Frame Shape Aerodynamics
10-02-11 | 06:54 AM
#1
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Frame Shape Aerodynamics
Hello. I was wondering how the bike got its shape. On modern TT bikes, the wheels are designed to create a laminar flow through them, and thus are shaped how they are. I was wondering why the frames are not completely covered. I would think that that would improve the aerodynamics, because the airflow would be parted once, rather than at the fork, and then again at the seat tube. Is is a UCI rule for bikes, and therefore, the manufacturers don't bother to test new designs?
Thanks!
Thanks!
10-02-11 | 07:12 AM
#2
He drop me
Joined: Jul 2004
Posts: 11,664
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From: Central PA
Bikes: '03 Marin Mill Valley, '02 Eddy Merckx Corsa 0.1, '12 Giant Defy Advance, '20 Giant Revolt 1, '20 Giant Defy Advanced Pro 1, some random 6KU fixie
And that doesn't even mention the 3:1 rule: https://www.google.com/search?aq=f&gc...q=UCI+3-1+rule
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10-02-11 | 09:06 AM
#3
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Joined: Feb 2007
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From: Tariffville, CT
Bikes: Tsunami road bikes, Dolan DF4 track
Back in the early days of aero they had solid frames, i.e. the whole triangle was filled. The surface drag was so high that it made the frame slower than a normal aero frame.
This is the idea with the Kamm design, where if you have the first 2/3 of the aero shape, you can skip the last 1/3. Air will flow as if that last 1/3 is there - look at a Prius - it has a dramatic dropoff in the back (no long tail) but it has a very low Cd.
This is the idea with the Kamm design, where if you have the first 2/3 of the aero shape, you can skip the last 1/3. Air will flow as if that last 1/3 is there - look at a Prius - it has a dramatic dropoff in the back (no long tail) but it has a very low Cd.
10-02-11 | 05:05 PM
#5
Most cyclists don't race, so the UCI regs are irrelevant to them. Even some races (notably triathlons) have much more relaxed regs.
That said racers do tend to buy a decent share of the higher-end gear, and the rest of people aren't sufficiently interested in performance to do the dorky things that will improve aerodynamics, such as using a fairing.
Aerodynamics is also highly counter-intuitive, which is why testing for it requires very expensive facilities and engineers.
And really, unless you are in an extremely competitive situation, it's mostly snake oil, as you're talking about (at best) advantages like "30 seconds over a 20km TT." Joe Average can barely quantify the differences produced by a $5000 aero road bike over a $1500 road bike in an accurate fashion.
Between the expense, narrow market and narrower advantages, there isn't much motivation to develop esoteric aerodynamic designs.
That said racers do tend to buy a decent share of the higher-end gear, and the rest of people aren't sufficiently interested in performance to do the dorky things that will improve aerodynamics, such as using a fairing.
Aerodynamics is also highly counter-intuitive, which is why testing for it requires very expensive facilities and engineers.
And really, unless you are in an extremely competitive situation, it's mostly snake oil, as you're talking about (at best) advantages like "30 seconds over a 20km TT." Joe Average can barely quantify the differences produced by a $5000 aero road bike over a $1500 road bike in an accurate fashion.
Between the expense, narrow market and narrower advantages, there isn't much motivation to develop esoteric aerodynamic designs.
