Kam

The cycling industry likes to pride itself in being cutting edge when it comes to Aerodynamics. This is just flat out false, but for many companies this sense of elite technology is what moves their goods. What I dislike most about the application of Aerodynamics in the bike industry, aside from producing some really dumb bikes,

is that it seems like research for bike aerodynamics is done completely backwards. For instance; in most industries that deal with aerodynamics (or any other technical designing), trade studies are first completed, followed by the creation of an initial design based on already proven knowledge. Computer models then run simulations on the design producing data to help optimize the initial design. Then finally, after several design iterations based on computer and analytical analysis, the wind tunnel is used as a proof of concept since very complex fluid phenomenon cannot be modeled in the computer.
The cycling industry seems to work in reverse. Go on any website and look for some claims of aerodynamic advantage that are backed by any research or legitimate science and you will be looking for a long time. More likely you’ll find something like this, from a Purdue Cycling Club alumni I might add, that makes the design process sound like it STARTS in the wind tunnel and is more like the process of sticking random shit in a wind tunnel (check out 0:50).
Speaking of Purdue Alumni taking over the bike industry, check this out:
Greg is such a Boss. Anyway the point I’m getting as is that when bike companies allocate their R&D funds (which I imagine is way smaller than their marketing budget), it seems like they just blow it all renting a wind tunnel for a day.
What would be more efficient (and thus cheaper to everybody), would be to do a little research. It’s no secret, except to bicycle manufacturers, that low speed fluid dynamics has been figured out for the past half century. There is a wealth of information and papers published on the subject. So instead spending all their time and money of re-discovering some great aerodynamic phenomenon for reducing drag that was actually used before WWII, they could instead learn about when they complete their trade studies. That would allow them to figure out better designs to test in the first place, and possibly cutting their wind tunnel time (which is VERY expensive).
Here’s a great example of a Aero tidbit of info that cyclist have just seemed to discover: the Kamm effect. It’s basically a very simple bit of optimizing the already very aerodynamic teardrop shape. Developed in the 30’s, the basic idea is to chop off the end of the teardrop at 50% of the maximum thickness. This will produce a relatively small increase in the drag, but reduce a large amount of the surface area (and thus material which = WEIGHT). It was originally applied to cars

This design concept lead to some pretty iconic cars including the original Ford GT and this classic ’62 Ferrari.

Finally, in the past year, the Kammback has made it’s way into the cycling industry in the form of helmets from not only Giro, but also Louis Garneau:

This is a good concept for helmets in particular. Most likely the design concept came from the idea that most TT guys will ride head down, and having a huge teardrop shape sticking up in the air is bad for drag.
The design is also making it into bike design with Scott, who apparently uses full aircraft wind tunnels for their tests. They’ve incorporated the idea into their new F01 bike for 2011

More importantly they’ve hit the nail on the head for why this type of design is important:
“achieve aerodynamic performance with a light and stiff profile”
By reducing the long tear drop tail of most aero frames you gain a few key benefits. Not only does this reduce a lot of weight, but it also makes the tubing closer to circular, which is much more structurally sound. Finally this chopping of the tail will reduce poor performance that a lot of aero bikes have in cross winds.
As with most other disciplines of designs, the name of the game is optimization. By giving up a little aero performance, the bike (or helmet) can have great gains in other design areas.
Anyway this is all just the opinions of someone who has never actually worked in the bike industry…so Zipp, I know I’ve insulted you in the past, but if you give me a job I’ll take it all back.
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3 Comments

  1. I think you’re way off base here. Look at that bike. The way the saddle nose curves down clearly helps to increase downforce, which is something race cars do to stay stuck to the road. Since race cars are fast, this is clearly good aerodynamic design.

    In a kaaaaaaaaaaaaaaam design (I’ve seen it with varying numbers of a’s, so I’m putting plenty here in case those other spellings need an extra), is there any importance in the sharpness of the “chop” of the tail (the radius of the wall transition from the turbulent wall to one of the streamline walls)? I’ve always wondered how differently the air reacts between a smooth transition that’s still too sharp for it to follow and a sharp transition.

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