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Friday, March 29, 2013

The dynamics of making big rigs aero

Posted by Bob Paetsch at on 03/19/13. Link to their site provided below:

Diesel prices have risen steadily over the last decade and currently hover 30 to 40 cents per gallon higher than regular gasoline. Commercial fleets used it in the past because it was cheaper and offered more miles per gallon compared with gasoline. However, U.S. environmental mandates for lower sulfur content, higher refining costs, increased demand from emerging markets, and use as a principal fuel source in many countries have helped any cost savings go up in smoke.
Enter the “SuperTruck.” Before we start conjuring up images of Optimus Prime in Transformers, SuperTruck transformations are much more subtle than tractor trailers taking human form and battling alien invaders. The “SuperTruck” program was initiated by the Department of Energy back in 2010 where nine projects split $187 million to improve fuel efficiency of heavy-duty trucks and passenger vehicles. Last week, one of the projects, the $38.8 million joint study between Cummins and Peterbilt Motors Co., shed a little light at the end of the wind tunnel. The results were a 54% increase in fuel economy in real-world driving conditions for a Peterbilt Model 587 equipped with a more efficient engine hauling an aerodynamic trailer.
That’s pretty cool. Cummins said that today’s 18-wheelers get 5.5 to 6.5 miles per gallon, and after 11 runs over the 312 mile test route in Texas, the Cummins/Peterbilt vehicle achieved 9.9 mpg. According to the study, the increased efficiencies could save 120,000 miles-per-year truckers $25,000 annually at today’s prices and reduce greenhouse gases by 35% per truck. Great, but what if I can’t afford a brand new big rig?
The CEO of Wabash National, a trailer manufacturer, highlighted a number of ways to make the nation’s haulers more efficient at an event sponsored by the Heavy Duty Manufacturers Association last week. He said under-trailer side skirts show a 4% to 7% improvement; lower-rolling resistance tires help by 3% to 5%; gap reducers between the cab and trailer are 1% to 2% more efficient; and trailer boat tails could improve fuel economy by 6.6%.
A boat tail on a truck? I suppose they are in the shipping industry. I saw one of these the other day—it looked like an oversized ironing board had fallen outside of open rear doors. And the trailer did have a skirt. As thrilled as I am to see these improvements, I still won’t commend truck drivers at rest stops on their nice skirts. It is great to see the industry isn’t just idling, but it must be tough knowing that all this time, effort, and money is spent on designs that are only semi aerodynamic.

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