Testing and experience prove streamlining saves money, but few people bother.
Whether you're a company driver or owner-operator, chances are the tractor you drive has some streamlining. Fuel prices began zooming in the early 1970s and by the mid-'80s, truck builders were designing aerodynamics into many models. Even square-nosed "large cars" will usually mount big deflectors on their roofs to smooth the flow of air over the van or reefer trailer behind.
Today's streamlined power units look like they've just emerged from aircraft wind tunnels, and they ease their way down the road and through the air. But trailers appear to have been riveted together in a box factory. They hide behind the tractors' air deflectors, but some sit too far behind for the fairings to do much good.
Couldn't some fuel be saved if aeroscience were applied to trailers? Why hasn't it been applied?
Actually, research has shown that aerodynamic trailers could save a lot of fuel and money. But most buyers want low-priced trailers, and they will not spend money on devices to improve aerodynamics. And many trailers spend a lot of time sitting in yards and at docks, where aerodynamics do no good. So truck owners have shown little or no interest in aerotrailers.
Maybe that's changing. Spikes in fuel prices have sparked a lot of calls to Nose Cone Manufacturing Co. in Buena Park, Calif., which sells patented, bulbous appendages built specifically for trailers. Nose Cone (800-227-3266) was started by the late Joe FitzGerald and is now run by his son, Jim, who went into business with his dad not long after the first "fuel crisis."
"Although OEM sales have been slow, we have seen a large increase in aftermarket retrofitting," Jim FitzGerald says. High fuel prices have caused truck users, most of them owner-operators, to install Nose Cones on their trailers, and they report a typical increase of a half-mile per gallon.
A Nose Cone is hung on the upper front of a trailer or truck body. It will save 5% to 15% in fuel, or customers can get their money back, the company advertises on its Web site, www.nosecone.com.
Made of reinforced fiberglass, a Nose Cone typically costs $550 to $750, weighs no more than 50 pounds and installs in less than two hours, says FitzGerald. A trailer version usually pays for itself in less than a year, or about 50,000 miles of operation.
Nose Cones come in many configurations and have been available for more than 20 years. The U.S. Postal Service bought about 200 compact versions several years ago, he said, but most customers are in the West and Midwest.
One is Curtis Matthes, president of C.D. Matthes Inc. of Fresno, Calif., which runs high-cube single- and double-trailer combinations within California. "We won't send a trailer out without it," he said of the Nose Cone. "In a crosswind, it saves almost a mile per gallon. Our drivers remark they can feel the difference if they pull a trailer without one - if we run a leased trailer that isn't equipped with it."
The gap between tractor and trailer produces considerable drag that the Nose Cone eliminates, Matthes explained. This becomes critical with any gap over 36 inches, FitzGerald says, but Matthes gets his fuel economy and vehicle stability gains even with a very tight gap - 12 inches.
"You're talking to a believer," Matthes said. "And I have been since 1983." Trailer builders and dealers haven't pushed aerodynamics like truck builders, FitzGerald says. Tractor-mounted fairings save 3% to 7% in fuel, Nose Cone's Web site says. But a Nose Cone saves additional fuel and is especially effective on a straight truck.
There are additional savings in reduced tire wear and safer handling, due to the stability that Matthes referred to. FitzGerald acknowledges that Nose Cones may not be cost-effective on trailers that sit a lot.
Carriers whose trailers are pulled by owner-operators have little incentive to save fuel. But a few O/Os have bought Nose Cones and installed them on company trailers to get the fuel savings, he says. It quickly pays for itself on a trailer that's "married" to a tractor.
His company also offers the Eye Brow, a small deflector applied to the upper edge of a trailer; side skirts, called Side Burns; and a rear-mounted deflector, called the Tail Cone. Eye Brows help a lot, but side skirts are more cosmetic than effective, and only a handful of operators buy them, he says. Tail Cones are used by specialty automobile haulers who run curtain-sided trailers. A Tail Cone is hollow, so a car's front or rear can extend into it, adding volume to the trailer while reducing drag at the trailer's rear. Such haulers also use a Nose Cone at a trailer's front.
Aero improvers like the Tail Cone are exempted by federal law from trailer length laws if they do not support the weight of a load, FitzGerald says. The Tail Cone is shaped like a boat tail, variations of which were tried and proved effective in experimental rigs in the early to mid-'80s. They let air flow off the trailer instead of being sucked into the vortex formed by the otherwise square end.
Full boat tails are impractical because they interfere with loading and unloading. A "truncated" boat tail can deliver most of the full boat tail's benefits, but still adds some weight and expense. Neither trailer builders nor buyers were interested when such devices were promoted. Smaller devices such as "vortex generators" (see article below) may be a partial answer. And high fuel costs may bring more solutions in the future.
Into the Wind
'Vortex Generators' Cut Drag by Controlling Air Flow
Truck aerodynamics is built on aircraft research because what works at hundreds of miles per hour also helps at highway speeds. But practicality keeps a big rig from being shaped like a jet plane, particularity at its rear. That's where Air Tabs help. They are small wishbone-shaped devices that control the flow of air as it leaves the surface of a truck, tractor or trailer.
Air Tabs are similar to the small slat- like "vortex generators" on the upper surfaces of wings on jetliners. These cause air to swirl and leave the wing's surface with less friction and without forming a vacuum at the wing's trailing edge. This increases lift, boosts payload, reduces drag and saves fuel.
Air Tabs are vortex generators for trucks, says Mark Adler, vice president of sales and marketing for Aeroserve Technologies Ltd., in Ottawa, Ontario. Placed at the trailing edges of a sleeper, they swirl the air so most of it flows past the gap between tractor and trailer instead of being sucked into it. Placed at the rear edges of a trailer, they make air swirl off instead of being sucked into the vacuum at the doors.
The tractor-trailer gap and the trailer's rear door area are notorious producers of fuel-wasting turbulence. The busy air remains attached to the vehicle's skin and pulls on it; the engine has to overcome this drag and that burns fuel.
"The tabs reduce turbulence in the gap by keeping the air from going in. At the trailer's rear, the tabs create air swirls well behind the trailer, where it's no longer attached," Adler says.
One operator who has tested Air Tabs can see the devices swirl the dusty air as his truck goes down a gravel road, Adler says. Less buildup of dirt and snow on rear doors is additional visual proof they work. When it rains, water spray is cut, improving rearward visibility for truckers and also motorists' view.
"Drivers can feel the difference," he says. "There is less sway and less pull. One guy in Australia stopped to get out to make sure he still had a full load aboard because it felt like the truck was lighter. And he was one of the skeptics."Air Tabs were developed in a wind tunnel, but are being used on rigs in Australia, Canada, Sweden
and the U.S. Aside from better handling, operators notice that trailer tires last up to 30% longer, Adler says, because of reduced sway.
Fuel savings - the main point of the devices - will be at least 4% if tabs are on tractor and trailer. The 4% is guaranteed, but some operators have seen 10% fuel savings, he says.
Each Air Tab is about 5.5 inches long by 3 inches high and 1 inch deep. It's molded in tough ABS plastic and comes with an adhesive-backed undersurface that attaches to the vehicle's skin.
White is standard, but custom colors can be added during molding; they can also be painted with standard auto paint.
"Pulling Ahead of Aerodynamic Drag" On-Highway Technology By Bill Siuru, Diesel Progress North American Edition July 2008. Page 58