Build a better body 04 December 2015

There’s far more to specifying a body optimised for mounting on your chassis cab than price alone. Toby Clark examines some of today’s key technical considerations

Specifying rigid bodywork might be seen as simple: it’s just a box, after all. But there are plenty of considerations apart from the price. That’s important to remember, given that the purchasing process continues to change subtly, with fleet engineers increasingly influenced by constraints from finance departments. As Don-Bur marketing manager Richard Owens puts it: “They have different demands put on them, and their range of functions is wider than ever, but we are here to help.”

So what’s changing technically? Starting with design and construction methods, these have improved dramatically – giving bodybuilders more confidence that payload and structural performance will be as predicted. Don-Bur, for instance, sends data directly from its Solidworks CAD (computer aided design) software to a laser cutter. Its latest £1 million installation can handle sheets of 20mm-thick steel at sizes up to 6.5 x 3.1m. The cutting speed is up to 85m/minute with an accuracy of 0.05mm/metre; the edges are clean; and the unit can also handle thinner material (down to less than 0.5mm) for precision components such as grilles.

Each piece can also be etched with a unique part number, to help stock control and reduce incorrect fitting: “The main issue for us is time,” says Owens. “It’s a far more structured and managed production flow than before.” Don-Bur is also looking at automated brake presses for bending components.

And the Whole Vehicle Type Approval process is also now well established. “Apart from the oddballs for which we get IVA [Individual Vehicle Approval], we’ve been going through NSSTA [National Small Series Type Approval] rather than European Whole Vehicle Type Approval,” explains Owens.

That said, this might have to change, as Don-Bur’s streamlined ‘Teardop’ trailers and bodywork, as used on DHL’s recent ‘City Quiet, City Safe’ concept 18-tonner has attracted the attention of Continental operators. “The UK market tends to be a little different, in terms of its diversity,” says Owens, adding that it’s not just the type of bodywork that’s different. “In Britain we tend to have an ex-works model. In Europe they expect [the vehicle] to be delivered to the doorstep licensed and ready to drive away.”

Aerodynamic bodies are not just a marketing tool: Owens insists the Teardrop body is not the radical package it was in 2007. “People are approaching aerodynamics more pragmatically, and saying we need to look at this more seriously,” he says. And he explains: “If you look at the cost versus benefits for aerodynamics on rigid bodywork, operating speed becomes important.”

Aerodynamic drag is proportional to the square of speed, so it becomes much more important at high speeds. Conversely, within an operating range of zero to 40mph the benefit is relatively small. “So, yes, if you use a rigid for trunking and secondary distribution, then it is worth looking at.” Some operators have seen fuel savings of 8—9%, he claims, but for local deliveries there is little benefit.

For stop-start operations, weight is more significant, and a variety of panel materials is now available. Don-Bur’s website clearly outlines the pros and cons of typical materials, from conventional GRP-faced ply to Technolite aluminium honeycomb. The latter weighs less than half a comparable GRP panel (around 7.4kg/m2 for a 20mm-thick panel, against 16kg/m2 for GRP).

However, Owens warns: “It is a particularly soft panel,” which requires careful design to keep flat and protected from impact. Omnia polypropylene/GRP honeycomb is even less dense (4.8kg/m2 for a 30mm-thick panel) but even more flexible. “With something very small like a 7.5-tonner, you can get away with it,” advises Owens.

Neil Brandrick, managing director of JC Payne, adds another note of caution. “We’ve actually found that on some of the bigger [vehicles] there’s been a slight readjustment the other way. Certain operators two to three years ago were adamant that payload was the way to go, so they wanted lightweight panels and associated designs. But then the use of the vehicles wasn’t suitable. They were giving them a bit of a bashing. So the cost savings from transporting more were being offset by damage to the vehicles. Now it’s time to renew these vehicles, they are moving away from light weight.”

A useful compromise is something like Don-Bur’s Blade material, consisting of a HDPE (high-density polyethylene) foam core with a galvanized and painted steel skin. A 7.5mm-thick panel weighs 11.8kg/m2, so “Blade is a little bit lighter than GRP but amazingly tough,” says Owens. “You can literally take a hammer to it.” The material is also highly resistant to corrosion and water ingress, and provides a good surface for graphics.

“Everything has to be approached on a case-by-case basis,” comments Owens, adding that, for example, there can be difficulties with load restraints. Brandrick agrees: “With some panels being only 11mm thick, you can bond strongly with an adhesive but not with a screw. In fact, because it’s been bonded so well, if you’ve got a heavy load fixed to the side panel, rather than the interior restraint pulling away from the panel, it’s been pulling the panel away from the side wall.”

Floor materials also need to be specified carefully, and you need to define what type of distributed or point loads your vehicle will undergo. This is particularly important for the latest variant of J C Payne’s range of box vans and Lutons. Its low-frame 3.5-tonners use low-height chassis cabs from the likes of Peugeot and Citroen, and even the rear wheel drive Mercedes-Benz Sprinter, to offer a loadbed height down to 600mm.

The chassis outriggers are not meant to support the floor, explains Brandrick. “So we’ve worked with Omnia to supply flooring with sufficient bending resistance.” Construction is mainly bolted – “for a combination of ease of repairability and production” – but Mercedes insists that the bulkhead be bonded to the B-pillar at the back of the cab.

And Mercedes has another requirement, related to its ESP stability systems. “Mercedes have their chassis programmed in terms of stability, and now they are asking our engineering team for a calculation of the gravity, on the basis of materials used and height of the body,” explains Brandrick. “We’re finding on these new chassis that Mercedes needs to revisit the vehicle at PDI [pre-delivery inspection] and reprogram the stability control.”

For Brandrick, this illustrates the importance of communication and interaction between the chassis manufacturer and the body builder. “Type approval and Euro 6 have all aided the communication and the expectation of the chassis manufacturer that the bodybuilder knows what he’s doing,” he says.

Noise reduction and PIEK

Another increasingly important aspect of urban operations is noise: Don-Bur’s Richard Owens says “Specifically in London we are doing a lot of work on making vehicles quiet”.

While specific components such as tail-lifts can get approval from the Dutch PIEK organisation (recognised too by the UK’s Noise Abatement Society) “the approval process is really just a dB threshold” — each item must produce no more than 60dB(A) at 7.5m — “although at least it is something that people recognise. It would be desirable to be able to approve a whole vehicle, like WVTA, and redefine the way vehicles are approved for urban areas.”

Toby Clark

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Related Companies
Don-Bur (Bodies & Trailers) Ltd
JC Payne (UK) Ltd

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