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October 30, 2015

Trailer Aerodynamics Gaining Traction

The show floor at the American Trucking Associations’ exhibit in Philadelphia last month showcased aerodynamics, with a focus on trailer devices and several interesting tractor aero aids that continue to chip away at percentage points of fuel savings.

A tandem airflow device from FlowBelow Aero calms the air flowing around a tractor’s tandem axles. Called the TractorAeroKit, it consists of wheel covers and a couple of fairings to fill the gap between the drive wheels and, according to the company, saves 2.25 percent in fuel. It is not especially attractive but if it works….

Personally, I prefer the aesthetics on Jon Fleck’s wheel covers that he sells as Deflecktors – using a play on his name – with a 2 percent savings when used on both tractor and trailer tandems. They’re good enough for Schneider and that says a lot.


Gaining traction fast is the TrailerTail, the folding origami-like boattail that was recently acquired from ATDynamics by Stemco. Having the Stemco organization behind it makes the Trailertail a much more viable product and we’ll be seeing more and more of them, which is good news for Stemco and for the inventor and prior principal of ATD, Andrew Smith who stays with the product. Smith, incidentally, has a slew of patents on the device which offers better than 5 percent fuel savings.

All the more curious, is a very similar device seen at the Transtex booth in the suite of aero devices under the Edge name. It is complimentary to the side skirts that are Transtex’ mainstream product and a new nose Edge Cone trailer gap filler, says the company. The Edge Tail is deployed by wind pressure alone, and is still in prototype. It will be interesting to see if it ever makes it to market. Stemco, after all, does have much deeper pockets to launch patent litigation than TrailerTail’s previous owner.

Plasma Stream Technologies

One product not at the show that is said to achieve the same effect as a set of tail panels comes from a start-up called Plasma Stream Technologies. Using a very obscure electrical/physical effect that emits a low, violet glow when operating, the plasma generator is said to keep the air attached to the surface it passes over, then the generator deflects the air in a broad, flat stream into the space behind the trailer, eliminating vortices in the same way as the hard surfaces of the Trailertail.

The concept is the brainchild of Pranay Bajjuri who is co-founder of Plasma Stream Technologies and in the past worked at Navistar and knows a thing or two about trucks.

Supposedly, two copper strips separated by a Teflon sheet and supplied with a relatively low voltage become a single dielectric barrier discharge plasma actuator. That mouthful comes from research into the subject at Notre Dame and means the combined strips generate a layer of plasma. Plasma is a fairly strange concept but is basically ionized atoms. These act on the passing airstream to ionize local air molecules which bend the whole airstream. At least, that’s how it was explained to me.

I seem to recall something of the sort being developed for helicopter rotary blades, and comments made then that nobody talks about how much voltage has to be generated to make the system operate. But if it works at the sort of voltages available on a truck, these plasma generators may prove just the ticket for the rear of the trailer as the strips are very low profile, so there is no need to push them out of the way to back on to a loading dock.

More than that, they could be switched off under braking to assist the engine and service brakes in slowing the truck.

Bajjuri says he could outfit a trailer for around $2,500 with systems in volume production and fuel savings at 12 percent to 20 percent (the figures are all over the place), the payback would be real and fast.

Although the literature and website do not suggest it, these plasma generators could fill an equally useful task in keeping air attached across the tractor-trailer gap. It’s pretty intriguing and is a technology to watch.


XStream gap-filler panels shown here partially deployed.
Meanwhile a here-and-now tractor-trailer gap filler was on the show floor at ATA’s exhibits. With another play on a name, XStream was showing its automatically deployed gap-filling panels that mount to the tractor.

There was precious little literature at the booth and the website is not a lot better, but the demonstration at the booth showed frame-mounted panels swinging out at the sides and up across the top.

In practice this would happen as the truck reaches cruising speed on the highway. The effect is like the typical Euro style truck with very tight tractor-trailer gap possible with the deep kingpin settings on the trailer.

As the truck slows, the whole thing collapses to give the swing clearance American trucks with relatively shallow king pins on the trailer need for low-speed maneuvers.

There’s a video at the website and it’s obviously early days for this company, as there are no claims for the actual fuel savings from the device. But given that most of the wind in North America is off several points from dead ahead for trucks crisscrossing the continent, a gap filling panel may prove to be one of the better ideas for trailer aerodynamics.

As demonstrated by the Department of Energy-sponsored Supertruck program, the industry can get to mandated fuel economy targets set for 2027 but only if tractors and trailers are dealt with as a combined unit. These trailer aero devices show there’s no shortage of innovative ideas to help reach those objectives.


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