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Scamdium strikes again!
http://weightweenies.starbike.com/ph...ic.php?t=19036
Aluminum BB axles are not a good material selection... -- Phil Lee, Squid |
#2
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Scamdium strikes again!
In article m,
"Phil Lee, Squid" wrote: http://weightweenies.starbike.com/ph...ic.php?t=19036 Aluminum BB axles are not a good material selection... No. Especially as the left side is more prone to breaking (subject to both torque and bending), and it will break under highest load which is while standing on it. Then you'll get dumped into the road, possibly right in front of a large motor vehicle. The only time I had this happen was in 1984 when I stood up at a stop sign to accelerate from a stop, snapped off the left side of the BB axle, and ended up on my ass in the road. Fortunately it was a low traffic side street. Gouged the heck out of my left ankle, too. |
#3
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Scamdium strikes again!
On Tue, 25 Jul 2006 08:50:30 -0500, Tim McNamara
wrote: In article m, "Phil Lee, Squid" wrote: http://weightweenies.starbike.com/ph...ic.php?t=19036 Aluminum BB axles are not a good material selection... No. Especially as the left side is more prone to breaking (subject to both torque and bending), and it will break under highest load which is Forgive the ignorance: does that apply to hollow axle, tapered square, XT b.brackets? If so, which are the ones not made of aluminum? TIA jbr |
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Scamdium strikes again!
BigBen wrote:
On Tue, 25 Jul 2006 08:50:30 -0500, Tim McNamara wrote: In article m, "Phil Lee, Squid" wrote: http://weightweenies.starbike.com/ph...ic.php?t=19036 Aluminum BB axles are not a good material selection... No. Especially as the left side is more prone to breaking (subject to both torque and bending), and it will break under highest load which is Forgive the ignorance: does that apply to hollow axle, tapered square, XT b.brackets? If so, which are the ones not made of aluminum? No major manufacturer makes or sells aluminum-axle bottom brackets. Your XT bottom bracket has a steel axle. If you look at the pictures, notice that the break does not traverse the 90-degree inner corner for most of the circumference, where one might expect it to break. Maybe the axle was notched during installation. -- Phil Lee, Squid |
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Scamdium strikes again!
Phil Lee, Squid wrote:
http://weightweenies.starbike.com/ph...ic.php?t=19036 Aluminum BB axles are not a good material selection... they're fine if they're dimensionally appropriate for the job. aluminum shimano axles anyone? the problem comes when you use the same size in aluminum as you do in steel given aluminum's much lower strength. presence of scandium in this situation is pretty much irrelevant. |
#7
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Scamdium strikes again!
jim beam wrote:
Phil Lee, Squid wrote: http://weightweenies.starbike.com/ph...ic.php?t=19036 Aluminum BB axles are not a good material selection... they're fine if they're dimensionally appropriate for the job. aluminum shimano axles anyone? the problem comes when you use the same size in aluminum as you do in steel given aluminum's much lower strength. presence of scandium in this situation is pretty much irrelevant. It was tongue in cheek, of course. I'm curious to know what proportion of high-mileage Ksyrium SSC SL riders get broken spokes compared to standard-spoke riders. -- Phil Lee, Squid |
#8
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Scamdium strikes again!
Phil Lee, Squid wrote:
jim beam wrote: Phil Lee, Squid wrote: http://weightweenies.starbike.com/ph...ic.php?t=19036 Aluminum BB axles are not a good material selection... they're fine if they're dimensionally appropriate for the job. aluminum shimano axles anyone? the problem comes when you use the same size in aluminum as you do in steel given aluminum's much lower strength. presence of scandium in this situation is pretty much irrelevant. It was tongue in cheek, of course. I'm curious to know what proportion of high-mileage Ksyrium SSC SL riders get broken spokes compared to standard-spoke riders. well, those spokes are 3x the size... interestingly, when those wheels first came out, it seemed like i'd see someone shipwrecked with a broken aluminum spoke once or twice a month. the last few years though, i can't say i've seen one. |
#9
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Scamdium strikes again!
jim beam wrote:
Phil Lee, Squid wrote: jim beam wrote: Phil Lee, Squid wrote: http://weightweenies.starbike.com/ph...ic.php?t=19036 Aluminum BB axles are not a good material selection... they're fine if they're dimensionally appropriate for the job. aluminum shimano axles anyone? the problem comes when you use the same size in aluminum as you do in steel given aluminum's much lower strength. presence of scandium in this situation is pretty much irrelevant. It was tongue in cheek, of course. I'm curious to know what proportion of high-mileage Ksyrium SSC SL riders get broken spokes compared to standard-spoke riders. well, those spokes are 3x the size... That's what I mean. However, with aluminum's lack of a fatigue limit... interestingly, when those wheels first came out, it seemed like i'd see someone shipwrecked with a broken aluminum spoke once or twice a month. the last few years though, i can't say i've seen one. The lack of a fatigue limit would almost ensure that higher-mileage wheels would have constant breakages, wouldn't it? Does the ball-and-socket method of the SSC SL spoke heads resist breakage better when compared to the J-bend of SS spokes? -- Phil Lee, Squid |
#10
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Scamdium strikes again!
Phil Lee, Squid wrote:
jim beam wrote: Phil Lee, Squid wrote: jim beam wrote: Phil Lee, Squid wrote: http://weightweenies.starbike.com/ph...ic.php?t=19036 Aluminum BB axles are not a good material selection... they're fine if they're dimensionally appropriate for the job. aluminum shimano axles anyone? the problem comes when you use the same size in aluminum as you do in steel given aluminum's much lower strength. presence of scandium in this situation is pretty much irrelevant. It was tongue in cheek, of course. I'm curious to know what proportion of high-mileage Ksyrium SSC SL riders get broken spokes compared to standard-spoke riders. well, those spokes are 3x the size... That's what I mean. However, with aluminum's lack of a fatigue limit... it has a definable fatigue limit, but not an endurance limit. stainless steel doesn't have an endurance limit either, so traditional spokes have no intrinsic advantage. interestingly, when those wheels first came out, it seemed like i'd see someone shipwrecked with a broken aluminum spoke once or twice a month. the last few years though, i can't say i've seen one. The lack of a fatigue limit would almost ensure that higher-mileage wheels would have constant breakages, wouldn't it? be careful of terminology. while there is a lot of confusion about which term describes what in certain quarters, where i came from, endurance limit describes the "knee" in the s-n graph of mild steel, while fatigue limit describes the stress level to survive an arbitrary number of stress cycles, say 10^7. it's the design, stress risers, material quality, etc., that determine fatigue life more than anything else, particularly once you get away from the simple alloys systems. don't be afraid of properly deployed aluminum alloys - aluminum alloy wings stay on planes for a good long time.... Does the ball-and-socket method of the SSC SL spoke heads resist breakage better when compared to the J-bend of SS spokes? in terms of design principle, yes it should do - no intrinsic bending. all the broken aluminum spokes i've ever seen have broken at the threaded end. |
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