Wind panels under the bus

[pengyou]

I have seen semis pulling trailers that have panels mounted lengthwise under the trailer. They are supposed to affect aerodynamics so that fuel efficiency is improved. Anyone know about this?

[CaptSquid]

Look at how high off the ground your standard dry-van and reefers are and compare that to how high off the ground your skoolie is. That's a lot of under-vehicle turbulence that the professional drivers are trying to avoid. That turbulence is drag. Drag increases fuel consumption, which, on A Class VIII vehicle combination, can amount to a great deal. Cut down on fuel consumption and you increase profit margin.

[miscrms]

From what I've read the biggest benefit is likely to be a "boat tail" to smooth the airflow off the back. IIRC numbers I've seen are in the realm of 5-8% improvement. The other common improvement areas on a tractor trailer, the gap between the tractor and trailer and the area under the trailer are probably less applicable to a school bus.

If you're getting 8mpg a 5% improvement is still only 8.4mpg, but IMHO that's a bit deceiving. A 5% improvement still results in 5% less fuel being consumed for a given distance, so the smaller the mpg the more significant the change. That's good if your goal is using less fuel, but likely not worth it if your goal is purely financial.

If you drive 8000 miles per year, let's say that's 1000 gallons of diesel at $2/gallon or $2000 dollars. A 5% improvement saves 50 gallons over that distance, or $100. Depending on how much the improvement costs it would probably take many years to recoup the cost. But again that's not as important if your goal is just to use less fuel.


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[Brad_SwiftFur]

I am inclined to agree with the above point. On a large fleet covering many thousands of miles a month, and a life expectancy of several years, it becomes sensible to invest in the wind panels and such to decrease wind drag. On a bus which is only driven a few thousand miles a year, we may never recoup the investment, and we have no easy way to measure the improvement.

[Rusty]

I wonder about these for fuel savings- spruce-up your ride at same time.

moon disc

[BlackJohn]

Those panels are used in Canada to keep low vehicles and pedestrians from being able to get under the vehicle. Lots of accidents when cars somehow got jammed underneath during lane changes on the highway. Also kids and bicycles in urban areas were getting dragged underneath so they became mandatory in most jurisdictions.

John

[PNW_Steve]

Take a look at Fuel Economy, Hypermiling, EcoModding News and Forum - Ecomodder.com Fuel Economy Forum

There is a lot of good information and discussion regarding aero mods for fuel economy.

I have to ask....... What kind of cars are the Canadians driving these days? I think my wife's Kia could get past those trailer skirts.

[BlackJohn]

"I have to ask....... What kind of cars are the Canadians driving these days? I think my wife's Kia could get past those trailer skirts."

Good question ...there are so many small cars out there nowdays, both domestic and imports and Canadians drive them all it seems. You wouldn't catch this body in any of them. I like protection and drive a Suburban for that reason and others.
Everyday we hear about highway accidents where cars are crushed under flatbeds or trailers of some sort. Not a nice way to go if you ask me.
Those panels look flimsy but do deflect vehicles and obstacles away from the wheels of the trailers. They have some strength built in so I think your wife's Kia might just bounce off rather than snowplow underneath the wheels. Also a lot of wrecks are seen with vehicles rear-ending a transport and going up underneath. The front ends are so low it would be hard to avoid.
And next July1 we are getting pot legalized up here so might see more stoned drivers under those big rigs.

John