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Aerodynamic cladding may save fuel but it adds weight and pushes up costs. On road tankers wind-cheating is a real possibility. So what's the solution? CM has been taking a look at some smooth operators...
Some reckoned that the styling put them in mind of a cruise missile carrier. Others took the more accurate view that it resembled a gigantic circus cannon especially when tipped— and half-expected a human cannonball to come flying out the end.
Almost everybody, however, was of the, opinion that the 38ma aerodynamic tanker semitrailer constructed in late 1995/early 1996 by Sutton Bridge, Lincolnshire-based Metalair-Filliat looked the business (see picture, below opposite). It was built for a British Sugar contract held by what was then P&O Roadtanks.
Fairings at the front enclosed the tipping gear and were attached to the chassis rather than the tanker itself. Fairings were mounted along the sides too, and a sculpted up-andover door concealed the valves at the rear.
It all proclaimed that British Sugar was a modern, high-tech operation with its sights set on success in the 21st century. At one stage it looked as though a further nine aerodynamically clad tankers would be constructed, says Metalair-Filliat sales director Ken Fisher. In the event, the nine were delivered without streamlining kits.
Distribution contracts change hands, and the work that P&O Roadtanks once handled is now done by Turners (Soham).
Based not far from Newmarket, the East Anglian company operates Metalair.Filliat's expensive triaxle air-suspended creation, but stripped of all the air management aids. The company's key reason for this helps explain why there is so little enthusiasm for air dams, sculpted side panels and valances among tanker operators.
"All that cladding added the best part of a tonne to the trailer's weight," explains Turner's general manager Frank Rycroft. That cut payload, and thus earning capacity, in an industry where operators are desperate to squeeze every last kilo of cargo on board.
Ken Fisher reckons that the cladding, made by urs of Norwich, added nearer 350kg to the weight of the trailer; it tipped the scales at a beefy 6.9 tonnes unladen. however, he doesn't dispute Rycroft's argument about the importance of payload— British Sugar itself felt the trailer was too heavy and expensive.
Outriggers
Metalair-Filliat technical director John Weatherhead says: "Payload is the priority. The problem with tanker air management panels is that although they themselves may be light, you usually have to hang them on outriggers. Making a tanker aerodynamic isn't like dealing with a box trailer because you don't have nice flat sides."
While Metalair-Filliat was happy to construct the tanker—"it was very sophisticated, and I was proud of it," says Fisher—it concedes that air management panels have practical drawbacks.
"If you have valances concealing the wheels and suffer a blow-out, you can easily do .E1,000 worth of damage," Fisher explains. "It can be just as expensive if the driver accidentally bashes one of the panels while manoeuvring. What's more, you're scarcely encouraging the driver to pay regular attention to his tyres if he cannot easily get at them."
Brake overheating due to possible airflow restrictions is a further concern.
Peter Allen, development manager at Fruehauf, says: "The Spirit 2000 range of tankers that we launched in 1989 was fully skirted and sold well, but some customers were unhappy at the cost of rectifying minor accident damage. They also claimed skirts made it difficult to clean the underside."
The new tanker that Fruehauf is currently working on won't have full skirts, Allen adds. Tankers have to be loaded and discharged, and fairings can impede access to valves, says Weatherhead. That can also be a problem when they require maintenance.
"There may be scope to fit one or two small panels to improve the flow of air underneath the tanker or along the sides," he adds, "and you can look at smoothing out the wings—but in the end, what are you achieving? Because you're essentially talking about a long tube with a domed front. most tanker trailers are more aerodynamic than curtainsiders anyway. A further difficulty is that you get a huge variety of tanker specifications, with a lot of different options fitted, so you can't easily standardise on panel mouldings. They end up costing a lot of money."
Accidental spillage
Composite panels can be damaged by the contents of certain tankers if there is an accidental spillage.
"Painting them can be difficult because adherence isn't all that brilliant," Weatherhead continues. "You can always mould them in the customer's corporate colour, but that's also expensive because everybody has a different one."
So how much does air management cost? One senior industry figure, who asked not to be named, says: "Depending on what you want to do it can add anywhere from £3,000£8,000 per tanker to your invoice, so you're talking about increasing the bill by anywhere from 10-25%.
"With competition intense, and profit margins pinched, it's not surprising there's so little interest among transport operators."
But surely the operator will be reducing his fuel costs? "A percentage of the fuel a tanker uses may not be affected anyway, because it is used to power on-board equipment which discharges the load," he continues. "You have to separate out that percentage and aim at a 10-15% cut in the amount of diesel which is used to propel the truck along."
But his assumes that you are pursuing the aerodynamic route for hard cash reasons, which is not always the case, says Allen.
Some major companies use their tankers as mobile advertisement hoardings so they want to make them look as good as possible. As British Sugar discovered, aerodynamic cladding can he helpful in this.
"Fairings can also muffle the noise a tanker makes when it is discharging its cargo," says Malcolm Ross, European business development manager at TDG subsidiary Nexus.
Diesel bill
So how likely is it that you will achieve a 10% cut in your diesel bill—which would go a long way towards offsetting any payload and front-end-cost drawbacks—by opting for streamlining? Leading aerodynamic consultant Val Dare-Bryan believes even better figures than this can be achieved; he reckons the trick is to concentrate on the tractor rather than the trailer.
Dare-Bryan has undertaken consultancy work for P&O Roacltanks—part of P&O Transeuropean since September—on the best way to improve the aerodynamics of general-purpose artic tankers. He has used one-tenth scale models and a wind-tunnel and figures taken from monitored track tests with full-sized vehicles.
"We found we could achieve a 20% fuel saving by fairing-in the tractor and trailer; a 17% saving by fairing-in the trailer alone; and a 17% saving by fairing-in the tractor alone," he says. "Bearing in mind that it costs three times more to fair-in a trailer than a tractor, we've recommended that P&O fairs in its tractors instead."
Controlled in-service tests indicated that a 14% saving could be achieved. Each truck is equipped with a roof-top moulding shaped a little like an upturned boat, with extensions to the rear of the cab.
The air management aids cost 11,000 per tractor and impose a modest 40kg weight penalty. They're made by AB Airflow Systems of Shefford, Beds. Fitment of the kits started in July, says Dare-Bryan, and 134 have been produced to date.
C by Steve Banner
CASE STUDY: ROB TOOZE, northern region general manager at P&O Roadtanks based in Middlesborough, says that the 61 tractive units fitted with aerodynamic kits so far are showing in-service fuel savings of up to 9%. But he stresses that these figures are not precise.
Dare-Bryan poinys out that because fitment only began in July, a full formal analysis of their effectiveness over an extended period has yet to be carried out. It remains to be seen how the trucks will perform in winter weather. "Aerodynamics are more effective in the winter because the air is heavier and denser and requires more effort to push it out of the way," he explains. In the summer air tends to be lighter and drier. `If you want to produce an aerodynamic tanker forget about the trailer," he insists. "Turn your attention to the tractor instead."