Long used as refuse collection vehicles, but now increasingly familiar on the streets of London and Cambridge as tippers, Mercedes-Benz Econics are also appearing in the capital with refrigerated bodies. Two 1830 18-tonners with single-compartment insulated boxes, built by Gray & Adams, are in service with fresh fruit and vegetable supplier Reynolds on multi-drop delivery work.
But the bodies are unusual too. With a curved roof to the front, these boxes have been designed to blend into the air deflectors on top of the low-entry, cyclist-friendly Econic cabs. Access doors have also been fitted to both sides of each body, along with aerodynamically-profiled panel cappings.
Also, both trucks have been mounted with under-slung UT-800 Thermo King fridge units. Meanwhile, measures taken to minimise noise during deliveries include the use of sound-deadening Marothaan coatings, from the Netherlands, for the cargo floors.
“The Econic comes at a higher capital cost than a conventional 18-tonner and our new trucks carry approximately 750kg less,” says Reynolds head of fleet support Steve White. “The reduced payload capacity is partly down to the fact that we’ve chosen to rack out our Econics, which is not something that we would usually do. This is not a problem though because we always bulk out before weight becomes an issue.”
But that’s far from always the case. Some rigid operators are desperate to shed every kilo possible. However, cutting the flab can turn out expensive. “If you’re talking about box bodies then one solution is to specify panels with an aluminium honeycomb core,” advises Don-Bur marketing manager, Richard Owens. “They’re roughly half the weight of grp and come with a glass-smooth finish.” Needless to say, there are drawbacks. “They’re fairly soft, can suffer damage and attract a 140—150% premium over grp.”
A better bet might be polypropylene honeycomb core panels. “They’re around a third of the weight of grp panels,” states Owens. “They flex a bit but that is not too much of an issue with a rigid, and they shouldn’t need reinforcing. They’re quite robust too... However, they cost 90—100% more than grp.”
Then there is Don-Bur’s own Blade panel, which Owens concedes is heavier than either of the honeycombs, but it’s also cheaper. “Blade uses a HDPE (high density polyethelene) foam core faced with 0.5mm galvanised steel and a polyester paint finish.” It weighs 11.8kg/m2, compared with 16kg for a 21mm grp panel, he says, but attracts a price premium of 40—50% over grp.
There are other choices though. Composite plastic-and-metal sandwich panels, as used in Cartwright Group’s 10-metre Streetwise urban semi-trailer, could be used on a rigid body, says technical director Lionel Curtis. “They’ve saved us half a tonne at 10 metres and the price premium on these panels is less than 10%,” he claims.
One reason they deliver weight savings is they are comparatively slim, at 10mm rather than 21mm. “They were developed as an architectural material,” comments Curtis, adding that body builders need to look at other industries’ approaches to cladding.
Other ways to reduce body weight include specifying a PVC fabric roof – although Owens counters that the savings are modest – or bonding the body floor directly to the chassis. “That means cross-bearers aren’t necessary and you can get away with a minimal sub-frame,” he says.
Such a floor will not stand up to heavy barrels or stillages though. And the other issue with bonding the floor to the chassis concerns wheel box intrusion into the load area. Lighter floors can always be specified, suggests Bevan Group managing director Anthony Bevan.
Incidentally, a plastic floor in a 6-metre box will save you 50kg – although it will also add £500 to the invoice. A better way of saving weight, says Bevan, might be to have the box bonded. “That will save 40—50kg because you won’t need the fasteners. And it won’t cost you more,” he says.
If you don’t want a bonded-down floor then opting for aluminium cross-bearers and runners will bring down weight. “So will aluminium side raves,” says Owens. “Use alloy panels on a curtainsider’s rear doors and you can save 30—40kg,” adds Curtis.
“Remember that steel weighs 8 tonnes per cubic metre, compared with 2.7 tonnes for aluminium,” says Owens. That said, there is the danger that some of this advantage will be offset by body builders using more aluminium to compensate for its strength issues – and aluminium is pricier than steel.
How about choosing expensive, high-strength, super steel? “Experience has taught us that, although we can use thinner PAS 700 super steel profiles, we have to increase the number of structural components to compensate for the reduction in rigidity,” Owens replies. “So we only use super steel sparingly these days and we would not recommend it as a light-weighting option.”
Moving on to aerodynamic aids, most rigid body builders can offer options, including side skirts, moulded Luton heads and collars that can bridge the gap between the rear of the cab and the front of the body. There are also curved roofs of the type found on the Econic fridge body in London. Bevan’s Icon body for 3.5 tonners, unveiled some years ago, is an exemplar of what can be achieved.
Such treatments are not proving particularly popular, says Bevan, probably because rigids tend to be deployed on stop-start, local distribution work where the benefit of such interventions is low. “Also, most of our customers don’t want something that is lower at the front or back,” he remarks. “They want an oblong box they can fill.”
One of the most interesting developments in rigid body building in recent years concerns low-floor Luton-bodied 3.5-tonners based on front-wheel-drive platform cabs, rather than chassis cabs. As well as offering easy load access, they deliver a weight saving, says Simon Partidge, sales and brand manager at Trucksmith, which specialises in this type of product.
“A front-wheel-drive chassis platform can be up to 180kg lighter than a front-wheel-drive chassis cab,” he observes. Such vehicles are clearly in demand. Earlier this year Trucksmith announced a £1.5 million extension to its Devon factory.
Other rigid body builders also report busy times and investments to match. JC Payne, for example, bought its existing 90,000sqft premises in Aldridge, West Midlands, outright and purchased a 40,000sq ft site next door. Bevan Group invested some £650,000 in equipment for its new headquarters and plant in Wednesbury, West Midlands, and is certainly not suffering from the post-Brexit-vote blues. Its Wednesbury factory is fully committed until next March, says Bevan, and its other factories are full until next April.
Raw material prices are starting to creep up, however, in the wake of Brexit and the fall in the value of sterling. “Timber is up by 10% while steel is up by 8—10%,” he reports. “Aluminium hasn’t gone up yet, but I’m sure it will.”