eavyweight decision time
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by Brian Weatherley • While the Department of Transport has been busy debating what constitutes a "railhead journey" many of the technical issues governing 44-tonne bimodal operation remain unresolved.
Originally due to be approved at the end of January, the final version of The Road Vehicles (Construction and Use) (Amendment) (No2) Regulations, which allows 44-tonners on British roads, is now expected to come into force at the end of the month. But some industry observers believe it could fall back to May or even June,leaving truck and trailer manufacturers unable to offer a definitive technical solution.
Cohn Ess, managing director of specialist trailer maker Maxilode, believes the DOT can't afford any further delays: "Politically they'll want to push it through because it's so significant-the Channel Tunnel would be a nonsense without 44 tonnes in place."
Some of the earlier technical caveats in the original consultation document, like a 15.5m minimum overall length, have been dropped. However, any truck running at 44 tonnes will still have to meet the 12.0m overall limit imposed on 38-tonne artics.
The proposed 15.5m limit appears to have been driven by worries over bridge loading: at least the bizarre prospect of trailers with pull-out rear bumpers (to keep two 44-tonners at the right distance on a bridge) has been avoided. But others remain, such as six-axles overall and a minimum 8.0m outeraxle spread between the last axle of the tractive unit and the last axle of the trailer.
What's more, the DOT is not permitting any change to the maximum 24tonne limit on "road friendly" trailer bogies. Inevitably this demands air suspension. While the draft legislation doesn't specifically require it on the trailer bogie if operators want to carry a 30-tonne payload at 44 tonnes they'll need a 24-tonne air sprung tri-axle trailer bogie; without air they'll be limited to a 22.5 tonne bogie by C&U regs.
By keeping the 8.0m axle spread requirement the DOT is also setting an important precedent. As part of its bi-modal legislation the DOT has set specific axle spreads for trucks running above 38 tonnes. At 44 tonnes the limit is 8.0m; at 40 tonnes it is 7.1m (see table right).
The big question is, will the DOT still demand some kind of axle spread limit when the UK harmonises with the EL: on 40 tonnes in 1999, even though there's no requirement for one under EU rules? Given the European Commission's desire to harmonise vehicle specifications this would be illogical, but having put a spread limit regulation into C&U for 44 tonnes, the DOT may not want to remove it for 40 tonnes.
Not only will 44-tonne tractors need three-axles; every driving axle "not being a steering axle" must be fitted with twin tyres and every driving axle must be fitted with road friendly suspension unless the axle weight is less than 8,500kg.This could lead to greater use of double-drive 6x4 tractors.
Whatever the final specification of 44 tonnes, trailer manufacturers are already predicting its effect on tractor buying patterns. Crane Fruehauf's technical manager Angus Spooner reckons that air suspension on tractor drive axles will become the norm. He also believes operators will need to pay more attention to tractor wheelbases and fifth-wheel positions.
Maxilode's Ess agrees, but only on trucks carrying 13.6m swap bodies or extra-long containers. "It's all a question of front swing clearance," he says. "Both the 13.6m swap body and the 45ft container locate on the 40ft twistlock position and a sixwheel tractor unit will be able to pull the special 30-tonne capacity Intermodal skeletal if only 40ft or 20ft containers are involved.
"If the longer swap bodies or containers are to be carried," Ess concludes, "not only will you need a long-wheelbase tractor but also a self-tracking rear axle in order to maximise weight distribution and conform to the turning circle corridors which are required for 13.6m trailer operation."