Cutting Through The Atmosphere
Truck builders and operators believe in aerodynamics to save fuel, but their thinking hasn't included trailers.
Tom Berg
Equipment Editor
Huge numbers of streamlined road tractors give rolling testimony that smoothing the flow of passing air cuts drag and fuel consumption. This belief was borne out by countless tests during the 1970s and '80s, following the first and second Arab oil embargoes. Two special vehicles built by Peterbilt Motors and Fruehauf Corp. 20 to 25 years ago showed that aerodynamic trailers improved fuel economy by 1 to 2 miles per gallon.
But streamlined trailers didn't excite truckers, whose aero thinking usually ends at the tractor's rear. Trailers are expected to carry cargo and otherwise stay out of people's minds. Even in the best-managed trailer fleets, the emphasis is on reduced maintenance, and purchasing departments want the lowest price possible. Aero trailers, when they appear, are viewed as ridiculous creations that would cost far more than they'd ever save and wouldn't last a week in everyday service.
Managers also point out that aero improvers wouldn't be worth installing because many trailers spend so much time sitting in terminals and customers' yards. When a trailer sits still, neither it nor anything on it makes or saves money, least of all an aerodynamic device. Will current spikes in fuel prices cause operators to think again? After all, the more costly fuel is, the quicker the return on an investment for a money-saving device.
Two aero products now on the market are the bubble-like Nose Cone from Nose Cone Industries
A Nose Cone smooths the flow of air past a vehicle's front wall, and Airtabs help streaming air detach from surfaces at the vehicle's rear. Both companies have compiled testimonials from users who have tried the devices on trailers and truck bodies, and say they work.
A COOL IDEA
The Nose Cone concept began in 1965, when the company's founder, the late Joe FitzGerald, was sales manager of Carrier Transicold. He suggested to engineers that the reefer's evaporator be moved from inside a trailer's front wall to outside, which would free up space for more cargo. He also suggested that the evaporator be wrapped in an angled enclosure to allow air to flow around it. Drivers said the trailer's altered front wall seemed to make a rig handle better, and FitzGerald knew he was onto something.
He consulted with aerodynamic experts and designed what became the Nose Cone. The first oil embargo in 1973 sparked interest in aero improvers, and he went into business. FitzGerald became a familiar figure at industry meetings and developed a steady following of customers. His son, Jim FitzGerald, now runs the company in Buena Park, Calif. Over the years, the FitzGeralds devised 145 configurations to make the fiberglass fixtures fit various trailers and truck bodies.
Satisfied customers testify that Nose Cone-equipped trailers are more stable and that fuel economy improvements are real. Often it's a half-mile per gallon, and this is usually in addition to anything a tractor's aerodynamics may contribute. Sometimes ignorance prevails, however. We knew one owner-driver of a tall-bodied straight truck who was happy with his newly installed Nose Cone. Did he get better mileage? No, he said, but the truck would now go more than 70 mph instead of only 60. He cut about 20 minutes off a 150-mile run, and never mind that he blew any fuel savings out the tail pipe.
Nose Cone has sponsored wind-tunnel research at universities to prove the scientific merits of its devices and questions the worth of tractor-mounted fairings. It claims the tests show that a tractor's aero package increases fuel economy by 13% in headwinds, but can actually increase drag by 5% in a 10-degree crosswind, which is much more common in everyday running than straight-on headwinds. A Nose Cone, however, improves fuel economy by 10% in a headwind and 12% in a 10-degree crosswind.
The company therefore argues that a Nose Cone weighs less and costs less than a third of what a tractor's full aero package costs, and therefore, is a more cost-effective way to reduce drag and fuel consumption.
Its most recently commissioned study suggests that the most aerodynamic tractor-trailer has only a Nose Cone. The tractor should have good basic aerodynamics, but needn't have fairings on its roof or cab sides. These devices cause a low-pressure vacuum in the gap between tractor and trailer, the company says, while the Nose Cone smoothly pushes air out of the gap.
The company also offers Side Burns, which are rounded panels fitted to the forward edges of a trailer's vertical front corners. These cut drag even more and are claimed to improve fuel economy by an additional 5%. Another product is the Tail Cone, installed on the rear of car-hauling van trailers.
A Tail Cone smooths the flow of air as it leaves the sides and top of the trailer, further reducing drag. It adds a couple of feet to a rig's overall length, but federal law exempts it and other aero devices from length restrictions, provided that they carry no cargo weight. The Tail Cone folds up to allow loading and unloading, but the company says it's not practical for use by most cargo vans and reefers that back up to docks.
MODIFYING AIRFLOW
Turbulence and suction at the rear of trailers, truck bodies and tractors cause fuel-burning drag and are the focus of Airtabs, the wishbone-shaped fixtures invented by a former car racer. They are related to the vertical tabs on the upper surfaces of airplane wings; these tabs generate air vortices that slow down air and thus increase lift.
A similar principle works on trucks and recreational vehicles, but here the idea is to cut wind drag and fuel consumption, explains Ron Davidson, vice president of operations at Aeroserve Technologies, maker of Airtabs in Ottawa, Ont. The wishbone shape, with the wide side leading, was found to bunch air together into a small tornado that leaves the flat surfaces with less resistance.
Davidson claims an Airtab-equipped rig is much more stable. In multiple-trailer combinations, the rear trailer "wiggles" less because it's less affected by wind gusts. He says Airtabs deliver a 4 to 6% mile-per-gallon improvement if also fitted to the trailing edges of tractor fairings, as well as the trailer. On the tractor, Airtabs work with a gap as long as 40 inches.
An independent SAE/TMC Type IV test showed a fuel economy improvement of 2% or 0.1 mpg when fitted only to the tractor's side extenders, not its roof fairing. None were put on the trailer. But that was enough to convince one fleet that observed the test. Last fall it said it will buy Airtabs on future new equipment.
Davidson said he is countering truckers' complaints that "I don't have the capital" by offering to lease Airtab kits to operators. A $200 kit includes 80 of the plastic, adhesive-backed devices, enough for one vehicle, plus an installation template and instructions.
He says three Airtabs per foot on the sides and top of a van trailer or tractor's trailing edges, within a few inches of the very rear, produce the vortex-generating effect.
When mounted on a vehicle, an Airtab is about 5 inches long, 4.25 inches high and 1 inch thick. As an aero device, it is exempt from width restrictions, but of course can be knocked off by a scraping incident. If so, it can be quickly replaced. Airtabs come in paintable white, black or clear plastic that's treated to resist ultraviolet rays.
Certain trailer builders are interested in offering Airtabs as options, says Davidson, who has several American and Canadian partners, and has signed an American distributor, Airtab LLC in Loveland, Colo. Meanwhile, he's concentrating on selling the idea to users, and he claims good response in advertising on a radio program aimed at truckers. And he says he's having much more luck selling the devices to RV owners.
Davidson and Nose Cone's marketing vice president, Kathy Rose, have met at trade shows, and sometimes recommend each other's products to prospective customers. But they've not conducted any tests using both products.
Trailer Innovations continued...
