Carriers Seek Lower Maintenance Costs Through Advanced Trailer Design, Products

This story appears in the Oct. 29 print edition of Transport Topics.

The makers of aerodynamic add-ons for truck trailers are focused on more than just improving fuel economy. They also must cut down fleets’ maintenance costs so fuel savings are not eaten up in the repair shop, manufacturers and carrier executives have said.

“We are currently installing trailer skirts on our dry-van trailers,” said Scott Perry, vice president of supply management for Ryder System’s Fleet Management Solutions in Miami. “The fuel economy benefit is in line with most manufacturers’ estimates of 3% to 4%, depending upon the application.

“There is little, if any, maintenance required on the trailer skirts,” he added, “The biggest challenge is in making sure any damage to the skirts, which can create aerodynamic drag, gets repaired quickly.”

In Europe, manufacturers are going beyond add-ons. At the IAA commercial vehicle show in Hannover, Germany, this year truck maker MAN SE joined forces with trailer builder Krone Group to produce the Concept S, which is longer than current European legislation allows. The integrated vehicle features a rooftop spoiler that brings the tractor and the slanted-roof trailer closer together. The truck’s wheels are covered with skirts, and the side mirrors have been replaced with video cameras. In addition, the supporting frame and the two fuel tanks are integrated into the external bodywork design, according to a MAN press release.

Also at the Hannover show, Daimler introduced the Mercedes-Benz Aerodynamic Truck & Trailer. The vehicle, Daimler said in a press release, could move into production “relatively quickly” and features an air deflector to close the gap between tractor and trailer, a “boat tail” rear taper, curved side panels and aerodynamic details on taillamps and landing gear.

In the United States, Keith Harring, president of K.L. Harring Transportation, Bethel, Pa., said he is getting “super results” by using a combination of the SmartTruck UnderTray System and a fin that goes on top of the trailer at the rear on 25 of his trailers.

He also said the devices are placed in ideal locations in terms of avoiding damage — and he has not had to make any repairs on them.

Mike Henderson, chief engineer and designer and CEO at SmartTruck Systems, was an engineer at Boeing for 32 years. He said the company’s flagship aerodynamic device, an unusual undertrailer tray, makes it much easier for the air that normally collides with the tandems to flow around them smoothly. Another device in the design mounts in front of the rear bumper and smoothes out airflow around it, and there are side- and top-mounted rear fairings, he said.

The UT1 undertrailer tray is certified by the California Air Resources Board and saves 5% to 6% of fuel consumption at 65 mph on a rig weighing 67,000 pounds, according to the company, based in Winnipeg, Manitoba, and Greenville, S.C.

Adding the second device to the front of the rear bumper saves an additional 2%, SmartTruck claims. Adding the side fairings can result in a total savings of 10% or more, Henderson said.

These products are designed not just to improve aerodynamics but to be “durable and maintainable,” SmartTruck President Mitch Greenberg said. “We don’t want these devices to add any extra maintenance problems.”

Installation of the undertrailer tray takes an hour, Henderson said, and subtle design compromises were made in determining the final configuration of the SmartTruck undertrailer tray to make it less susceptible to road damage. The company focused on finding an extremely durable material for it, he added.

Harring said many of his drivers do consistent runs under nearly identical conditions, which has helped him calculate fuel savings — between 0.45 and 0.65 mile per gallon, or an average of about half a mile per gallon.

The drivers noticed that because of the add-ons, the trucks “are more stable when empty, especially when turning in and out to pass,” Harring also said.

“We’ve done some work with flatbeds, but van-trailer skirts are our bread and butter,” said Sean Graham, president of Freight Wing Inc., another trailer accessory maker. “The engineering is intense because of the need to customize.”

Freight Wing skirts are sold and installed by Carrier Transicold dealers across the country.

Graham said fuel savings can vary from 4% to 7%, depending on how fast a fleet’s vehicles run.

Freight Wing, based in Seattle, grew out of a project Graham worked on in engineering school during the past decade. Product development reached a peak in 2005, when a $200,000 U.S. Department of Energy grant allowed him to share development costs with fleets. As many as 250 different configurations were tested.

The company introduced its AeroFlex side skirt in 2008, after finding that side skirts and gap fairings were the most effective trailer aero devices. It had installed 10,000 of the side skirts by 2010.

Freight Wing just introduced a 2012 version of the side skirt at a reduced price, which the company said allows the units to pay for themselves in as few as 35,000 miles. They use “a dense matrix polyethylene material” that Graham described as “a custom-engineered automotive plastic.” He said that it offers the greatest durability, flexibility and lightest weight on the market.

Chuck Cole, manager of technical sales and product training for Utility Trailer Manufacturing Co., City of Industry, Calif., said his company adds side skirts to its vehicles because, “of the things we put on trailers to improve their aerodynamics, they save by far the most fuel” — as much as 5% to 7%.

And to offset maintenance costs, Utility’s recent improvements have helped with durability, Cole said. Customers indicated that maintenance was a primary concern, and during development of the products, the manufacturer duplicated the conditions customers said was causing damage.

“To help ensure durability, we build in flexibility, and this means the material itself will flex, along with its braces,” Cole said, adding that when a panel that stretches 22 to 23 feet from just behind the landing gear to the front of the rear axle on a trailer, it inevitably is going to scrape curbs now and then.

After trying out skirts from two suppliers, one was dumped because the material “became brittle,” Cole said. The one that survived has been tested to bend to within 6 inches of the bottom rail of the trailer, even though it is 34 inches deep. This flexibility, Cole said, allowed Utility to put a 5-year warranty on the product.

He said that recent improvements, which include a joint that allows braces to slip temporarily to a new position, have been supplied to fleets that bought the earlier design.

“These devices convert turbulent airflow to smooth, laminar [streamline] flow,” Cole said.

Potential buyers of such modifications should note that they need to remain stable, Cole said: “Watch trailers that have them, going down the road. If they flutter or wave back and forth, they are probably not as effective.” The reason is that the motion recreates turbulent airflow.

“Ours are flexible enough to minimize damage, but we design them so they are stiff and strong enough not to flutter,” he said.

Marc Bolduc, general manager of Flex Skirt supplier TransTex Composite, said his company’s main product is known as the “MFS” for Maximum Flex Skirt, which carries a 10-year warranty. The skirt is made of galvanized hot lead rather than zinc-plated, which Bolduc claims gives it five to eight times the corrosion resistance of its competitors.

Bolduc said that the Flex Skirt is more expensive than most, but “when you add up all your costs, at the end of the day, you’ll save.”

TransTex Composite’s products are made at its headquarters in Montreal, a “harsh climate” that is ideal for testing a device designed to be durable, Bolduc said, adding that customers have a choice of three different grades of skirts. All use the same attaching hardware, but the lower-grade models use a slightly different skirt material, he said.

Bolduc also said 3,000 units are being tested by Celadon Group, Indianapolis.

Aerofficient, Livonia, Mich., makes an ad-justable side fairing designed to keep the gap between the back edge of the fairing and the tandems at a minimum. Company literature claims that testing shows that a 35-inch gap there can reduce a fairing’s efficiency by 80%. The company also makes conventional fairings.

“Durability is the result of three factors: design, material selection, and engineering,” CEO Jim Reiman said. “Beginning with design, the fairing needs to be able to flex both inwards and outwards to accommodate the inevitable contacts with curbs, yard hazards, snowbanks, extreme drop-down docks, etc.

“Aerofficient’s design specification for all of its fairings is a minimum of 10 years and 1 million miles,” Reiman said. Consulting firm Frost & Sullivan recently gave Aerofficient an award based on its slider technology, which they described as “a game changer,” as well as their products’ durability.

Wabash Composites, a unit of Wabash National Corp., Lafayette, Ind., manufactures aerodynamic skirts for full-size and less-than-truckload trailers called DuraPlate AeroSkirts. Since this product debuted in 2009, more than 60,000 trailers are equipped with this device, which has been approved by the Environmental Protection Agency’s SmartWay program.