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#41
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MA3 rim failure, where to now
On Wed, 10 Sep, Just zis Guy, you know? wrote:
It is not reasonable, because it fails to explain the observed fact that with the spokes on which the hub stands removed, the hub remains supported, No it doesn't. The wheel collapses. regards, Ian SMith -- |\ /| no .sig |o o| |/ \| |
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#42
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MA3 rim failure, where to now
In article ,
"Pete Biggs" wrote: Ted Bennett wrote: If it hangs from the top, then the tension in the top spoke would increase with load. But it doesn't; the tension in the lower spoke decreases. A simple test, plucking a few spokes, may help convince you. That alone doesn't convince me because rim deformation may be responsible for the decrease in tension in the lower spokes (for all I know). Yes, that is exactly how it works. A the rim, across span of about 4 spokes, flexes slightly towards the hub, which in turn causes a reduction in the tension of those spokes. The tension in the rest of the spokes may be increasing for all I can tell by plucking the spokes because the load could be spread over so many spokes (not just those right at the top) that the change in pitch is not enough to notice by ear. Unless you are tone deaf, you'd hear the change if the tension was rising enough to hold up the load by hanging off the top spokes. Tiny changes in tension create audible chanes in frequency- any guitar player can demonstrate this for you easily. That's not to say that I'm convinced the rim hangs from the top, just that you need better arguments. This has been discussed ad nauseum in hundreds of threads and thousands of posts over the past 10 years at least. This discussion has been settled, much like the discussion of whether the Earth is round has been settled. |
#43
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MA3 rim failure, where to now
Java Man (Espressopithecus) writes:
In article , bikerider@- nospam-thanks-rogers.com says... So the spokes are compressed. This is understood by analyzing the changes in loading rather than absolute loads. But it is confusing to many non-technical people. The spokes at the bottom of a loaded bicycle wheel are "compressed" relative to their unloaded condition, but are not "in compression". If they aren't in compression, they aren't compressed, they're just less extended. Nor are they compressed wrt their unloaded condition. When the wheel was built they were extended wrt their unloaded condition, and they will remain so until either they break or the integrity of the wheel is destroyed. The spokes remain in tension--the net axial force acting on the spokes is tensile, not compressive. Exactly. -- (Simon Brooke) http://www.jasmine.org.uk/~simon/ 'Victories are not solutions.' ;; John Hume, Northern Irish politician, on Radio Scotland 1/2/95 ;; Nobel Peace Prize laureate 1998; few have deserved it so much |
#45
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MA3 rim failure, where to now
"Ian Smith" wrote in message ... On Wed, 10 Sep 2003, Simon Brooke wrote: Some stuff that's so badly wrong I have trouble believing he actually meant it. However, just in case he believes what he wrote, I'll go through it slowly... Does the following quote from Simon Brooke help? "It simply amuses me to take the **** out of people who will earnestly argue that their particular form of words is 'right' and everyone else (even when they describe exactly the same phenomenon) is 'wrong'." |
#46
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MA3 rim failure, where to now
Ian Smith writes:
On Wed, 10 Sep 2003, Simon Brooke wrote: Consider a tug of war. Two teams heave on a rope, and the hankerchief stays over the line, because each team is heaving equally hard. Now suppose the North team go off and get a beer. Their end of the rope goes slack, and the handkerchief moves. Is this because the North team are doing more work? That is your argument. Sorry, no. My argument is that the north team pulls less hard, and teh handkerchief moves. Which team caused teh handkerchief to move? You're saying the south team did, but they are doing nothing different, so it's not sensible (by cause and effect) to say they caused teh change. The South team _do_ cause the change. That's simply an observable fact, and no amount of distortion of reality can alter it. They are still doing work, whereas the North team are driking beer. If the South team had dropped the rope at the same time the North team did, the handkerchief would not move. -- (Simon Brooke) http://www.jasmine.org.uk/~simon/ 'Victories are not solutions.' ;; John Hume, Northern Irish politician, on Radio Scotland 1/2/95 ;; Nobel Peace Prize laureate 1998; few have deserved it so much |
#47
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MA3 rim failure, where to now
wrote:
David Damerell writes: I think you (and many other people) are missing the fact that Simon (and Guy) are disputing the terminology only. No-one is claiming anything other than that there is a tension change in the bottom spokes. Because this is not a semantic difference but a technical one, No. There is potential for a technical disagreement as to which spokes actually show a change in tension, but that is not the disagreement here. The discussion is purely about the semantics used to describe what everyone agrees happens. -- David Damerell Kill the tomato! |
#48
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MA3 rim failure, where to now
"Ian Smith" wrote in message
... You are saying the effect of a large stress change is caused by nothing happening. Nope, I'm saying it's due to the coincidental deformation of a rim which is not inifinitely rigid. Meanwhile, no stress change is caused by the spokes carrying teh weight applied to the wheel. Nope, "no stress change" is caused by that part of the rim not deflecting. -- Guy === WARNING: may contain traces of irony. Contents may settle after posting. http://www.chapmancentral.com |
#49
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MA3 rim failure, where to now
"Java Man (Espressopithecus)" wrote in message
ble.net... The methaphor "standing on its spokes" is illustrative but does not fully explain the phenomenon. That is the problem. It is worse than that: it is actively misleading. Consider a more rigid rim. Suddenly the change in tension in the lower spokes is significantly reduced. So on wheels with more rigid rims the hub doesn't stand quite so hard on the bottom spokes, raising two questions: (a) is "stand" meaningful if the degree of "standingness" is dependent on the rim rigidity not the mass applied at the hub and (b) what happens to the component of the mass which is no longer "standing" on the bottom spokes as a result? Is some of that now hanging from the upper spokes? IOW, the "stand" terminology raises more questions than it answers. The wheel is supported by the spoke nipples pushing on the rim, I say... -- Guy === WARNING: may contain traces of irony. Contents may settle after posting. http://www.chapmancentral.com |
#50
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MA3 rim failure, where to now
"Ian Smith" wrote in message
... Actually, they elongate at teh bottom - alongside teh contact patch. In fact, the greatest elongation is in the lower half of the wheel. They have a negative modulus then? -- Guy === WARNING: may contain traces of irony. Contents may settle after posting. http://www.chapmancentral.com |
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