General Discussion Triathlon Talk » Toroidal vs Non-Toroidal Rss Feed  
Moderators: jmk-brooklyn, Ron Reply
2012-10-26 11:58 PM

User image

Extreme Veteran
1136
100010025
Subject: Toroidal vs Non-Toroidal

It seems, based on popular opinion and aero test data that I have seen, that the toroidal wheel shape is better across multiple angles of yaw than the traditional "V" shape.

I recently came across a new wheelset from Profile Design that is not toroidal, but claims to be better suited for those of us not planning a 29mph HIM bike split anytime soon.  PD apparently spent quite some time getting to that conclusion, and posted the following to back up its claim:

http://www.profile-design.com/profile-design/wheels/technology.html

Any aero gurus care to chime in on this?  I'm wondering if it's all pretty much a wash anyhow... what I mean is the difference between a box section rim and an aero rim is far greater than the difference between "V" and toroidal of similar depth.



2012-10-27 8:13 PM
in reply to: #4471427

User image

Master
1485
1000100100100100252525
Sedona, AZ
Subject: RE: Toroidal vs Non-Toroidal

They are only showing half of the equation. Don't forget, there is the other side of the wheel too. The 'magic' of the newer u-shape (torroidal is the shape prior to the u-shape) is that the rear part of the wheel is way more aerodynamic whereas the v-shape is very unaerodynamic (when the 'point' of the 'V' is into the wind).

In the end, get what you can afford. They are all more aerodynamic than standard box rims. The difference between the newer and older shapes is minimal compared to the difference between box rims and deeper rims.

2012-10-27 10:49 PM
in reply to: #4471427

Master
7420
50002000100100100100
Northern IL
Subject: RE: Toroidal vs Non-Toroidal
This feels like marketing playing games.
2012-10-27 11:03 PM
in reply to: #4471427

User image

Pro
5097
5000252525
Subject: RE: Toroidal vs Non-Toroidal

Hed, Zipp and FLO all seem to feel differently.  Heck- I'll believe anybody, as long as they provide the data to back it up.  this CFD analysis seems good, but it certainly only part of the equation.

Profile Design, in my book, makes great products.  Are they quite as fast as the best from Zipp?  hmmm.  I'd love to see the comparative wind tunnel tests.  Other tests on Deep V wheels don't fair quite as well at 10-15 degree aspect.  It's not intuitively obvious by my aerodynamic eye.

Me- I like the Hed H3's... because they look the coolest.

2012-10-28 9:53 AM
in reply to: #4472188

User image

Extreme Veteran
1136
100010025
Subject: RE: Toroidal vs Non-Toroidal

MonkeyClaw - 2012-10-27 8:13 PM

the v-shape is very unaerodynamic (when the 'point' of the 'V' is into the wind).

This doesn't make logical sense to me; a tapered leading edge should be more aerodynamic than a blunt leading edge.  My guess is it's more about the airflow coming off the trailing edge and how it interacts with the rest of the wheel/spokes/frame.  However, i'm not a scientist or mathematician so does anyone have some data or rationale to prove this? 

MonkeyClaw - 2012-10-27 8:13 PM

The difference between the newer and older shapes is minimal compared to the difference between box rims and deeper rims.

I would agree with this.

brigby1 - 2012-10-27 10:49 PM This feels like marketing playing games.

I would also agree with this.

morey000 - 2012-10-27 11:03 PM

Other tests on Deep V wheels don't fair quite as well at 10-15 degree aspect.

Again, not a scientist, but this may be key.  I do know that an airfoil with a lower thickness to chord ratio will typically have a higher stall speed.  It's possible that the toroidal rims with their added thickness are able to keep smooth air flowing around them (i.e. not stall) for greater degrees of yaw.  This would provide a faster rim on average in many more wind conditions.

2012-10-28 10:49 AM
in reply to: #4472346

User image

Champion
8963
5000200010005001001001001002525
Montague Gold Mines, Nova Scotia
Subject: RE: Toroidal vs Non-Toroidal
wbattaile - 2012-10-28 11:53 AM

MonkeyClaw - 2012-10-27 8:13 PM

the v-shape is very unaerodynamic (when the 'point' of the 'V' is into the wind).

This doesn't make logical sense to me; a tapered leading edge should be more aerodynamic than a blunt leading edge.  My guess is it's more about the airflow coming off the trailing edge and how it interacts with the rest of the wheel/spokes/frame.  However, i'm not a scientist or mathematician so does anyone have some data or rationale to prove this? 



While the v-profile works well when the tire is the leading edge, as it basically is the wing shape at the bottom with a Cd = 0.04, when the sharp edge of the v meets the airflow, it tends to behave more like the triangle. While it isn't nearly as bad as the triangle (since I believe that is based off a trangular pyramid placed in a fluid flow) the idea behind the toroidal rim profile is that you have a nice streamlined leading edge when the tire meets the airflow and when the rim meets the airflow.

You are correct that the most important interface is when the tire is meeting the airflow, since it is meeting undisturbed air but the meeting the airflow is still important to the overall aerodynamics of the wheel.



Shane


2012-10-28 8:34 PM
in reply to: #4471427

User image

Extreme Veteran
612
500100
Illinois
Subject: RE: Toroidal vs Non-Toroidal
Interestingly enough profile, Easton, john Cobb/Blackwell and another brand I can't think off all like the thin rim, while hed, zipp and Flo go with the toroidal. The big change recently is the shape of the inner rim (first done by Cobb). Plus there is the semi recent trek study on thickness of the rim intersecting with the fork. Personally I fall in the thin blunted edge preference. Thin (wide forks) to help manage the airpressure, the blunt edge for attachment at small angles of attack (10ish degree) and to mimic how the katana cuts better than a claymore by having the flesh/air contact less of the sword/wheel and creating a boundary layer after the leading edge. If you want to see more examples of thick verse thin check out wwii wing design and then early super sonic design to get an idea of air separation and yaw angles. AlsojAlsojavelin and john Cobb did a nice video on aerodynamics that may help some in this case.
New Thread
General Discussion Triathlon Talk » Toroidal vs Non-Toroidal Rss Feed