Tried and true

Steve Sturgess (Photos by Steve Sturgess) | March 01, 2012

COVER STORY

Cascadia quickly earns street cred as an aerodynamic leader on nation’s highways

Freightliner’s Cascadia is such a familiar truck on the road it’s hard to remember what a startling sight it was when introduced in the summer of 2007. The huge grille opening, the sculpted doors, the visorless windshield, the pedestal-mounted mirrors, the stubby side extenders — all of it was new. And all of it was the result of extensive wind tunnel tuning of a finely wrought design.

 

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Ever since the introduction of Kenworth’s T600 more than 25 years ago, truck manufacturers have been refining the aerodynamics of the conventional tractor. After all, a wind-cheating design has become critically important in truck design, since at speeds more than 50 mph, the effort in pushing the wind aside is the major contributor to fuel use.

To develop the Cascadia, Daimler Trucks designed and built its own wind tunnel in Portland, Ore. More than 2,500 hours were spent testing, redesigning and retesting using full-size models to create the new truck.

And since its introduction, the Cascadia has been back in the wind tunnel to make it possibly the most aerodynamic truck ever.

The extension of the fender line into the doors is no styling exercise — though it does make the Cascadia distinctive from the side. The flowing lines help manage the airflow along the cab and sleeper. Lately, the visor is back as an option, though it performs a useful function in helping move the air over the rooftop. The side extenders have grown a little to keep the air attached and flowing onto the trailer sides.

And the big grille and the huge 1,625-square-inch radiator still make the Cascadia distinctive since truck grilles have become smaller over the years. But the grille’s function is simple: The big opening draws in as much air as possible to minimize fan-on time. Reducing fan use lowers the corresponding parasitic draw on the engine and the small but significant penalty in fuel used.

Fuel use is also minimized by the engine choices, 13-, 15- and 16-liter Detroits and the Cummins ISX 15, all optimized to run with selective catalytic reduction to meet the 2010 emissions regulations.

Another distinctive feature of the Cascadia is the small windows in the sleeper. They don’t help with fuel economy but they do eliminate the potential water leakage path that is always possible with conventional mounting of glass in rubber.

The test vehicle

The Freightliner here features the Detroit DD15 at 475 horsepower and 1,650 lb.-ft. of torque backed by an Eaton FRO-16210C 10-speed transmission. The 125-inch BBC cab and sleeper are trimmed in vinyl with Mordura cloth for the seats, and up front is a nicely equipped dash. There’s woodgrain on the panel and a grey-on-grey interior to give the cab a luxury feel. Rubber mats are over sound insulation for practicality in the cab. Carpet covers the sleeper floor. Suspension seats are featured on both sides.

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