New regs on brakes sought
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• THE EUROPEAN Transport Maintenance Council is to try to get the EEC braking legislation amended to overcome compatibility problems experienced by some operators. At its conference in London, a draft standard was circulated for debate.
As current legislation stands, wide tolerances are set on the "lead" allowable on tractive units and prime movers. The lead is a pressure differential deliberately introduced to make the trailer brakes come on at the same time as those of the towing vehicle.
In practice, operators have found that a particular tractive unit may perform perfectly well with one trailer but badly with another. It is this inconsistency and unpredictability that is worrying ETMC members.
The operational concerns caused by compatibility problems stem from the tractive unit brakes coming on before those on the trailer or vice versa. The linings on the first part of the combination which brakes can wear rapidly while those that come on later can become glazed.
Operators expressed concern that, under initial braking, the situation can arise whereby the unbraked trailer is pushing the braking tractive unit. In these conditions there is a risk of jackknifing.
At the end of the session it was decided to use the draft as a starting point for further work. To that end, some of the brake, truck and trailer manufacturers present offered to meet with the ETMC team that prepared the draft. The meeting is due to take place early in 1990, but the aim of changing legislation will take some time to achieve.
In the meantime, the ETMC has produced recommendations on predominance settings for most tractive units, prime movers and trailers.