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Pickup Truck aerodynamic cap concept

Discussion in 'Sketchup Gallery' started by NeilBlanchard, Jun 15, 2011.

  1. NeilBlanchard

    NeilBlanchard Member

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    Greetings,

    Here's a SketchUp model of an aerodynamic cap for a pickup truck, that could be made out of foam (hence the pink color!) with the Phlatprinter to make ribs, and then form 1/4" foam to form the surface, and then fiberglass over that.

    [​IMG]
    [​IMG]

    Uploaded with ImageShack.us

    Here's a video animation of this:
    http://www.youtube.com/watch?v=pEEzbnT5dKs


    If you would like a copy of the SketchUp file, I'd be happy to email it to you.
     
  2. kram242

    kram242 Administrator Staff Member

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    Nice job Neil! Did you use Sketchup to make this? or did you import it from another program into SketchUp?
    I love the way the cab makes the truck look :good:
    Mark and Trish
     
  3. NeilBlanchard

    NeilBlanchard Member

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    It was done all in SketchUp. The truck itself is from the 3D Warehouse, of course, and I scaled it to be close to the size of someone on EcoModder, who is building a cap for his truck. He is using foam ribs about 12" apart, and then 1/4" foam skin. If it works aerodynamically, he'll then fiberglass it.

    If it does work aerodynamically, it can save a lot of fuel -- several other folks on EcoModder have saved 10-20% with similar caps.
     
  4. Helno

    Helno Member

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    I wonder how much of an improvement this would actually make. Don't trucks form a sort of bubble in the bed behind the cab? I remember reading somwhere that having the gate open actually increases drag because it changes the shape of the bubble that forms.

    I suspect that a greater improvement would come from lowering a pickup closer to the ground and flattening the windsheild angle.
     
  5. NeilBlanchard

    NeilBlanchard Member

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    Lowering might help, but windshield angle means very little. Yes, pickups form a pocket, but aero caps help a lot -- like 10-20% in fuel economy. Check the threads on this over at EcoModder.com. My design might be a bit too steep of a taper, for pickups with short(er) beds, anyway.

    The trailing shape of a vehicle is actually where most drag is created or avoided. The angle/arc of the taper is determined by atmospheric pressure pushing the air back, and also a "springing" compression generated by the front of the vehicle. The localized higher pressure helps to close the air back together. And if the trailing surfaces can maintain attached air flow, then it avoids turbulence and a low pressure pocket on the back that actually pulls on the back of the car.

    This is a very low drag design from 1938 called the Schlörwagen, that illustrates a close to ideal shape (though not perfect):
    [​IMG]
    [​IMG]
    [​IMG]

    Also, check out my CarBEN EV open source design. It may well be as good or better than the Schlörwagen, and it will have a much smaller frontal area. The front wheels are able to be covered at highway speeds, but then the hinged panels allow room for the wheels during sharp turns.
     
  6. NeilBlanchard

    NeilBlanchard Member

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  7. rcav8r

    rcav8r Moderator Staff Member

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    Gee how did I miss this thread when it was first posted...

    Wind tunnel/real world testing should prove interesting, and any improvement is a great thing. Baby steps...

    I saw a thing on the MythBusters where they did the no tail gate vs tail gate. Wind tunnel testing showed that an airbuble was formed with the gate up that gave better aerodynamics. Real world testing showed that to be true.
    http://dsc.discovery.com/fansites/mythb ... ption.html

    I did a very non-scientific test a while back. I have an 03 4-Runner. Not the most aerodynamic vehicle on the road. I was making the same trip on the PA turnpike for work a few different times. I reset my fuel consumption computer when I got my ticket at the booth; Cranberry Exit. (Before EZ pass) and checked it at the next ticket booth, one exit past the Breezewood exit.
    One one trip I set my cruise for 70 MPH. I got around 27, 28 MPG (Forget the exact numbers now). On another trip I set the cruise to 60MPH. I got around 32MPG. Nothing earth shattering. Trips were very early AM, so there wasn't much traffic, so I didn't have to get off the cruise. Winds COULD have been different, not sure, but nothing stood out. My cruise holds the speed rock solid. It was during the summer months, so the temps were around the same. Being Western PA, there were some large hills, both up and down. As it was the same trip it was equal. I also run 40 PSI in my tires as I found it increases mileage, and lessens tire wear without adversely effecting the ride. I only did this once (probably out of boredom).
    So from my very non-scientific testing, drag goes up with speed enough to effect gas mileage by a fair amount (12.5% with a 10 MPH differential) OF course as speed goes down I would expect this gain to diminish.
     
  8. NeilBlanchard

    NeilBlanchard Member

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    There are several folks over at EcoModder.com who have made aero caps for pickup trucks and they usually get 15-20% fuel economy.

    My earlier pink model is probably too steeply sloped. The later blue one is probably much better.
     

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