Trailer Trials

by Steve Bouchard

A box on wheels. That pretty much sums up your average modern-day trailer. Trucks are a different story. Aerodynamics experts have been trying to soften the curves on tractors since they first appeared on the road. But trailers have remained the drag-reduction underdog.

A number of manufacturers have marketed trailer-add ons designed to cut fuel consumption, but only very recently have they been subjected to any type of rigorous testing.

Last fall, however, Transport Canada’s test track in Blainville, Que., was invaded by a small army of researchers from various organizations determined to learn whether these inventions — trailer skirts, tail wings, aerodynamic skirts and fenders — made any fuel-consumption difference.

“The whole project started with a suggestion from Réjean Laflamme, from Robert Transport, and Alain Boutin from Cascades Transport, who wanted to use the Blainville tracks to do some testing,” says Yves Provencher, program leader for FPInnovations-Feric, the firm that managed the tests in order to ensure their scientific validity.

Participants included Transport Canada, the Quebec Transportation Ministry, the Agence de l’efficacité énergétique du Québec and the Institut du transport avancé du Québec, which measured the opacity of the emissions for the technologies. PMG Technologies manages the Blainville’s test and research center.

A dozen suppliers of trailer-add ons accepted the invitation to submit their technologies for scrutiny.

Transport Robert and Cascades supplied nine tractors and 11 trailers and in total, the team of about 30 researchers tested 16 configurations of devices and techniques.

The tests were performed on the high-speed track of the 6.4-km, high-banked, oval track. The length of a test run was 100 km and the drivers reached speeds of 100 km/h, measured by a radar gun.
The driving patterns included:

Idling time; Quick acceleration; Cruising at 100 km/h; Driving on the right side of the track as close as possible to the painted line without touching it; Normal cruising with the vehicle free to change lanes; Decelerating, with the driver instructed to only use the service brakes.

Each test consisted of a baseline run, using non-modified vehicles followed by a test run with outfitted trailers.

The tests met SAE J1321 Joint TMC/SAE Fuel Consumption Test Procedure-Type II standards. Fuel consumption was accurately measured by weighing the temporary tanks before and after each trip.

FPInnovations-Feric’s Marius-Dorin Surcel explains the methodology: “For the baseline stage, an initial test was conducted before modifying the vehicle. For this test, the control and test trucks completed a minimum of three test runs until it was statistically established that the results of a group of three tests were within a two-percent variation.

“During the final test, the same trucks completed the same trips a second time, after being modified. As in the baseline test, the trucks completed at least three test trips until it was statistically established that the results of a group of three tests were within a two-percent variation.”

Drag King: Researchers install the boat tail drag
reduction made by Transtex Composite of Montreal.

The fuel consumption was determined by weighing the temporary tanks, before and after each trip, using a calibrated scale with a capacity of 150 kg and capable of measuring 0.05 kg. The repeatability of the scale was periodically checked during the tests using a set calibration weight.

Results shows that the savings possible with trailer aerodynamic trailers go from 1.4 to 7.2 percent, depending on the device installed (see Tail of the Tape).

However, Surcel points out that aerodynamic saving percentages cannot be arithmetically added.

The next experiments, he says, will establish how combining the devices would affect fuel consumption.

So where is the most critical turbulence zone on a trailer?

Says Surcel: “Usually, we consider that on a contemporary trailer for highway hauling, aerodynamic technologies can achieve a 15-percent improvement, distributed equally — five-percent between the tractor and the trailer; five percent under the trailer and five percent at the back of the trailer. You can also get an improvement of five percent with the tractor.”

One final note. The results were obtained under virtual lab conditions; i.e., a closed track, constant speed, very high-quality pavement and nearly perfect weather.

“Many experts believe that, if an SAE-type test on a track shows an eight-percent improvement for a given technology, the actual saving for a real-life operation could be four percent,” says Surcel.

In general, results obtained with the aerodynamic devices met the expectations, except for the skirts, which exceeded the expectations by one to two percent.

An operation similar in size to the participating fleets — averaging 200,000 km per year; using an average of 40 litres/km at $1 per litre — could reap a gross annual saving of about $800 per one-percent of fuel saved.

Translated, that’s $800 in your pocket for each percent of fuel saved. Per truck.


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