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#31
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Cup & Cone Bottom Brackets - Any Sources?
On 2008-04-01, Jay Beattie wrote:
On Mar 31, 5:10*pm, John Thompson wrote: On 2008-03-31, Tom Sherman wrote: John Thompson wrote: How do you "wear out" a frame? Damage, yes -- either through neglect or abuse, or what have you. But "wear out?" Corrosion (metal frames), I'd file that under "neglect." fatigue (metal and composite) Not an issue with a properly designed steel frame, but certainly a potential issue with aluminum. I'm not aware of composites having fatigue failures, but I may just be ignorant on that point. and degradation of epoxy and adhesives (composite). Disposable frames, then. I'll stick with steel, thank you. Steel as a material has an infinite fatigue life with the loads applied by whimpy cyclists, but as actually used in bicycle frames, it does not -- at least based on my experience. I think what Jim was saying was only some kinds of steel have an infinite fatigue life (or "no endurance limit"). I think it's mild steel that does. So maybe a $60 Roadmaster Fury has an infinite fatigue life below some load. If so someone should tell their marketing department. The steel used for decent bikes is different alloys, with cleverly-designed impurities in it (and maybe more carbon?) which make it stronger but mean it does fatigue eventually just like aluminium, whatever the load. You might think "no endurance limit" meant "endures forever", but it doesn't, it means "no stress below which you don't get any fatigue". |
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#32
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Cup & Cone Bottom Brackets - Any Sources?
In article ,
jim beam wrote: Michael Press wrote: In article , still just me wrote: On Fri, 28 Mar 2008 22:28:35 -0700, jim beam wrote: otoh, by not simply replacing a worn out frame, you're deliberately avoiding bothering to research improvements in frame design such as over-size tube which help mitigate shimmy. or aluminum. or carbon. as someone that like to express opinion on these materials, the least you should do is bother to actually use them. otooh, but fixing a frame that is otherwise still serviceable he not only avoids wasting resources but keeps a valued old friend by his side for years to come. Not everyone buys into the throwaway world or has to always run with the supposedly latest and greatest. Of course, since you're goal wasn't really to comment intelligently on the thread, but instead just to flame Jobst, I guess that's irrelevant. jim beam is a salesman in the `real world.' gosh, the terrible things bored people will say when having a slow day. only 3,418,427 unread web pages between you and being able to not be a schmuck in public. Is it something I said? -- Michael Press |
#33
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Cup & Cone Bottom Brackets - Any Sources?
John Thompson wrote:
Steel as a material has an infinite fatigue life with the loads applied by whimpy cyclists, but as actually used in bicycle frames, it does not -- at least based on my experience. I have cracked a number of steel frames -- probably due to overheating of the lugs or some other glitch in fabrication. My longest surviving high mileage frame is a 1986 Cannondale T1000. That's old school aluminum. I am not so sure about the new stuff. My oldest frames are a couple of steel Atalas from the early 70s (1970 and 1972). The older one is built up as my daily commuting bike, the other is a fixed gear I ride 100 or so miles a week spring through autumn. The older Atala failed at the BB/seat tube joint 20 some years ago, probably due to a cheap pressed BB shell. The failure was a crack that extended all the way around the base of the seat tube socket. The seat tube itself was not involved, so I was able to sweat the old shell off and braze in a nice investment cast shell to replace it. It's been going strong ever since. Well that still doesn't answer the question about how many miles "old" the bicycle is. I generally ride 10,000 miles per year according to my odometer, so a 20 year old frame has some significant miles on it. The only frame fatigue failures I have experienced were with Cinelli style (sloping) fork crowns that typically have internal lugs that cannot be feathered at the transition to the fork blades. They broke exactly where the fork crown ended in the fork blade. Since then I have stayed away from such forks that seem to have taken over nearly all major brands that used brazed fork crowns. Too bad. It was a stylishly bad mechanical design. Other than that, I had plenty of crank fatigue failures, about one every year or more until I modified that interface to a more reasonable design, of a tapered conical seat instead of the fretting flat faced pedal axle that augers itself into the crank until failure. Since modification I have ridden Shimano cranks from that era but with modification and haven't had a failure since. Jobst Brandt |
#34
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Cup & Cone Bottom Brackets - Any Sources?
Michael Press wrote:
In article , jim beam wrote: Michael Press wrote: In article , still just me wrote: On Fri, 28 Mar 2008 22:28:35 -0700, jim beam wrote: otoh, by not simply replacing a worn out frame, you're deliberately avoiding bothering to research improvements in frame design such as over-size tube which help mitigate shimmy. or aluminum. or carbon. as someone that like to express opinion on these materials, the least you should do is bother to actually use them. otooh, but fixing a frame that is otherwise still serviceable he not only avoids wasting resources but keeps a valued old friend by his side for years to come. Not everyone buys into the throwaway world or has to always run with the supposedly latest and greatest. Of course, since you're goal wasn't really to comment intelligently on the thread, but instead just to flame Jobst, I guess that's irrelevant. jim beam is a salesman in the `real world.' gosh, the terrible things bored people will say when having a slow day. only 3,418,427 unread web pages between you and being able to not be a schmuck in public. Is it something I said? yes, you said a great deal. 1. that you're bored. 2. that you regard try picking a fight as somehow entertaining. 3. that you hold your employers time in contempt since you're posting during the hours they pay you to be doing other things. 4. that you have no guilt for making negative or false presumption. 5. that you have no guilt for using presumption to provoke. [see point 4 above.] 6. that you need no provocation yourself. 7. that you're so slow-witted that it takes you the better part of a day to think up a response when your provocation gets a reaction. i could go on, but further analysis of something best summarized as "schmuck" is boring. |
#35
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Cup & Cone Bottom Brackets - Any Sources?
John Thompson wrote:
On 2008-04-01, jim beam wrote: still just me wrote: but fixing a frame that is otherwise still serviceable he not only avoids wasting resources but keeps a valued old friend by his side for years to come. nonsensical claptrap. How so? It makes sense to me. i really don't give a flying one about who says what. i state the facts. repairing an old frame with known flaws is a failed opportunity to gain first hand experience of improvements that have occurred in the last 3+ decades of frame design and manufacture. For a top notch racer that might be an issue. But for most riders and bikes, the improvements in frame design and manufacturing of the last several decades are much less compelling. And I suspect many more people fall into the latter category than the former. most anyone can achieve sufficient speed downhill to experience shimmy on a large frame steel tube bike. small frame users may not view this as a concern since their frames don't have this problem as frequently, but those of us that use big frames find this to be a big deal. and it's one easily solved on modern frames with big tubes and thus higher torsional stiffness. i think that to dismiss this as "much less compelling" is failure to understand the issue, and more, inability to understand how easily it is solved. |
#36
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Cup & Cone Bottom Brackets - Any Sources?
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#37
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Cup & Cone Bottom Brackets - Any Sources?
Ben C wrote:
On 2008-04-01, Jay Beattie wrote: On Mar 31, 5:10�pm, John Thompson wrote: On 2008-03-31, Tom Sherman wrote: John Thompson wrote: How do you "wear out" a frame? Damage, yes -- either through neglect or abuse, or what have you. But "wear out?" Corrosion (metal frames), I'd file that under "neglect." fatigue (metal and composite) Not an issue with a properly designed steel frame, but certainly a potential issue with aluminum. I'm not aware of composites having fatigue failures, but I may just be ignorant on that point. and degradation of epoxy and adhesives (composite). Disposable frames, then. I'll stick with steel, thank you. Steel as a material has an infinite fatigue life with the loads applied by whimpy cyclists, but as actually used in bicycle frames, it does not -- at least based on my experience. I think what Jim was saying was only some kinds of steel have an infinite fatigue life (or "no endurance limit"). that's muddled. an endurance limit is where infinite fatigue life is demonstrated. I think it's mild steel that does. correct. So maybe a $60 Roadmaster Fury has an infinite fatigue life below some load. If so someone should tell their marketing department. The steel used for decent bikes is different alloys, with cleverly-designed impurities in it (and maybe more carbon?) which make it stronger but mean it does fatigue eventually just like aluminium, whatever the load. correct. You might think "no endurance limit" meant "endures forever", but it doesn't, it means "no stress below which you don't get any fatigue". endurance limit, is the maximum cyclical load at which you can still achieve infinite fatigue life. |
#38
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Cup & Cone Bottom Brackets - Any Sources?
On 2008-04-02, jim beam wrote:
Ben C wrote: On 2008-04-01, Jay Beattie wrote: On Mar 31, 5:10?pm, John Thompson wrote: On 2008-03-31, Tom Sherman wrote: John Thompson wrote: How do you "wear out" a frame? Damage, yes -- either through neglect or abuse, or what have you. But "wear out?" Corrosion (metal frames), I'd file that under "neglect." fatigue (metal and composite) Not an issue with a properly designed steel frame, but certainly a potential issue with aluminum. I'm not aware of composites having fatigue failures, but I may just be ignorant on that point. and degradation of epoxy and adhesives (composite). Disposable frames, then. I'll stick with steel, thank you. Steel as a material has an infinite fatigue life with the loads applied by whimpy cyclists, but as actually used in bicycle frames, it does not -- at least based on my experience. I think what Jim was saying was only some kinds of steel have an infinite fatigue life (or "no endurance limit"). that's muddled. Correct. I always get that muddled. an endurance limit is where infinite fatigue life is demonstrated. I think it's mild steel that does. correct. So maybe a $60 Roadmaster Fury has an infinite fatigue life below some load. If so someone should tell their marketing department. The steel used for decent bikes is different alloys, with cleverly-designed impurities in it (and maybe more carbon?) which make it stronger but mean it does fatigue eventually just like aluminium, whatever the load. correct. You might think "no endurance limit" meant "endures forever", but it doesn't, it means "no stress below which you don't get any fatigue". endurance limit, is the maximum cyclical load at which you can still achieve infinite fatigue life. Yes, so if you have no endurance limit, then you can't have infinite fatigue life. |
#39
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Cup & Cone Bottom Brackets - Any Sources?
Ben C wrote:
On 2008-04-02, jim beam wrote: Ben C wrote: On 2008-04-01, Jay Beattie wrote: On Mar 31, 5:10?pm, John Thompson wrote: On 2008-03-31, Tom Sherman wrote: John Thompson wrote: How do you "wear out" a frame? Damage, yes -- either through neglect or abuse, or what have you. But "wear out?" Corrosion (metal frames), I'd file that under "neglect." fatigue (metal and composite) Not an issue with a properly designed steel frame, but certainly a potential issue with aluminum. I'm not aware of composites having fatigue failures, but I may just be ignorant on that point. and degradation of epoxy and adhesives (composite). Disposable frames, then. I'll stick with steel, thank you. Steel as a material has an infinite fatigue life with the loads applied by whimpy cyclists, but as actually used in bicycle frames, it does not -- at least based on my experience. I think what Jim was saying was only some kinds of steel have an infinite fatigue life (or "no endurance limit"). that's muddled. Correct. I always get that muddled. an endurance limit is where infinite fatigue life is demonstrated. I think it's mild steel that does. correct. So maybe a $60 Roadmaster Fury has an infinite fatigue life below some load. If so someone should tell their marketing department. The steel used for decent bikes is different alloys, with cleverly-designed impurities in it (and maybe more carbon?) which make it stronger but mean it does fatigue eventually just like aluminium, whatever the load. correct. You might think "no endurance limit" meant "endures forever", but it doesn't, it means "no stress below which you don't get any fatigue". endurance limit, is the maximum cyclical load at which you can still achieve infinite fatigue life. Yes, so if you have no endurance limit, then you can't have infinite fatigue life. correct. there is a mechanism for this too, it's not a random phenomenon. in low strength steel alloys, it's associated with solute carbon atoms being able to diffuse into the lattice voids of dislocations and "lock" them in place. [no dislocation movement, no fatigue.] in some titanium alloys, the same phenomenon exists with diffusing oxygen atoms. |
#40
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Cup & Cone Bottom Brackets - Any Sources?
In article ,
jim beam wrote: Michael Press wrote: In article , jim beam wrote: Michael Press wrote: In article , still just me wrote: On Fri, 28 Mar 2008 22:28:35 -0700, jim beam wrote: otoh, by not simply replacing a worn out frame, you're deliberately avoiding bothering to research improvements in frame design such as over-size tube which help mitigate shimmy. or aluminum. or carbon. as someone that like to express opinion on these materials, the least you should do is bother to actually use them. otooh, but fixing a frame that is otherwise still serviceable he not only avoids wasting resources but keeps a valued old friend by his side for years to come. Not everyone buys into the throwaway world or has to always run with the supposedly latest and greatest. Of course, since you're goal wasn't really to comment intelligently on the thread, but instead just to flame Jobst, I guess that's irrelevant. jim beam is a salesman in the `real world.' gosh, the terrible things bored people will say when having a slow day. only 3,418,427 unread web pages between you and being able to not be a schmuck in public. Is it something I said? yes, you said a great deal. 1. that you're bored. 2. that you regard try picking a fight as somehow entertaining. 3. that you hold your employers time in contempt since you're posting during the hours they pay you to be doing other things. 4. that you have no guilt for making negative or false presumption. 5. that you have no guilt for using presumption to provoke. [see point 4 above.] 6. that you need no provocation yourself. 7. that you're so slow-witted that it takes you the better part of a day to think up a response when your provocation gets a reaction. i could go on, but further analysis of something best summarized as "schmuck" is boring. But you are a salesman, so why all the howling? -- Michael Press |
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