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Equipment manufacturers always advise operators to plan for tomorrow when
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buying equipment today that's particularly true with cranes and low-loaders where replacement cycles are longer than average. Machinery-lifting cranes, for example, have a typical life of more than 10 years, while low-loaders are famously long-lived—trailers with 15 or 20 years' service are common. Sharon Clancy reports.
Apart from improved manoeuvrability on the road, the solus trailer can be manoeuvred on site via a wanderlead. Tyre scrub is also minimised—a major factor on axles that are usually twin-tyred for enhanced traction and to help spread the load.
On trailers with Four or more axles the front axles are often fixed but liftable to minimise scrub when running empty.
Hydraulic suspension is also universal on heavy-duty plant carriers. It equalises the load between the axles more evenly than air suspension, is more stable under heavy loads and provides about 3oomm of travel, compared with 200111m on air. Spring centres can be slightly wider, too, because there is no need for the air bags to be in-board of chassis rails for protection.
Air-suspended step-frame trailers and rigid machinery carriers have become popular for their flexibility— lexibiIity Andover Trailers reports that some operato. are switching to drawbar trailers to increa; their delivery options still further. Some ste; frame machinery carriers have a continuo" raked deck; others have a ramp between tlmain deck and the neck over the kingpin. TI advantage over conventional low-loaders the increased load deck length (about 12t from the kingpin to the front of the rear axle The sloping deck makes loading easier an offers more flexibility to carry different size plant on the same trailer.
The advent of 44-tonners has enabled moi plant hauliers to operate within tl; Construction 84. Use regs, avoiding the spee and route restrictions that come with 4( tonne Categoryi STGO operations.
Payload is around 25 tonnes but CSEU axl limits must be adhered to; operators also nee to know the centre of gravity of the load t avoid axle overloads. When operating undE 46-tonne Category i STGO regs you can loa the axles up to their design weight.
Machinery sets some design challenges fc trailer engineers; there is no univers; agreement on the best method of spreac ing the weight.
With some machinery more load i carried on the outer edges of th trailer than in the centre. Andove Trailers believes the strongest desig is achieved with conventional long tudinal main rails with extra to; sional stiffness achieved by makin every third cross-member the sam depth as the main rails.
Ivan Collins, Andover's sales an larketing director, claims that the firm's FCL 40 step-frame has the strongest frame its weight category with a payload capacy of more than 30 tonnes. A fabricated :ass-member with deeper wheel arches ad reinforced and integrated side extenon boxes gives the trailer extra strength vett the rear axles.
"On a plant carrier axles are set as far ack as possible into the beaver tail," ollins explains. "That means there is a lot F weight imposed behind the axle at the ip of the beavertail."
itrength
Mg Vehicle Engineering designers prefer have four 1-beam rails on trailers up 10 70 innes; they have found that this ensures ifficient strength in all the areas where Tight is likely to be imposed. The air susension is positioned below the I-beam metrails so all weight is imposed in-board f the springs, spreading weight more evenly trough the trailer frame.
King Trailers has developed a version of its lopebed step-frame plant carrier with a loadig angle of 5° for low.ground-clearance quipment such as roadsweepers. Operating t 44 tonnes gross, the load bed and ramp )r_in a continuous gentle slope. The single imp also helps loading because there is no Lsk that sweeper jockey wheels will drop into le gap left by twin-ramp access.
At the other end of the weight scale is :ing's GTL 112 Hyclroneck low-loader. This .111y-steered trailer is designed mainly for 30o-tonne payloads being carried under STGO Category a, but it can carry up to 85 tonnes for Category 3 work. For additional flexibility the gooseneck can be hydraulically separated from the main bed to allow unobstructed loading from the front.
Dennison, Faymonville and Montracon plant carriers all rely on a central longitudinal load-bearing spine with additional cross-bearers and outriggers.
Dennison's step-frame machinery carrier comes with a choice of suspensions and disc or drum-braked axles. The optional outriggers extend the width to 3m and there are hinged front ramps in the lower deck.
Montracon's Plantmaster is a 48-tonne gross trailer with a deck height of 850mm (with lowered air suspension). The original clip-on ramp that gave access to the front deck has been replaced with an air-assisted lifting section; the main deck is 7.3m long with a 4.5m front deck and i.5m beavertail.
Belgian low-loader manufacturer Faymon\Tulle plans to boost its UK sales with the appointment of Leeds-based heavy-haulage operator and recovery specialist Rydam Universal as its UK agent.
Like Nooteboom it uses pre-cambered hightensile steel members that produce a flat deck once loaded and also save weight, increasing payload. Faymonville can use a pendular axle system on its low-loaders, which is effectively an independent suspension unit rather than a normal fixed-axle configuration. An added benefit is that maximum axle weight in Germany increases to 12 tonnes.
Korbweight
The combination of pendular axle and high. tensile steel produces a kerbweight of 16,170kg for a three-axle extendible low. loader, says Rydam, saving more than three tonnes on a conventional design.
Faymonville and Nooteboom have devel
oped extendible stepframes with a channel at the rear to house the boom of a 45-tonne excavator. It also permits such machines to be transported on trailers with a shorter overall length than would otherwise be possible.
Dutch low-loader manufacturer Broshuis has introduced an automatic pressure reset system so all the hydraulic pipes on its trailers are at the same pressure (32 bar). This eliminates oil pressure expansion in the pipes which is said to allow the hydraulic cylinders in the bogies to react more quickly, giving more positive steering.