Elio reverse trike aerodynamics

[NeilBlanchard]

84MPG will be tough - they'll need to get the exhaust system flush, and get the gearing right, and figure out the swirl and dead zones in the combustion zone, etc. It is telling that GM and Ford and Toyota have only managed this sort of FE in prototypes, and Edison2 achieved 102MPGe Combined - with E85, and that is with a Cd of about 0.16 (Elio won't get this low) and with a curb weight of ~830 pounds (Elio won't achieve this either), and with a turbo 250cc engine.

So, Elio has their work cut out for them.

[Xist]

Hopefully they do not consider what gets other companies in trouble, inflating their EPA figures. They might not be able to survive that.

[aerohead]

Elio might have at least 'built' their vehicle completely,on paper,or within a digital domain before they ever came out of the closet.
Successful automakers can for the most part,totally create and test their products analytically with numerical algorithms.It's all mathematics,since pre-WW-II.
Waffling does not inspire investor,nor consumer confidence.It's a fabulous way to burn precious capital resources and get poor quick.

[brucepick]

Aerohead and NeilBlanchard, how close do you think the current body shape comes to the template? Any guess as to Cd?

Ima specifically asking about the main body. The enclosed front fairings are improved over the previous open fender version. The need to turn for steering seems to preclude adding a tapering tail to the fairing.

[NeilBlanchard]

The main thing that helps the aero drag of the Elio is the smaller frontal area. Tandem seats and tapered top, and slightly tapered sides are also good. It is the outboard front wheels - yes they are now covered, but they have truncated trailing shape, and the exposed suspension and drive shafts add several unknowns.

The Aptera went from 0.11 to 0.15 when it went to front wheel drive - essentially just by adding the driveshafts. The front fenders on the Aptera were much cleaner than the Elio's units and the body shape of the Aptera was exceptional.

I'd guess the Elio is at least 0.20-0.21 or so, and could easily be 0.25 or so.

[Frank Lee]

I don't think it needs to closely conform to template because it's taller than it is wide.

[Big Dave]

The trade-off that has to be made is low coefficient of drag versus frontal area.

Any ultra-narrow vehicle has a huge problem – side winds. To combat that problem you need the widest possible track. At least at one end.

If you enclose the front wheels inside the main body, you reduce coefficient of drag. You could maybe get the whole thing more or less inside the template. But you necessarily increase frontal area.

“Outrigger” wheels offer potentially less frontal area but higher coefficient of drag.

It may be counter-intuitive but what if you put the outriggers so far from the main body that there is no “venturi” between them?

Incorporating something like these might reduce the amount of width the whole thing needs to have to resist crosswind overturning moment.

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Leaning the vehicle into the cross wind reduces the amount of front wheel spacing needed to offset the overturning moment of a crosswind.

Many fixed landing gear light planes fair their wheels for less drag.

https://www.google.com/search?q=whee...ml%3B750%3B526

I think that’s a “must” for a reverse trike vehicle.

[elhigh]

RE: the drag of the front suspension, I bet it could be markedly improved by adding pants to the legs, so to speak. I know many small planes pick up a few mph cruise speed just by adding fairings to their wheels. They add a small amount of frontal area but the drag of the wheels just drops right down. Works on struts and cables, too.

[aerohead]

Originally Posted by brucepick

Aerohead and NeilBlanchard, how close do you think the current body shape comes to the template? Any guess as to Cd?

Ima specifically asking about the main body. The enclosed front fairings are improved over the previous open fender version. The need to turn for steering seems to preclude adding a tapering tail to the fairing.

I'm with Frank,in that she's taller than she is wide,so you might predicate the aero on a wing section rather than the Template.If she weren't a tandem they could boat tail the cabin as with the P-38 Lightning,or Varna Diablo,etc. and that would help with the roofline,as most air would be going besides,rather than over.You might kill any vortices this way.
The thing Neil says about frontal area I think is it's strong point.Porsche is only recently giving up on it's high drag steep roof,as with Panamera.They've relied in part of relatively small frontal areas for performance.Elio is quite small in that way.
The simple front gives a nod to stability and the spectre of product liability class-action lawsuits should owners invert and crash with terrestrial objects passing through the vehicles canopy.
The simplicity helps hold cost down and it leaves room for incremental improvements in future units which could retrofit to the existing fleet.
I don't guess worth a flip.I think Neil's appraisal on potential Cd is very realistic.
She's no Edison-2,Aptera,or Sylph.

[Xist]

My Forester has teardrop-shaped crossmembers (in my closet). Could you fair the struts and whatnot with coroplast?