in wet state.

NOTE. Due to the distance between the two rollers, the effective adhesion coefficient may be lower than

the above values.

A.1.7 The test equipment shall be able to operate at an ambient temperature of at least

5 °C~40 °C (can be lower than 5 °C). If it is necessary to operate at a temperature

outside this range, the local ambient temperature shall be controlled or a tester designed

for more extreme conditions shall be used.

A.1.8 The installation and use of roller brake test equipment shall comply with national

workplace safety standards. In the absence of such standards, the following minimum

requirements apply.

a) If the test device is equipped with an automatic roller start function, the roller

can only start after the axle is placed on the roller for 3 seconds or more.

b) An automatic cut-off function shall be provided to avoid tire damage. If the

slip between the tire and the roller is detected to be beyond the range of

27%±3%, the test shall be terminated automatically.

c) The roller drive shall stop automatically once the vehicle axle leaves the roller

tester.

d) It shall have a safety function to ensure that the two pairs of rollers can only

be started when the left and right wheels of the tested vehicle are loaded

simultaneously.

e) The working foundation pit where the roller brake tester is installed shall be

equipped with a foundation pit safety system.

f) If installed on a foundation pit, the roller brake tester shall have an automatic

stop function. When someone enters the dangerous area in the pit (the entire

pit length or within 2.5 m from the roller in any direction), the roller drive shall

stop.

g) It shall have an emergency stop function, and its button shall be located in a

conspicuous position.

h) It shall have a protection function to ensure that electrical/electronic control

and transmission are free from electromagnetic interference and any other

interference.

i) There shall be measures to prevent the roller drive motor from starting

accidentally.

A.2 Measurement system range and resolution

A.2.1 Measurement range

The measurement range of single-wheel braking force shall be calculated according to

A.1.1.Table A.1 lists several common axle loads and their corresponding maximum

design braking forces.

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