Pickup truck aerodynamics

[aerohead]

Originally Posted by slowmover

I'm surprised that a bed topper (cab-height, flush-fit) shows so well. I was under the impression it was "worse than" a full tonneau cover.
.

Hucho and others have shown squarebacks with lower drag than some notchbacks.Auto makers consider a pickup to be a notchback sedan without trunklid,so it kind of makes sense.
We pay for that enormous vorticity behind the cab.It travels with us wherever we go,continuously robbing power.

[aerohead]

Originally Posted by KamperBob

This is a great thread - thanks, Phil!

Grain of salt: not all pickup trucks are the same. Differences in height, width, length, cab shape, step vs. fleet side, weight, driveline (gearing, horsepower, valves per cylinder, fuel type & delivery, aspiration, two vs. four vs. all wheel drive) vary across make, model and production year. For trucks X and Y the optimal aero-mod may not be the same solution.

yes,very much so.When Sport Truck Magazine did an article about pickup aero they had quotes from the truck division guys from at least the Big-Three,who emphasized that pickups should always be considered on a case-specific basis.

[aerohead]

Originally Posted by Sven7

So this is the TIworks shell?


I looked on the SAE's website for the papers but they are not available for free.

Yes,it started on the Dodge,then got moved and morphed to the T-100.After goats destroyed it,I chopped Poco-Loco,a Chrysler Marine sailboat,to take the place of the destroyed shell.It's very 'goat-proof',has nice compound form,and tuft-tested very well.
If you'll send me a PM,the paper might appear at your place.

[aerohead]

Originally Posted by Sven7

If this isn't it, the thing uses the same principle.


Here's the Banks Sidewinder. Notice the half tonneau.


The next question is, why? It would seem that this opening would impede the vortex that leads high speed air over the virtual template.

That's it.I'll have to see if I have the text of the patent.I may have just printed the table.

[aerohead]

Originally Posted by Sven7

If this isn't it, the thing uses the same principle.


Here's the Banks Sidewinder. Notice the half tonneau.


The next question is, why? It would seem that this opening would impede the vortex that leads high speed air over the virtual template.

Sven7,I have the patent in hand.U.S.Patent No.4,573,730,'DRAG REDUCING PARTIAL TONNEAU FOR PICKUP TRUCK,' by Theodore R. Gondert,and Richard A. MacDonald,Assignee: General Motors Corp.,Detroit,Michigan.Filed:May 16,1984,Date of Patent: Mar. 4, 1986.
After going back through the text of it,they make no mention of the physics involved,only that the 50% tonneau demonstrates lower drag than the 100% length.
At some point I'll re-visit the Texas Tech paper 'n see if they talk it out.Whatever it is,it revolves around the locked-vortex and how the outer flow is playing over that.
If I had no expectations of what I thought the air would prefer to do,I'd have a lot less trouble with reality.

[KamperBob]

If the bed is long enough that air could reattach to a full tonneau what I suspect happens is the separation bubbles (mirror pair with center forward flow to balance boundary conditions) are smaller and rounder. As a result less energy to stir them. Hence less drag. (I wish I had better words to explain that, sorry.)

[Sven7]

Here's the table. Phil, feel free to quote this post into your first post for newcomers!

[aerohead]

Originally Posted by Sven7

Here's the table. Phil, feel free to quote this post into your first post for newcomers!

Thanks Sven7,I've had the table in my photo-archive for years now.But its off the beaten path,so probably most won't even be aware.

[kach22i]

Was not sure where to put this, but it illustrates the aerodynamics of pickup trucks, at least when carrying a mattress.

MORE random pics...... - Page 2939 - Pelican Parts Technical BBS

[Xist]

A Google search for:

"ITworks" "double-geometry"

Simply led me back to this thread, but I am intrigued.