Division 7.4

In the case of hydraulic brakes, the following shall be determined:

1. 7.4.1.

   Reduction ratio i_g′ (see Figure 8 of Appendix 1)

2. 7.4.2.

   Pressure p* for braking torque M*

3. 7.4.3.

   Torque M* as a function of the pressure p* applied to the brake cylinder in hydraulic transmission systems.

   The rotational speed of the braking surfaces shall correspond to an initial vehicle speed of 30 km/h in the case of Class C1 vehicle, 40 km/h in the case of Class C2 vehicle, 60 km/h in the case of Class C3 vehicle, when the towed vehicle moves forward and 6 km/h when the towed vehicle moves rearward. The following shall be derived from the curve obtained from these measurements (see Figure 7 of Appendix 1):

   1. 7.4.3.1.

      The retraction pressure p_o and the characteristic ρ′ when the towed vehicle moves forward;

   2. 7.4.3.2.

      The retraction pressure p_or and the characteristic ρ′_r when the towed vehicle moves rearward;

   3. 7.4.3.3.

      Maximum braking torque M_r up to the maximum permissible fluid volume V_r when the towed vehicle moves rearward (see Figure 7 of Appendix 1);

   4. 7.4.3.4.

      Maximum permissible fluid volume V_r absorbed by one braking wheel when the towed vehicle moves rearward (see Figure 7 of Appendix 1).

4. 7.4.4.

   Surface area F_RZ of the piston in the brake cylinder.