Robust wheels for a sequoia elite
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FWIW. I generally disagree with the notion of double-butted spokes despite that being the consensus preference at this point in time ...daveornee said:
BUT, more so because if a spoke breaks while you are abroad, the odds of finding a replacement DB spoke is probably lower than finding one at your friendly, CONUS LBS.
Simply substituting a straight gauge spoke (presumably on the drive-side) while leaving all the others as DB results in disparate spoke tension will result in a wheel which could have further subsequent problems ... so, if you do opt for DB spokes AND if you do break one, then remember to have the entire side relaced with kindred spokes.
You could carry a couple spare spokes of the appropriate length(s). Testing has proven Double Butted spokes to be more durable than straight guage spokes.alfeng said:
However, if you chose not to carry any spare spokes or even the "fiber-fix" one, you can replace a broken spoke with another one of the same length. If you replace a double butted spoke that has 100 kgf tension with a straight guage spoke, it will also need to have 100 kgf tension. The amount of stretch (elasticity) in the 14 g spoke will be less and it's tone when plucked will be different, but it isn't going to result in a problem.
Since quality spokes from Sapim and DT have improved over the years, you will likely have less chance of breaking a spoke. However, if it were me, I would carry a couple spare spokes along. Some touring bicycles have a set of frame fittings on the left chainstay for that purpose. Since I don't own one of those bicycles, I made my own "fixture" that stores up to 4 spare spokes inside my seat post.
It has been a long time since I broke a spoke, but I now carry Stein Mini Cassette Lock tool should the broken spoke be on the rear drive side while touring and away from easy access to the "LBS".
Well, this isn't the moment to debate the drawbacks to following the religion of wheelbuilding with double-butted spokes ... but, let me just observe that test results are not always interpreted objectively ... yes, there is bias in so-called scientific interpretaton!daveornee said:
Regardless, if you tension the single gauge spoke at 100 kgf, the remaining double-butted spokes will probably need to be tensioned closer to ~120 kgf to true the wheel ... alternatively, the single gauge spoke will be tensioned at a lower kgf than the double-butted spokes if the desired tension of the double-butted spokes is maintained ... OR, your non-drive spokes could have the disparity -- loose & looser.
Does that matter?
Well, the general belief is that it does matter that equally tensioned spokes (at the proper tension!) build a stronger wheel ...
So, carrying spare spokes is the only option, IMO, if a wheel is laced with double-butted spokes for a foreign excursion.
100 kgf tension is the same force no matter what type of spoke. There is no religion involved here.alfeng said:
You are correct that equally tensioned spokes at the proper tension build a stronger.... and more durable wheel.
Double butted spokes, because of their more elastic mid section, help spread dynamic loads over more spokes (broader section of rim and more spoke holes on the hub as well). The spokes themselves are more durable and they also make the wheel more durable. Reference "The Bicycle Wheel" by Jobst Brandt. Also read what is says under "Double-butted spokes" section in the following link:
http://sheldonbrown.com/wheelbuild.html
However, all spokes will eventually fail given long enough fatigue cycles. It is a good practice to carry spares of the correct length with you.
I have replaced other riders spokes due to fatigue failure from Alaska to Prince Edward Island. It sure makes it easier when they pull out the konwn correct length spoke to replace the broken on.
Bzzzt. Incorrect. The tension would be the same regardless of what spoke you used to replace the broken one. Tension being in Newtons. It's the stress that may change which is the tension divided by the cross-section area of the spoke. Not a big deal. Seriously.alfeng said:
You would definitely not have to replace all the spokes so that they are the same thickness. As an example, did you know that Fulcrum uses slightly thicker spokes near the valve hole to help dynamically balance the wheel?
There is absolutely nothing at all wrong with using double-butted spokes. The strength and durability of the wheel will not be compromised in any way whatsoever. The lateral stiffness of the wheel may be slightly less compared to a wheel with thick straight-guage spokes, but that is all.
John Swanson
www.bikephysics.com
I need to nitpick a bit here. The central portion of a double-butted spoke is not more elastic. Elasticity is a measure of how much something stretches for a given load (stress versus strain). This is a material property that is not dependent on the shape. So brass has a different elasticity than steel, for example.daveornee said:
So what's going on in a double butted spoke? Let's say the spoke is under tension. 100 kgf or something. The tension is the same everywhere in the spoke. What changes is the cross sectional area. More area in the thick part and less in the thin part. Remember that stress is tension divided by area. So... the stress is higher in the thin part of the double-butted spoke than the thick part.
This can help in durability because materials under higher stress show better fatigue properties than materials under lower stress. The worst is if the spoke is tensioned so low that it goes slack. This is why it's possible for wheels with double-butted spokes to last longer than wheels with straight gauge spokes.
Trivia: If the stress in a spoke is too high, the material will yield (i.e., permanently deform - exceed the linear part of the stress vs strain curve). This will never happen in practice, though because the spoke will pull out of the rim way before that happens. In other words, the soft aluminum rim will yield first.
John Swanson
www.bikephysics.com
Let's see if I get the nit you are picking with a simple, but not real example:ScienceIsCool said:
I take a 14 g. 2.0 mm diameter piece of stainless steel wire and I draw it down so that one portion is 15 g. 1.8 mm diameter.
I cut the wire so that there is exactly 150 mm length X 2.0 mm diameter segment and 150 mm length 1.8 mm diameter segment.
I then support one end with something strong enough to handle more than 100 kg. I hang a 100 kg weight from the unsuported end of the wire.
Which part of the wire stretches more?
Maybe the way I used "more elastic" is the nit you are picking.
If that's it, I will change my wording to "the center section streches more per unit length in the elastic range of stainless steel than the larger diameter end segments of the spoke".
Yup. That was it. I know it's rather minor, but an essential point. I'm sure that you undertood the meaning, but the meaning of elasticity may not have been obvious to others. The actual amount that the spoke stretches is really small...daveornee said:
John Swanson
www.bikephysics.com
Point taken,,, you can have your nit for future picking :].ScienceIsCool said:
Yes, the amount is small.
The amount the a straight 14 g. spokes stretches under 100 kgf is very small. The amount the a DB 14/15 spokes stretches under 100 kgf is very small, but a little more than a straight 14 g. spoke of the same length.
Yes, the essential point is taken: elasticity is not changing; only the very small amount of additional stretch within the elastic range of the stainless steel... provided by the thinner center section of 14/15 DB spoke.
I think we all agree that it isn't a bad idea to carry spare spoke(s) of the appropriate length(s) when riding unsupported and far from your LBS. It also doesn't hurt to know how to replace the spoke in a built wheel... and have the spoke wrench that fits the nipples you use.
FINALLY! One of the deacons who worships at the alter of double-butted spokes has conceded that "the lateral stiffness of a wheel will be slightly less (with double-butted spokes than when) compared to a wheel (laced) with thick straight-guage [sic] spokes ..."ScienceIsCool said:
Now class, you may all have presented valid sounding arguments, but consider:
... while the semi-tangential force (for want of a better phrasing) may be equalibrated by the tensiometer, wouldn't the respective spoke either pull the rim less (if a double-butted spoke replaced an absent straight gauge spoke) or similarly more (if a single gauge spoke was a mismatched replacement on a wheel laced with double-butted spokes) AND the resultant rim will be laterally out of true if you tried to maintain 100 KgF?
Of course it would!
Adjustments to the non-drive side can be made to true the wheel, but the tension on most of the other spokes will subsequently need to be tweaked.
OR, are both of you saying that you would ride with the rim wobbling left-to-right?!?
Hopefully, not.
Simply stated, to achieve the same lateral stiffness of a spoke laced at 100 KgF, the 14/15 double-butted spoke would have to be tensioned to about 120 KgF.
Think about it rather than parrot what two of cycling's high priests have pronounced ...
So, I must apologize for continuing to be apostate from the religion that worships double-butted spokes, but I am unconvinced as to the superiority of lacing a bicycle wheel with double-butted spokes AND the inferiority seems more obvious. As I've said before (disclosure), I've intentionally laced wheels with double-butted spokes despite knowing their limitations (because they were spokes I had bought before I knew better ... yeah, that's my story) AND in the very distant past when I didn't know better.
Heck, some people still recommend -- or, build their wheels with -- alloy nipples!
FWIW. A x4 lacing with straight 14 gauge spokes on the drive side and x3 on the non-drive side is probably a better way to provide the sought after "elasticity" (if unnecessary rim deformation is what you want to achieve) than to use 14/15 double-butted spokes laced while maintaining suitable lateral stiffness (the better compromise is probably a x3 lacing on the drive side & x2 lacing on the non-drive side).
You are mixing lateral stiffness and tension.alfeng said:
More or less tension does not change lateral stiffness.
True and tension balance at appropriate tension is the goal.
I will also state that 14/15 DB spokes make the wheel less stiff in both lateral and radial directions compared to a wheel built the same with straight 14 g. spokes. I have never stated otherwise.
Lateral stiffness, like weight, is easy to measure, but they are only two factors to look at when considering a wheel.
No. That is not correct. 100 kg of force is 100 kg of force no matter what it is pulling on. If you hang a 100 kg weight from a scale, it will read 100 kg. It does not matter what size, shape, or length of rope you use to hang that weight. It will still read 100 kg. You can try this for yourself if you don't believe me.alfeng said:
Similarly, it does not matter what size, thickness, or length of spoke you use. If you apply 100 kg of tension, then the rim will experience 100 kg of force. Period.
And please, leave out all the invective and non-relevant editorializing. If you wish to make an argument, stick to some cogent, well expressed thoughts.
John Swanson
www.bikephysics.com
Okay, on all counts except the second statement ("More or less tension does not change lateral stiffness.").daveornee said:
Regardless, I've got to believe that a laterally stiffer wheel has to be preferable 99.99% of the time ...
Granted, you don't want a wheel as (vertically) stiff as a wheel off an ox cart ... which is why a radially laced wheel is generally a bad idea BUT why it undoubtedly deemed acceptable for mountain bikes whose tire PSI is significantly lower than most properly inflated road tires.
If a wheel which is laced with double-butted spokes yields a wheel that is less laterally stiff, then it begs the question as to why a cyclist would want to handicap his/her wheels (at a price premium, on top of it!) unless s/he was following a "religious" practice that has been preached & dutifully repeated.
If I wanted a "robust" wheelset, I would not recommend double-butted spokes.
Well, clearly, there is a failure to communicate -- either on your part, or mine ...ScienceIsCool said:
Invective?!? What's with the "Bzzzt. Incorrect." remark? You were just trying to be cute while nonetheless mocking, n'est-çe pas?
So, how would YOU describe the religious adherence to & promulgation of an idea? That is:
There is absolutely nothing at all wrong with using double-butted spokes. The strength and durability of the wheel will not be compromised in any way whatsoever. The lateral stiffness of the wheel may be slightly less compared to a wheel with thick straight-guage spokes, but that is all.
It's a misstatement ... plain & simple despite any future (or, past?) declaraton or protestation to the contrary.
Again, I pose the question:
Why would a cyclist would want to handicap his/her wheels (at a price premium, on top of it!) unless s/he was following a "religious" practice that has been preached & dutifully repeated?
No offense, but repeating a misstatement where data has not been correctly interpreted is probably best categorized as bad science -- or, is the Earth still flat?
Well I did recommend 14/15 DB spokes and will stick with that recommendation. "Robust" isn't jsut about stiffness. There are plenty of parameters besides wheel stiffness that have a much larger bearing on bicycle performance, such as aerodynamics, duarbility, and suitability to the kind of riding. Stiffness also comes from many other things than using straight 14 guage spokes. The rim I recommended to the OP is one off the stiffest, strongest, and most durable rims out there... and I conclude that it is one of the most robust.alfeng said:
I also recommended Phil Wood hubs. Phil Wood hubs are some off the stiffest, strongest, and most durable hubs out there... and I conclude that they are one of the most robust.
I also recommended to the OP that he use the best wheel builder he can find. I am confident that the wheel builder will have his own recommendations in attained what he thinks is robust.
Now to your issue about lateral stiffness/spoke tension/14 g Vs 14/15 DB:
I have built and measured identical 36 spoke wheels: one built with straight 14 g. spokes and another with 14/15 DB spokes. I mounted them in a milling machine base and secured the with steel pieces milled to hold the locknuts in place. I also mounted a dial indicator on the milling machine base so I could measure lateral deflection accurately and repeatably. I hung a a 25 pound weight from a 1/8" diameter steel cable off various points on the rim to provide deflecting force. I took multiple measurements and repeated them to make sure the results were consistent and repeatable. The load is applied at the the rim's brake track, normal to the plane of the wheel. I measured deflection at a spot within 3/8 of an inch (10 mm) of the point of load application, which I consider to be essentially at the point of load application.
The wheels I built were Sun CRT16-II 36 spoke front built 3-cross using DT 2.0 mm & DT Competiton DB 14/15 2.0/1.8 mm spokes and brass nipples on a 1993 Campagnolo Chorus hubs.
Deflections were 1.45 mmfor the straight 14 g and 1.52 mm for the 14/15 DB. This is about a 5% difference in lateral stiffness.
I reduced the tension on the spokes of bothe wheels from 100kgf each to 50 kgf each. I took the same group of measurements again. Deflections were 1.45 for the straight 14 g and 1.52 mm for the 14/15 DB. These series of test proved to me "More or less tension does not change lateral stiffness".
I recommend keeping to spoke tensions even and at the tension recommended by the rim manufacturer.
The measurements were exact enough and repeatable enough to give me confidence of the results. I performed the test and used the machinery and measuring devices from my Uncle John Ornee's machine shop. His shop machined products form the airline industry. His measurement ability and NBS traceability allowed him to meet .001 mm accuracy requirements.
I have seen similar and much more expansive test by Damon Rinard when he had access to the machine shop and over 100 wheels while at the University of California in San Diego.
I would not expect any riding conditions to apply a lateral force approaching 25 pounds.
The rims I recommended to the OP are stiffer & more robust than Sun CR16-II. The hubs are also stiffer & more robust than Chorus 1993 hubs. I would expect the lateral stiffness & robustness of wheels built based on my recommendations to be more than adequately stiff & more robust than the OP has now.
The butted section of a 14/15 DB spoke when built to the correct tension allows for the more absorption of energy than straight guage spoke while weighting and un-weighting the wheel in the process of riding.
DT-Swiss, Sapim, and Wheelsmith have all tested their spokes for durability. Each of their testing methods were quite different, but all of their results showed 25% increased fatique life of 14/15 DB spokes over straight 14 g.
DB spokes are more expensive because they require additional processing.
In a typical wheel build involving 72 spokes the difference in cost for the spokes is around $15.
Now would you quit referencing religion and all your other extraneous remarks?
First, thanks for the measurements. They don't change my opinion about spoke selection, however; and, in fact, re-enforce it for reasons that I am quite certain you must find to be ineffable despite your best efforts to convince me otherwise!daveornee said:
And, I do not believe that I suggested that your immediate hub or rim recommendations were incorrect although in another, recent thread, I believe that my indirect reply better answered the OP's query about his possible rim choices.
Since the price premium you rightly observe is not that great in the scheme of things, you should ask yourself why the engineers at MAVIC & SHIMANO (to name two obvious purveyors of wheels) don't use double-butted spokes ... after all, they would simply pass the additional cost (which would be less for them) to the end user.
Now, with regard to so-called referencing of religion -- I once remarked to someone (a couple of decades ago) that he was exhibiting a "parochial attitude." He looked at me, and with all seriousness said that he wasn't a Catholic & reminded me that he was a Seventh Day Adventist -- using words like "religion" which are commonly associated with God/etc. are not limited to the exclusive use of such references.
And, as far as extraneous remarks ... well, you may-or-may-not be guilty of extraneous remarks, but certainly some threads are entirely excessive banter which can probably be expunged. You may want to monitor those, too; and, let the posters therein know that you are disappointed with their activity.
BTW. Unfortunately I am without data; and, don't care to make calculations. But, while most of the force exerted on a wheel may be radial (or, not), I would reckon that your suggestion that a lateral force of greater than 25 lbs being applied to a wheel on a bike that is being ridden is grossly underestimated unless you are only presuming straight line riding (yes, I know you wrote "any conditions" ... I was just allowing a proviso) ... and, even then (during straight ahead riding), there is a lateral force that is induced through the wheel's rotation. Think about it.
Oh, and I do agree with you that spoke selection is not the only factor in building a "robust" wheel ...
Shimano, Mavic and others choose aero-section spokes which are more aerodynamically effecient but often not as stiff or inexpensive than round section 14 g. spokes.alfeng said:
I am satisfied to hold a different opinion than you regards the use of butted spokes for building wheels. Howard Sutherland is quoted as saying "One measurement is worth 50 expert opinions".
