Why don't sprinters use aero frames?
- Thread starter lefeur
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An aero frame is designed and intended to be ridden in the aero position only, notice the small headtube. The position over an extended period of time would be too uncomfortable.
Just wanted to highlight this line as Art has hit the nail on the head. Why? please read their calculation assumptions again: 1) Steady State airflow - NOT sprint conditions 2) Results are based on 40k flat course - ie TT - in calm conditions 3) Body positions based on aero positions (ie TT's)artmichalek said:
Question for the OP: Do any of the above assumptions sound like a sprint finish? The advantages they talk about in frame aero go out the window in a sprint finish when you consider the total system of rider and bike. This is before you even take into account the stiffness under sprint forces of a P2, P3 or any other true aero frame - airfoil tube shapings just aint stiff enough under sprint loadings (yet), which means way too much frame flex and wasted energy when Rockin Robbie hits the jets....Pro sprinters aren't that dumb (some may argue
) and if there were noticeable benefits, they would be on it. Stiffness and body position (ie flat back) are the most critical factors. OP - you also need to remember that there are 'lead out' men involved in sprints and all good sprinters fight for a good wheel to suck onto....they don't need an aero frame, they got the best aero aid in the world to sit behind
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Arty, I didn't want to have to do this, but you have forced my hand. It is clear from your posts that you are no scientist. Your posts contains no details, data or any attempt to relate the problem to basic aerodynamics. All you can do is rage against the dying of your light (Pardon the Dylan Thomas reference. I know that will only confuse you.). Your quote about a TT bike being a TT bike and a road bike being a road bike... Why that makes it all clear. Any self respecting investigator worth their weight in salt would accept that at face value and move on to another problem. What exactly is it about a road bike that makes a road bike? What exactly is it about a P2 frame that makes it UCI illegal? Methinks you do not know. I have at least tried to abstract the problem into basic principles of aerodynamics. I have cited scources of data and I have proposed a theory. You on the other hand have only tried to discredit my investigative prowess. That's not very nice.artmichalek said:
BTW if you follow the links, you will find that I interpreted the data correctly. ...And it's change tack, not "change track", and I think you did.
I've got your number, Arty.
Carefull now. You've almost exhausted your ability to be entertaining. As a scientist (and yes that is my day job) I'm at least careful enough to cite data that's relevant to the discussion. As Dini77 (another person here who knows a lot more about aerodynamics than you do) pointed out above, the links that you posted lead to data that is explicetly stated to be invalid for the case we're discussing.lefeur said:
Which underscores the fact that even if those assumptions were valid, a savings of 1:51 over 40km breaks down to something in the neighborhood of zero when you're only in the wind for 200m.Dini77 said:OP - you also need to remember that there are 'lead out' men involved in sprints and all good sprinters fight for a good wheel to suck onto....they don't need an aero frame, they got the best aero aid in the world to sit behind
Oh, Arty. I'm just getting started. I never said nor do I believe that the data I cited is 100% relevant. However, what I am saying is that there is likely some relevance of the steady state TT data to a field sprint situation. To the extent that there is some laminar flow around a frame in a field sprint situation, one can gain a speed advantage by leveraging basic "2nd year undergraduate aerodynamics" and using tubes that are shaped like an airfoil. Since you claim to be a scientist, I will put it into the form of an equation for you.artmichalek said:
Drag(total) = t(laminar flow)/t(total) * drag(laminar flow) + t(turbulent flow)/t(total) * drag(turbulent flow)
t = time
total refers to the duration of a field sprint
Colour me entertaining,
Lefeur
I calculate the time difference in one bike length @ 45mph to be 0.05 seconds. Is that close enough to zero for you, or are you going to make me look up the time difference between Peter Weening and Andreas Klöden @ Stage 8 of this years TdF.artmichalek said:
FYI, here is a quote from Tyler Hamilton form the Cervelo website. Now he's no sprinter but he is at least somewhat inerested in aerodynamics of road frames.
Switching bike manufacturers throughout your professional career is sometimes unavoidable. For a lot of guys, making the adjustment to a "new ride" is a nerve-wracking process. But I'm happy to report the riders on CSC have been extremely happy with their new Soloists. The frames are stiff and responsive in addition to being really light. These bikes offer a comfortable seat angle and incredibly aerodynamic tubing. The Soloist is the complete package for our team and any cycling enthusiast who wants to ride fast.
- Tyler Hamilton
Hey everybody, look at the big brain on letroll. How silly of you to try to address his original question. We can't talk about fight club or the reason sprinters don't use aero frames. Letroll, you should write a letter to Boonen informing him of your discovery so that he can guarantee his dominance in the years to come.
Quoting Tyler Hamilton on ANYTHING automatically ruins any semblance of an arguement you may have had. Aero tubes do not make a stiff bike. As a sprinter I want something as stiff and light as possible, to hell with "aero". See the note on the "pendulum effect" above and work those into your 2nd year undergrad physics calculations... [watch smoke come out of lefeur's ears]. All of the calculations are meaningless when you take into consideration all of the positioning and comparitive leadout strength that goes into a field sprint. Ever actually WATCH a bike race, or do you just read books about them?lefeur said:
ALTHOUGH (playing devil's advocate), nobody has entertained the thought that by using aero tubes throughout the course of maybe a 200km stage will save that sprinter just enough energy to have a higher burst output for the final 200m for the sprint. Of course, that's another arguement for another time perhaps...
Jimmer, Jim, Jim, Jim,jimmer23 said:
As I recall a few posts back, I was buying the stiffness argument. However, I then suggested we take stiffness out of the equation and just look at the aero effect. I suggested a very clever thought experiment to do this which assumed that aero frames and standard frames are of equal and adequate stiffness. It even included the cloning Robbie McEwen. It was beautifuly simple. I realize that it was purely an acedemic exercise, but it was directed more towards the other "scientists" on the thread, and not for a sprinters paltry frontal lobes. Hmmm...It appears from your second paragraph that you are acknowledging that there may be some value to aero tubing. That's the 1st chink in the armor, Jiminny. Soon you will be singing the praises of ol' LetRoll (apparently that's how I am now known in Sao Paulo. I am a little unsure as to whether that's witty or not. *****, please advise.)
Hey! Where's Arty? Please don't tell me we're through. There are almost 1500 views of this thread, Arty. So many people wondering if Lefeur and Arty are still together. Let's not keep the kids at home waiting.
That's just it Leffy, you simply CAN'T make all of these assumptions. It's not clever, you're on drugs. Get out on a bike sometime and do some riding. Can you take out of your little theoretical equations that you have to actually PEDAL the bike to make it move forwards? Pedalling creates more wind resistance so it must be bad right? Why don't you go click into your pedals and do that and let us know how your scrapes are healing? Everything is correlated here. In your paper and pencil world you can't pick and choose what you would like to leave in and take out of the equation - it's simply not practical and has no bearing on a real-life situation.lefeur said:
You want to assume same stiffness and strength of frame? Aero tubing is going to weigh more. How do you account for that Lefferino? Lateral rigidity will also suffer so that means even more weight to make aero tubing comply with your arguement. Work that out for us and let us know what your equations tell you. Hey, remember the "pendulum effect"? Throw that into the equation too since you'll have to add more weight to make the tubing aero in all directions. WAIT, what do we have now? ROUND TUBING. Wow, imagine that.
I acknowledge that there may be a slight benefit to aero tubing, but the energy-saving arguement over the entirety of a race is not what you've based your rickety house of cards on Leffer. Only the sprint. The aero benefits in this theoretical 200m sprint are negligible, and the tubing may actually turn out to be a hindrence when you take into account all of the other factors which make it less than desirable. Empty your head of your faulty equations, re-read the above thread, and get back to us when you have something sensible to say, thanks.
I'm making an assumption that the aero wheels are stiff (due to the added rim material) and I know they are not super light. Hyperions or Neutrons are lighter. I have a set of Protons and I can certainly vouch for their stiffness.wilmar13 said:He does? I have seen a lot of pics of his bike with Cosmic Carbones, but maybe they were older. Either way they are both about the same aero and maybe the Bora is as stiff as the Carbone (with the Bora being way lighter). Im not sure I agree with you dismissing it as stiffness though, for sure he uses them for the aero advantages as well, if he just wanted to use stiff wheels he would be on Hyperion or Nucleons
Sorry kid, I was on my bike all day. There are some of us who ride our bikes rather than just thinking about them.lefeur said:
Got in 116 miles meself this weekend. While riding I came up with the following scenario. (I can think and ride my bike at the same time.) Let's say McGrady's leadout gives him a 2 bike length lead on McEwen and an even longer lead on the rest of the field. The wind is calm. McEwen is the stronger sprinter. ...But wait because McGrady has a more aerodynamic frame, which includes airfoil shaped tooling, and because he is clear of the rest of the field there is largely laminar flow in his axial direction, he wins the sprint. "Drat that aero tubing", says McEwen.artmichalek said:
I'm not arguing the point that sprinters desire stiff and light frames, and that those two properties may even be more important that aerodynamics. However, you have suggested that aerodynamics has no importance in a field sprint because of the absence of laminar flow. I submit that in the above scenario there is indeed a presence of laminar flow.
You can add that to your list of meaningless assumptions. At 45mph, the Reynolds number around a 4cm diameter tube is ~5e6.lefeur said:
Ooh, grasshoppa! You trying to see what Lefeur made of. However in your zeal to expose me, you've made my point for me. Any 2nd year undergraduate knows that the Reynolds number around an airfoil shaped tube would be significantly less. This is too easy.artmichalek said:
Depends on what bottom tier safety school you're studying at. The 2nd year undergrads at good schools know that the Reynolds number is dependant on on the characteristic length (either diameter or chord length) of the immersed body and has nothing to do with the shape.lefeur said:
Is there really a point to this exercise? Has anyone watched any of the sprinters and their bikes? The front wheel spends a significant amount of time out of the plane of the frame. You could prolly make the conclusion that the turbulence off the front wheel, then, at any given point follows some sinusoidal trend (in very gross terms). It' pretty safe to assume that at maximum deflection of the front wheel to either side, wake turbulence reaches a maximum and the aero benefit of a shaped downtube goes all pear shaped.
If you want a reasonable approximation of what might happen model a rider and bike at the various positions they're gonna be in a sprint, from rider full right, max wheel deflection, bike full left, to the same positions reversed about the vertical axis.
Nasty problem, I bet. About as far from steady state as someone can get. I'll bet you'll find that who wins the sprint....the guy on the trad frame or the guy on the aero frame....is more sensitive to errors in the alignment of the finish line camera to the finish line.
Thinking that there is going to be some undiscovered aero benefit here is a lot like losing sight of the forrest because of a freakin' maple sprig.
If you want a reasonable approximation of what might happen model a rider and bike at the various positions they're gonna be in a sprint, from rider full right, max wheel deflection, bike full left, to the same positions reversed about the vertical axis.
Nasty problem, I bet. About as far from steady state as someone can get. I'll bet you'll find that who wins the sprint....the guy on the trad frame or the guy on the aero frame....is more sensitive to errors in the alignment of the finish line camera to the finish line.
Thinking that there is going to be some undiscovered aero benefit here is a lot like losing sight of the forrest because of a freakin' maple sprig.
