Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

User Tag List

Reply
 
Thread Tools Search this Thread
Old 09-25-05, 10:56 PM   #1
TheKillerPenguin
Nonsense
Thread Starter
 
TheKillerPenguin's Avatar
 
Join Date: Sep 2004
Location: Vagabond
Bikes: Affirmative
Posts: 12,524
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 164 Post(s)
Aren't flat bladed spokes less aero than round spokes?

Am I insane, or are bladed spokes more for show than anything? A round spoke directs air around it because of its shape. A bladed spoke, however, in addition to having flat sides also has a flat front end, which should cut through the air less efficiently, creating more drag and more air turbulence. Am I right, or does the bladed nature of the spoke counteract the turbulence created by the front end smashing through the wind? It seems to me that rather than aiding a rider, a bladed spoke does nothing more than create drag and catch crosswinds. If a wheel were to be really aero, one would want teardrop shaped spokes, followed by round spokes, and then finally the bladed spokes one finds on Ksyriums and Race Lites.

Am I right, or am I just another carpet smoker?
TheKillerPenguin is offline   Reply With Quote
Old 09-25-05, 11:18 PM   #2
rmwun54
Senior Member
 
Join Date: Apr 2004
Bikes:
Posts: 898
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Well from my experience I have ridden with a friend who have bladed spokes on a deep dish wheel (Mavic's). I on the other hand have a radial laced Velocity aerohead rim (32 spokes 14/17/14 DT Swiss). Both our bikes weigh the same and I am about 10 lbs. heavier than him. On a downhil ride, the Crest HWY we both take off rolling evenly and coast. As we both do the tuck thing we are rolling down the hill quite evenly at about 35 mph for quite a long while. So my feeling is that there is no difference between the two spoles set up.
rmwun54 is offline   Reply With Quote
Old 09-25-05, 11:21 PM   #3
shimanopower
Senior Member
 
shimanopower's Avatar
 
Join Date: Jul 2005
Location: chicago
Bikes: lemond zurch, felt f55 '05
Posts: 822
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Well according to God (sheldon brown)...

"Æro (elliptical) spokes are a variety of double-butted spoke in which the thin part is swaged into an elliptical cross section, which makes them a bit more ærodynamic than round-section spokes. The most widely available spoke of this type is the Wheelsmith Æro. These are 1.8mm (15 gauge) at the ends, and the middles are equivalent to 16 gauge, but in the form of a 2.0 x 1.6mm ellipse. The Wheelsmith &Aelig;ro is my favorite spoke for high-performance applications, not just because of whatever ærodynamic advantage it may offer, but because the flat center section provides an excellent visual indicator to help the wheelbuilder eliminate any residual twist in the spoke. This helps build a wheel that will stay true.

Æro (bladed) spokes have a more pronounced æro shape, flat, rather than elliptical. Although they are the most ærodynamic of spokes, they won't normally fit through the holes in a standard hub because they are too wide."

http://sheldonbrown.com/wheelbuild.html
shimanopower is offline   Reply With Quote
Old 09-26-05, 12:17 AM   #4
MrAmazin17
Member
 
Join Date: May 2005
Location: Sacramento, CA
Bikes:
Posts: 45
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by shimanopower
Well according to God (sheldon brown)...

"Æro (elliptical) spokes are a variety of double-butted spoke in which the thin part is swaged into an elliptical cross section, which makes them a bit more ærodynamic than round-section spokes. The most widely available spoke of this type is the Wheelsmith Æro. These are 1.8mm (15 gauge) at the ends, and the middles are equivalent to 16 gauge, but in the form of a 2.0 x 1.6mm ellipse. The Wheelsmith &Aelig;ro is my favorite spoke for high-performance applications, not just because of whatever ærodynamic advantage it may offer, but because the flat center section provides an excellent visual indicator to help the wheelbuilder eliminate any residual twist in the spoke. This helps build a wheel that will stay true.

Æro (bladed) spokes have a more pronounced æro shape, flat, rather than elliptical. Although they are the most ærodynamic of spokes, they won't normally fit through the holes in a standard hub because they are too wide."

http://sheldonbrown.com/wheelbuild.html
And on the 7th day, he rested...
MrAmazin17 is offline   Reply With Quote
Old 09-26-05, 12:52 AM   #5
Eatadonut
You know you want to.
 
Eatadonut's Avatar
 
Join Date: Jun 2005
Location: Norman, Oklahoma
Bikes: Pinarello Prince, 1980's 531 steel fixie commuter, FrankenMTB
Posts: 1,896
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I thought bladed spokes were for eliminating the threat of squirrels jumping into your front wheel and getting stuck.
__________________
Weather today: Hot. Humid. Potholes.
Eatadonut is offline   Reply With Quote
Old 09-26-05, 12:54 AM   #6
53-11_alltheway
"Great One"
 
53-11_alltheway's Avatar
 
Join Date: Feb 2005
Location: Might as well be underwater because I make less drag than a torpedoE (no aero bars here though)
Bikes:
Posts: 4,463
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by PenguinDeD
Am I insane, or are bladed spokes more for show than anything? A round spoke directs air around it because of its shape. A bladed spoke, however, in addition to having flat sides also has a flat front end, which should cut through the air less efficiently, creating more drag and more air turbulence. Am I right, or does the bladed nature of the spoke counteract the turbulence created by the front end smashing through the wind? It seems to me that rather than aiding a rider, a bladed spoke does nothing more than create drag and catch crosswinds. If a wheel were to be really aero, one would want teardrop shaped spokes, followed by round spokes, and then finally the bladed spokes one finds on Ksyriums and Race Lites.

Am I right, or am I just another carpet smoker?
The most overall aerodynamic spokes are oval (like the sapim cx-ray, etc).

The big flat blades are aero only in one direction (particullary the large aluminum Kysrium SSC SL blades), but at any angle greater than zero they can actually increase drag.
53-11_alltheway is offline   Reply With Quote
Old 09-26-05, 01:45 AM   #7
NZLcyclist
MaNiC!
 
NZLcyclist's Avatar
 
Join Date: Feb 2003
Location: Hamilton, New Zealand
Bikes: 2004 Cervelo Soloist 105, 2005 Apollo Apex, 2006 SCOTT Speedster S30
Posts: 1,600
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
From www.velomax.com

Q. Why doesn't Velomax use bladed spokes?

We carefully considered using bladed spokes, but decided against it. In wind tunnel tests, bladed (and ovalized - hereafter "profiled") spokes have proven to be very effective. The caveat here is that they show their greatest advantages vis-a-vis round spokes when the airflow is from straight ahead. As soon as you introduce even a small component of side wind (yaw angle as low as 2 degrees), the larger surface area of profiled spokes acts either as a lifting surface, or develops airflow separation (with related generation of vortices), or both. The bottom line - creation of lift cannot be accomplished without corresponding increases in drag.

Simply stated, a profiled spoke in a static or head-on air stream can be very effective. However, a profiled spoke in a side wind is a propeller.

A round spoke always presents the same small profile to the air stream, whether the angle of attack is head on or from the side. When you consider the wind direction, speed of the bicycle, and rotational speed of the wheel, it becomes apparent that there is an alphabet soup of aerodynamic considerations happening throughout the course of the ride. For this reason, we believe that swaged (butted) spokes present the best real-world aerodynamic profile.
NZLcyclist is offline   Reply With Quote
Old 09-26-05, 02:06 AM   #8
fogrider
Senior Member
 
Join Date: Sep 2003
Location: fogtown...san francisco
Bikes: Ron Cooper, Time VXSR, rock lobster, rock lobster, serotta, ritchey, kestrel, paramount
Posts: 2,276
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I pretty much agree with what has been said here, oval is the most aero. I had a front wheel built with oval spokes and if you spin it and put your hand near it you can feel the air being displaced. I compared it with round spokes and oval is the way to go. I also have a front wheel with flat spokes...its still more aero than round spokes. you have to remember flat spokes are litterally created by taking a round spoke and flattenning it. This creates a narrower front and this wheel has 24 spokes. I have not noticed any control issues, but I don't use it in windy conditions.
fogrider is offline   Reply With Quote
Old 09-26-05, 04:38 AM   #9
roadwarrior
Senior Member
 
roadwarrior's Avatar
 
Join Date: Oct 2002
Location: The Bike Business!!!
Bikes: Cannondale Super Six High Mod, Evo, Sram Red, CAAD9 Rival
Posts: 10,502
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
I guess if you are a really good rider, it does not truly matter...

I ride SL's and have for over two years...stiff, bulletproof, and no problems in side winds.
roadwarrior is offline   Reply With Quote
Old 09-26-05, 05:07 AM   #10
EURO
My toilet-Floyd's future
 
Join Date: Sep 2005
Bikes:
Posts: 1,776
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
and no problems in side winds.
That should be 'no perceivable problems in side winds'. For all you know, you could be loosing 2% of your power.

I can’t perceive a 100g decrease in weight, but all other things being equal, I would take the lighter bike into a race.

Pros and pros mechanics don't always know best. Many are still operating under cycling's 'old wives tails'.
EURO is offline   Reply With Quote
Old 09-26-05, 06:59 AM   #11
badkarma
Know Your Onion!
 
badkarma's Avatar
 
Join Date: Aug 2005
Location: Boston, MA
Bikes: Kestrel Talon, Motobecane Le Champion SL
Posts: 2,011
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Why do you think airfoils (i.e. airplane wings) have the shape they do? They create lift (irrelevelant in the case of bicycles), but they also have a low coefficient of drag due to their profile. Round spokes leave a large wake (i.e. more pressure drag) than bladed spokes. Let it be said though, the decrease in pressure drag due to bladed spokes is rather minimal, yet it is finite.
badkarma is offline   Reply With Quote
Old 09-26-05, 07:25 AM   #12
53-11_alltheway
"Great One"
 
53-11_alltheway's Avatar
 
Join Date: Feb 2005
Location: Might as well be underwater because I make less drag than a torpedoE (no aero bars here though)
Bikes:
Posts: 4,463
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
The sapim cx-rays don't have much side profile though and that is why you can use them with regular hubs and not elongate the spoke holes at the flange.
53-11_alltheway is offline   Reply With Quote
Old 09-26-05, 07:35 AM   #13
biker7
Senior Member
 
biker7's Avatar
 
Join Date: Feb 2005
Bikes:
Posts: 2,850
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by NZLcyclist
From www.velomax.com

Q. Why doesn't Velomax use bladed spokes?

We carefully considered using bladed spokes, but decided against it. In wind tunnel tests, bladed (and ovalized - hereafter "profiled") spokes have proven to be very effective. The caveat here is that they show their greatest advantages vis-a-vis round spokes when the airflow is from straight ahead. As soon as you introduce even a small component of side wind (yaw angle as low as 2 degrees), the larger surface area of profiled spokes acts either as a lifting surface, or develops airflow separation (with related generation of vortices), or both. The bottom line - creation of lift cannot be accomplished without corresponding increases in drag.

Simply stated, a profiled spoke in a static or head-on air stream can be very effective. However, a profiled spoke in a side wind is a propeller.

A round spoke always presents the same small profile to the air stream, whether the angle of attack is head on or from the side. When you consider the wind direction, speed of the bicycle, and rotational speed of the wheel, it becomes apparent that there is an alphabet soup of aerodynamic considerations happening throughout the course of the ride. For this reason, we believe that swaged (butted) spokes present the best real-world aerodynamic profile.
Da real truth.
George
biker7 is offline   Reply With Quote
Old 09-26-05, 07:38 AM   #14
nova
hill hater
 
nova's Avatar
 
Join Date: Aug 2005
Location: norton ohio 5.5 miles from center road tow path trail head
Bikes: cannondale t400 1987 model and a raleigh gran prix from 1973
Posts: 2,127
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Eatadonut
I thought bladed spokes were for eliminating the threat of squirrels jumping into your front wheel and getting stuck.
Lol slice and dice
nova is offline   Reply With Quote
Old 09-26-05, 08:30 AM   #15
Nessism
Senior Member
 
Nessism's Avatar
 
Join Date: Jun 2004
Location: Torrance, CA
Bikes: Homebuilt steel
Posts: 2,333
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
The air drag of the spokes is proportional to its forward facing thickness. Wheelsmith/DT oval spokes are approx. 1.2/1.3mm thick which exposes less area to the wind. The advantage is far greater than the losses from side winds since the spoke velocity is greater as the wheel rotates at high speed around the hub.

In practical terms, blade spokes do not fit though the holes in the hubs unless the hub is designed for the purpose. For that reason, oval spokes are used.

For a real world comparison, I have several friends with Ksyriums and when coasting down hill these guys leave me with my round spoked Dura Ace/Open Pro wheels, alll other things equal. I'm convinced but not enough to get me to spend big $$ on wheels.

My next purchase is going to be a conventional wheelset using oval spokes.

Ed
__________________
Becareful buying/selling bike parts on-line. I learned the hard way. :(

Good/Bad Trader Listing

Last edited by Nessism; 09-27-05 at 10:37 AM.
Nessism is offline   Reply With Quote
Old 09-26-05, 08:42 AM   #16
TheKillerPenguin
Nonsense
Thread Starter
 
TheKillerPenguin's Avatar
 
Join Date: Sep 2004
Location: Vagabond
Bikes: Affirmative
Posts: 12,524
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 164 Post(s)
Maybe I'm being unfair to ksyriums.

My old wheelset (Gipiemme Grecal Parades) had bladed spokes, but the front wasn't tapered at all; they were long rectangles, not oval, so the front of the spoke was flat and wouldn't really cut through the air. I assumed that they had the same spokes as my crap wheels, which is unfair.
TheKillerPenguin is offline   Reply With Quote
Old 09-26-05, 12:57 PM   #17
bike756
Hair Free
 
bike756's Avatar
 
Join Date: May 2005
Location: Massillon, Ohio
Bikes: specialized allez with misc. upgrades,commuter mtb
Posts: 378
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
How do they get those things into the rim?
bike756 is offline   Reply With Quote
Old 09-27-05, 06:09 AM   #18
NJWheelBuilder
Senior Member
 
Join Date: Jul 2004
Location: Cental New Jersey
Bikes: Klein Quantum Pro
Posts: 469
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
For the average rider, I doubt any of the choices makes a huge difference in performance. I'm sure riders at the pro level reap some benefit from the slight aero benefits of particular spokes, but they are also pushing 30 mph on a regular basis.
My approach to building wheels has always been a practical one. Unless there is a compelling reason to do otherwise, I tend to pick spokes that could be replaced in the middle of nowhere if necessary (round).
NJWheelBuilder is offline   Reply With Quote
Old 09-27-05, 10:00 AM   #19
formulaben
Senior Member
 
formulaben's Avatar
 
Join Date: Sep 2004
Location: Les Bois
Bikes: Felt F2C, Scott Spark 40, and Custom Fixie
Posts: 1,173
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by 53-11_alltheway
The most overall aerodynamic spokes are oval (like the sapim cx-ray, etc).

The big flat blades are aero only in one direction (particullary the large aluminum Kysrium SSC SL blades), but at any angle greater than zero they can actually increase drag.
Well, Velomax says the same thing, but Zipp disagrees (pdf file), and puts it in writing. Check out the first chart. If the wind angle is 0 degrees, it is riding behind the wheel and rim, so it is in turbulent air. It makes sense that as the angle is increased that drag goes down.
__________________
"Strong, light, cheap. Pick any two." — Keith Bontrager
formulaben is offline   Reply With Quote
Old 09-27-05, 10:10 AM   #20
TheKillerPenguin
Nonsense
Thread Starter
 
TheKillerPenguin's Avatar
 
Join Date: Sep 2004
Location: Vagabond
Bikes: Affirmative
Posts: 12,524
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 164 Post(s)
That's an awesome link ben. Thanks.
TheKillerPenguin is offline   Reply With Quote
Old 09-27-05, 10:15 AM   #21
formulaben
Senior Member
 
formulaben's Avatar
 
Join Date: Sep 2004
Location: Les Bois
Bikes: Felt F2C, Scott Spark 40, and Custom Fixie
Posts: 1,173
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
No problem. Zipp has some great info on the site. Here is a link to the Tech Articles index.
__________________
"Strong, light, cheap. Pick any two." — Keith Bontrager
formulaben is offline   Reply With Quote
Old 09-27-05, 10:47 AM   #22
DocRay
Guest
 
Bikes:
Posts: n/a
Mentioned: Post(s)
Tagged: Thread(s)
Quoted: Post(s)
Quote:
Originally Posted by badkarma
Why do you think airfoils (i.e. airplane wings) have the shape they do? They create lift (irrelevelant in the case of bicycles), but they also have a low coefficient of drag due to their profile. Round spokes leave a large wake (i.e. more pressure drag) than bladed spokes. Let it be said though, the decrease in pressure drag due to bladed spokes is rather minimal, yet it is finite.
This is the theory used to sell bladed spokes. In practical application, it is total bull****. Bladed spokes would only make a significant difference if the wheel had no rims and tires, the air turbulence generated by the tire and rim causes eddys that mean that clean air is not being seen by the spokes. The air is coming from all angles, and with a wider spoke, will just give more drag. The larger surface area of the bladed spoke means more drag. Airplane wings are not designed to reduce drag, they are designed for lift. The airplane fuselage is designed to reduce drag. The best spoke shape is good old boring round. If there is any difference, I would put it as miniscule compared to riding with a stiffer, lighter round spoked rim.

I would not quote Zipp sites for opinions on Zipp products. They try very hard to justify the most expensive wheels in the world.
  Reply With Quote
Old 09-27-05, 10:54 AM   #23
2manybikes
Dog is my co-pilot
 
2manybikes's Avatar
 
Join Date: Jun 2003
Bikes: 2 many
Posts: 15,765
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 130 Post(s)
Quote:
Originally Posted by Eatadonut
I thought bladed spokes were for eliminating the threat of squirrels jumping into your front wheel and getting stuck.
Flat bladed spokes are better for advertising stickers.
2manybikes is offline   Reply With Quote
Old 09-27-05, 12:17 PM   #24
gcasillo
Maglia Ciclamino
 
gcasillo's Avatar
 
Join Date: Jul 2004
Location: Fairfield, OH
Bikes: 2011 Bianchi Infinito, 2010 Surly Long Haul Trucker
Posts: 3,072
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by Velomax dude in white lab coat
a lifting surface, or develops airflow separation
Lift and separate? How can that be a bad thing?
gcasillo is offline   Reply With Quote
Old 09-27-05, 12:20 PM   #25
spacefuzz
Senior Member
 
Join Date: May 2005
Bikes:
Posts: 137
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Aerodynamics is complicated. You have to take into account shape, radius, eddy currents, direction, surface effect, air pressure, ect. I have yet to see a decent bike-rider combo fluid flow model. Also a lot of the wheel models I have seen are just for the rims, ignoring the spokes. I was thinking of creating a model for my senior design project, If I do I will post it. Bike manufacturers are not infallable, a couple years ago some students at my university did a stress analysis of Trek's forks. They found stress concentrations so severe Trek ended up redesigning the fork.

As to bladed spokes vs round. I am not sure on the aerodynamic properties. I figured that they were to help make the wheel stiffer. The flattened spokes are stiffer because they have a higher moment of inertia, Ix. This would help them to resist bending. So then you have to take into account power lost due to wheel flex vs. power lost due to drag. Sounds like a fun research project.
spacefuzz is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 03:15 AM.