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Old 09-04-2012, 10:35 PM   #27 (permalink)
slowmover
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Join Date: Oct 2009
Location: Fort Worth, Texas
Posts: 2,442

2004 CTD - '04 DODGE RAM 2500 SLT
Team Cummins
90 day: 19.36 mpg (US)
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I thought some of his asides (about air flowing back under the tow vehicle) were certainly of interest. I don't see him selling anything, or acting as a stalking horse. I added these links primarily as being representative of current RV world discussions. I saw no real reason to add ones from Class 8 trucks as that world is pretty well understood by its members (industry leadership).

The RV world tries in re FE, but is short on leadership. Air deflectors have been around quite a while (I certainly remember the discussions after October, 1973), but there has not ever been decent consensus due, again, to record-keeping and accounting for the system noise of a combination vehicle, where (unlike a 5'er or tractor-trailer) some time & care in achieving formula results in hitch rigging can "drown out" aero aids.

There are any of a number of hypotheticals where I believe I could show that an aero aid cannot be separated out where the gain is a small percentage.

It's easy to say it works (and I'm hopeful, not doubtful), but verification is difficult (unless one has worked the numbers necessary). Rigging, alignment, brake drag and steering wander are all to the point. (And new vehicles are not to be assumed correct).

Were I in Colorado, I would take the rig to Transwest Truck Trailer RV in Frederick to start sorting out trailer brake drag, bearing adjustment, trailer axle alignment after a stop at a CAT Scale to get weight scale tickets for the vehicles separately and lashed up; with and without WD activated. (I can provide a fill-in-the-blank chart for collecting all the numbers).

The same basics apply to the tow vehicle. New does not constitute proof of zero brake drag and zero steering wander, much less alignment. Small differences are magnified in towing.

I realize the rig owner may not want someone else spending his money, yet on the other hand the best performing rig may be to his interest. And a relationship with a talented shop is that first step.

My point to this second post would be that there is no downside to any of this. The difference between an "okay" rig and one that has numbers nailed down is night & day while on the road.

This is when the "feel" of an aero aid becomes palpable.

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Last edited by slowmover; 09-04-2012 at 10:57 PM..
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