Elio reverse trike aerodynamics

[NeilBlanchard]

Right, the suspension struts can be streamlined, but the driveshaft is a bit more of a challenge. There were other changes (like outside mirrors), but when the Aptera went from rear wheel drive to front wheel drive, adding the rotating driveshaft exposed to the air, the Cd jumped from 0.11 to 0.15. The Edison2 Very Light Car has a Cd of 0.164 and it has 4 outboard wheels, and it solves this exposed mechanicals by moving the suspension into the wheels and the wheel fairings so the mechanicals can be enclosed in a faired housing.

The other big unknown with outboard wheels is interaction between the main chassis and the wheel fairings. Both the Aptera and the Edison2 had asymmetrical wheel fairings and both were fully tapered to a crisp trailing edge. The bluff fairings on the Elio are very likely to have strong wake turbulence. What they avoid though is a really tight clearance to the chassis at full steering lock, and steering "bump" from side winds.

[brucepick]

Thanks to all for your recent notes here.

I hadn't estimated the exposed suspension items & driveshafts as causing as much drag as expected by Neil Blanchard and aerohead. I expect you guys are right on that.

Just to point out - the most recent prototype (orange, P4 designation) has the coils moved into the man body, but the driveshaft and arms are indeed exposed.

I've long hoped that a tapering tail could be added to the wheel fairings to mitigate losses there. Unfortunately it seems that at full steering lock, the current fairings come very close to the body. One photo I saw showed that but I can't seem to locate it right now. I don't hold out much hope for DIY fairing tails, but you never know. On the right side (no door there), one could possibly build a fixed tail anchored to the main body. It would work properly only when the wheel is pointed straight ahead.

Front track is 66.8". Compare with 2014 Civic at 59". Overall width is even more of course due to wheel housing width. I don't see Elio further widening the configuration in an effort to get the wheels further away from the body for aero purposes. The up side is, Elio claims superb stability, practically tipover proof, and cornering G-forces better than some performance cars (numbers not provided).

If there's room for even a short tail added to the wheel fairings, I'm sure it will be a favorite mod for any Elio's owned on this board.

I'm also considering a boat tail for the back end. That's more challenging of course, and needs to include fully legal rear lighting.

[cbaber]

Do you think an F1 style spoiler on the front could be used to direct the air more smoothly over the tires and suspension components?



I've read about downforce in F1 and the front spoiler is only a tiny part of that, I think the main purpose is to help with the same issue the Elio is going to have. F1 is not allowed to have wheel fairings so this is what they came up with. Now I realize the F1 spoiler is extremely aggressive and does produce downforce, but like most technology from race cars it could be tamed down.

And personally I think it would look cool.

I am also wondering just how big of an effect the open wheel design has at highway speeds. It's been studied extensively in F1, but for speeds 60 mph and under should we focus this much on it? IMO the car looks much better without the wheel fairings. If I get one I'll be sure to do some ABA testing with/without wheel fairings.

[doviatt]

http://www.youtube.com/watch?v=ftq8jTQ8ANE

[spacemanspif]

If you aren't worried about scratching the paint, use a spring to attach "front wheel boat tails" to the current fairings. That way when you turn and the boat tail hits the body, it just flexes out and then returns when the wheels start turning back to straight. Could be easily done and only 2 holes would need to be drilled so the spring hook could attach to the fairing. Using a hinge to mount the tail to the outside would ensure that it returns to its proper spot when driving in a straight line.

Just get the darn thing to market and stop trying to make it perfect the first time. An enclosed motorcycle would help out so many highway commuters including myself. And so what if it "only" gets 70mpg, that still double what I get now...and for only $7,000. Where else are you going to find a deal like that?

[NeilBlanchard]

The leading face of the wheel fairings is not the issue; but rather the trailing surfaces. Which are truncated, but at least cleanly:

[elhigh]

The Elio is riffing on an old theme:



Not that that's a bad thing. The Freeway couldn't be had with a back seat. I saw one once with a passenger, but it was a kid stuffed onto the parcel shelf.

[some_other_dave]

Originally Posted by cbaber

I am also wondering just how big of an effect the open wheel design has at highway speeds.

I'd say the answer would be "quite noticeable". Considering that you can detect aero effects as low as 30 MPH, at 60 MPH they are four times as strong. So yeah, it's worth at least thinking about.

But I agree with other posters: They seem to be making the perfect the enemy of the good.

-soD

[aerohead]

Here are some numbers to consider for fairings.Race cars,record cars,solar racers,SAE Ecothon cars fair and sculpt everything licked by the airstream.

[spacemanspif]

Originally Posted by NeilBlanchard

The leading face of the wheel fairings is not the issue; but rather the trailing surfaces. Which are truncated, but at least cleanly:

I think the above was directed at my comment. Sorry for the confusion but I was referring to the back of the front wheels. I re-read my post and saw how it could be misunderstood.

So let me clarify: Make a "boat tail" for the back edge of the front wheels. Attach these boat tails with a hinge and spring. When you make a tight turn, the tail hits the side of the car and flexes the spring while the wheels continue to turn tighter. The spring then returns the tail to its proper position when the wheels return to their normal straight line driving orientation.

For the urban owner of an Elio, front wheel boat tails might not make much sense but for highway commuters, like myself, I think it would be worth the effort of testing boat tails' benefit.

Not sure but maybe Elio is using truncated rears for the aesthetics at the cost of efficiency but better profit. Lets be honest, the people on this board are a small sect of the general population and even if everyone active on this site bought a 2014 Elio, the company would fail. So they need to appeal to a more broad spectrum of car buyers and styling is a great way to do so. Will it cost 5 or even 10mpg? Maybe. But it might sell 10,000 more units...