I'd like to put this one out there:
http://www.slowtwitch.com/..._58_and_72_3957.html

Calling all aero nerds and geeks! I'm curious - what do you think of their white paper, data, and way of thinking? What about the high drag/high lift vs low drag/low lift designs? Some of their wheels' design elements remind me of the H3 (i.e. sharp ID), so I have to think that that there is validity to it - but then things like the stepped-down rim edge are really unique (and they wouldn't really tell me what it actually does). They were clear to say that dimples don't work, but didn't really say that they do anything bad, either. They say that their rim shape is low drag/turbulence, but again - not much of the 'how/why'. Constructive thoughts/comments are welcome.

Ultimately, I actually liked riding the wheels, despite all of the info that seemed strange. Oddly enough, they *did* seem very stable on very gusty descents - and I went in to it fully expecting the opposite. I have a few front wheels in my stable that I'd like to compare it to back-to-back - H3, Dura Ace 50 2013 (similar shape to Reynolds), Profile-Design TwentyFour 58mm (it's wide/blunt).

“It is common that small disturbances in airflow in localized regions can improve the overall aerodynamic performances. This is common particularly near leading edge contours and trailing edge re-attachment zones. This is the case for the ISH. Tire size varies depending upon rider selection and the tire shape is dynamic; it is always changing depending upon terrain, air pressure and tire design, and molded tire tolerances. The ISH helps to create a predictable airflow over the surface of the rim in a situation where the airflow would otherwise be unpredictable based upon the tire variability and environmental conditions.”

Greg-
It feels like there is a lot of double speak coming from Paul Lew in regards to his explanations of how the wheels work aerodynamically. He says that tripping the air to stimulate the airflow doesn't work, and then gives an almost perfect description of a trip when describing the ISH technology...



While Mr. Lew is correct that aerospace engineers speak of Lift vs. Drag I believe he has his axis mixed up. Lift is defined as a positive force along the Z axis (with the Z axis pointing up) and Drag is most commonly defined as a negative force along the Y axis (with the Y axis pointing forward i.e. along the direction of travel). He makes some interesting points about his High Drag/High Lift vs. Low Drag Low Lift concepts. An object can have drag in one area and then produce negative drag in another area and they cancel each other out producing an object with low total drag. Or an object can just be low drag all over and not have the negative components anywhere in the foil. While this is an interesting discussion a wind tunnel is not the place to attempt to measure this phenomenon because it will only give you the total drag of an object, it will not break down the drag into multiple components. CFD will tell you what part of you object is contributing what drag to the total, which it appears he is using. Overall he is correct that it is multiple ways of skinning the same cat. I also think that he is trying to optimize the leading edge of the front half of the wheel while Zipp/HED/Flo are trying to optimize the leading edge of the back half of the wheel. More skinning the cat differently.

I can't blame Mr. Lew for misusing the word 'Lift' though. I believe it's misuse started when Zipp started bragging about their discs achieving lift in the tunnel at high yaws. If they achieved lift athletes up and down the Queen K would be losing contact with the road as they were lifted off by their 808s. What Zipp say in the tunnel was negative Drag, which propels the object forward. This is good, but I suspect the marketing people had a hard time explaining why a negative thing was actually good.

It is fantastic to see another good wheel option out there, but I agree with your conclusion that Reynolds needs to spend a little time cleaning up their message to consumers about why their wheels work. Right now their message is confusing to the point of seeming contradictory.

Some might see that as being snobby of picky? Or reminding us that "real" aircraft designers use the "right" terms? If so he's not completely alone. Some guys (like Kraig Willet) insist on using CxA instead of CdA: the "x" is defined as the bike's direction.

One other thing that occurred to me is that maybe the bike guys are rotating the traditional aerospace, and also automotive, coordinate system on it's side so that what I am calling Sideforce is being called lift. Anyone in the industry care to comment on this?

Compare drag and side force components of the net aero force vector in bike coordinates and wind coordinates.

At zero yaw, the two coordinate systems are aligned and there's no confusion.

At non-zero yaw, then it matters which convention you're talking.

Cheers,

I do not see anything odd, I see an error, but nothing odd. Plenty of people get confused by vectors. The forward thrust vector just does not have to connect to that "resolved vectors" from the side force because you want it to. The "side force" vector should be acting through the center of pressure and so should the thrust vector.

Do wheel fixtures in tunnels usually have the ability to measure moment around the Z axis? How is he determining the position of the center of pressure?

If they are using CFD for the moment data I hope they have a way of physically backing up their models. When it comes to engineering models it pays to trust but verify.

I don't know if this is right or wrong or even what I'm talking about, but the charts here http://www.aerospaceweb.org/...dynamics/q0194.shtml seem to show that an airfoil, like the reynolds wheels seem to be, has low drag/low lift at 0 and 180 degrees, the leading/trailing edges of the wheel

Also, did they give any motivation for picking the 16 degrees of yaw in their comparison other than it's the one in which they did the best?