...but will it make me faster!

I think the question we need to ask is not how pretty the wheel is, but does it fit the biker. A wise man once said fit is the most important component of a bike. Just giving you a hard time Tom, happy new year

they are pricey...and are not really made in italy...
but in Taiwan, therefore you pay a premium for the name.
not that manuf. in taiwan is not worth it. Gerard said a few
times that it was pretty good actually. but making bikes there mean, lower costs and it should show for the consumer...

According to the website: "The carbon fiber skins of the disc are now embossed with over 4900 golf ball-like dimples in 5 different sizes patterned to force the airflow to form less turbulent boundary layers."

This is a curious statement to me. As far as I was taught, golf balls have the dimples so that turblent flow is created. While turbulent flow has a thicker boundary layer (and therefore causes an increase in viscous drag), it sticks more to the surface, which means there is less separation on the back half of the golf ball. Less separation means less pressure drag, which is the most significant contributor of drag on spherical objects.

So, maybe they are not intending to draw an analogy to golf ball aerodynamics (rather an analogy to golf ball appearance), but I still don't see how a "rough" surface would decrease turbulence. Or, on the other hand, they are trying to use this same theory of creating a more "sticky" flow (and the PR statement is incorrect), however, I don't see how that will help on a rotating disk.

Does anybody understand the theory behind this design? Opinions?

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"What the mind can conceive and believe, the mind and body can achieve; and those who stay will be champions."

Man, I didn't say anything about the performance or design. This was simply a commentary on the wheel's appearance in kind of a Kate Winslett, Thora Birch type adoration. No comment about substance, just looks. You think people don't make buying decisions based on that? Despite our best efforts, it happens every day. I don't know Kate Winslett or Thora Birch, they may be intelligent, engaging and fun to be with or conceited, bitchy and self important. But they sure are beautiful. I haven't ridden these wheels, I don't know if they are faster than Hed, Renn, Corima, or Mavic. But they sure are beautiful. Sadly, I can't have Kate or Thora, but I do have a half dozen of these disks. Admittedly, a distant second.

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Tom Demerly
The Tri Shop.com

Yeah, I know what you mean. It just spurred my curiosity when you said they had golf ball dimples and I went on a tangent. I'd just like to learn more about it, and thought with the knowledge that shows up here everyday, someone might have some insight.

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"What the mind can conceive and believe, the mind and body can achieve; and those who stay will be champions."

The technical insight is coming. Right now it's just lust. If they suck that goes out the window though. Beauty is only skin deep. Form follows function. I'm a firm believer in that.

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Tom Demerly
The Tri Shop.com

  I've been waiting not so patiently for the dimple technology to really hit the bike world. Sure, the pros have been using dimpled helmets for some time, but thats been about it. I'm no engineer, but friends who are have assured me that it can make a material difference in performance. One even said that bikes with large surface areas like Cervelos, Softrides and the like could benefit from the technology. Of course how to do that with a frame material is well beyond my layman's understandings. It would probably require a carbon monococque design. I'm not sure how it would affect a metal's structural integrity.

Of course, as noted in discussions elsewhere in the forum, most of this cutting edge tech will only REALLY benefit the cutting edge athletes like Lance or Tim or Peter who are eaking out seconds over their competitors... The rest of us would be better advised to invest in better training...

the blackbird (SR-71) didn't have dimples I am sure but it sure was fast! Coast to coast in an hour wasn't it?

One thing about golf balls and airplanes. The wind is ALWAYS directly from the front. In bicycles, it rarely is.

Frank

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Frank,
An original Ironman and the Inventor of PowerCranks

That's exactly what caught my attention. It seems that on round objects like seat posts and downtubes, etc. dimples would make complete sense. There would be a reduction in pressure drag, since the turbulent flow would follow the surface longer before it separates. I don't know if it would work on something like a cervelo tube, since this type of a shape is supposed to keep the flow attached as it passes over the surface (same thing for the SR-71 blackbird). I just can't figure out in my head how it would be beneficial for dimples on a wheel, (or how dimples can reduce turbulence). I'm probably thinking of the situation the wrong way, it's real easy to get confused with this stuff.

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"What the mind can conceive and believe, the mind and body can achieve; and those who stay will be champions."

Wheel manufactures need something to set them apart. It is like fins on a car. May not do anything other than look cool and Tom says they look very cool. That is enough for many, especially for products that are relatively equal in performance.

The wind tunnel data should let us know if it really performs better than other designs and under what conditions. May or may not have been done.

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Frank,
An original Ironman and the Inventor of PowerCranks

If only you had called PowerCranks, AeroCranks...who knows? If you change the name I want a free set when your sales go through the roof.

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"What the mind can conceive and believe, the mind and body can achieve; and those who stay will be champions."

Not a new Orang. I thought we were done with that. Where's Dan? By the way, we do sell Power Cranks now.

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Tom Demerly
The Tri Shop.com

I hope you're not talking about me, if so I am going to have to work on my forum etiquette so I don't come across the wrong way. Maybe I've been a bit carried away today thinking about dimples. I'm not about to start any arguments one way or another though, just good old fashioned curiosity. I know enough about aerodynamics to be dangerous, and thats it (and I know even less about marketing strategies).

So I apologize if I offended.

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"What the mind can conceive and believe, the mind and body can achieve; and those who stay will be champions."

I am actually trying to make my cranks more aerodynamic. Where can I find formulas for optimum airfoil shape at bicycle speeds.

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Frank,
An original Ironman and the Inventor of PowerCranks

I dunno about that. I just got back from a 1 hr 20mile TT with some friends [god I love headwinds] on my Colnago and I feel it was worth every penny I paid for it. The quality of its' ride is everthing I look for in a bike.

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"on your Left"

Here's an article on dimpling and it's effects, at least in golf balls. The previous poster was correct in recalling that dimples seem to cause turbulence but the supposition, at least from this article, is that the 'mini' turbulent areas around the dimples help the overall aerodynamics:

http://www.physlink.com/Education/AskExperts/ae39.cfm

As usual, only Cobb or someone with similar expertise will be able to give an objective answer to the effectiveness, but they sure do look nice.

Does that mean the dimples on my cheeks will make me go faster ;).

An no "which cheeks" jokes, if you please.

I don't know if they will make you go faster but this whole thing started becasue the wheel has dimples and so do Kate Winslett and Thora Birch. I don't know if that makes them any "faster". I can only hope.

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Tom Demerly
The Tri Shop.com

Gerard's the man to talk to about this (not me), at least this is the impression I've gotten from reading about his bicycle designs and talking with him personally.

I was really impressed that he used NACA data, and therefore a NACA airfoil for his bikes. (I'm a grad student in the aerospace department at the University of Michigan, so I get off on stuff like this.)

As far as my schooling goes, I had most of my aerodynamics in undergrad, so I am by no means an expert. Although, most of what I have had in grad school has been with rotating systems and unsteady flow, such as present on helicopters - a big reason why I am so intrigued by bikes and the research that bike companies perform on things like wheels. I never thought about cranks, but they're in the same boat, just slower rotational velocities.

The interesting thing I noticed with cranks, and aero spokes is that they don't have a NACA profile like gerard's tubes. They seem to be more diamond shaped. I am not sure why this is. Helicopter's, I believe, use a true airfoil shape. I don't know why there is a difference, I can only assume wind tunnel tests show this is a better design for the speeds bikes see, but I really have no clue if this is the case or not. Again, seems like Gerard would know the reasons.

So, that's a pretty long explanation that doesn't really give you any information, sorry. As I started to answer, I started thinking of more questions. Hopefully, Gerard will chime in soon.

The short of it, is that if I (which I laugh at this statement, since I have no business making this stament), were looking for formulas for improving aerodynamics on cranks, I would look at NACA data. NACA was the national aerospace agency before NASA was created. One of the most important studies they did was on different airfoil shapes and the aerodynamics they produced at subsonic speeds. Anyways, it's where I would start, I have no clue if it applies to cranks or not, and I am sure there are other people out there who know a lot more than I do.

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"What the mind can conceive and believe, the mind and body can achieve; and those who stay will be champions."

<< the blackbird (SR-71) didn't have dimples I am sure but it sure was fast! Coast to coast in an hour wasn't it?

and it was made with a lot of titanium, but we all know thanks to Gerard that titanium isn't aerodynamic ;-)

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Mike Plumb, TriPower MultiSports
Professional Running, Cycling and Multisport Coaching, F.I.S.T. Certified
http://www.tripower.org

that helicopers and wheels have similar problems, except wheels do not have to provide lift. But, if memory serves me properly, one of the big problems confronting helicopters is the difference in blade speed when the helicopter is moving. bicycle wheels and cranks face the same problem. The speed relative to the air is much greater at the top of wheel (2X bike speed) than at the bottom where it is at rest relative to the ground.

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Frank,
An original Ironman and the Inventor of PowerCranks

their bikes are nice for sure. However because an italian law says that if something is assembled in italy then it can have the label "made in italy".
colnago are made in taiwan, then assembled in italy (the eaxct law is 10% of the manuf. time has to be in italy to have that label), then they put the "made in italy" label...

to me it doesn't matter where the point of MFG is. What matters is did I get what i wanted in terms of fit, ride quality, frame material, and frame workmanship. the 61 cm Steel Master x Light fit the bill for me and the type of riding the courses around here demand

color me happy

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"on your Left"

there in an other idea behind the dimples and it has to do with hydrodynamics. When airflow goes over a surface it is the molocules of air rubbing over the molocules of the material, dis-similar surfaves, hence drag.If you rough up the surface, some of the air molacules get trapped in the "holes", thus you have air molacules rubbing against air molacules yielding less friction. Before doing tri's I raced sail boats, we would fair our hulls with 800 grit sandpaper to get the same results.

so if we faired our frames and helmets would we go faster??????????/