DoE probes trailer braking
Page 18
If you've noticed an error in this article please click here to report it so we can fix it.
C-type couplings investigated
by Trevor Longeroft
LARGE NUMBERS of articulated vehicles could be running with trailer brakes that are unable to operate correctly, The DoE is investigating reports that in some cases the cause of poor trailer brake operation can be traced to lack of standardisation in the design of C-type brake conneotions with self-sealing valves.
Until the investigation is complete no firm conclusion can be drawn, but it seems that trailer braking is most likely to be adversely affected when male and female couplings from different makers are matched.
Although the design of connection housings is controlled by a British Standard, no standard exists for valve construction. So, when coupling a male connection with valve to a female with a valve release adaptor, there is no safeguard to ensure that the adaptor has sufficient length to lift the valve fully off its seat.
If the valve stroke is limited, air flow from the tractive unit will be restricted and the trailer brake response to brake pedal depression will either be retarded or non existent. From our own inquiries it is obvious that until valve construction is regulated by British Standard, operators would be wise to stick to couplings from one manufacturer, so that both halves are designed to provide a matched pair.
Bass Charrington first experienced problems with Ctype coupling matching as long ago as 1972. The company has now standardised on just one make of coupling—Feeny & Johnson. During the interim period, while all other couplings were phased out of its fleet, Bass Charrington, in agreement with F & 3, modified the self-sealing valves to ensure coupling with any connector. A spacer was fitted on the slide valve to ensure that the valve opened by, at least, the minimum required, regardless of the make of the other half of the coupling.
Representatives of other UK brake coupling manufacturers, Berg Manufacturing and Intertruck, each said this week that they were not aware of any coupling problems.
DORADA HOLDINGS Ltd has expanded its commercial vehicle distribution interests in Scotland by taking over S and N Motors Ltd. Based in Glasgow, S and N holds the Ford psv franchise for the whole of Scotland.