[F1ANNEX III U.K. Method of measuring the reaction time for vehicles with compressed-air braking systems
Textual Amendments
1. GENERAL REQUIREMENTS U.K.
1.1. The reaction time for the braking system shall be determined with the vehicle stationary, the pressure being measured at the opening of the least favourable brake cylinder. In the case of vehicles fitted with combined compressed-air/hydraulic braking systems, the pressure may be measured at the opening of the least favourable pneumatic unit. For vehicles equipped with load sensing devices, these shall be set in the ‘ laden ’ position. U.K.
1.2. During the tests, the stroke of the brake cylinders of the individual axles shall be that corresponding to the most closely adjusted brakes. U.K.
1.3. The times determined in implementing the provisions of this Annex shall be rounded to the nearest 10th of a second. If the figure representing the 100ths is five or more, the reaction time is rounded up to the next highest 10th. U.K.
2. MOTOR VEHICLES U.K.
2.1. At the start of each test, the pressure in the reservoirs shall be equal to the minimum pressure at which the governor starts feeding the installation again. In installations not fitted with a governor (e.g. pressure-limited compressor) the pressure in the reservoir at the start of each test shall be equal to 90 % of the pressure stated by the manufacturer, as defined in point 1.2.2.1 of Annex IV, to be used for tests prescribed in this Annex. U.K.
2.2. Reaction times in terms of actuation time (t f ) shall be obtained by a series of actuations to the fullest extent, starting from the shortest possible up to a time of about 0,4 seconds. The values measured shall be given on a diagram. U.K.
2.3. Reaction times corresponding to an actuation time of 0,2 seconds shall be determinant for the test. This reaction time can be obtained from the diagram by interpolation. U.K.
2.4. In the case of the actuation time of 0,2 seconds, the time elapsing between the beginning of actuation of the control pedal and the moment when the pressure in the brake cylinder reaches 75 % of its asymptotic value shall not exceed 0,6 seconds. U.K.
2.5. In the case of motor vehicles having a brake coupling for trailers, in addition to the requirements of point 1.1 the reaction time shall be measured at the extremity of a pipe 2,5 m long with an internal diameter of 13 mm which shall be joined to the coupling head of the control line of the service braking system. During this test a volume of 385 ± 5 cm 3 (which is deemed to be equivalent to the volume of a pipe 2,5 m long with an internal diameter of 13 mm and under a pressure of 6,5 bar) shall be connected to the coupling head of the supply line. U.K.
Tractive units for semi-trailers shall be equipped with flexible pipes for making the connection to semi-trailers. The coupling heads will therefore be at the extremity of those flexible pipes. The length and internal diameter of the pipes is entered at point 2.6.3 of the test report (Annex IX, Appendix 2).
2.6. The time which elapses between the start of the activation of the control pedal and the moment when the pressure measured at the coupling head of the control line reaches x % of its asymptotic value shall not exceed the values listed in the table below: U.K.
| x (%) | t (seconds) |
|---|---|
| 10 | 0,2 |
| 75 | 0,4 |
2.7. In the case of motor vehicles authorised to tow trailers of category O 3 or O 4 fitted with compressed-air braking systems, in addition to the abovementioned requirements, the prescriptions in point 2.2.1.18.4.1 of Annex I shall be verified by conducting the following test: U.K.
(a)
by measuring the pressure at the extremity of a pipe 2,5 m long with an internal diameter of 13 mm which shall be joined to the coupling head of the supply line;
(b)
by simulating a failure of the control line at the coupling head;
(c)
by actuating the service braking system control device in 0,2 seconds, as described in point 2.3.
3. TRAILERS (including semi-trailers) U.K.
3.1. The reaction times for trailers shall be measured without a towing vehicle. To simulate the towing vehicle it is necessary to provide a simulator to which the coupling heads of the control line and of the supply line of the trailer are to be connected. U.K.
3.2. The pressure in the supply line shall be 6,5 bar. U.K.
3.3. The simulator shall have the following features: U.K.
3.3.1. It shall have a reservoir with a capacity of 30 litres which shall be charged to a pressure of 6,5 bar before each test and which shall not be recharged during each test. At the outlet of the braking control device the simulator shall incorporate an orifice with a diameter of from 4,0 to 4,3 mm inclusive. The volume of the pipe measured from the orifice up to and including the coupling head shall be 385 ± 5 cm 3 (which is deemed to be equivalent to the volume of a pipe 2,5 m long with an internal diameter of 13 mm and under a pressure of 6,5 bar). The control line pressures referred to in point 3.3.3 shall be measured immediately downstream of the orifice. U.K.
3.3.2. The braking system control shall be so designed that its performance in use is not affected by the tester. U.K.
3.3.3. The simulator shall be set, e.g. through the choice of orifice in accordance with point 3.3.1, in such a way that, if a reservoir of 385 ± 5 cm 3 is joined to it, the time taken for the pressure to increase from 0,65 to 4,9 bar (10 and 75 % respectively of the nominal pressure of 6,5 bar), shall be 0,2 ± 0,01 seconds. If a reservoir of 1 155 ± 15 cm 3 is substituted for the abovementioned reservoir, the time taken for the pressure to increase from 0,65 to 4,9 bar without further adjustment shall be 0,38 ± 0,02 seconds. Between these two pressure values the pressure shall increase in an approximately linear way. These reservoirs shall be connected to the coupling head without using flexible pipes and shall have an internal diameter of not less than 10 mm. U.K.
3.3.4. The diagram in the Appendix to this Annex gives an example of the correct configuration and use of the simulator. U.K.
3.4. The time elapsing between the moment when the pressure produced in the control line by the simulator reaches 0,65 bar and the moment when the pressure in the brake actuator of the trailer reaches 75 % of its asymptotic value shall not exceed 0,4 seconds. U.K.
4. PRESSURE TEST CONNECTIONS U.K.
4.1. On each independent circuit of the braking system a pressure test connection shall be fitted at the closest readily accessible position to the brake cylinder which is the least favourably placed as far as reaction time is concerned. U.K.
4.2. The pressure test connections shall comply with clause 4 of ISO standard 3583-1984. U.K.
Appendix EXAMPLE OF A SIMULATOR (see Annex III, point 3)
1. Setting the simulator U.K.
2. Testing the trailer braking system via the simulator U.K.
A
=
supply connection with shut-off valve
C1
=
pressure switch in the simulator, set at 0,65 bar and at 4,9 bar
C2
=
pressure switch to be connected to the brake actuator of the trailer, to operate at 75 % of the asymptotic pressure in the brake actuator CF
CF
=
brake actuator
L
=
line from orifice O up to and including its coupling head TC, having an inner volume of 385 ± 5 cm 3 under pressure of 6,5 bar
M
=
pressure gauge
O
=
orifice with a diameter of not less than 4 mm and not more than 4,3 mm
PP
=
pressure test connection
R1
=
30 litre air reservoir with drain valve
R2
=
calibrating reservoir, including its coupling head TC, to be 385 ± 5 cm 3
R3
=
calibrating reservoir, including its coupling head TC, to be 1 155 ± 15 cm 3
RA
=
shut-off valve
TA
=
coupling head, supply line
TC
=
coupling head, control line
V
=
braking system control
VRU
=
emergency relay valve]