Aero hub caps

[Weather Spotter]

Thanks, I did not expect that much improvement my self. I had read through the forums but peoples claims of 3-5% seemed way over the top (also there was not much testing data to back them up). I decided that my car needed them for looks if nothing else. But like a good ecomodder I tested them to see what they did.

I also think that they add to the look of my AeroTrix!

[cfg83]

cycleguy -

Originally Posted by cycleguy

Wow, I am surprised it made that much of a difference. Nice job! Now I really want to finish my aero hub caps. BTW, I like your Kammback and skirts.

I agree. From what I can see that's a great looking test. The wind is orthogonal to the test runs so the A-B-A should not be biased in either direction. I've been thinking of making a little booklet on the mods I have and keeping it in my car. That would make a great page for showing evidence of aero-hub-cap benefits.

CarloSW2

[Weather Spotter]

Feel free to use the data if you want. For you book, check out the wiki pages, there is now lots of data up! Add yours as well!

Graphs are great!

[Weather Spotter]

During my testing yesterday the pizza pans made a racket, I though they might be coming off, nope still on tight. It took me a few min to figure out what was causing the noise. If I push in on the center of the pans they flex in about 1/8" this makes the edges lift off the outer edge of the rim. when they come back they make a popping sound (try this at home, take a pan hold the edges and push in at the middle, release and that is that I have).

to fix this I was thinking of some felt pads on the inside of the pan, but they would not handle the wet weather very well. After some wondering around the workshop I got an inspired idea. I took some plastic tubing, slit it down one side and put it over the outer edge of the pizza pan:





I used some hot glue at the joint. Once on the car the bolts hold it tight to the rim!



After a test drive that pizza pan stopped making noise (I can hear the others still). Now I need to make a run to the hardware store for some more tubing (4.5" per pizza pan).

[cfg83]

Weather Spotter -

Pretty cool. I like that your "clear gasket" is being held against the steel wheel, so it is snug as a bug in a rug.

CarloSW2

[Weather Spotter]

yep it holds on nicly, I bet the tubing will cost more than the pizza pan did

[Otto]

Great idea!

If the pans were wider and extended out over the wheel rims to touch the rubber sidewalls of the tires, would that give a smidgen of aero efficiency? Would contact with the rubber sidewalls act to dampen vibrations like your tubing did, or would sidewall vibration be transmitted directly to the pans, making noise like cymbals?

How is noise/vibration with these pans? More or less noise than before?

Would a small round piece of Dynamat, placed at exact center of the inner surface of each pizza pan, make noise significantly less?

Got plans for tire fairings?

[Weather Spotter]

I think that if they went out to the tire it would make it worse.

These pans without any tubing are not too bad (can just hear them with widows rolled up). with tubing I can not hear it at all. side note: if you added more bolts it might also fix the issue.

As for the mat in the middle, I do not know if it would help. there is nothing touching the pizza pan from the bolts to the middle.

I have rear wheel skirts, as for the front, I am not sure yet.

[Otto]

Originally Posted by Weather Spotter

I think that if they went out to the tire it would make it worse.

These pans without any tubing are not too bad (can just hear them with widows rolled up). with tubing I can not hear it at all. side note: if you added more bolts it might also fix the issue.

As for the mat in the middle, I do not know if it would help. there is nothing touching the pizza pan from the bolts to the middle.

I have rear wheel skirts, as for the front, I am not sure yet.

Good to know. Thanks!

My concern about noise is that the pans might act like cymbals or drum heads, what with aero excitation and transmitted vibes through the tire/wheel. A spot of Dynamat at the center (point of max occilation?) of each pan might keep it from vibrating, or at least change the frequency.

Now, good as this fairing of the outer surfaces of wheels is, you still have the problem of poor aero flow at fronts and backs of tires, and inner surfaces of wheels. So, flow fences and/or fairings are needed for that, too.

Hucho shows Opal Calibra in wind tunnel, and smoke trail from nose moves laterally outboard at about 60 degrees to hit and move around tire/whee. So, fairings need to be pidgen-toed and cant inboard at front, for front wheels. Rear wheel fairings presumably Prius-like, but better, although more in line with the long axis of the car.

[Weather Spotter]

with out the tubing on the edges they do act like cymbals. with it I do not hear them.

I will have to look into the farings, I need to see a pic to understand what to make.