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24-04.-2004, 03:42 AM
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#1 |
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Is corrosion stress the biggest cause of part failures?
One of my enemies broke the head off a bolt that mounts the rear rack
on the seat stays this bolt is under a lot less stress than the one on the dropout. Non stainless steel spokes will often break at the nipple when you try to true them. Several people have told me that non stainless steel spokes are stronger than stainless steel spokes one of them was Gary Fischer. |
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24-04.-2004, 04:42 AM
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#2 |
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Re: Is corrosion stress the biggest cause of part failures?
charles ramsey wrote:
> One of my enemies broke the head off a bolt that mounts the rear rack > on the seat stays this bolt is under a lot less stress than the one on > the dropout. Non stainless steel spokes will often break at the nipple > when you try to true them. Several people have told me that non > stainless steel spokes are stronger than stainless steel spokes one of > them was Gary Fischer. I believe a new "rustless" spoke is stronger in terms of ultimate tensile stress than a stainless spoke, but in the real world (and my own experience) they break more often. |
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24-04.-2004, 05:19 AM
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#3 |
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Re: Is corrosion stress the biggest cause of part failures?
On 23 Apr 2004 11:42:56 -0700, currentresident@veloemail.com (charles
ramsey) may have said: >One of my enemies broke the head off a bolt that mounts the rear rack >on the seat stays this bolt is under a lot less stress than the one on >the dropout. Non stainless steel spokes will often break at the nipple >when you try to true them. Several people have told me that non >stainless steel spokes are stronger than stainless steel spokes one of >them was Gary Fischer. In my experience, corrosion is not the major cause of fastener breakage. I find that it's about equally due to the presence of underspec hardware and due to installer error. In the majority of cases that I've seen, corrosion only comes into the picture in older units that have been left out in the rain a lot. Broken spokes, on the other hand, usually can be traced to lack of oil on the threads when assembled, often coupled with or perhaps aggravated by the use of aluminum nipples. Brass nipples don't seem to sieze onto the threads as much as aluminum, at least not for me. -- My email address is antispammed; pull WEEDS if replying via e-mail. Typoes are not a bug, they're a feature. Words processed in a facility that contains nuts. |
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24-04.-2004, 05:31 AM
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#4 |
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Re: Is corrosion stress the biggest cause of part failures?
Charles Ramsey writes:
> One of my enemies broke the head off a bolt that mounts the rear > rack on the seat stays this bolt is under a lot less stress than the > one on the dropout. Non stainless steel spokes will often break at > the nipple when you try to true them. Several people have told me > that non stainless steel spokes are stronger than stainless steel > spokes one of them was Gary Fischer. Such failures are fatigue failures and just happen to break when you apply torque with a wrench. Any advantage you might find in non-stainless spokes is undone by their corrosion. It is not the corrosion itself but the locking of the thread in the nipple that makes this a poor choice. Besides, spokes are not highly stressed except by residual stresses that are left over from manufacture and especially from wheel building. That is why stress relieving after building is one of the most important operations for a durable wheel. Jobst Brandt jobst.brandt@stanfordalumni.org |
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24-04.-2004, 06:24 AM
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#5 |
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Re: Is corrosion stress the biggest cause of part failures?
In article <g2fic.7787$Fo4.96752@typhoon.sonic.net>,
<jobst.brandt@stanfordalumni.org> wrote: >Charles Ramsey writes: > >> One of my enemies broke the head off a bolt that mounts the rear >> rack on the seat stays this bolt is under a lot less stress than the >> one on the dropout. Non stainless steel spokes will often break at >> the nipple when you try to true them. Several people have told me >> that non stainless steel spokes are stronger than stainless steel >> spokes one of them was Gary Fischer. > >Such failures are fatigue failures and just happen to break when you >apply torque with a wrench. Any advantage you might find in >non-stainless spokes is undone by their corrosion. It is not the >corrosion itself but the locking of the thread in the nipple that >makes this a poor choice. I bought a used Powertap wheel (DT stainless spokes) last year which I found out afterwards had been built with copious green Loctite. Just like a rusty zinc spoke! Unfortunately when the wheel needed work I moved a few nipples which resulted in breakage where the threads begin, several weeks later. If I had realized what I was up against I would have heated them, hindsight... |
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24-04.-2004, 11:06 AM
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#6 |
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Re: Is corrosion stress the biggest cause of part failures?
charles ramsey wrote:
> One of my enemies broke the head off a bolt that mounts the rear rack > on the seat stays this bolt is under a lot less stress than the one on > the dropout. Non stainless steel spokes will often break at the nipple > when you try to true them. Several people have told me that non > stainless steel spokes are stronger than stainless steel spokes one of > them was Gary Fischer. From what I can gather, Stainless Steel does not have a particularly high 'Shear Stress' capability compared to other metals, but I'm guessing that spokes are not subjected to 'Shearing' forces as much as 'stretching' (definitely guessing tho) . Stainless fasteners should still be strong enough for any Cycling related task anyhow, and I always try to use it, always with some type of thread lubricant. Stainless has a tendency to 'bind up' when rubbing against other stainless, such as when a stainless bolt is used with a stainless nut and then over tightened. |
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24-04.-2004, 11:30 AM
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#7 |
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Re: Is corrosion stress the biggest cause of part failures?
On Fri, 23 Apr 2004 20:19:17 GMT, Werehatrack
<rault00@earthWEEDSlink.net> may have said: >Broken spokes, on the other hand, usually can be traced to lack of oil >on the threads when assembled, often coupled with or perhaps >aggravated by the use of aluminum nipples. Brass nipples don't seem >to sieze onto the threads as much as aluminum, at least not for me. I should have said "Spoke breakage which occurs only after the nipple is turned...". Spokes that break in service are mostly due to lack of stress relief, sometimes due to damage caused by abrasion or impact with foreign objects, and only infrequently due to other causes such as crummy spokes, action of ex-wife's diagonal cutters, attempt at "repair" by bored urchins, etc. -- My email address is antispammed; pull WEEDS if replying via e-mail. Typoes are not a bug, they're a feature. Words processed in a facility that contains nuts. |
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24-04.-2004, 02:13 PM
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#8 |
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Re: Is corrosion stress the biggest cause of part failures?
is corrosion stress a common cause? depends where you live. corrosion
stress is something like where rust expands and bursts a pipe. is stress corrosion a common cause? not common for stainless spokes in normal bike riding environments. do spokes often break at the nipple? in my experience, not anywhere near as often as they break at the elbow. are steel spokes stronger than stainless? depends what you mean by "stronger". if you mean fatigue, high tensile materials like these will not have a fatigue endurance limit, regardless of whether they're stainless or steel, so they are not necessarily "stronger" in that respect. fatigue resistance in modern spokes is much more a function of using clean [vacuum degassed] steels and paying attention to surface quality than anything else. if you mean stronger in terms of modulus, steel is marginally "stronger" than stainless. if you mean stronger in terms of ultimate tensile strength, again, steel is marginally stronger than stainless, but not so you'd really notice in practice. why did the bolt head break? probably fatigue. if the bolt head was not sufficiently radiussed where it transitions from the shaft to the head, it'll be a prime fatigue candidate under load. if your "enemy" wants to avoid this failure in future, have them try a machine screw rather than a cheap bolt. typically a much better design. charles ramsey wrote: > One of my enemies broke the head off a bolt that mounts the rear rack > on the seat stays this bolt is under a lot less stress than the one on > the dropout. Non stainless steel spokes will often break at the nipple > when you try to true them. Several people have told me that non > stainless steel spokes are stronger than stainless steel spokes one of > them was Gary Fischer. |
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