jim beam wrote: > Peter Cole wrote: >> jim beam wrote: >>> that's absolutely untrue. if a manufacturer does the testing >>> necessary, then publishes their findings in the form of a spoke >>> tension spec, that /is/ "Proper Tension".
>> It's also "what the rim will bear" -- *their* rim.
> in "real" application!!!
I don't know what "real" application!!! means (jimbo-ese).
The max tension has got to be determined by either buckle or bed failure -- unless you have another candidate? If the rim doesn't buckle anywhere near the max, then it must be the bed. Mavic shaved the bed on their lightweight rims, then further compromised with crappy materials (Chalo) and anodize finish. Their (hidden) specs reflect this. Stop hiding behind mumbo-jimbo and accept the obvious. Or at least make a *coherent* counter-argument.
>>> no, the author doesn't understand that strength is not increased by >>> increasing spoke tension.
>> Of course it is.
> no it's not. you're making the jobstian error of looking at a load > calculation and assuming that it tells you something about strength - it > doesn't!
>> Most of the stiffness (lateral and radial) of a wheel is provided by >> the spokes.
> er, so how stiff would a wheel with no rim be then???
They have these on your planet, too?
>> This stiffness disappears when the spokes go slack.
Not *all* the stiffness, slow one, just *most* (read above again slowly -- you may move your lips).
>> The amount of load a wheel can take before spokes go slack is >> proportional to the spoke tension.
> no, the amount of load a wheel can take before the spokes go slack is > the amount of load a wheel can take before the spokes go slack.
The sound of one hand wanking.
>> Spoke tension compresses the rim.
> indeed.
deedy-do.
>> Compression will cause the rim to buckle once it exceeds the amount >> that the spokes can constrain.
> indeed.
deedy-do, too.
>> Wheel loading doesn't significantly change rim compression.
> indeed. but increasing spoke tension does.
Threedy-do. Duh.
>> Therefore, the higher the spoke tension, the stronger the wheel, up to >> the point where the rim buckles.
> no, that's a fundamental disconnect. if increasing spoke tension is > increasing rim compression, it gets closer to compressive yield than > before! [duh.]
Buckle [duh - over]?
> in that respect, increasing spoke tension is /reducing/ > the available load capacity for the rim.
No, because load doesn't increase rim compression significantly, so it doesn't bring the wheel closer to buckle. [duh?] [duh?] [anybody home?]
>> If rim manufacturer's want to shave grams off the spoke bed and sell >> rims that have to be run with much lower spoke tension than the other >> components (hubs, spokes, nipples) can bear, that's their choice. It >> doesn't make it a better rim, it does make for a weaker wheel.
> eh? that's a red herring.
No, it's a Mavic!
>>> and he doesn't understand the nature of the materials.
>> Like what? Endurance limit of spokes? That's a dead horse. "Vacuum >> degassing"? Done that, too. "Anisotropy of extrusions"?
> eh? jobst had no clue about anisotropy and why it would affect cracking > until i raised the subject.
No, I'm sure he never heard about it before. No of us has ever looked closely at an extrusion, or [gasp] even used one. We're totally clueless about metal forming except what we learned from the village smithy.
>> How come Mavic can make some rims that can take >160kg? Why can all >> Sun's take more?
> er, because they can?
Other hand wanking.
>>> he's even confused about what he's witnessing with his "finite >>> element" load calculation. all he's seeing is deformation of an >>> elastic rim causing a change in spoke tension where the deformation is
>> Elastic rim *and* elastic spokes. So what? BTW, he's not only >> "seeing", he's modeling in a very precise and provably correct manner.
> no he's not!!! he's modeling load, then claiming it demonstrates > strength!!! that's a fundamental error!!!
Warning Will Robinson!!! Tilt!!! Tilt!!! Where do you get this stuff? How about just a *pinch* of coherence? Substance?
>>> - a perfectly rigid rim would not deform there and so spoke tension >>> figures would be completely different, leading of course to a >>> completely different conclusion and therefore wheel theory.
>> Who cares about a "perfectly rigid rim"? What's this "wheel theory"?
> er, /you/ should care if you want to understand this stuff!
Good answer! I'm still waiting for the PRR "theory". We haven't heard it yet on this planet.
>>>> A few >>>> readers, I imagine, are disappointed. Bizarrely, one individual >>>> gives the author an answer and then says he is wrong.
>>> you mean that i disagree with the theoretical arguments? yes i do. >>> and for the reasons i've explained.
>> Except you've explained nothing.
> er, i have. but that doesn't stop /you/ saying different. because you > always do, rhyme, reason, or none.
You are so busted.
>>> you may want to dispute them, in which case, feel free to present >>> your own technical reasoning, but don't just say it's wrong because >>> you don't understand or don't want to know.
>> When shall we expect your FEA?
> when you show me how a load calculation can be called a strength > calculation when it isn't.
jim beam wrote: > Peter Cole wrote: >> jim beam wrote: >>> Peter Cole wrote:
>>>> My question was what is the actual tension achieved with Jobst's >>>> method using rims that fit his criteria. He implies that will get >>>> you to around 100kg.
>>> how does he "imply" it? he does not discuss tension numerically in >>> this context at all.
>> No, but he does use that figure in several places in the book.
>>>> All the equations in the back of the book seem to take 100kg as >>>> nominal spoke tension. I assumed that the "buckle point" method got >>>> him there with the typical rims he referenced, otherwise I don't >>>> know why he'd use it as a nominal number.
>>> but he doesn't say that! for all we know, "100" simply makes the >>> math easier for the example.
>> Right, it's all even numbers.... like it makes a difference to the FEA >> program.
> that's precisely my point!!!
What, the FEA program is integer only? Really, try to communicate.
> but /you/ were trying to say that the > "100" was a derived number - there's nothing to support that supposition.
No, I'm sure you're right, it's a cruel hoax designed to break wheels.
>> The 1000N figure is a nominal in many places, like spokes operating at >> 1/3 yield.
> but spokes /do/ operate at ~1/3 yield - that's easily calculated.
Try reading for comprehension this time.
>>>> That's what he said. If spoke breakage isn't a limit (as shown), >>>> then the only limits to spoke tension are rim buckling and bed >>>> cracking. Buckling can be experimentally determined easily with his >>>> method.
>>> but cracking can't!!!
>> No, and manufacturer's are free to make the spoke beds as thin as they >> wish.
> eh? that's missing the point of what i said. [deliberately?]
If you tell me where your point was lurking, I shall go back to try to find it. You think that bed cracking has nothing to do with bed thickness? You think Mavic can't control their bed thickness? Sorry, just throwing out possibilities. I'll make it full multiple choice if that's easier.
>> Your claim is that Jobst's method of finding the buckle point and >> backing off will result in spoke tensions of 175kg.
> i cited real numbers i measured specially for you since i have those > wheels to hand. want to call me a liar?
>> That would be twice the max limit of Mavic "classic" rims.
> which is precisely the point! excess tension /is/ the result of this > jobstian process.
>> Perhaps the spoke beds in the Open Pro, etc. are 1/2 the strength of >> the MA2. I don't know why Jobst would suggest a method that would give >> 175kg final then use 100kg everywhere in the book. I'm not too bad >> with a spoke wrench, but I can't imagine getting a wheel to 175, never >> mind the 200 you claim.
> first, don't say i said 200, i said >175. second, your imagination > doesn't come into it. those are measured numbers.
OK, if you really used the Jobst method [nudge, nudge -- wink, wink], then while reading the copy you don't own, paying special care not to read any of the other sections (so you wouldn't be able to freely misquote), you might have noticed that Jobst says to back off all nipples 1/2 turn. Say, that reminds me! How did you buckle your rim without "yielding" it? Didn't you find that irritating? OK, sorry, back to the main thread. So after you got to the buckle point and backed off all nipples 1/2 turn, your final tension was >175kg? And the buckle tension was what? (You can "use your imagination").
>>>> As for bed cracking, if Jobst's method gets you to 100kg for >>>> "classic" rims, you're good for all Sun road rims (according to >>>> them), but a bit high for Mavic. Since Mavic knows how to make rims >>>> that can take 160kg or more,
>>> which rim? i've called them and they didn't say that high on any of >>> the rims i asked about. and that statement doesn't address cracking >>> at all.
>> Their data sheets are online, that's where I got the numbers.
> link them then!
I did! These have been linked before, don't you remember *anything*? Being the Mavic wonk you are, I figured you'd have printed and papered your tool shed with them (or, more in keeping with corporate policy, memorized and eaten them).
>>>> it seems like they made their "classics" a bit on the dainty side. >>>> Perhaps they should have made that better known -- even a feature: >>>> "Our rims require 20% less spoke tension!".
>>> typical peter cole.
>> OK, the maximum spoke tension spec on their "classic" rims is more >> than 20% less than Sun's.
> so what???
So, they suck! Next question?
>> I see that as an admission that their spoke beds are that much weaker >> -- unless they're going by buckle limit. How else could you interpret it?
> what's to "interpret"? do you /always/ have to argue the freakin' toss > just for the sake of it?
OK, give me another reason for spoke tension max limit -- carpal tunnel for wheel builders? I'm warning you, I can't continue arguing unless you give me something to work with -- you're really not holding up your end.
jim beam wrote: > Ozark Bicycle wrote: >> On Oct 1, 8:57 am, Peter Cole <peter_c...@comcast.net> wrote:
>> <snipped for brevity and clarity>
>> - on Brandt's wheelbuilding technique - >>> What this approach does is determine the maximum spoke tension by >>> finding the rim buckling point and then backing off considerably to >>> establish a safety margin.
>>> The buckling point is determined by the rim cross section (thin column >>> buckling). The load that causes this buckling is circumferential >>> compression. It's not obvious to me that the wider, less tall cross >>> sections of older rims like the MA-2 buckled under less load than the >>> newer narrow/tall cross sections (Reflex, Open Pro). My guess is that >>> the MA-2 would be (a little) more buckle resistant, if anything.
>> The only way to know is to "suck it and see". IME, a box section rim >> such as an MA-2, etc., will "taco" at lower tension than will a rim >> of similar weight but taller cross section. Try it yourself and see >> what results you get.
> peter cole will /never/ do anything that might contradict one of his > preconceptions.
Oooh, another "beam's law". Riddle me this lightning-wit, how does a "guess" (see above) equal a "preconception"? You're such a pompous twit.
Example: <mega thread fully quoted>
"indeed!" (he beamed)
Example: <thread fully quoted>
insert lame ad hominem of your choice (see above).
jim beam wrote: > jobst.bra...@stanfordalumni.org wrote: >> Peter Cole writes:
>>>>> This is NOT torquing a bolt until it starts to strip and then >>>>> backing off a little. Stop pretending it is. The phrase "as high >>>>> as the rim can bear" does NOT equal "higher than the rim can >>>>> bear."
>>>> you don't understand the problem. because the rim doesn't pretzel >>>> doesn't mean it's not at its strength limit.
>>> Which "strength limit"?
>>>> pretzel means yield.
>>> No, it doesn't. It means to buckle.
>> I might point out that pole vault poles buckle visibly and there is no >> yield. Maybe buckling is a more complex subject than I thought.
> and the material is???
You could look it up.
Vault poles are typically fiberglass, but they have been made in aluminum.
>> However, making rims that split down their center in short order at >> spoke tensions far below buckling is a wast of effort and material,
> er, except that if the manufacturer has bothered to do their homework > and has determined the spoke tension - they didn't just pull some crazy > notion out of thin air, which makes no account of the materials > involved, and which ignores how rims have compressive yield limits.
"compressive yield limits" -- you keep using that fuzzy phrase, why not just say buckle like the rest of us?
If the spoke tension limit isn't set by rim buckle or bed strength, then what is it? (for the second or third time).
>> producing a weaker wheel than the rims could offer had it been made >> with sockets and eyelets to load the inner wall as well. That load on >> the inner wall is the important one because it is spread over an area >> several times that of the eyelet in the rim bed.
> indeed, why not go the while way and have an even /thinner/ inner wall > and use a single eyelet to save weight. oh, wait...
>> In other words the >> MA-2 is a far more durable and stronger rim than the MA-3 and its ilk.
>> Of course those who have tried them probably know that already.
> and those that don't know a damned thing about materials or their > applications still presume to lecture on them!
Why don't you answer the man's question? Why not *any* question? We'll wait. Take your time. Take a break from the Jobst-bashing and prick-calling. You can still go back to it, we won't run away.
b...@mambo.ucolick.org wrote: > On Oct 2, 12:27 pm, Peter Cole <peter_c...@comcast.net> wrote: >> b...@mambo.ucolick.org wrote: >>> On Oct 2, 12:27 am, Ben C <spams...@spam.eggs> wrote: >>>> If I hypothetically build with a normal MA-2, but leave out every other >>>> spoke, then will I need more tension in the 18 I've got to avoid slack >>>> spokes for a given load than I would have done if I'd used all 36? >>> Since the rim has the same rigidity, it's likely >>> that the flattened area at the bottom when loaded >>> will be about the same. >> Nope. The rim is supported (stands on) the spokes. If you take out half, >> you increase the unsupported span. Beam deflection goes as the cube of >> span (beam theory -- no relation).
> Okay, but I think you are going to increase the forces > from the bottom-most spokes (the tension reduction which > supports the rim against load force from the ground). > Just because there's only so much of the rim that actually > deforms against the vertical load (Once you get to ~4 o'clock > and 8 o'clock, the angle of the rim sections is not so > favorable for deforming against that load, I suspect.) > Increase in the spoke forces tend to counteract the > increased deflection, although they won't cancel it. This > is kind of a vacuous argument since I can't do the FEA, > but I'm quite sure that an 18-spoke wheel will suffer > higher cyclic loads on the spokes than a 36 spoke wheel.
At this point I'm not exactly sure of who's saying what, so I'll try to state my view simply.
If you consider a railroad track and take out every other tie, the track will deflect more, both between the ties and at the ties. You could, in the case of a wheel, increase spoke tension to compensate for the additional deflection (increasing the point where slacking occurs), that won't make the wheel stiffer, and there's (still) a limit due to buckling. Half the spokes should generate half the rim compression, so theoretically you could double the tension, but the rim is less well supported laterally against buckling, so the limit of compression will be lower (exactly how much I don't know). The net effect is that the wheel will be less stiff (higher cyclic stresses/strains) and probably won't achieve the same load capacity.
>>> There's another issue from the fact that box rims are >>> not as stiff radially as something like a Deep-V, >>> and probably a bit less stiff side-to-side. >> I'm not so sure about the side-to-side. If the same amount of material >> is used, it seems unlikely that moments on both axes will be greater -- >> all other things being equal.
> Yes, I specifically mentioned a Deep V because it's > a stout heavy rim that I suspect would in fact be harder > to bend sideways, even though no wider than an MA-2.
If you don't keep the mass the same, then it's apples to oranges. If you compare 2 "U" columns (for simplicity), the wide, squat "U" will bend more easily vertically and less easily horizontally than the tall, narrow "U". I think it's the horizontal bending that dominates in buckling. The specific profile comparison I had in mind was between the MA-2 Jobst references in his book and the similar, but taller and narrower, rims that immediately replaced them (Reflex, Open Pro).
> Peter Cole wrote: >> jim beam wrote: >>> that's "corrective", not "anti-jobst".
>> Who do you think you are fooling?
> why are you so fucking argumentative?
Not argumentative, observant.
> jb: "the sky is blue" > pc: "liar!"
jb: "CF talks to people" "materials lecture more than 30 years ago on composite helo rotors" "CF fatigue properties same as CF damage tolerance" "yadda, yadda, yadda" r.b.t: "bullshit, lying fraud tard"
On Oct 3, 8:18 am, Peter Cole <peter_c...@comcast.net> wrote:
<snipped for brevity and clarity>
- on Brandt's wheelbuilding technique, cont'd -
> The max tension has got to be determined by either buckle or bed failure > -- unless you have another candidate? If the rim doesn't buckle anywhere > near the max, then it must be the bed.
Yes, and, IME, the rim profile changes the tension at which the rim will "taco" (I assume this is what you mean by "buckle"). So, a rim with the same "resistance" to cracking at the spoke holes as an MA-2, but with a more "modern" profile, will bear higher tension prior to tacoing, meaning it will be more likely to crack if one uses Brandt's method. IMO, his book is simply in need of updating to reflect modern rims and the use of highly dished rear wheels.
> jim beam wrote: >> Peter Cole wrote: >>> jim beam wrote:
>>>> pretzel means yield.
>>> No, it doesn't. It means to buckle.
>> which is permanent. which is yield. [which is plasticity.]
> Not necessarily, it depends on the degree of buckle.
And when the rim returns to its pre-buckle shape after loosening spoke tension, that's called elastic deformation. Boy, that "metarialas skool" didn't teach beamboy much...
>>> Hoo boy! Just how do you relate spoke tension to fatigue *at the spoke >>> bed* without knowing the thickness of the bed? What a howler!
>> er, when the rim cracks, it's the spoke bed cracking. boy.
Er, not a rule, beamboy, and not always true.
>> ok, this is bullshit.
Glad you say that, but go on anyway:
>> rim extrusions /are/ anisotropic. your ignorance or lack of willingness >> to understand what effect this has on fatigue fundamentally disqualifies >> you from making /any/ credible comment on this subject.
Wow, that IS bullshit.
Rims are extruded because that is the most economical way of producing long parts with constant cross-section. The product's final characteristics are dependent upon a complex interaction of the alloy system and thermal and mechanical processing steps (billet temperature, extrusion speed, product cross-section, extrusion and final heat treatment, stretch straightening, etc.). Extrusions do not necessarily end up imparting anisotropic properties to the material, unless the material itself has anisotropic properties to begin with. So, "your ignorance or lack of willingness to understand what effect this has on fatigue fundamentally disqualifies you from making /any/ credible comment on this subject."
>>> Tell Mavic (as an interested and passionate consumer advocate) that they >>> shouldn't be so coy about publishing the (weak) specs on their rims. >>> They like stickers, tell them to add one. Problem solved.
>> i agree, they /should/ sticker their rims with this info. but that >> doesn't mean /you/ can suddenly be ignorant of the theory and then >> presume to lecture people on these subjects you [proudly] know nothing >> about. "Anisotropic, my eye." what a prick!
> Peter Cole wrote: >> He explicitly excluded them. He realized that his rule of thumb would >> only apply to rims with specific characteristics.
> he told you that? everything i've seen suggests ignorance of this matter, > not calculated exclusion.
Well, we all know about your cognitive abilities, does tell us what the problem is.
> if he knows about this stuff, he should discuss - this does purport to be > an engineering treatise after all...
Come now, been there done that, but you already know that....
>> Increasing spoke tension does make a stronger wheel. The higher the >> initial tension, the greater the load the wheel can support before the >> spokes go slack. Slack spokes don't support the rim from buckling.
> spokes need to be tense enough to resist slackness. but the higher the > spoke tension, the closer the rim to compressive yield. and that means > failure.
No, it doesn't. The rim will yield if you ever exceed the yield limit, but loading the wheel DECREASES tension in the lower spokes, not increase them. You can't see this because you don't have the ability to do so.
> you're repeating the jobstian error of only looking at the spoke loading > and mis-concluding that it's indicative of whole wheel strength.
Rubbish - you need to look at the loaded areas of the wheel and the effect of the loads on the wheel - and if you understand the mechanism for wheel structural loading (which you don't), you'll see that that the area os interest is where the wheel takes up the loads.
>> This was a method to determine the maximum spoke tension for a specific >> category of rims, as determined by rim buckling.
> but that gives spoke tension too high and which causes rim cracking!!!
But, but, but...... Mom......
> no, because he never acknowledges it in any way!
But, but, but...... Mom......
> and rim cracking, the obvious evidence that his theory is incomplete, is > mis-attributed to anodizing, again by ignoring simple observational fact.
That's observational "opinion", not "fact".
>> Well, by your logic, if there's no real minimum tension, why bother?
> no, that's not my logic. you /do/ need tension to avoid spoke slackness > which causes spoke fatigue and spoke nipple unscrewing. but tension above > that limit achieves nothing for wheel strength and is *detrimental* in > terms of rim cracking.
That's not logic, that's a misunderstanding on your part. "metarials skool" sure didn't pay off for you....
>> Of course the first 2 rims are 559, since the buckle load varies with the >> square of length, that alone will give you a 25% or so error.
> but my open pro was about that level too. i'm not in a position to > re-measure for you as i've re-tensioned that wheel, but you could easily > verify for yourself. if you were genuinely curious of course.
> Jambo wrote: >> "jim beam" <spamvor...@bad.example.net> wrote in message >> news:TPmdnf6eFZT-WZzanZ2dnUVZ_rvinZ2d@speakeasy.net... >>> spikenett...@earthlink.net wrote: >>>> On Oct 1, 8:17 am, jim beam <spamvor...@bad.example.net> wrote: >>>>> spikenett...@earthlink.net wrote: >>>>>> I've learned from previous threads to not believe anything you say. >>>>> that's a personal issue for you spike. >>>> Actually, it's not a personal issue; it's a personal observation. The >>>> same observation made by many others who have read your posts. >>>> -- >>>> Spike
>>> you want to align yourself with jambo???
>> And everybody else, except maybe Dougy Taylor, Bill S, you know, the >> "winners" here in r.b.t.
> translation: "everybody's with me - except for those that aren't!" what a > fucking moron!
That's right beamboy. Everybody's with me, except those (2 or 3) that aren't. You may have learned something from "metarials skool" after all.....
"jim beam" <spamvor...@bad.example.net> wrote in message > if it's so "obvious" why is it not stated in any books, "faq"'s or even > mentioned in /your/ contributions on this subject?
And not stated by manufacturers in manuals and in their rims? You lying fraudtard, you just sunk yourself again...
> strange statement from one so curiously uninterested in "obvious" facts > and ensuring they're actually disseminated.
Yeah, just like the "cracking sounds of CF doom" being used by CF users to detect damage....
carlfo...@comcast.net wrote: > On Wed, 03 Oct 2007 07:51:16 -0000, "b...@mambo.ucolick.org" > <b...@mambo.ucolick.org> wrote:
> [snip]
>> . . .I'm quite sure that an 18-spoke wheel will suffer >> higher cyclic loads on the spokes than a 36 spoke wheel.
> [snip]
> Dear Ben,
> If the 18-spoke wheel has a *significantly stronger rim* than a > traditional 36-spoke rim, it will deform less and the spokes may see > the same (or even lower) cyclic loads.
> I _think_ that this is what Jim Beam has in mind.
[emphasis mine]
Of course that's a separate question.
If you look at the limit of a 4-spoke wheel with infinitely stiff rim, I calculate a ~2.5x greater* spoke cyclic loading. An 8-spoke wheel would have around the same* spoke loading. The loads would continue to diminish as you add spokes.
To look at an actual reduced spoke aero wheel, like the Mavic Kyserium Equippe 08, the 20 spoke rear wheel is spec'ed at 130-145kg, as opposed to the 70-90 for their "classic" rims, so I guess the rim is rather far from being "infinitely stiff". An even more deep section rim on Mavic's COSMIC ELITE wheels, specs 135-165kg.
Perhaps, given the spoke spacing and dish, the greater tension is merely to give more buckle resistance. I don't really know. But otherwise I don't know why they'd use such comparatively high spoke tensions if the "stronger" rim gave "lower cyclic loads".
> > . . .I'm quite sure that an 18-spoke wheel will suffer > >higher cyclic loads on the spokes than a 36 spoke wheel.
> Dear Ben,
> If the 18-spoke wheel has a significantly stronger rim than a > traditional 36-spoke rim, it will deform less and the spokes may see > the same (or even lower) cyclic loads.
> I _think_ that this is what Jim Beam has in mind.
I was only answering Ben C's question about what would happen if you built an MA-2 type rim with 18 spokes instead of 36. This was quoted in my original response but has since gotten lost. I agree that a deeper or heavier rim is stiffer, but changing more than one thing at a time (rim stiffness and spoke number) makes it hard to isolate effects. Collective experience suggests that an MA-2 with 18 spokes would not make a great wheel.
I don't have a lot of luck figuring out what jim beam has in mind, but he seemed to be taking the limit of an infinitely stiff rim, which I argued isn't a useful limit for then dialing back to figure out what a stiff, but not infinitely stiff, rim will do. The indeterminacies in the structure are different if you crank one of the moduli up to infinity - an infinitely stiff rim won't deform under load, so the spokes won't be cyclically stressed in the same way as in a real wheel.
> Certainly Jobst wrote that aero rims were stronger:
> "With large cross section mountain bike and deep section aero rims the > tension of 36 spokes may not exceed the strength of the rim. For such > heavy rims and conventional road rims using fewer than 32 spokes, > tensioning is usually at the limit when the nipples can no longer be > tightened easily."
Ozark Bicycle wrote: > On Oct 3, 8:18 am, Peter Cole <peter_c...@comcast.net> wrote:
> <snipped for brevity and clarity>
> - on Brandt's wheelbuilding technique, cont'd - >> The max tension has got to be determined by either buckle or bed failure >> -- unless you have another candidate? If the rim doesn't buckle anywhere >> near the max, then it must be the bed.
> Yes, and, IME, the rim profile changes the tension at which the rim > will "taco" (I assume this is what you mean by "buckle"). So, a rim > with the same "resistance" to cracking at the spoke holes as an MA-2, > but with a more "modern" profile, will bear higher tension prior to > tacoing, meaning it will be more likely to crack if one uses Brandt's > method.
Well, that depends on two things. First, that more "modern" (taller, narrower) rims have a higher second moment in the direction that buckling occurs. I'm not convinced (I suspect the opposite), but I don't have the means to directly measure this.
Secondly, even if the rim were slightly more resistant to buckling because of a different profile, this would mean it could take higher spoke tensions (and be overall a stronger wheel) just by adding a little more strength to the spoke bed. This could be done in a variety of ways, the simplest being just to make the bed a little thicker.
It would seem the smart way to design a (light) rim is to match the buckle strength to the bed strength. Or, in other words, design a rim that can take reasonable spoke tensions. If Sun specs 110kg, why does Mavic spec 70-90 for a more expensive rim?
> IMO, his book is simply in need of updating to reflect modern > rims and the use of highly dished rear wheels.
He did explicitly exclude all rims other than <36 spoke, <430g. The method of determining maximum spoke tension wouldn't apply to many modern wheels, nor is it necessary if the makers publish specs. I guess you & you-know-who think he should add a one-liner: "Always consult manufacturers specifications" or some such. I think that's implicit, myself.
carlfo...@comcast.net writes: >> I noticed a misrepresentation of "the Bicycle Wheel" in this thread >> on which a line of argumentation is built, a classic straw man. >> "The error of looking at a load calculation and assuming that it >> tells you something about strength - it doesn't!" >> There are NO loads calculated in "the Bicycle Wheel" nor values for >> strengths of wheels. > [snip] > Dear Jobst, > Fig. 16 "Lateral force and spoke tension graph" in "Strength and > Durability" in the 3rd edition:
> *** > "If its spokes are tensioned to 1000 N, a 36-spoke wheel will > support approximately 400 kg. This is considerably greater than the > average rider's weight. However, loads of 400 kg or more sometimes > occur when a wheel strikes a bump in the road at high speed. If such > overloads occur often, the nipples of slack spokes can unscrew, > reducing tension to affect both wheel alignment and strength." > --3rd edition > *** > "A concern has been expressed that, unless the two spokes adjacent > to the joint cross on the way to the hub, the joint will separate in > use. This concern ignores that the tension of all the spokes is > supported by the rim as an arch in compression, a load of about a > half ton for a 36-spoke wheel." > --3rd edition > *** > "Equations" > "3. Spoke elongation from tension ... > P = 180kg Tension in spoke" > [Possibly a mistake cleared up later--I seem to recall Joe Riel asking > about something like this?] > --1st edition, p. 135 > *** > "Equations" > "7. Rim Compression from spoke tension... > T = 90 kg Tension in each spoke" > --1st edition, p. 136 > *** > "Finite Element Computer Analysis... > Load = 50.00... [presumably kg] > Fig. 70 Radial load (see fig. 8) > --p. 141, 1st editionq > [The same load appears for the next 5 pages of equations, all > labeled "load" such-and-so.] > *** > For lagniappe, here are two passages across three editions, showing > the historical side of the "Bicycle Wheel." > "AERODYNAMIC RIMS" > The 1st edition of 1981/3 has no such section. > Here the aero rim section appears in the second edition: > "Streamlined rims have deep, rounded "V" shapes. Most of these rims > are heavier and more rigid than their conventional counterparts. > Their braking surfaces are not perpendicular to the surface of the > brake pads and they have no reinforcement for spoke nipples. > Structurally, they give a strong wheel but their aerodynamic > advantage is achieved at the expense of these deficiencies." > --2nd edition 1988 > The aero rim passage was expanded considerably in the 3rd edition: > "Streamlined rims have deep, rounded "V" shapes. Most of these rims > are heavier and more rigid than their conventional counterparts. > Often their braking surfaces are not perpendicular to the brake pad > motion, and they usually have no steel inserts for spoke nipples > because their deep cross section makes them adequately strong. > However, nipples can easily gall rims without steel inserts, and > bind during tightening and retruing. Although `aero' rims may be > structurally strong, their minimal aerodynamic advantage often comes > at the expense of greater weight, greater side wind sensitivity, and > higher cost." > --3rd edition 1993 > The historical pattern is clear. Deep aero rims didn't even appear > in the first edition, were briefly disparaged a few years later in > the second edition, and were extensively criticized in the third > edition. > Ignoring the merits of the criticism, it's plain that the book was > written in the era before the modern deep low-spoke-count rim > replaced the 36-spoke shallow box rim as the industry favorite. > *** > The other passage of interest is too long to reproduce for all three > editions, but suggests how far off the radar deep low-spoke-count > modern rims were. > The first edition of 1981/3 described wood and wood-filled tubular > rims in detail and concluded: > "These disadvantages have contributed to the decline in popularity > of these [wood-filled] rims." > The same detailed consideration of wood and wood-filled tubular rims > appeared in the second edition of 1988, with this stronger > conclusion: > "Because they have these disadvantages, wood-filled (and wooden) > rims are rarely used now." > In the third edition of 1993, the long discussion of wood and > wood-filled rims still appeared, but was prefaced by this frank > admission that they had become obsolete: > "Wood-filled rims have followed wooden rims into history, and the > tubular tires that were mounted on them are likely to disappear > next." > So wood rims were vanishing, but as the aero rim passages show, the > book failed to see that deep low-spoke-count rims were going to > replace the MA2. (And tubulars still occupy their niche.) > For those unfamiliar with tubular wood rims and why tubular metal > rims were sometimes filled with wood, here are the details: > "Wooden rims are strong and light, and are ideal for gluing tubular > tires. Since wood is a good insulator, heat produced by braking > will not soften tubular tire glue and cause tire creep. However, > the disadvantages of wood outweigh these positive features. Wood is > brittle and will not dent or fail partially. Wooden rim failures > usually result in wheel collapse and dangerous splinters. Moisture > causes wooden rims to distort and lose spoke tension and makes > repeated truing necessary. Low thermal conductivity keeps wooden > rims from absorbing braking heat and causes brake pads to burn away > rapidly. In addition, wooden rims require greater braking force > than metal rims because high temperatures soften the brake pads and > reduce their coefficient of friction." > "WOOD-FILLED RIMS FOR TUBULAR TIRES" > "Wood-filled rims have followed wooden rims into history, and the > tubular tires that were mounted on them are likely to disappear > next. Instead of sockets or washers, these rims use wooden filler > pieces inside the hollow aluminum alloy rims. These pieces > distribute the load to both surfaces of the rim as steel sockets do > and require much smaller holes in the rim. Because the holes need > be only large enough to accept nipple shafts, less material is lost > from the rim. Because little material is lost, these rims can have > thinner walls with the same strength as heavier rims. Although > wood-filled rims are extremely light, they have the disadvantage of > losing tension when the wood compresses under spoke nipple pressure > aggravated by the effects of moisture. Loss of tension causes the > wheel to lose both alignment and strength." > "Wood-filled rims present other problems. The nipples cannot swivel > in the rim to accommodate the different spoke angles produced by > different spoke patterns. Therefore, spokes may bend excessively > at the nipple. The holes must be drilled in the rim at angles to > match a specific spoke pattern. Wood rims and wood-filled rims > require long nipples. They must reach from the bed of the tire > through the rim to expose flanks that can be engaged by a spoke > wrench. Long nipples make wheel truing difficult because they often > bind while being turned, and they weigh more then standard nipples." > --3rd edition 1993 > Cheers,
I think you just showed that no load and strength calculations of wheels are made in the book. However, you seem to go into publishing unrelated parts of the book as in copyright infringement.
On 2007-10-03, jobst.bra...@stanfordalumni.org <jobst.bra...@stanfordalumni.org> wrote:
> carlfo...@comcast.net writes: [...] >> overloads occur often, the nipples of slack spokes can unscrew, >> reducing tension to affect both wheel alignment and strength." [...] > I think you just showed that no load and strength calculations of > wheels are made in the book.
Perhaps you can help clarify this point then.
What does "strength" mean? Technically we know it means breaking stress. Can it also be used of a structure, as opposed to of a material, to mean the force (or stress?) at which the structure collapses, even if collapsing doesn't involve anything breaking, and might not even involve anything even yielding?
If it can, then it's correct to say in that sense that high spoke tension increases strength. If it can't, then it's not correct-- high spoke tension doesn't change the breaking stress of any of the components in the wheel. I think that's jim beam's point. Since his expertise is in materials he naturally takes "strength" to mean "breaking stress".
Putting define:strength into Google retrieves this:
very general term that may be applied to a material or a structure. In a material, strength refers to a level of stress at which there is a significant change in the state of the material, eg, yielding or rupture. In a structure, strength refers to a level of level of loading which produces a significant change in the state of the structure, eg, inelastic deformations, buckling, or collapse.
> What does "strength" mean? Technically we know it means breaking stress. > Can it also be used of a structure, as opposed to of a material, to mean > the force (or stress?) at which the structure collapses, even if > collapsing doesn't involve anything breaking, and might not even involve > anything even yielding?
Only if the structure relies on friction joins, i.e. something like lego blocks. You can break a lego structure simply by causing individual blocks to separate, as in pulling two blocks apart.
There are no similar such in a bicycle wheel - to collapse the wheel structure, you need to deform a section through weakening or removal of a support member, or loading the wheel in directions and points where there is little support (as in perpendicular to the rim radius). In any case, something will deform or break.
> If it can, then it's correct to say in that sense that high spoke > tension increases strength. If it can't, then it's not correct-- high > spoke tension doesn't change the breaking stress of any of the > components in the wheel.
It's not a dichotomy.
> I think that's jim beam's point.
His point is to be contrary despite scientific fact.
> Since his > expertise is in materials he naturally takes "strength" to mean > "breaking stress".
Beamboy takes strength and any other term to mean what he wants them to mean, and often not what their scientific definitions are.
He has no expertise in materials, despite his bleatings about attending "materials skool".
> Putting define:strength into Google retrieves this:
> very general term that may be applied to a material or a structure. > In a material, strength refers to a level of stress at which there > is a significant change in the state of the material, eg, yielding > or rupture. In a structure, strength refers to a level of level of > loading which produces a significant change in the state of the > structure, eg, inelastic deformations, buckling, or collapse.
>> "If its spokes are tensioned to 1000 N, a 36-spoke wheel will >> support approximately 400 kg. This is considerably greater than the >> average rider's weight. However, loads of 400 kg or more sometimes >> occur when a wheel strikes a bump in the road at high speed. If such >> overloads occur often, the nipples of slack spokes can unscrew, >> reducing tension to affect both wheel alignment and strength."
>> --3rd edition
>> ***
>> "A concern has been expressed that, unless the two spokes adjacent >> to the joint cross on the way to the hub, the joint will separate in >> use. This concern ignores that the tension of all the spokes is >> supported by the rim as an arch in compression, a load of about a >> half ton for a 36-spoke wheel."
>> --3rd edition
>> ***
>> "Equations"
>> "3. Spoke elongation from tension ... >> P = 180kg Tension in spoke"
>> [Possibly a mistake cleared up later--I seem to recall Joe Riel asking >> about something like this?]
>> --1st edition, p. 135
>> ***
>> "Equations"
>> "7. Rim Compression from spoke tension... >> T = 90 kg Tension in each spoke"
>> --1st edition, p. 136
>> ***
>> "Finite Element Computer Analysis...
>> Load = 50.00... [presumably kg]
>> Fig. 70 Radial load (see fig. 8)
>> --p. 141, 1st editionq
>> [The same load appears for the next 5 pages of equations, all >> labeled "load" such-and-so.]
>> ***
>> For lagniappe, here are two passages across three editions, showing >> the historical side of the "Bicycle Wheel."
>> "AERODYNAMIC RIMS"
>> The 1st edition of 1981/3 has no such section.
>> Here the aero rim section appears in the second edition:
>> "Streamlined rims have deep, rounded "V" shapes. Most of these rims >> are heavier and more rigid than their conventional counterparts. >> Their braking surfaces are not perpendicular to the surface of the >> brake pads and they have no reinforcement for spoke nipples. >> Structurally, they give a strong wheel but their aerodynamic >> advantage is achieved at the expense of these deficiencies."
>> --2nd edition 1988
>> The aero rim passage was expanded considerably in the 3rd edition:
>> "Streamlined rims have deep, rounded "V" shapes. Most of these rims >> are heavier and more rigid than their conventional counterparts. >> Often their braking surfaces are not perpendicular to the brake pad >> motion, and they usually have no steel inserts for spoke nipples >> because their deep cross section makes them adequately strong. >> However, nipples can easily gall rims without steel inserts, and >> bind during tightening and retruing. Although `aero' rims may be >> structurally strong, their minimal aerodynamic advantage often comes >> at the expense of greater weight, greater side wind sensitivity, and >> higher cost."
>> --3rd edition 1993
>> The historical pattern is clear. Deep aero rims didn't even appear >> in the first edition, were briefly disparaged a few years later in >> the second edition, and were extensively criticized in the third >> edition.
>> Ignoring the merits of the criticism, it's plain that the book was >> written in the era before the modern deep low-spoke-count rim >> replaced the 36-spoke shallow box rim as the industry favorite.
>> ***
>> The other passage of interest is too long to reproduce for all three >> editions, but suggests how far off the radar deep low-spoke-count >> modern rims were.
>> The first edition of 1981/3 described wood and wood-filled tubular >> rims in detail and concluded:
>> "These disadvantages have contributed to the decline in popularity >> of these [wood-filled] rims."
>> The same detailed consideration of wood and wood-filled tubular rims >> appeared in the second edition of 1988, with this stronger >> conclusion:
>> "Because they have these disadvantages, wood-filled (and wooden) >> rims are rarely used now."
>> In the third edition of 1993, the long discussion of wood and >> wood-filled rims still appeared, but was prefaced by this frank >> admission that they had become obsolete:
>> "Wood-filled rims have followed wooden rims into history, and the >> tubular tires that were mounted on them are likely to disappear >> next."
>> So wood rims were vanishing, but as the aero rim passages show, the >> book failed to see that deep low-spoke-count rims were going to >> replace the MA2. (And tubulars still occupy their niche.)
>> For those unfamiliar with tubular wood rims and why tubular metal >> rims were sometimes filled with wood, here are the details:
>> "Wooden rims are strong and light, and are ideal for gluing tubular >> tires. Since wood is a good insulator, heat produced by braking >> will not soften tubular tire glue and cause tire creep. However, >> the disadvantages of wood outweigh these positive features. Wood is >> brittle and will not dent or fail partially. Wooden rim failures >> usually result in wheel collapse and dangerous splinters. Moisture >> causes wooden rims to distort and lose spoke tension and makes >> repeated truing necessary. Low thermal conductivity keeps wooden >> rims from absorbing braking heat and causes brake pads to burn away >> rapidly. In addition, wooden rims require greater braking force >> than metal rims because high temperatures soften the brake pads and >> reduce their coefficient of friction."
>> "WOOD-FILLED RIMS FOR TUBULAR TIRES"
>> "Wood-filled rims have followed wooden rims into history, and the >> tubular tires that were mounted on them are likely to disappear >> next. Instead of sockets or washers, these rims use wooden filler >> pieces inside the hollow aluminum alloy rims. These pieces >> distribute the load to both surfaces of the rim as steel sockets do >> and require much smaller holes in the rim. Because the holes need >> be only large enough to accept nipple shafts, less material is lost >> from the rim. Because little material is lost, these rims can have >> thinner walls with the same strength as heavier rims. Although >> wood-filled rims are extremely light, they have the disadvantage of >> losing tension when the wood compresses under spoke nipple pressure >> aggravated by the effects of moisture. Loss of tension causes the >> wheel to lose both alignment and strength."
>> "Wood-filled rims present other problems. The nipples cannot swivel >> in the rim to accommodate the different spoke angles produced by >> different spoke patterns. Therefore, spokes may bend excessively >> at the nipple. The holes must be drilled in the rim at angles to >> match a specific spoke pattern. Wood rims and wood-filled rims >> require long nipples. They must reach from the bed of the tire >> through the rim to expose flanks that can be engaged by a spoke >> wrench. Long nipples make wheel truing difficult because they often >> bind while being turned, and they weigh more then standard nipples."
>> --3rd edition 1993
>> Cheers,
>I think you just showed that no load and strength calculations of >wheels are made in the book. However, you seem to go into publishing >unrelated parts of the book as in copyright infringement.
>So what makes you so testy of late?
>Jobst Brandt
Dear Jobst,
Please quote something from that post that I wrote that was testy.
You stated that there are no loads calculated in your book, so I quoted passages like this one, where you seemed to be doing calculations involving loads and strength:
"If its spokes are tensioned to 1000 N, a 36-spoke wheel will support approximately 400 kg."
--3rd edition
As for copyright infringement, I hope that you know more about engineering than you do about the fair use laws.
It's curious that so many posters make claims about what a text says without quoting it.
Ben C wrote: > On 2007-10-03, jobst.bra...@stanfordalumni.org <jobst.bra...@stanfordalumni.org> wrote: >> carlfo...@comcast.net writes: > [...] >>> overloads occur often, the nipples of slack spokes can unscrew, >>> reducing tension to affect both wheel alignment and strength." > [...] >> I think you just showed that no load and strength calculations of >> wheels are made in the book.
> Perhaps you can help clarify this point then.
> What does "strength" mean? Technically we know it means breaking stress. > Can it also be used of a structure, as opposed to of a material, to mean > the force (or stress?) at which the structure collapses, even if > collapsing doesn't involve anything breaking, and might not even involve > anything even yielding?
> If it can, then it's correct to say in that sense that high spoke > tension increases strength. If it can't, then it's not correct-- high > spoke tension doesn't change the breaking stress of any of the > components in the wheel. I think that's jim beam's point. Since his > expertise is in materials he naturally takes "strength" to mean > "breaking stress".
Have you ever seen a "broken" wheel? That is, a wheel broken from excessive load?
A wheel will break two ways, flat spotting (denting) the rim and "tacoing". From Sheldon Brown's glossary:
-------------- Taco To bend a wheel so that it assumes a saddle shape. A Tacoed wheel is more than just out of true, it has bent far enough that the spokes have assumed a new equilibrium position and lost tension. Two spots, 180 degrees apart will be way off to the left, two other spots, halfway between, will be way off to the right. A tacoed wheel is also known as a "potato chipped" wheel.
First you have to convince yourself that higher spoke tension means better radial support. Consider the analogy of railroad tracks. When the rim deflects enough to slack the spoke, the spoke is out of the picture, you might as well remove it. This is like removing a railroad tie. As the wheel deforms more, more spokes become effectively removed, and a longer span of rim is unsupported, just like a span of railroad track. The combination of track and tie is much stiffer than track alone.
Now consider that the wheel is still under a great deal of circumferential compression. This is akin to putting the railroad track under longitudinal compression. As you remove ties, the railroad track will also want to spread (buckle).
A wheel "wants" to taco. If you keep increasing the spoke tension it eventually will. It is constrained from doing so by the lateral rim stiffness and the spoke tension. Imagine tensioning a wheel with no dish (removing the lateral spoke support), it will taco more readily. When you load a wheel radially enough to slacken spokes, the compression is still there and the wheel will want to taco. This is often aided by some lateral forces. Jumping a bike onto a less than straight wheel is the classic way to taco.
The railroad track analogy is technically accurate. Without spoke support, the wheel becomes more prone to both tacoing and denting.
Spokes, hubs and rims all operate in high cycle loading, meaning breaks (fractures) come from fatigue. There is no way you can normally overload these components to fracture. What happens in bicycle wheel failure is a structural failure, the rim just deforms, buckle, dent, or both.
High spoke tensions make for a strong wheel structure. The context is engineering, not metallurgy.
Ben C? writes: >>> overloads occur often, the nipples of slack spokes can unscrew, >>> reducing tension to affect both wheel alignment and strength." >> I think you just showed that no load and strength calculations of >> wheels are made in the book. > Perhaps you can help clarify this point then. > What does "strength" mean? Technically we know it means breaking > stress. Can it also be used of a structure, as opposed to of a > material, to mean the force (or stress?) at which the structure > collapses, even if collapsing doesn't involve anything breaking, and > might not even involve anything even yielding?
How much load the wheel can carry. Lets not get this confused with structural or engineering terms of materials.
> If it can, then it's correct to say in that sense that high spoke > tension increases strength. If it can't, then it's not correct-- > high spoke tension doesn't change the breaking stress of any of the > components in the wheel. I think that's jim beam's point. Since his > expertise is in materials he naturally takes "strength" to mean > "breaking stress".
You seem to jump to jb's aid at the drop of a suggestion. Forget it. he can insult great numbers of folks at a single bound... up up and away!
> Putting define:strength into Google retrieves this: > very general term that may be applied to a material or a structure. > In a material, strength refers to a level of stress at which there > is a significant change in the state of the material, eg, yielding > or rupture. In a structure, strength refers to a level of level of > loading which produces a significant change in the state of the > structure, eg, inelastic deformations, buckling, or collapse. > urban.arch.virginia.edu/~km6e/references/glossary/struc-glossary.html > So I think you're both right and this is another misunderstanding.
To assume this a misunderstanding leans toward the naive.
> Ben C wrote: [...] >> What does "strength" mean? Technically we know it means breaking stress. >> Can it also be used of a structure, as opposed to of a material, to mean >> the force (or stress?) at which the structure collapses, even if >> collapsing doesn't involve anything breaking, and might not even involve >> anything even yielding?
>> If it can, then it's correct to say in that sense that high spoke >> tension increases strength. If it can't, then it's not correct-- high >> spoke tension doesn't change the breaking stress of any of the >> components in the wheel. I think that's jim beam's point. Since his >> expertise is in materials he naturally takes "strength" to mean >> "breaking stress".
> Have you ever seen a "broken" wheel? That is, a wheel broken from > excessive load?
No. If you keep increasing the load I strongly suspect the wheel will buckle long before it breaks.
[...]
> First you have to convince yourself that higher spoke tension means > better radial support. Consider the analogy of railroad tracks. When the > rim deflects enough to slack the spoke, the spoke is out of the picture, > you might as well remove it. This is like removing a railroad tie. As > the wheel deforms more, more spokes become effectively removed, and a > longer span of rim is unsupported, just like a span of railroad track. > The combination of track and tie is much stiffer than track alone.
> Now consider that the wheel is still under a great deal of > circumferential compression. This is akin to putting the railroad track > under longitudinal compression. As you remove ties, the railroad track > will also want to spread (buckle).
With you so far.
> A wheel "wants" to taco.
I remember Michael Press mentioning something about this once. Is a tacoed wheel in a lower energy state than a true wheel, or is it a slightly higher energy state, but a local minimum?
If so you would need to put in a bit of energy to snap it into a taco (easily done when you hit a bump etc.) but once it starts to go, it will "want" to sink towards the local minimum of a taco shape.
> If you keep increasing the spoke tension it > eventually will. It is constrained from doing so by the lateral rim > stiffness and the spoke tension. Imagine tensioning a wheel with no dish > (removing the lateral spoke support), it will taco more readily.
By "with no dish" do you mean using a hypothetical hub in which both the flanges were right next to each other and in the centre of the wheel? In other words, not just no dish in the sense that a normal front wheel has no dish, but no bracing?
[...]
> Spokes, hubs and rims all operate in high cycle loading, meaning breaks > (fractures) come from fatigue. There is no way you can normally overload > these components to fracture. What happens in bicycle wheel failure is a > structural failure, the rim just deforms, buckle, dent, or both.
Agreed.
> High spoke tensions make for a strong wheel structure. The context is > engineering, not metallurgy.
Fair enough.
So, does a stiffer rim with rather looser spokes produce a wheel that's less prone to buckling? What if the build isn't that great and the tension is a bit uneven-- is the stiffer rim combination more tolerant of that? It seems like the bendy rim with lots of tight spokes and uneven tension could be a taco waiting to happen.
I also wonder if it might be easier to achieve even tension with a lower spoke count, since the low-spoke-count wheel is less over-constrained: uneven tension means out-of-true and therefore easily corrected when the wheel is built.
> Peter Cole wrote: > > jim beam wrote: > >> Tom "Johnny Sunset" Sherman wrote: > >>> "jim beam" aka evan williams wrote: > >>>> Ryan Cousineau wrote: > >>>>> ... > >>>>> I make no submission on most bike design books, but regular > >>>>> contributor here Jobst Brandt literally wrote the book
> >>>> /a/ book.
> >>>>> on bicycle wheels, called "The Bicycle Wheel," and it covers both > >>>>> the theory of wheels and the proper procedure for wheelbuilding.
> >>>> procedure, yes. theory? some of it is badly awry. spoke tension > >>>> "as high as the rim can bear" for example is based on a fundamental > >>>> misunderstanding by the author and that is of the most practical > >>>> [and costly] consequence to the novice builder - excess tension can > >>>> cause a higher propensity for rim buckling and directly cause rim > >>>> cracking. the book should should be amended to specify spoke > >>>> tension "as determined by the rim manufacturer".
> >>> I wonder if "jim" has a macro for anti-Jobst replies?
> >> that's "corrective", not "anti-jobst".
> > Who do you think you are fooling?
> why are you so fucking argumentative?
> jb: "the sky is blue" > pc: "liar!"
At midnight? The sky is definitely not blue. When raining, the sky is not blue. When overcast, the sky is not blue.
"The sky is blue". What is the sky? Is it an object to be taken into a laboratory? Is it an object at all? What do we mean when we say "is"?
When I step out into the open air and look upward, sometimes I observe a blue field.
> spikenett...@earthlink.net wrote: > > On Oct 1, 11:03 pm, jim beam <spamvor...@bad.example.net> wrote: > >> spikenett...@earthlink.net wrote:
> >> <snip for brevity>
> >>> It would be nice if there was a single, easy, and all encompassing > >>> answer to the question: What's The Proper Tension? But, such an answer > >>> is not possible; the situation does not allow for it. > >> that's absolutely untrue. if a manufacturer does the testing necessary, > >> then publishes their findings in the form of a spoke tension spec, that > >> /is/ "Proper Tension".
> >>> The author of > >>> course knows this, and so doesn't provide such an answer. > >> no, the author doesn't understand that strength is not increased by > >> increasing spoke tension. and he doesn't understand the nature of the > >> materials.
> >> he's even confused about what he's witnessing with his "finite element" > >> load calculation. all he's seeing is deformation of an elastic rim > >> causing a change in spoke tension where the deformation is - a perfectly > >> rigid rim would not deform there and so spoke tension figures would be > >> completely different, leading of course to a completely different > >> conclusion and therefore wheel theory.
> >>> A few > >>> readers, I imagine, are disappointed. Bizarrely, one individual > >>> gives the author an answer and then says he is wrong. > >> you mean that i disagree with the theoretical arguments? yes i do. and > >> for the reasons i've explained. you may want to dispute them, in which > >> case, feel free to present your own technical reasoning, but don't just > >> say it's wrong because you don't understand or don't want to know.
> > <snip for brevity>
> >>> It would be nice if there was a single, easy, and all encompassing > >>> answer to the question: What's The Proper Tension? But, such an answer > >>> is not possible; the situation does not allow for it.
> >> that's absolutely untrue.
> > Really? Very glad to hear this; it makes things much simpler. Tell me > > then, what is this single universal proper tension for all rims and > > wheel systems? Is it 17.5 Kgf or maybe it's 175Kgf? Or is it some > > other intermediate?
> er, how long is a piece of sting spike? tell me the single universal > length of all strings and string systems!
> > And if there is no universal single value, then what is the single > > easy method that one can use that is all encompassing, unlike Brandt's > > stress relief method which he restricts to classic wheels?
> there is no single value!!! it's empirically determined and depends on > the rim material, dimensions, etc. if all rims were identical, then > maybe there would be a single tension. but there isn't, so...
> > What is > > the single easy method that applies not only to classic wheels but to > > all types of rims in all types of wheel systems? Please let us know, > > unless of course you're saving this revelation for /your/ book?
> see above.
> >> if a manufacturer does the testing necessary, > >> then publishes their findings in the form of a spoke tension spec, that > >> /is/ "Proper Tension".
> > Obviously it's the manufactures' proper tension. Once again you are > > displaying your penchant for stating something that is obvious as if > > you are imparting new knowledge.
> if it's so "obvious" why is it not stated in any books, "faq"'s or even > mentioned in /your/ contributions on this subject?
> > Nothing precludes a reader of Brandt's book from acknowledging and > > using manufacturers' values -- when they are available and reliable > > -- except their own total lack of common sense and intellectual > > honesty.
> eh???
> > Admittedly the author my have erred by not anticipating this > > pathology in a few readers, but then presumably he was writing the > > book for those he assumed where actually interested in understanding > > the principles of bicycle wheels and building them.
> strange statement from one so curiously uninterested in "obvious" facts > and ensuring they're actually disseminated.
Last Monday I said:
>> It would be nice if there was a single, easy, and all encompassing >> answer to the question: What's The Proper Tension? But, such an answer >> is not possible; the situation does not allow for it.
To which you replied:
>that's absolutely untrue.
But then, the very next day, you agreed, posting::
>there is no single value!!! it's empirically determined and depends on >the rim material, dimensions, etc. if all rims were identical, then >maybe there would be a single tension. but there isn't, so...
Frankly, this lack of coherence from one day to the next has me concerned. There seems to be even more than a total lack of common sense and intellectual honesty going on here.
Later, in this same post you also said 'eh???':
>> Nothing precludes a reader of Brandt's book from acknowledging and >> using manufacturers' values -- when they are available and reliable >> -- except their own total lack of common sense and intellectual >> honesty. >eh??? >> Admittedly the author may have erred by not anticipating this >> pathology in a few readers, but then presumably he was writing the >> book for those he assumed where actually interested in understanding >> the principles of bicycle wheels and building them.
You say 'eh' a lot I've noticed. But you have to say more than just "eh' to address valid points. Expletives, incidentally, don't work for you either.
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