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Old 01-20-2015, 05:41 PM   #11 (permalink)
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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?

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Old 01-21-2015, 04:11 AM   #12 (permalink)
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Quote:
Originally Posted by aerohead View Post
*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.


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%
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Old 01-21-2015, 05:58 PM   #13 (permalink)
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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.
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Old 01-22-2015, 05:44 AM   #14 (permalink)
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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



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:
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Old 01-22-2015, 07:36 PM   #15 (permalink)
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can you?

Quote:
Originally Posted by Vekke View Post
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



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:
*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!

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