ksyrium trash talking? - Page 3

ScienceIsCool · #31 07-30.-2007

Nice. You chose to whip out your credentials rather than elucidate... always the sign of a strong technical argument and a full understanding.

Your entire hypothesis and model is nullefied by the test data which shows that lateral stiffness changes with spoke thickness, but not spoke tension even as the spokes get close to zero tension. And yes, the hub width changes the stiffness of a wheel, for the same reason that a truss is stiffer than a beam. Yes, spoke tension is required for structural integrity due to radial loading (otherwise the spokes will go into compression and buckle). Not side loading.

John Swanson
www.bikephysics.com

Dietmar · #32 07-30.-2007

Quote:

Originally Posted by ScienceIsCool

You chose to whip out your credentials rather than elucidate...

Come again? I am sorry, but you are getting a bit disingenious here. Assuming that you do have some reading comprehension, you must have noticed the context in which I made my remark, which was solely as a way to tell you that I do not need your, hmm, "explanations". Other than that, I gave you a whole series of elucidating pointers, which you obviously choose to ignore. Why is that?

Quote:

Your entire hypothesis and model is nullefied by the test data which shows that lateral stiffness changes with spoke thickness, but not spoke tension even as the spokes get close to zero tension.

More nonsense. You clearly have no understanding of the mechanics of this problem whatsoever. The observations you mention above are exactly what one would predict based on what I said. Spoke tension will not affect wheel stiffness simply because the system is in the area of linear elasticity. Anybody who knows anything at all about mechanics and basic math would immediately conclude that spoke tension will have no effect. Like I said, this is in stark contrast to the case of a tensioned spoke subject to bending loads. In that situation you would obviously have enhanced lateral stiffness for higher spoke tension, due to the adverse bending moment created by the tensile forces.

Otherwise, since you clearly refuse to be educated on this subject, there is no point in continuing this debate.

P.S.: If you need even more "elucidation", you might want to study the FE analyses presented here and here. You should pay particular attention to the way the spokes are modelled: As elements that do not carry any moments. If you study these articles carefully, you should be able to get some understanding of the mechanics of this problem. Pay particular attention to what the first author says about linear superposition, in case you still have trouble understanding the effect, or rather non-effect, of spoke tension.

melslur · #33 07-30.-2007

Quote:

Originally Posted by Dietmar

P.S.: If you need even more "elucidation", you might want to study the FE analyses presented here and here. You should pay particular attention to the way the spokes are modelled: As elements that do not carry any moments.

As a recovering mechanical engineer, I love talking aobut the science, but at the end of the day, "the proof of the pudding is in the eating". I would rather see debates about a valid experiment (e.g., appropriate method and amount of loading) to determine emperically the product performance. Talk all you want about the mechanics and FEA, but at the end of the day, if you have the real product, measure it! I like that the Scienceiscool is trying to do that.

Finally, as an aside, I am still perplexed that bike magazines do not try to measure bike performance. Reviews are "stiff, comfortable,..." but I would prefer to see an inclusion of numerical test results. Given that the magazines have been reviewing bikes for years, you would think they could have a testing procedure, and improve the procedure as time goes on.

ScienceIsCool · #34 07-30.-2007

Quote:

Originally Posted by Dietmar

Come again? I am sorry, but you are getting a bit disingenious here. Assuming that you do have some reading comprehension, you must have noticed the context in which I made my remark, which was solely as a way to tell you that I do not need your, hmm, "explanations". Other than that, I gave you a whole series of elucidating pointers, which you obviously choose to ignore. Why is that?

More nonsense. You clearly have no understanding of the mechanics of this problem whatsoever. The observations you mention above are exactly what one would predict based on what I said. Spoke tension will not affect wheel stiffness simply because the system is in the area of linear elasticity. Anybody who knows anything at all about mechanics and basic math would immediately conclude that spoke tension will have no effect. Like I said, this is in stark contrast to the case of a tensioned spoke subject to bending loads. In that situation you would obviously have enhanced lateral stiffness for higher spoke tension, due to the adverse bending moment created by the tensile forces.

Otherwise, since you clearly refuse to be educated on this subject, there is no point in continuing this debate.

P.S.: If you need even more "elucidation", you might want to study the FE analyses presented here and here. You should pay particular attention to the way the spokes are modelled: As elements that do not carry any moments. If you study these articles carefully, you should be able to get some understanding of the mechanics of this problem. Pay particular attention to what the first author says about linear superposition, in case you still have trouble understanding the effect, or rather non-effect, of spoke tension.

Both of the FEA you show are for *radial* loading. In which case, yes, it is widely accepted that it is a change in tension (strain) in the spokes and deflection of the rim that provides structural integrity.

A lateral force (one that is parallel to the axis of rotation) on the rim causes the rim and spokes to bend. I.e., a lateral deflection. This moment is what provides structural integrity.

John Swanson
www.bikephysics.com

Dietmar · #35 07-30.-2007

Quote:

Originally Posted by melslur

As a recovering mechanical engineer, I love talking aobut the science, but at the end of the day, "the proof of the pudding is in the eating".

I do not disagree with that.

Quote:

I like that the Scienceiscool is trying to do that.

I agree with that as well, despite my contention that it would benefit him, and his work in that area, if he tried to understand some of the principles of the systems he is measuring. But ultimately, I really couldn't care less if he is or is not interested in the theory.

Quote:

Given that the magazines have been reviewing bikes for years, you would think they could have a testing procedure, and improve the procedure as time goes on.

Ahh, but that assumes that these magazines are anything other than catalogs of product advertisements, held together by the thinnest of glues, of endlessly repeated mostly contentless "technical" articles, and a bit of reporting here and there. Their product reviews, in particular, are mostly useless.

vascdoc · #36 07-30.-2007

Quote:

Originally Posted by bobbyOCR

gedanken experiments, though I have an extremely limited knowledge, have helped to procure some important physical constants and theories. Instead of a physical experiment, this is a mental experiment, but you appear to be too caught up in an argument.

Actually this is how the structure of the benzene ring was discovered. It was in an armchair with a good drink of brandy and a dream!

Dietmar · #37 08-06.-2007

Quote:

Originally Posted by vascdoc

Actually this is how the structure of the benzene ring was discovered. It was in an armchair with a good drink of brandy and a dream!

Not to be misunderstood, there is nothing wrong with a Gedankenexperiment, of course, if it is properly done. The problem with Swanson's "experiment", however, is that it assumes its conclusion, and wrongly so.

A friend of mine just came over with Jobst Brandt's "the Bicycle Wheel", 3rd edition. If anybody is still interested in the issue of how a bicycle wheel supports its load, they may benefit from reading this book. As far as lateral loads are concerned, Brandt's Figure 16 is the one to study...

oldbobcat · #38 08-07.-2007

Quote:

Originally Posted by jhemp_00

I am trying to figure out why so many people are bashing Ksyrium sl and ES wheels? After reading several, supposed scientific wheel test's done that rate the Ksyriums poorly, I am begining to think that these test are flawed, or just fake test done up by other wheel manufacturers!
I have been riding and racing for over 7 years and I have tried all sorts of wheels, from Zipp's to custom wheels. I found the ksyriums were the best feeling wheels I have ever been on, supper stiff, and great acceleration, and I have not had any problems with them. When ever I switch to my spare wheelset (DA hubs, open pro, 32) I immiedatly notice a difference, it's not huge, but the Ksyriums just feel faster. I am sold on the mavics!
I agree, that I am tired of seeing so many of them on the roads, but I think that might be a testiment to how good they are.

As an amateur linguist I'm curious about your usage. Why do you use an apostrophe to make Zipp plural (Zipp's), but not for ksyrium or mavic? For that matter, why is Zipp capitalized while Mavic and Ksyrium are not? Just curious.

leestevens · #39 08-07.-2007

OK Dietmar and Science is Cool, My understanding of a spoke is that if the rim deflects sideways the spoke doesn't bend but protrudes further into the rim and looses all tension, this is why the nipples will loosen, because they are under zero load. The wheels that do not do this are R-SYS Mavics and Lightweights, and that is why they are stiffer than 32 spoke wheels even though the spoke tension may be less than the steel spokes. http://www.rouesartisanales.com/article-6833227.html I am not a scientist so do not shoot me down with your scientific language, please. I am just trying to add something.
Back to the original topic, my Ksyrium Elites have been great for the past 5 years but i imediately sold the SL's i got with my new bike. Out here on the flats it is aero all the way!!

Dietmar · #40 08-07.-2007

Quote:

Originally Posted by leestevens

My understanding of a spoke is that if the rim deflects sideways the spoke doesn't bend but protrudes further into the rim and looses all tension, this is why the nipples will loosen, because they are under zero load.

That's close, but not the whole story. First of all, for small deformations, the spoke on the side towards which you are deforming will lose tension, but usually not all of it. The other part of the story is that the spoke on the opposite side will increase in tension. The resultiung forces are shown in Figure 16 in Brandt's book. The sum of these two effects, plus the resistance to bending of the rim itself, is what creates the stabilizing sideways force. The effect of spoke bending is pretty much negligible, as the little back-of-the-envelope calculation I suggested before will readily show.

Quote:

Originally Posted by leestevens

The wheels that do not do this are R-SYS Mavics and Lightweights, and that is why they are stiffer than 32 spoke wheels even though the spoke tension may be less than the steel spokes. http://www.rouesartisanales.com/article-6833227.html

Interesting article, by the way, and very relevant to this discussion. However, I have my doubts how important the "very high lateral loads" are in normal use of a bicycle wheel. My understanding was that lateral loads are usually quite small, so the case of the spokes on one side losing tension completely should be rare, although Brandt's figure shows that it indeed does not take much for that to happen.

rplace13 · #41 10-30.-2007

Hello, not looking to drag up old arguments. But I have been lurking/reading a lot about new wheels so thought I would post a question.

I get the general feeling that Ksyriums have plenty of people not digging them all that much. I gather that they are not the greatest wheels, but also not the worst. Those that like them seem to like them from riding them. A lot that bash them seem to do it with numbers...at least that is my take from the reading I have done.

So I we can all agree they are not that great "for the money" at what price do they become a good deal? I am putting together a new bike, my first in 15 years and have always liked Campy components and Mavic rims. Typically I trained on Mavic and raced on Campy. In my mind I thought the Ksyrium ES was a great looking wheel (that counts some) and most likely (based on my other mavics) was going to be a good all around wheel. After reading the forums I am not so sure.

So now the big question. At $647 for a brand new set with skewers and bags are they a good deal and will they server me well? I cannot justify 1300 for any wheels, but this seems like a great sale.

Other contenders are Zondas in the 500 dollar range and Eurus around 800. However, 800 is pushing my comfort level.

Open to any other suggestions you might have in that price range.

Thanks a ton, Rich

Tech72 · #42 10-30.-2007

This thread's argument seems to be focused on the Ksyrium SL's spokes. If the big, fat "Zircal' aluminum spokes on the SL are inferior, then the standard bladed stainless steel spokes on the Elites are preferred? I rarely see much testing done on the Elites. How do the SL and Elites compare to each other? The SL are the higher end model and is lighter due to the machining between the rims and has a fancy hub design but overall, are there advantages/disadvantages between the Ksyrium SL and Elite? There is a good $350 difference in price though. Anyone ever do a side by side comparison/test ride of the SL and Elite ?

As a sidenote, Campy and its alter ego Fulcrum have started using big, fat aluminum spokes, very similar to Mavic Zircals on the higher end wheelsets. Why? Spokes are only one component to the entire wheel, but it's such a critical part. Why would Campy go with a spoke design that have shown to be inferior in independent tests?

BikingBrian · #43 10-30.-2007

Quote:

Originally Posted by Tech72

-snip-

As a sidenote, Campy and its alter ego Fulcrum have started using big, fat aluminum spokes, very similar to Mavic Zircals on the higher end wheelsets. Why? Spokes are only one component to the entire wheel, but it's such a critical part. Why would Campy go with a spoke design that have shown to be inferior in independent tests?

$$$

....as in "let's squeeze even more out of our customers...hey, it works for Mavic!"

artemidorus · #44 10-30.-2007

The Ksyrium wheels with bladed steel spokes and elliptical section rims are probably quite good aerodynamically, as they look pretty similar to the well-rated Shimano wheels. Once you start getting into box rims and fat alloy spokes, ie SL and especially ES, aerodynamic merit goes out the window, unless you spend all your time climbing 10+ degree slopes.
Weight-wise, none of the Ksyriums are anything special, although the SL and ES are better than average.
Looks-wise, I think the SL and ES are contenders, although eclipsed by every deep composite rim.
For durability, all Mavic wheels tend to get a pretty good rap.
(Lateral stiffness and moment of inertia are, I think, pretty unimportant measurements unless you are a 90kg sprinter with brake pads kept 0.1mm off the rim.)

artemidorus · #45 10-30.-2007

Quote:

Originally Posted by rplace13

So I we can all agree they are not that great "for the money" at what price do they become a good deal?

Given the manifest superiority of Shimano R550/560, when they cost less than A$190 the pair.

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