Aerodynamic wheel fairings/mudguards/housings
 

Hi,

As you propably have noticed I am building my next fuel sipper and its gonna be bad ass ride.

What I havent yet seen in any tests or talks is that you put spare wheel cover on top of your wheels.

In general the less aerodynamic drag you will have smaller the wheel housing volume is. Easiest way to get most smallest volume is put wheel housings on top of your wheels.

So my plan is to use this kind of housings:
http://www.boostclassifieds.com.au/d...er_6789751.jpg

Cut them to correct shape and attach over each wheel.
- Front wheel can still turn without any problems.
- Tire housing volume is minimal, I am shooting for 15-20mm gap to tire
- They could actually look cool and futuristic
- Tire vortices should have minimal effect to aero

Now those wont fit in place on most cars but the A8 has quite big room there specially with smaller diameter tires which was one of the reasons to move 195/65R15 size.

I think you will hit a bump or turn hard and the sidewall will flex enough to rub and grab the tire at speed. I think you are talking about mounting them to the spindle and then cutting out a bottom chunk for the contact patch of the tire. The 1969 Plymouth Roadrunner had some promo discs that worked that way just covering the wheel and none of the tire. I don't think this would work on a car w/o a stationary spindle but there are some spinner type wheels that use bearings to create a stationary center piece rather then the normal spinning center piece. here is the Roadrunner in action
https://www.youtube.com/watch?v=EBcRIRYWRHM

The Plymouth is using a product similar to CapAds... ;)
http://www.capads.com/

11 years ago AdFleet rolled out a similar product....
Have You Seen These Wheel Cover Ads? - Motor Trend News

No not like that, like this:
https://scontent-b-ams.xx.fbcdn.net/...ad&oe=5525A75C

So only wheels will roll/rotate these will turn along tires in the front and follow suspension. When painted to body color will look better IMO than hubcaps. You can still intall hubcaps under that cover, but effect will propably be neglible to none.

I think these should save over 5% of fuel?

All tires bulge with heat. You'll also have to mount that thing on there really well (x4) then you have issues with checking your pressure and making sure there are no general problems with the tire.

If you can make this work, I'd highly suggest weekly removal for inspection which is something you should keep in mind while figuring out a mounting situation.

Great idea, if you can make a sturdy bracket/baseplate on the struttower and keep enough space between wheel and cover there should be no problems right? Try keeping the unsprung weight low.

Yes metal brackets etc will be needed. I have ligthened the unsprung masses about 11kg per front corner so little bit more back is not that much big problem. That inside will still be open and heat should not be a problem anyway in finnish climate and with my driving style. Structure migth be problem in winter when snow fills that volume and freezes and when it got loose its solid ice block. So will not work in winter propably, but time will tell.

Basicly there should not be no problems but I am trying to get more data is closer the tire better clearance like I have read from aerodynamic books...

Great idea, and just what I've been looking for.

Keep in mind:
The Ford Probe IV Concept did the same thing with a flexible, deforming skirt over the wheelwell opening.
http://files.conceptcarz.com/img/For...pt-1983-01.jpg

Have you ever seen a slingshot drag racer spin the tires at the starting line? Admittedly they're low-pressure bias-ply tires, but they grow 3 or 4 inches in diameter before the car starts to move. The whole rear of the car raises up.

That said; go for it.

housing
 

*Wheelhouse drag has to do with the volume of the wheelhouse in which the wheel/tire occupies.
*You could calculate the difference in the overall 'void' attributed to the addition of the wheel covers.
*You'd want to test for the entire wheel-flop range of motion to ensure that nothing collides with the wheel arch.
*I'm unsure of what the flow over the wheel will do when the cover protrudes so far from the wheel.Technically this is a no-no aerodynamically.Some of the air will try and ride the wall of the cylindrical covers,while a portion will attempt to spill over the outer edge.Since it's spinning,the 'trailing edge' cannot be boat tailed,giving the wheel a larger overall frontal area.
*Un-skirted,having the outer face of the wheel even with the body is good only if the tire is even too.
*Would not the articulated skirts as on AEROCIVIC not be easier to deal with?

There are few reasons why this in better in my opinion and one them are looks. I know I can build nice lookin hinged front skirts, but they would still look not cool IMO. At least I will test these in action.

This car had 225/60R16 and now I will propably have 195/65R15. There happens to be that 42mm diameter difference to that original tire diameter, so the cover is same size as oem tire so no problems should occur.
http://www.willtheyfit.com/wheelimag...6.2&aspect2=65

I am not understanding the bigger frontal area as its in the wheel housing and only will come flush to cars outer edge?

I do understand the wheel rotating and riding that cover cylindrical wall, but it migth be possible that air somehow stop with the cover so it wont leave the cover.
Block the inside of the cover edge etc


http://ltces.dem.ist.utl.pt/lxlaser/...apers/15_1.pdf


Here I dont understand the Scx Scale? Its related to wetted area which means the frontal area or the volume. Anyway in that study best and worst case delta cd was about 5%

frontal area
 

*originally,you were going to mount the cover to the wheel.That infers a growth in frontal area.
*Adding the cover as an inner fender,mounted to the steering,with a smaller wheel/tire is something altogether different.
*You still have not reduced the wheelhouse volume.
*You're only going to reduce the clearance between the tire tread and inner face of inner fender.
*You still have the void between the outside of the inner fender and the interior face of the wheelhouse.
*You'll still have windage within the cavity of the inner fender.
--------------------------------------------------------------------------
*If you can pull this off it's a good thing.
*The 1984 Probe-IV,with inner fenders and elastic urethane skirts was reported to enjoy a 9% drag reduction just with these front wheel modifications.
*There is no data for the a drag reduction for the inner fenders themselves.
*Full wheel skirt performance has been reported as low as 2% for total drag reduction.
-------------------------------------------------------------------------
*The addition of wheels to a low drag car can double the drag,as in the case of the CNR car of 1978.
*Wheels on the 'Template' raise the drag from Cd 0.08,to 0.13.
*The 'cleaner you make your car,the more important will be the effect of the wheels/tires.

For me there is actually two different problems occurring:
1. The rotating wheels that create lots of turbulence. In all highly aerodynamic vehicles they are fully covered so the wheel "swirls" dont effect the outer surface flow. If we can stop that swirl as close to the wheel the original inside fender volume should not be so big problem. Like regular cars engine bay if you have a grill block is no problem even there is huge volume of air... Same priciples as dampening sounds etc fix the problem as close to where its generated and its easier thing to do.
2. That fender volume which is still open for air flow from specially under the car, underside is not totally smooth, so air can enter that fender at high surface area through the lower suspension arms etc. Wheels turn specially in the front so you cannot block it fully or can you? Of course you can if you are a engineer... Then then outer cover shell which is facing the cars outer surface has quite small clearance to the wheel well that it will not disturb much air flow of the outer car as its "flush" to body

https://encrypted-tbn2.gstatic.com/i...VmZwAVJT1TW1KA

I have looked the interesting aerodynamic car topic almost through and found that Dubonnet Dolphin actually had pretty similar structure.
http://www.autominded.com/3831_1936-dubonnet-dolphin/features#!prettyPhoto[Gallery]/3/

This is what I am shooting for with 20mm gap to tire:
https://fbcdn-sphotos-c-a.akamaihd.n...4f45307a4316e2

can you?
 

*The 1996 HONDA Dream 2 solar racer used 'lazy-susans' to support the front steering wheels.
The steering was accomplished just as the double cable pull on an outboard motor boat.There was virtually zero gap,anywhere around the wheels.
*Here is a link to a contemporary transit bus with wheel strakes as you envision for your car.There are a lot of bus concepts with these.
http://upload.wikimedia.org/wikipedi...s_BRT_Metz.jpg
*Build as light as you possibly can.When striking pot holes,the inertia of the housings will tend to have them deform and strike the tires during this instantaneous 'jerk' loading.
*The inner half will be required to handle the lion's share of the structural loads since the outer half will be removable.
*Striking a pothole on a driveway ramp,while the steering is racked all the way to either side will be the worst-case-scenario as far as clearance goes.
*What a fun project!:D