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Old 12-21-2012, 01:38 PM   #51 (permalink)
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So, you think that I'd be wasting my time/effort with individual front wheel airfoils? The thought I had was to do the front of the wheels like the F1, the take the basic shape that they put in front of the rear tires and turn it around, and taper a little air push inward toward the back of the car. The bottom wing platform would have sloped up slightly and tapered to the back of the passenger compartment. Too much work with little or no gain in cd? The Aptera claimed .19 cd I think, while the new Tesla S claims a .24 cd. On the reverse trike, if that is the range that I have control over, would it make a huge difference on mileage? If I go gas or diesel on the first one I would hope to be close to 100 mpg as claimed by some who have built the XR3.

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Old 12-21-2012, 04:52 PM   #52 (permalink)
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I notice you're up to 5 posts with a join date in this month. Here is a thread that came and went in the Hybrids forum, before you joined. You may also find comments of interest in Motorcycles /scooters

The Zing! (Custom-built prototype hybrid tadpole trike)


There is more going on here than you may realize at first, use the Search function to see if terms of interest have been discussed before. Here's a current thread with a parallel discussion: Linner StrÝmlinet Vogn II

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So, you think that I'd be wasting my time/effort with individual front wheel airfoils? The thought I had was to do the front of the wheels like the F1, the take the basic shape that they put in front of the rear tires and turn it around, and taper a little air push inward toward the back of the car.
A vertical airfoil around the tire—maybe; horizontal airfoils around the A-arms—not so much. A separate pontoon fender that turns with the wheel has less frontal area but can act like a rudder.

The problem area with tadpoles IMHO is the turbulent air behind the front tires. The Zing for instance has a rapid rise on the underside of the front fender. It could be lowered and truncated for access to the cabin. (The peak of the fender is maybe a foot behind the axle centerline, and it has no plan taper.)

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The Aptera claimed .19 cd I think, while the new Tesla S claims a .24 cd. On the reverse trike, if that is the range that I have control over, would it make a huge difference on mileage?
.19/.24=~80%. Assume drag is 1/2 aero and 1/2 rolling resistance, then maybe 10% difference.
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Old 12-21-2012, 05:37 PM   #53 (permalink)
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Freebeard, thanks for the leads. I'll try to get a sketch or something in Solidworks close enough to post for critique. Lots of projects on here, love to see it. Thanks!
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Old 12-21-2012, 05:38 PM   #54 (permalink)
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Hey, for rolling resistance tires, are people liking the Ecopia tires?
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Old 12-21-2012, 08:54 PM   #55 (permalink)
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Happy to help; it's why we're all here.

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Freebeard, thanks for the leads.
If you click the Thanks button then Karma accrues to me. For instance I see you've been Thanked once all ready. You posted at 2:37 and 2:38. Just click the Edit button.

But yeah, Ecopia is a name everybody seems to like.

Last edited by freebeard; 12-21-2012 at 09:01 PM..
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Old 01-03-2013, 12:23 AM   #56 (permalink)
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Gonna try to load a couple pics. This is my basic concept but is minus many contours and details. Solidworks is not an easy DIY program.

The biggest question I'll end up with is: by skirting the wheels vs. blocking in the entire front end, any thoughts as to the percentage of CD that I may gain with it open? I like the looks, so if there were even a 5% gain without a big construction difference I would prefer the skirts. What I don't have time to figure out how to draw are the fairly flat wings that would connect the skirt sections with the main body. They would line up with the a-arms to reduce turbulence. The top wing would taper off quickly behind the wheels, while the lower skirt would continue to the back of the wheel skirt. Of course the rear wheel would be skirted on the front and maybe sides. The main body is still basically a block representation here.
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Old 01-03-2013, 09:28 AM   #57 (permalink)
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There is a fairly significant improvement in the Cd by having a single volume chassis; Mercedes studied this and that is what they concluded. The "interference" and interaction between the three volumes in your model will raise the drag more than the reduction of the frontal area.

Keep in mind that the wheels are spinning - the top of the wheels are moving forward at twice the speed of the vehicle.

The underside can't be sloped as much as the side and top; since the ground constricts the air flow, and fully covering the rear wheel will help lower the drag significantly.

Once the surfaces are tapered, they need to stay at the same angle or curve. The air needs to smoothly close back together, and the straightening on the tail of your model will disrupt this, and cause more turbulence than if you removed the "concavity" on the sides; or better yet narrowed the back.

In an ideal shape, the top and the sides can be tapered more than the bottom, and that if the vehicle is roughly square in section, this means that the sides will determine the length; forming a "fish tail" rather than a "beaver tail".

With a tadpole trike, you need the two wheels to be pretty far apart for stability, so the section will be roughly rectangular, so the top and the bottom tapers might allow you to keep the beaver tail. You also could consider two rear wheels with a narrow track, so you can keep the width in the front to a manageable dimension. Take a long hard look at Dave Cloud's Dolphin for a nearly ideal aerodynamic shape:

The *Ultimate* Aerodynamic Car? Dave Cloud's "Dolphin"

I've made a model (in SketchUp) of the Dolphin:
SketchUp Models of Concept Vehicles
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Old 01-04-2013, 06:01 AM   #58 (permalink)
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Thanks Neil,
I had my hopes set on doing something that looked 'cool' as well as having great CD, but reality is what it is, so I'll look at re-drawing the design. I'll post another drawing soon and let y'all take another look. It does make the overall labor much less. Is the basic Riley XR3 pretty close to optimal aero for something with a small/medium size chassis? My frame and front end design will be a little different and I don't want to do all the foam work, but I sure don't mind doing a simpler body design. Down the road I can do one with separate fenders just for fun, but for now I'd like to concentrate on mileage.
Thanks for the input!

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