H APPY COUP 1 ri the next few weeks the
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first of a new generation of lighter, safer fifth-wheel and drawbar couplings will appear on the UK market. Many of the design changes are being driven by (surprise, surprise) a European Union directive, 94/20/EC, which introduces strength tests for all couplings. Those which comply have a D-rating measured in kiloNewtons.
The new standard takes into account the maximum laden weight of the tractive unit, the maximum vertical load imposed on the fifth wheel and the total weight of the tractor-trailer combination.
However, 94/2o/EC is not compulsory and although the UK government has published a White Paper, it has not suggested an implementation date. Coupling manufacturers agree that the strength tests are an important safety advance, despite
widespread criticism of 94/2o/EC as badly written. Many couplings on sale in the UK have now been tested and certified as complying because other EU states have adopted the directive.
Some manufacturers now incorporate extra safety features as standard while others offer them as options. Kingpin height sensors, for example, are designed to prevent miscoupling between tractor and trailer, which usually occurs because the kingpin is sitting on top of the locking jaws rather than between them.
Similarly, the traditional clipand-chain secondary locking mechanism is being replaced by other devices.
Standard fifth-wheels
The UK market fol tifth-wheel couplings is averaging 16,00018,300 a year; the three major players are Big 1), Jost and VBG.
Couplings have traditionally been a dealer-fit option, but increasingly truck manufacturers now fit them. ERF, for example, includes fifth wheels and lead-on ramps in its "Road Ready" pack.
Unlike Continental operators, who generally opt for cast-steel fifth wheels, most UK operators still prefer pressed-steel couplings because they are usually lighter and cheaper.
For example, Big D. part of the Wordsworth Holdings Group, says its pressed-steel Euro D model is 3okg lighter than some rivals.
However, Eurohitch, a subsidiary of the US-based Holland group, claims its latest cast-steel fifth wheel can match pressedsteel models on weight. This is the first Fleetmaster to be manufactured in the UK—production starts at the company's Tipton plant next month. Eurohitch quotes 119kg for its Generation III cast-steel Fleetmaster 8000.
It is still beaten by VBG's S PL2 pressed-steel coupling which, at 113kg, is claimed to be the lightest available.
The locking mechanism secures the kingpin round both circumferences and the jaw has a
On Jost sliders, the sliding frame and kingpin height sensor. An coupling are a complete unit trunnions extended locking handle is avail are used to vary the coupling height, able, to avoid the driver having to
clamber under the trailer.
'As a further safeguard, VBG plans to introduce an audible warning if the mechanism is not properly locked. The SLP2 has a load rating of 20,000kg and a D value of 15 okN. It gives a minimum articulation angle of 120, compared with VGB's nest-selling SPL2 pressed-steel the ISO recommended mini
mum of 7°. so there is less risk of fouling when combinations are negotiating bumps and inclines such as ferry ramps.
VBG's latest cast-steel fifth wheel, the t5oCI, weighs about 130kg; it will be launched later this year.
If weight is critical, remember to check what is included in the fifth wheel: the mounting plate can add 50kg and not all chassis manufacturers fit one. Lead-on ramps can add another 454.
Sliders
To cope with the variety of trailers on UK roads, more than half the couplings sold in the UK are sliding fifth wheels. The extra flexibility offsets the extra weight, says Jost managing director Lionel Morris, and the add-on cost is minimal. Jost quotes 275kg for its SV36DVRL slider compared with 120kg for a fixed coupling.
"It's not just the ability to couple up to different trailer lengths," he adds. "On operations where trailer weights change, the fifthwheel position can be adjusted to ensure enough load goes through the kingpin onto the tractor unit."
Eurohitch and VBG use a single slider frame and adjust the coupling height with different feet. Jost prefers to use a standard fifth wheel, altering the coupling height with different trunnions for the carriage. It says this is more precise.
VBG starts production of the all-bolted 135 S F slider next month.
Including fifth wheel it weighs 223kg, making it the lightest in the UK, according to VBG. Coupling heights range from 1732 92mm and spacings on the slider are reduced from 75mm to 37.5mm centres to give more precise control of load distribution. The open rails eliminate dirt traps while the tapered notches help the plungers automatically seat further in the rail as they wear to retain optimum lock.
Eurohitch's FW2535 sliding fifth wheel also has a universal sliding frame, adjustable in 38mm increments; travel varies from 467-622mm.
Excluding any sub-frame, heights are 168mm, 194mm and 219mm. Release can be manual or air-operated.
Low maintenarm
Low-maintenance cast-steel wheels that eliminate the nee grease the top plate are also crating interest in the UK. major benefits are savings grease and a cleaner wonl environment for the driver.
Jost and Eurohitch both grease-free cast-steel fifth-wh with a replaceable wear pad ii into the top plate—Jost pre& pad life of around five ye depending on the operation.
Dual-height fifth-wheels
Dual-height fifth-wheel coupli allow low-chassis tractors to c ple to high-cube trailers or ventional semis. Dual-height plings are also used to con tractors into yard shunters.
Eurohitch points out that brings a yard shunter within financial reach of many opera who cannot afford a purpose-t model. Its FW6700 couplin air operated to eliminate the ward and backward movemer the trailer that can happen N hydraulic lifts.
Fifth-wheel couplings shunters and heavy-duty op tions have been a Davis M4 speciality since it became pai the Douglas Equipment grc Sister company Reliance Men makes the Haulrnajor shunt( the 114 coupling features doi jaws for locking security.