Years ago, Zipp produced a three spoke composite wheel. They have not made them for years now. Why not? It seems that there is a market for three and four spoke composite wheels as hed, Xentis, Corima, Xlab, etc produce them.
Hugh Blake
a total guess but id say its because the 3 and 4 spoke wheels are not legal for road racing (TT and Triathlon yes). So they have found one basic design that works for everything, and just have different depths of rims. Im sure this is totally wrong though.
They would probably tell you that what they have now is faster than a 3 or 4 spoke wheel.
Simply put, if you take the total amount of carbon, which can roughly be approximated as proportional the surface area of the wheel, you are better off shaping that into a toroidal rim and then using spokes. For example, the H3 and the 1080 have roughly equivalent surface area. According to Zipp’s windtunnel testing (and I don’t know if there is other data to confirm or deny this), the 1080 is significantly faster than the H3 yet has roughly equivalent behavior in crosswinds (surface area is probably what people feel most in crosswinds). According to Zipp’s own testing (and I know there is other data that disputes this, which according to Zipp has to do with the tires used in the test), the 404 is the wheel that is aerodynamically equivalent to the H3, yet it is significantly lighter. The 1080 is the wheel that is weight-equivalent to the H3, yet it is significantly faster. Again, this is all based on Zipp’s data (some of which has been coroborrated in other locations), and of course, your own values of significant may vary. I do not recollect exact watts @ 30mph and yaw angles. I do know this is probably for a 0-15 or 0-20 sweep, as the H3 performs extremely well at high yaw angles (30deg+), but whether or not that is actually relevant for most riders is debateable.
So that’s the long answer. The short answer is that you can make an equal aerodynamic wheel lighter and an equally heavy wheel more aerodynamic, at least according to Zipp’s own internal engineering.
If they did they would charge 3 grand per wheel…
I am a sales rep for Zipp, and I completely agree with this answer, could not have said it better. Maybe shorter, but not better.
As far as Zipp and 3 spokes go, been there, done that, came up with a better way.
im guessing zipps have a better ride quality?
My guess on the business side is that it wouldn’t work in Zipp’s favour, and I’m sure they’ve analzyed that. It would push more business to the Heds and Xentises of the world, away from Zipp. Building wheels like that would lend all that much more credibility to what the others are doing (“why look, now Zipp is copying ______, those wheels must be faster”), and for a lesser price than Zipp. It wouldn’t be a good business move.
They’ll justify it any other way they can (some of which might be true, some of which might not be), but bottom line in my opinion is that it would be a bad decision for their business.
An H3 type design vs a deep spoked wheel with the same total surface area will handle better in crosswinds.
Think about where the surface area is
and think about leverage.
and which is faster depends on the average yaw angle =)
There is more interaction between the wheel and the frame bodies surrounding it with a multi-carbon spoke wheel than a standard design. When Zipp discovered this phenomenon in the wind tunnel, they shut the door on that design completely.
I personally think that a 808 rim mated to some 14 or 15mm wide carbon airfoil shaped spokes would be supremely awesome.
Chris
I think FIR tried a deep wheel with about 8 spokes, about 10mm wide x 2 to 3mm thick. The Italian pros rode it in the mid 90s including Chiappucci. It ended up being a wind tunnel disaster. Maybe it wasn’t done well though. I doubt that a picture could be found of it easily, I’m fairly positive I saw it in velonews. It is so hard to track down pre-internet things! I actually saw a video today of Merckx’s hour record in '72 in Mexico City, thought I’d never see anything like that! L.A. posted it on his twitter site. (yes, that L.A.).
http://www.youtube.com/watch?v=9-U0gWRhIh4&feature=related
BJ
they tried- zipp 3000- but they couldn’t build a better mousetrap than the specialized tri spoke… which became the HED3. Lance A. could use any wheels he wants… but at the last TT he did- he was sporting a front and rear H3.
700c Composite Spoke Wheel weight(grams) drag(grams)
Specialized (3-spoke) 1330 114
Zipp 3000 (3-spoke) 850 129
That was a really poorly conceived wheel. I believe the rim was a Regida and the spokes/hub were built or at least commissioned by Giant. I believe they were 16 spokes total, which was most of the reason they sucked in the tunnel. The rest was because the rim wasn’t that deep.
Take a Shamal rim and 12 spoke it => with the right tire, it’s still a damned fast setup.
Chris
Chris-
Actually, I still use a shamal 16 spoke on my front. Doing mostly triathlons during the morning in the summer there just isn’t much wind, so a Shamal is probably as fast as anything at 0 deg. yaw. In fact I saw a plot of wind speed vs. elevation (0 to 30 feet) on a sailing website. I think most people are way over estimating the wind speed at 30" AGL. Airports measure wind typically at 15 to 25 feet AGL.
Glad to see you remember the wheel I was thinking about, better than I did I suppose. I still think it had 8-12 spokes though. Also wanted to tell you I did an internal cable route on my Softride TT7 inspired by your ideas on BTR.
BJ
I think zipp doesn’t make one because they don’t have the balls to take on HED.
I’m saying this in the hopes that zipp will be tricked into giving it a try just in case they come up with something better
=)
I think zipp doesn’t make one because they don’t have the balls to take on HED.
I’m saying this in the hopes that zipp will be tricked into giving it a try just in case they come up with something better
=)
and charge triple 
An H3 type design vs a deep spoked wheel with the same total surface area will handle better in crosswinds.
Think about where the surface area is
and think about leverage.
and which is faster depends on the average yaw angle =)
Here’s another interesting question for you to ponder, though. At any given moment, with a H3, how much surface area is in front of the fork and how much is behind it? Ever felt the “shudder” from a stiff gust with an H3? What do you think that is? I actually talked with Kraig Willett about measuring axial force as a function of time to see if you could pick up the asymmetry of the wheel, which I think would be some sort of sinusoidal curve. The other issue with just considering surface area is that the entire surface of a 1080 is not perpendicular to even a direct crosswind. The hoop has significant curvature. Furthermore, I’d be interested to see how the air actually flows around the blades of a H3 in a stiff crosswind. Where is it actually pushed. It’s definitely not as simple as simple considering integrating points based on their distance from the steering axis.
Your ideas intruige me =)
I’ve never ridden on an H3, only a deep spoked wheel because I’m too fast for an H3 to be optimum! (in sprints…lol)
Here's another interesting question for you to ponder, though. At any given moment, with a H3, how much surface area is in front of the fork and how much is behind it? Ever felt the "shudder" from a stiff gust with an H3? What do you think that is? I actually talked with Kraig Willett about measuring axial force as a function of time to see if you could pick up the asymmetry of the wheel, which I think would be some sort of sinusoidal curve. The other issue with just considering surface area is that the entire surface of a 1080 is not perpendicular to even a direct crosswind. The hoop has significant curvature. Furthermore, I'd be interested to see how the air actually flows around the blades of a H3 in a stiff crosswind. Where is it actually pushed. It's definitely not as simple as simple considering integrating points based on their distance from the steering axis.
Here’s another interesting question for you to ponder, though. At any given moment, with a H3, how much surface area is in front of the fork and how much is behind it?
He was right about the leverage issue. At any given time the 1080 will have more surface area closer to the Rim (read front) of the wheel. Hold a paper plate at a yaw angle against a house fan and you will see that the front always catches the and turns away from the wind.
I think the phenomenon is similar to how a crane and proper rigging (splitter bar i think) can pick up unbalanced loads- I don’t know for sure, but the forces just seem intuitively similar.
Thanks,
- Jeff
I cant find the article, but the Shamal HPW12 was and still is every bit as aero as a 404.