Go Back  Bike Forums > Bike Forums > Road Cycling
Reload this Page >

Aero spokes, potential problems?

Search
Notices
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

Aero spokes, potential problems?

Thread Tools
 
Search this Thread
 
Old 01-03-06 | 02:13 PM
  #1  
Patriot's Avatar
Thread Starter
Faith-Vigilance-Service
 
Joined: Jul 2004
Posts: 8,330
Likes: 1
From: Port Orchard, WA

Bikes: Trinity, Paradisus, Centurion, Mongoose, Trek

Aero spokes, potential problems?

Just pondering some thoughts.

It ocurred to me today, that aero spokes in all there splendor and beauty, may actually pose some serious problems at high speed. I got to thinking about the absolute necessity of making sure they are perfectly aligned when tightened, or truing up a wheel. They are a great visual guide to help you make sure your spokes are not twisted, compared to round spokes, but if one was, the result could be catastrophic.

Suppose for instance, that one aero spoke on a wheel was ever so slightly twisted. The resulting force would be likened to a miniature propeller that would want to pull the wheel to one side or the other while spinning very fast.
My thought on this, from building airplanes myself, seems reasonable. If you had one propeller blade slightly offset with differant pitch, the result is an enormous amount of vibration which would tear the airplane apart. This would not be quite as serious on a bike, due to the small cross section of the bladed spoke itself. However, I would think that one spoke slightly out of alignment could be a contribution to noticable shimmy, when the bike frame itself seems to be the unlikely cuplrit due to it's engineering. Does this not make sense?
I suppose one could figure out the actual thrust produced by a specific spoke with a certain cross-section at a given speed of say 50mph. Those Mavic spokes are pretty wide. I wonder how much of a concern this really is, when the designers build wheels with these spokes.
__________________
President, OCP
--"Will you have some tea... at the theatre with me?"--
Patriot is offline  
Reply
Old 01-03-06 | 02:42 PM
  #2  
bvfrompc's Avatar
Senior Member
 
Joined: Sep 2005
Posts: 1,277
Likes: 0
ahhhh, ok, thats a good question,

I did find out that the 19.99 Db4 Wireless computer from Performance doesn't have a Aero spoke compatable magnet, that was a problem. Then when asked if they sold Aero compatable magnets I was told no, so I finished my order then googled aero spoke magnet, guess who came up first, thats right Performance, then I had to call back and amend my order which turned out to be a good thing becuase they had it on hold becuase they don't sell Size 13 booties even though the web site said 'in-stock", so I was able to cancel the said booties and order the compatable magnet ($1.95).

Did that answer your question?

mmmm, beer for lunch, but I digest.....
bvfrompc is offline  
Reply
Old 01-03-06 | 02:54 PM
  #3  
Retro Grouch's Avatar
Senior Member
Titanium Club Membership
20 Anniversary
 
Joined: Feb 2004
Posts: 30,225
Likes: 649
From: St Peters, Missouri

Bikes: Catrike 559 I own some others but they don't get ridden very much.

I think that you worry too much.
Retro Grouch is offline  
Reply
Old 01-03-06 | 03:13 PM
  #4  
Mo'Phat's Avatar
Scum, Freezebag!
 
Joined: Dec 2005
Posts: 4,546
Likes: 0
From: Poway, CA

Bikes: 2007 Leader 796R w/ 10sp DA and 2005 Jamis Dakar XLT FS MTB

For bvfrompc, do your aero spokes go round when they reach the nipple? I have shimano wheels with bladed spokes, but the blades turn round at the nipple. I had to mount the magnet right near the rim and the magnet-picker-upper-transmitter-thingamabob just under the brake pad on the fork, but it worked. Cheapo Ascent computer, too.

For Patriot - without talking out of my a** about aeronautics and propulsion, I think there are formulae which take surface area of the blades, angle of blades, rpm's, etc which would accurately compute how much side force could be imposed by misaligned bladed spokes. However, I think that a majority of the spokes would need to be misaligned in exact wrongness in order to have any effect. If one spoke is tweaked at a 45 deg. angle and the next is only tweaked 15 deg, there's a certain turbulence that is created from one to the next.

Theoretically, I don't think (even with the wider blades) you have enough blade surface area pushing air at a fast enough rpm to generate any noticeable side force. To pull an airplane, you have 3-5 blades that are 3' +/- long and probably 6" wide, all pitched to the same angle, spinning 2-3 thousand rpm...and probably much faster...since I don't really know squat about airplane motors.

Bicycle wheels have 1/4" - 1/2" blades spokes spinning about (at most) 200 rpm on quick descents.

.
Mo'Phat is offline  
Reply
Old 01-03-06 | 03:23 PM
  #5  
webist's Avatar
Huachuca Rider
20 Anniversary
 
Joined: Jun 2002
Posts: 4,275
Likes: 0
From: Charlotte, NC

Bikes: Fuji CCR1, Specialized Roubaix

I've avoided Aero Spokes precisely because I don't want to go fast enough to find out the answer to your question.
__________________
Just Peddlin' Around
webist is offline  
Reply
Old 01-03-06 | 03:29 PM
  #6  
DannoXYZ's Avatar
Senior Member
Titanium Club Membership
20 Anniversary
 
Joined: Jul 2005
Posts: 11,754
Likes: 26
From: Mesa, AZ

Bikes: Moots RCS, tandem, beach-cruiser, MTB, Specialized-Allez road-bike, custom track-bike

I'm switching to sharpened aero spokes after seeing the damage from that squirrel...
DannoXYZ is offline  
Reply
Old 01-03-06 | 03:33 PM
  #7  
Patriot's Avatar
Thread Starter
Faith-Vigilance-Service
 
Joined: Jul 2004
Posts: 8,330
Likes: 1
From: Port Orchard, WA

Bikes: Trinity, Paradisus, Centurion, Mongoose, Trek

My thoughts are more or less with Mo'Phat. I really don't think it would be all that noticable, but was just curious. I know that on model airplanes, you're taking about blades going 10,000rpm, so if a bike wheel went that fast, you'd have bigger things to worry about, I think.
__________________
President, OCP
--"Will you have some tea... at the theatre with me?"--
Patriot is offline  
Reply
Old 01-03-06 | 03:47 PM
  #8  
TCR's Avatar
TCR
Riding Heavens Highway
Sheldon Brown Memorial - Donating
20 Anniversary
 
Joined: Apr 2004
Posts: 1,778
Likes: 0
From: Sunny SoCal

Bikes: '04 Giant TCR

Originally Posted by Retro Grouch
I think that you worry too much.
I agree.
__________________
https://vvbc.us
TCR is offline  
Reply
Old 01-03-06 | 04:46 PM
  #9  
Senior Member
20 Anniversary
 
Joined: Sep 2001
Posts: 6,521
Likes: 3
From: Montreal

Bikes: Peugeot Hybrid, Minelli Hybrid

At 30 mph the wheel will be turning at 400 rpm which is pretty slow for a propeller, and the propeller will be operating in the wake of the tire. The side force and the drag reduction will therefore be pretty small. The main benefit will be the avoidance of spoke twist in the build.
AndrewP is offline  
Reply

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.