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LIGHTEN NG THE LOAD

24th May 2007, Page 50
24th May 2007
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Which of the following most accurately describes the problem?

Trucks are getting heavier, but customers are demanding

less weight in order to carry more. One way to achieve

this is to use lighter materialr Steve Banner 2ports.

With the ability to operate at 44 tonnes now well established, the days when operators had to specify trucks and trailers in minute detail to obtain the maximum possible payload capacity ought to be long gone.

And for most firms running at the higher gross weights they are, because the trucks tend to bulk out before they weigh out. But for certain key areas of the market, weight remains a crucial consideration.

Many owners of light commercials, for example. want to be able to carry as much weight as possible without having to venture over the 3.5-tonne barrier and wrestle with tachographs and 0-licences.

Unfortunately, the unladen weight of 3.5-tonners has risen sharply over the past 20 years. As a result, precious few of them can carry much more than 1.5 tonnes.

That poses particular problems for people running refrigerated vehicles —the burden of the fridge unit plus all the insulation pushes up the unladen weight even further —or tippers transporting aggregates.

No compromise

Bodybuilders are rising to the challenge, however, says Jarvis MacDonald, managing director of Westbuty,Wilts-based fridge body specialist Trumac. It is lightening its products in an attempt to maintain or even improve on payloads, but without compromising strength.

"We used to use timber or steel body bearers, but we now use pultruded foam-filled composite bearers instead," he explains."In addition to saving around 35kg at 3.5 tonnes, they have the added benefit of providing better insulation than steel or timber.

--Something else we've done is to move away from four or five-element insulated panels to three-element panels," he continues. -They've got thicker skins, but they don't have the heavy timber content.

"Along with using composite bearers, this is allowing us to achieve a respectable payload of approaching 1.2 tonnes at 3.5 tonnes— and with quite a reasonable length of body" "Getting weight down at 3.5 tonnes is often about placing metal exactly where it is needed and not where it isn't,' says Justin Gallen, managing director of Telford bodybuilder "That is where alloy extrusions can prove invaluable, because they can be thinner and thicker in different places as required. By contrast, steel is usually of a uniform thickness."

Reducing weight can also be about combining the functions of parts so that one can do the job of two.The more parts used, the more weight is added to the body.

Reducing the weight of a factory-built van body can he a real challenge for converters, although removing the dual-passenger seat and spare wheel can make useful contributions.

Lloyds TSB Autolease's Specialist Commercial Vehicle Unit has come up with a Volkswagen Transporter Sportline van fitted with a load-area storage system and roof racking made from carbon fibre. It is lighter than metal, leading to a better payload— up by 100kg in this case if the storage system alone is specified—as well as being durable and corrosion-free.The carbon fibre roof rack is approximately half the weight of a conventional rack.The vehicle has been developed in conjunction with Chambers Vehicle Conversions of Stafford.

Last year the unit unveiled a box-bodied Land Rover Defender capable of handling a 1.000kg-plus payload thanks largely to a body using honeycomb GRP panels sourced from PD Stevens of Market Drayton.

The 7.5-tonne sector

Weight savings at 75 tonnes can be almost as useful as at 3.5 tonnes.Although it is not quite the barrier that 3.5 tonnes is, the fact remains that anybody asked to drive a vehicle grossing at above 7.5 tonnes has to take a separate test. Operators have to recruit employees with the necessary licence entitlement and pay them more too, so their desire to stick at 7.5 tonnes is understandable.

"Using composite bearers at 7.5 tonnes saves around 50kg, and we also offer a subframe, under-run bars,and a step assembly all in aluminium as an option,"MacDonald says.

"We'll probably standardise on this approach because it saves 70-80kg. Remember that the subframe is usually made from galvanised steel.

"We're also trying out tapping plates made from a mixture of nylon and carbon fibre rather than steel or aluminium,he adds. "They provide the necessary support for shelves and hinges, and at 7.5 tonnes they're saving us 15kg to 20kg."

There are drawbacks to employing materials such as aluminium, however, warns Chris Berridge, managing director of Hull fridge body specialist Paneltex."Substitute alloy for steel and you'll reduce the weight of the material used by around a third," he comments. "However, alloy can be corroded by brine, and when you're making door frames you have to use more of it than you would steel to maintain the necessary strength.

"As a consequence we make less use of alloy than a lot of other bodybuilders, and rely more heavily on stainless steel instead."

Counting the cost There is the expense to bear in mind too, says Andy Hawkvard,managing director of Aire Truck Bodies, which has sites in Bradford, Leeds and Tipton. "Make extensive use of alloy and you'll push up the cost of the body in terms of raw materials by up to 25%,he points out.

"There is no way you can lighten a body without putting the price up,he adds.-But don't forget that the lighter a vehicle is, the less fuel it will use." That is a point being taken on board by artic operators, says Richard Owens, group marketing manager at Stokeon-Trent body and trailer maker Don-Bur. "In response, one of the things we're doing is offering Tech nolite body panels." he says.

"They've got an alloy honeycomb core with alloy facings, and will save you around 1,000kg on a liftingdeck trailer." However. they will also add around £1,500 to the final invoice.

-We can also use Omnia panels,Owens continues. 'Again, they have a honeycomb core, but they're polypropylene, and even lighter than alloy."

That sounds like good news, but they will boost the bill for your trailer by i3,000, he points out.

Cheshire's Cartwright Group has recently built a 13.6m triaxie straight-frame doubledeck trailer for the Royal Mail capable of carrying 90 York cages and using Omnia panels for the sides and roof.The prototype, which also has aluminium floors, is some 2,000kg lighter than a standard step-frame double-decker.

"Another way of reducing trailer weights is to use high-yield steel," says Owens. "It's really expensive, but you use less of it than you would more conventional steel, and you can save 500kg."

Certain categories of haulier — tipper and tanker operators for example — need to reduce weight to maximise payload even at 44 tonnes because the loads they transport are so dense and heavy. "You can get 29 tonnes on a 44-tonner and we're all now chasing the elusive 30 tonnes," says John Howard, chief engineer at Grantham tipper builder Fruehauf.Again, alloy has a crucial role to play Fruehauf is using 6nun-thick abrasionresistant Herkal alloy for trailer body floors rather than standard 8mm alloy."It brings the weight down by around 115kg," says Howard.

Customer focus -You constantly have to balance weight reduction against the ability of the body to keep doing the job,however, and take into account the likely reaction of customers to any changes,he says.

"With one of our bath-tub bodies we took out a rib in order to cut the weight, and the customers really didn't like it," he recalls. "We ended up calling it 'a rib too far'."

Trailer makers and bodybuilders on the other side of the Channel have been cutting weights too, with Belgium's Composittrailer making the sort of extensive use of composites that its name might suggest.

It contends that a steel trailer weighing 11,000kg can he reduced to 7,800kg by liberal use of alloy, hut to 6,000kg by the widespread use of composites.At 40 tonnes that means payloads of 22 tonnes, 25.2 tonnes and 27 tonnes respectively, allowing for the weight of the tractor unit.

Metal and plastic

Metal has not yet been rendered obsolete though. B urscough,Lancs-based tanker maker Clayton Commercials recently unveiled a vacuum tanker constructed for the removal of leachate water from landfill sites that weighs in at a skinny 5.100kg. Aluminium has been used to construct the chassis. tank shell, landing legs and a variety of other items, cutting the weight by 500kg.

If you want to be truly radical, why not construct your body completely out of plastic? That is what Strong's Plastic Products of Tamworth has done, with a Polybilt body mounted on an Iveco Daily chassis that weighs just 650kg,excluding the door shutters.

It has been built primarily with an eye to meeting the requirements of fire brigades for compact appliances —Strong's has already constructed a number of bodies for the fire services on both large and small vehicles — but could he used for other applications.The plastic used is said to be chemical-resistant, obviously will not corrode, can be painted, and is completely recyclable.

"It's also impact-resistant," says a spokesman for Strong's."Fire engines fitted with it have variously turned over, gone through a brick wall and hit a tree.The plastic has stood up to all of this remarkably well."

Polybilt bodies are lighter than their alloy equivalents, he adds, and can withstand high temperatures. 'The tyres will burst before the body catches fire," he remarks.

The bodies are easy to repair too," he contends. "All you need to do is cut the damaged section out, and weld in a new one."

As a one-off, the Daily's body costs 0,000, but the price would fall if Strong's went into volume production.

Most operators are cautious about the adoption of new materials. Understandably, they are concerned about durability, the impact on residual values, and how easily and how cost-effectively they can be repaired. "It's very difficult to break down long-held preconceptions," says Gallen.

But if new materials can boost payload and reduce fuel bills, it would be foolish not to investigate them further.


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