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Old 03-03-2003, 03:09 PM   #1
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A/S Wind Tunnel testing

As Airstream owners we are fortunate to own a TT with such desirable towing characteristics.

It has been suggested that Auto manufacturers are wasting millions on teams of power train and chassis engineers and big-buck computer systems with sophisticated software to establish vehicle parameters like tow ratings and no doubt there is a lot of truth to that.

A computer program / system is only as good as the quality and amount of the data that is inputted into the program. Unfortunately the auto manufacturers are working in the dark with this issue. They do not know what type of trailer will be towed, where or how often, the experience level of the driver, or how it will be connected. ( bumper hitch, Dual Cam, Hensley, Pullrite) etc.

The aerodynamic advantage of A/S's design is explained in the following chart. (research was done at the University of Maryland). Towing an A/S with a sedan, for instance requires only "HALF" of the horsepower when compared to a sedan connected to a square trailer.

We are fortunate here in Canada to have an organization like Can Am that takes the science of towing many steps past ( the basic tow rating ) and looks at the whole package, the entire combination. Analyzes, tests, modifies, adjusts, and then passes on their knowledge and experience to its customers and any others who are interested in the concepts.

Again...Tow vehicle, TT, combinations are personal preference based on likes, needs, or usage. Every one and every case is different.
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Old 03-03-2003, 04:13 PM   #2
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Wayne, do you have a copy of the actual study done, or just this unsubstantiated claim... from Can-Am, I'm guessing.
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Old 03-03-2003, 04:35 PM   #3
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I said this in another post, I hope this isn't getting personal. I think you both have great info you share with us all, and I respect both of your opinions very much.... it's just that my Spidie sense is tingling here......



Regards,

Eric
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Old 03-03-2003, 06:03 PM   #4
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No... this isn't gettin' personal... but I'm not going to stand by and watch newbies be provided with dangerous misinformation.

The reason that I asked about the study here, is:

1. aerodynamic drag increases with the square of the increase in speed.

2. horsepower to overcome aerodynamic drag increases with cube of the increase in speed.

The horsepower numbers here are roughly based on the square of the increase in speed from 30 to 55 mph, and look to be calculated by someone not aware of point #2. Given that, I find them questionable.
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Old 03-04-2003, 09:03 AM   #5
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I also would like a copy of the study, as the numbers do not compute.
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Old 03-05-2003, 08:32 AM   #6
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Question Test Data

Good Day to all

This chart has been around for many years. I suspect the van mentioned is a full size van. One would think that any A/S dealer would have this positive data as it could in be used in the promotion of A/S TT's to prospective customers. That all I know re data.
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Old 03-05-2003, 08:50 AM   #7
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Apple, didn't you report a while back that you were actually involved in computing tow ratings, and that you found that the A/S was really easier to pull, (except on hills)?

Wayne: sorry, buddy, but I can't resist: how much horsepower does it take to stop an A/S, as compared to a box trailer of the same weight? LOL!!
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Old 03-05-2003, 08:57 AM   #8
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More realistic number

Quote:
Several years ago we did some studies on trailer wind resistance and the effect on the tow vehicle. We found the Airstream wind resistance to be about 30% less than a square front...
Apple 1, I picked this from a former post you made. 30% seems to me to be a much more realistic number for Airstream drag vs white box drag.
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Old 03-05-2003, 09:16 AM   #9
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John,
The test refered to in my post was done in the early 90's at Chrysler Arizona Proving grounds using instrumented draw bars.
I may still have a copy of the test results in my trailer tow files. I retired from Chrysler 2 years ago and kept most of my trailer tow information. My last 14 years were in truck Vehicle development which was responsible for GCWR numbers and trailer tow testing.
Jim
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Old 03-05-2003, 09:33 AM   #10
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I sent an email to Dr. Steve Buckley at UofM. It turns out that he is not the professor who's name appears on the chart but he was kind enough to make some enquiries and came up with a professor Frank Buckley who he believes did this research back in the late 70s or early 80s. Steve continues to work on an email address for Frank Buckley.
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Old 03-05-2003, 10:14 AM   #11
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Me too. Got the same response. Wonder how many emails Steve is gonna get from Forum members! LOL!
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Old 03-05-2003, 01:27 PM   #12
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Thanks guys..
This what I found to date:
Professor Emeritus Frank Buckley
The search continues..
Maurice,
Check your PM..Thanks
ciao
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Old 03-05-2003, 08:33 PM   #13
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Wind tunnel testing

Very interesting info and questions.

Has anyone purchased the DVD's from VAC?
On one of them it has an amusing wind tunnel test simulation, as well as some other testing which they had put an airstream through. Found these DVD's very entertaining.
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