Weight Vs Aerodynamics -Wheelset Selection

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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby twizzle » Fri Feb 01, 2013 2:46 pm

__PG__ wrote:... of a large out-of-shape rider who rides with a flipped stem, spacers and can't ride with a flat back.

Hey, I resemble that remark!
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by BNA » Fri Feb 01, 2013 6:05 pm

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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby Alex Simmons/RST » Fri Feb 01, 2013 6:05 pm

winstonw wrote:you provided an overly simplistic application of a few physics equations that does not reflect real world riding conditions.

Well the equations I use are those that specifically pertain to the motion of a cyclist, have been published in the scientific literature for about 20 years and have been validated many times against real world data. One of the (several) authors of the original paper is a leading scientist at the AIS. Ya canneh change the laws of physics winstonw

I don't know about you but I use my wheels in the real world. One of them was used to win a State title and set an (able bodied) national record. I test wheel performance for others as part of my profession. Been doing just that (again) recently for a client who will be attempting to set a new world record for his age category. But maybe that's not real world enough for you.

winstonw wrote:you state aerodynamics is a more influential variable than wheel weight, with acceleration from 0kph.

Because it is, and for that not to be the case, it would require a large mass differential versus only modest aero gains, or for the acceleration to never see the rider go beyond 25 km/h, which I am assuming any performance oriented cyclist will manage without problem, and will likely spend significant chunks of their training and racing time above such speeds (the exception being steeper hill climbs).

winstonw wrote:you confidently imply aero is always more influential than wheel weight, when climbing up all but the steepest of hills.

Well that's the case on the better roads we have here on planet earth, but perhaps not where you live. But then steep might be subjective too. Certainly the ratio of energy demand to overcome air resistance to that required to overcome gravity varies with gradient, and at some point one becomes more important than the other. I have done the analysis on that too. In fact I did just that not so long ago and it was published in an Australian MTB mag (not that having something published suggests something is right - but it does mean it's open for validation/correction). If I am wrong in things I publish, then I'm more than happy to be corrected. But show me how, where and/or why I am wrong. It's a great chance to educate - so go for it.

winstonw wrote:I don't buy unqualified absolutist generalizations.

I'm not selling them.

But then neither are all the other people who have done the assessment and analysis, some of whom do so professionally as well, and I already have provided a link to one such resource. What I have done though is to provide you with some information to enable you to do the work yourself. You can then add that to the other factors that go into making a wheel choice that I have already outlined.

A very specific question was asked about the relative difference in performance resulting from mass and aero differences. I gave a specific answer to a specific question. If you choose to then misinterpret, misrepresent or totally misunderstand that, well I can't help you.

Now, do you have anything constructive to add, or do you want to keep digging that hole?
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby ausrandoman » Fri Feb 01, 2013 6:08 pm

winstonw wrote:
Alex Simmons/RST wrote:Do you have anything constructive to add?


you provided an overly simplistic application of a few physics equations that does not reflect real world riding conditions.
you state aerodynamics is a more influential variable than wheel weight, with acceleration from 0kph.
you confidently imply aero is always more influential than wheel weight, when climbing up all but the steepest of hills.

I don't buy unqualified absolutist generalizations.


May I state the blindingly obvious?

1. Every objectively measureable factor (rider power, mass, acceleration, angular momentum, gradient, bearing friction, rolling resistance, wind speed and direction, air density etc etc ) involved in speed can be calculated and the speed resulting from any power input can be calculated with good accuracy.

2. The effects of teams, tactics, rider perception and reflexes, rider road craft, motivation etc etc are highly variable and difficult to quantify.

I will clap and cheer if winstonw or Alex can give us a map of the speed and acceleration for various combinations of rider power, gradient, wheel weight and Cd, holding all other variables constant. The ball is in your court, winstonw: tell us the speeds, gradients and rider power outputs for which wheel weight is more important than aerodynamics.
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby Alex Simmons/RST » Fri Feb 01, 2013 6:44 pm

ausrandoman wrote:The ball is in your court, winstonw: tell us the speeds, gradients and rider power outputs for which wheel weight is more important than aerodynamics.

To help, I suggest winstonw starts by reading the following paper:

Validation of a Mathematical Model for Road Cycling Power
James C. Martin, Douglas C. Milliken, John E. Cobb, Kevin L. McFadden, Andrew R. Coggan
Journal of Applied Biomechanics, 1998, 14, 276-291

Work since that paper has mostly been to incorporate additional refinements to the physics that apply in special circumstances, in particular track cycling performance, where the normal forces on the tyres is variable, and the position of the centre of mass of the athlete varies relative to the wheel placement resulting in a pseudo sinusoidal pattern of speed for both the COM and the wheels (but is amplified at the wheels). In spite of that, the same model (indeed a simplified version of that which appears in the paper) still works exceptionally well at predicting real world performance even on a track where such refinements to the physics need to be considered. Put it this way, I can achieve field testing precision equivalent to the best low speed wind tunnels with this simplified physics stuff.

But I digress (for the interest of anyone out there that likes this sort of info).
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby mjd » Fri Feb 01, 2013 8:14 pm

Touché
This topic will self destruct in 5 4 3......
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby Xplora » Fri Feb 01, 2013 9:17 pm

A fine boned breakdown of the physics might be helpful for some, but I think we just have to live with 3 key factors. Will the wheel survive your task? Will you survive this task? Can you afford the wheels? Bad yaws, less durable and overly heavy wheels and epic price tags are the key restraint for us.
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby winstonw » Fri Feb 01, 2013 9:19 pm

Alex Simmons/RST wrote:Put it this way, I can achieve field testing precision equivalent to the best low speed wind tunnels with this simplified physics stuff.


I read that paper a long time ago Alex. It didn't measure acceleration, certainly not from 0kph.
There's a lot of work undone regarding the effect of variable wind velocity and variable yaw.
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby twizzle » Fri Feb 01, 2013 10:28 pm

And for his next trick, see winstonw argue that black IS white.


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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby Alex Simmons/RST » Sat Feb 02, 2013 7:18 am

winstonw wrote:
Alex Simmons/RST wrote:Put it this way, I can achieve field testing precision equivalent to the best low speed wind tunnels with this simplified physics stuff.


I read that paper a long time ago Alex. It didn't measure acceleration, certainly not from 0kph.
There's a lot of work undone regarding the effect of variable wind velocity and variable yaw.


As I was kindly reminded and having had my memory refreshed, the original study was conducted under very windy conditions and covered a wide range of yaw angles, and Jim Martin has since shown that the model works quite well even for world-class trackies in events that begin from a standstill (i.e., maximum rate of acceleration any cyclist is ever likely to experience).

Got anything constructive to add?
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby ironhanglider » Sat Feb 02, 2013 1:27 pm

twizzle wrote:And for his next trick, see winstonw argue that black IS white.


Sent from my iThingy...


... and gets killed on the next zebra crossing.

Cheers,

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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby Mulger bill » Sat Feb 02, 2013 7:40 pm

ironhanglider wrote:... and gets killed on the next zebra crossing.

Cheers,

Cameron

Beaten by hours :D

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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby mrgolf » Sat Feb 02, 2013 8:38 pm

I think TLL is writing as a bigger rider, probably good at sprinting and not having strengths as a climber. I am the opposite. I would much prefer a light non-aero wheel over a heavier aero wheel. I am sure aero wheels can be beneficial, but as soon as you start going uphill, the advantages go. As someone else wrote, there is no reason why you cant have a light aero wheel, but getting a reasonably priced light aero wheel is tough. I have tried with little success. But then, my idea of lightweight is around 12-1400gms. Anything over 1600gms is heavier than it needs to be. However, I only weigh 65kgs.

It also depends on how deep a rim needs to be to be considered aero. I have some 1450gm wheels with a 27mm deep rim that are reasonably aero. At what depth do rims become aero?

Summing up, aero vs weight with price considerations depends on where your strengths as a cyclist lie. If your strengths are with climbing, stick with light. If you like sprinting, go aero.

This is only my experience. Others have the god given right to have their own view which would be equally relevant and correct to them.

Edit: the other consideration to take into account is crosswinds. Its not as much of an issue with heavier riders, but I have some serious issues in big gusty crosswinds.

Also, I read a bit about tour riders unable to use their TT wheels on road stages. From what I see on grand tours, some use aero wheels and others don't when riding the same stage. That intrigued me.
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby toolonglegs » Sat Feb 02, 2013 9:18 pm

No I will never have strengths as a climber ( or a pure sprinter for that matter :lol: )... my aim is to have two sets of wheels this year.
The 58/88's will be for flat or rolling races. Still to decide on my climbing wheels, but they will still be aero... thinking about Zipp 101's or getting a set of light weight carbon tubs made up. Not as light as you go mrgolf for sure... my aim is to only stay in contact on the climbs, as long as I can finish the bigger climbs I do within a minute or so of the front guys I can usually get back on on the descents. 100-200 grams of wheel weight won't help me stay with the wippets on climbs, but a fast aero wheel ( strong, good braking etc ) will help me where I need it to get back on.
Here is a couple of strava files for the hilly races I do... last year I did OK in them, this year I will be back to full strength and hopefully can do a lot better :D . They are far from flat... but we never have " mountain top " finishes.
http://app.strava.com/activities/10945926
http://app.strava.com/activities/11032857
http://app.strava.com/activities/8111557
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby winstonw » Sun Feb 03, 2013 6:10 pm

Alex Simmons/RST wrote:Got anything constructive to add?


At least you've convinced a peanut gallery Alex. I've got two real world physicist mates who think you're stepping outside your expertise. But then, I understand the reputation of aero-coach.com is at stake. I'd encourage you to become an expert in lumbar disc herniation too, if you are going to push amateur riders into an aero position.

When you get the formula sorted to account for variable yaw and wind velocity, and rider experience, from 0kph, I'll look forward to your plot of weight vs aerodynamics.
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby bipsychal » Sun Feb 03, 2013 6:32 pm

winstonw wrote:
Alex Simmons/RST wrote:Got anything constructive to add?

I've got two real world..mates.


I'm sorry you're going to have to substantiate this claim
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby toolonglegs » Sun Feb 03, 2013 6:36 pm

Provide any evidence about anything...
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby warthog1 » Sun Feb 03, 2013 6:37 pm

winstonw wrote:
Alex Simmons/RST wrote:Got anything constructive to add?


At least you've convinced a peanut gallery Alex. I've got two real world physicist mates who think you're stepping outside your expertise. But then, I understand the reputation of aero-coach.com is at stake. I'd encourage you to become an expert in lumbar disc herniation too, if you are going to push amateur riders into an aero position.

When you get the formula sorted to account for variable yaw and wind velocity, and rider experience, from 0kph, I'll look forward to your plot of weight vs aerodynamics.


Nope.
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby Alex Simmons/RST » Sun Feb 03, 2013 6:38 pm

winstonw wrote:
Alex Simmons/RST wrote:Got anything constructive to add?


At least you've convinced a peanut gallery Alex. I've got two real world physicist mates who think you're stepping outside your expertise. But then, I understand the reputation of aero-coach.com is at stake. I'd encourage you to become an expert in lumbar disc herniation too, if you are going to push amateur riders into an aero position.

When you get the formula sorted to account for variable yaw and wind velocity, and rider experience, from 0kph, I'll look forward to your plot of weight vs aerodynamics.

Two more strawmen, an appeal to anonymous authority, and non sequitur.
The list of logical fallacies grows. Keep 'em coming. :lol:
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby Mulger bill » Sun Feb 03, 2013 6:46 pm

I'm not sure I like being called a peanut :? :roll:
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby winstonw » Sun Feb 03, 2013 7:31 pm

Alex Simmons/RST wrote:Two more strawmen, an appeal to anonymous authority, and non sequitur.
The list of logical fallacies grows. Keep 'em coming. :lol:


Just substantiate your absolutes with plots Alex. I'm really interested to gain insight into your physics and spreadsheet skills.
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby ausrandoman » Sun Feb 03, 2013 8:53 pm

May I fix that for you?

winstonw wrote:
Just substantiate your absolutes with plots winstonw. I'm really interested to gain insight into your physics and spreadsheet skills.


Imagine the crushing victory that will be yours! Reddit will erupt with applause! The /b/rothers will invite you to join Anonymous! You will get a heavily accented phone call from Stockholm! Your physicist mates will ask you to co-author a letter to Nature! BNA will beg you to become a moderator! Mark Cavendish will ask you to build his wheels! You will be a legend! All you have to do is provide the measurements and calculations.

Seriously, though, of course there are some combinations of speed, power, gradient and acceleration where a lighter wheel will be faster than a wheel with lower Cd. Just tell us the boundaries. I for one would like to know specific values, preferably in time for the next Alpine Classic.
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby mjd » Sun Feb 03, 2013 9:08 pm

ausrandoman wrote:May I fix that for you?

winstonw wrote:
Just substantiate your absolutes with plots winstonw. I'm really interested to gain insight into your physics and spreadsheet skills.


Imagine the crushing victory that will be yours! Reddit will erupt with applause! The /b/rothers will invite you to join Anonymous! You will get a heavily accented phone call from Stockholm! Your physicist mates will ask you to co-author a letter to Nature! BNA will beg you to become a moderator! Mark Cavendish will ask you to build his wheels! You will be a legend! All you have to do is provide the measurements and calculations.

Seriously, though, of course there are some combinations of speed, power, gradient and acceleration where a lighter wheel will be faster than a wheel with lower Cd. Just tell us the boundaries. I for one would like to know specific values, preferably in time for the next Alpine Classic.


LOL
Roasted peanut anyone ?
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby Alex Simmons/RST » Mon Feb 04, 2013 9:18 am

winstonw wrote:
Alex Simmons/RST wrote:Two more strawmen, an appeal to anonymous authority, and non sequitur.
The list of logical fallacies grows. Keep 'em coming. :lol:


Just substantiate your absolutes with plots Alex. I'm really interested to gain insight into your physics and spreadsheet skills.

Why, is this a job interview? Didn't know I was applying for one. Are you are failed lawyer or something? Your tired attempts to lure people into non-existent traps is rather dull.

There are hundreds, maybe thousands of power meter using racing cyclists around the world who have used my previously published spreadsheets on the physics of cycling to perform aerodynamic testing, I think my competency is pretty well established in this area. Guess what the Aerolab feature written by Andy Froncioni in Golden Cheetah software is based on?

Of course I don't for one moment claim to have developed the concepts (I didn't), nor even some of the original workings (e.g. the classic regression method as originally described by Dr Andy Coggan or the method of virtual elevation modelling as described by Prof. Robert Chung), only sought to bring them to people's attention and in a more user friendly form. Heck, I even delivered a lecture on these thing with Prof. Chung in the audience. That was fun.

I've also developed models for the assessment of pacing in time trial and similar events that incorporate not only the basic physics, but also account for the variations in environmental conditions, and the individual rider's physiological capacity. But that's for another discussion.

Have you anything constructive to add?
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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby skull » Mon Feb 04, 2013 10:05 am

You're doing it wrong Alex.

The mantra is 'always attack, never defend'.

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Re: Weight Vs Aerodynamics -Wheelset Selection

Postby boss » Mon Feb 04, 2013 10:20 am

skull wrote:The mantra is 'always attack, never defend'.


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