How about dimples?

[Scruffy]

The dimples on a gof ball are to assist the induced spin and give greater accuracy, just like a spinning bullet. The larger golf ball with larger dimples gave more distance and greater accuracy.

The maths of trajectory, spin, construction and weight, I'm sure some one out there will be pleased to supply.

[tomislavp4]

I found this article today about NIKE´s new suits to be used by the US athletes at the OS http://asia.cnet.com/crave/2008/07/23/u ... t-apparel/

Seems like they are reducing drag even on non rotating surfaces afterall... (only on low velocity ones maybe?)

Anyway I have an idea for the tyres, what if you make dimples on the tyre´s wall? It rotates and we know that dimples work on rotating things so it would reduce drag significantly right?

You can also make the whole tyre surface with dimples but then you´ll lose contact area

What do you think guys?

[syguy]

Just to clarify:

Dimples aren't specific to rotating objects. The dimples are to induce a turbulent boundary layer where otherwise there'd be a laminar boundary layer. This is only an advantage when the laminar boundary layer is likely to separate from a bluff body, such as a sphere or cylinder. A turbulent boundary layer will tend to stay attached longer and therefore reduce the pressure drag on such objects.

In terms of tires, I think you're correct, by using dimples on the tread (not the walls) the overall pressure drag should be reduced.

[tomislavp4]

I´m not an aero-guy it´s just an idea, but can you clarify why not on the walls? I mean, dimples on the bikes rim are located on the side so why wont it work on the walls (also on the side of the wheel) Thanks

[Conceptual]

I´m not an aero-guy it´s just an idea, but can you clarify why not on the walls? I mean, dimples on the bikes rim are located on the side so why wont it work on the walls (also on the side of the wheel) Thanks

It would seem to be a matter of tyre construction I would think.

You would need to have thicker sidewalls to actually make the dimples, and since most of the suspension travel in an F1 car is in the sidewall of the tyre, thickening them may actually change the way the suspension is engineered.

Maybe that would be a good thing, but I don't know!

Chris

[syguy]

can you clarify why not on the walls? I mean, dimples on the bikes rim are located on the side so why wont it work on the walls (also on the side of the wheel)

The biggest bang for your buck with dimples is if separation is inevitable (as it is behind a sphere and a cylinder) you can trip a laminar boundary layer to go turbulent.

On the walls (relatively flat surface) of a wheel it's not given that separation is inevitable. So maybe in certain conditions dimples might help, but there's also the risk that you'll needlessly trip a boundary layer increasing overall drag if it wasn't likely to separate.

I guess with a bicycle wheel the tread is so narrow that the dimpled rims might be there to try and make the boundary layer stay attached a little longer to the tread after leaving the rim or vice versa (as the flow leaves the tire and covers the rim). With a wide F1 tire you would be able to apply dimples directly to the tread.

[syguy]

I just came across an article from Racecar Engineering titled: Dimpled Aerodynamic Surfaces.

It relates bicycle rim dimples to possible race car applications.

[Ciro Pabón]

Thanks, syguy, as most of the articles from "Scarbs' group" this is a good one.

[Project Four]

I found this article today about NIKE´s new suits to be used by the US athletes at the OS http://asia.cnet.com/crave/2008/07/23/u ... t-apparel/

Seems like they are reducing drag even on non rotating surfaces afterall... (only on low velocity ones maybe?)

I has been common for the last few years for cycle suits to have dimples on the arms and on the legs, similar to the NIKE suit's to reduce drag.

I think the original development for this came through Lance Armstrong F1 program, with Nike the developer and manufacturer of the US Postal / Disco team wear.

Regarding bike aero developments you may find these two links of interest:-

http://www.thefastestbikeintheworld.com ... ge=english

http://www.thefastestbikeintheworld.com ... ge=english

[tomislavp4]

Thanks both of you, very nice reads

[Shi Ruan]

I found this article today about NIKE´s new suits to be used by the US athletes at the OS http://asia.cnet.com/crave/2008/07/23/u ... t-apparel/

Seems like they are reducing drag even on non rotating surfaces afterall... (only on low velocity ones maybe?)

I has been common for the last few years for cycle suits to have dimples on the arms and on the legs, similar to the NIKE suit's to reduce drag.

I think the original development for this came through Lance Armstrong F1 program, with Nike the developer and manufacturer of the US Postal / Disco team wear.

Regarding bike aero developments you may find these two links of interest:-

http://www.thefastestbikeintheworld.com ... ge=english

http://www.thefastestbikeintheworld.com ... ge=english

You can also see it on some TT helmets, though for the most part they are gimmicks.

The most prevalent use of dimpled surfaces are on ZIPP's 404, 808, and 1080 deep section carbon wheels(as well as their disk wheels for TT's). As a rider, I can feel a distinct increase in descending speed using dimpled 404's compared to smooth wheels of a similar depth, and that's at around 40-45mph, with max air-speed over the wheel at around 80mph. So yeah, I wouldn't at all be surprised if dimples started popping up, the only thing I can see being an issue is making sure the disturbed air doesn't get to the wings.