6. Coupling heads U.K.
6.1.Coupling heads shall be designed so that they can be used safely with the coupling balls described in Figure Ap 1-1 of Appendix 1.U.K.
6.2.Coupling heads intended to be fitted to unbraked trailers, shall be fitted with a secondary coupling device or at least attachment point(s) to permit the connection of a secondary coupling device(s). The attachment point(s) shall be positioned such that when in use, the secondary coupling device(s) does not restrict the normal articulation of the coupling.U.K.
6.3.An endurance test shall be performed with an alternating test force and a static test (lifting test) on each test sample.U.K.
6.4.The dynamic test shall be performed with a suitable coupling ball of appropriate strength. On the test rig, the coupling head and ball shall be arranged as instructed by the manufacturer and in a way corresponding to their attachment in a vehicle. There shall be no possibility of extra forces in addition to the test force acting on the sample. The test force shall be applied along a line passing through the centre of the ball and inclined downwards to the rear at 15° (see figure Ap3-1 of Appendix 3). An endurance test shall be performed on a test sample with the following test force:U.K.
Equation 3-3:
6.5.The coupling ball used for the test shall have a diameter of 49 – 0+0;13 mm in order to represent a worn coupling ball. The lifting force FA shall be increased smoothly and quickly to a value of:U.K.
Equation 3-4:
and held for 10 seconds, where:
C
=
mass of the trailer (sum of the axle loads of the trailer carrying maximum permissible load) in tonnes.