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Odd spoke behavior
Never mind why, but I recently tortured some spokes.
I bent them at their midspans, stuck them in a vise with their free ends pointing straight up, and applied a propane torch to the bends. None of the spokes stood up to torture. Old, used, 2 mm carbon spokes curled up when heated. This bend _| became _\ when an old used spoke was heated. But a new, unused, 1.8 mm stainless steel spoke uncurled when heated. This bend _| became _/ when an unused ss spoke was heated. Is torture unreliable where spokes are concerned? Why does the same 90-degree bend respond differently to heat in the different spokes? Someone on RBT ought to know what's going on. Is it carbon plated versus stainless steel? Different thicknesses? Used versus unused? Something else that I'm too ignorant to think of? Here are some before and after diagrams and pictures. On the left is the used, plated, carbon 2 mm spoke. On the right is the unused stainless steel 1.8 mm spoke. bent heated c s c s | | \ / carbon | | carbon \ / ________| | ________\ / vise| | vise| / ____|_____| ____|_____/ stainless stainless The bent spokes stick up || like this: http://server5.theimagehosting.com/i...inlessbent.jpg After heating, they splay apart \/ like this: http://server5.theimagehosting.com/i...lessheated.jpg It's not an optical illusion. The pegboard and ruler are about a foot past the yellow hammer handle, and the yellow hammer handle is about a foot past the spokes in the vise: camera spokes hammer ruler-on-pegboard Cheers, Carl Fogel |
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#2
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Odd spoke behavior
wrote in message ... Never mind why, but I recently tortured some spokes. I bent them at their midspans, stuck them in a vise with their free ends pointing straight up, and applied a propane torch to the bends. None of the spokes stood up to torture. Old, used, 2 mm carbon spokes curled up when heated. This bend _| became _\ when an old used spoke was heated. But a new, unused, 1.8 mm stainless steel spoke uncurled when heated. This bend _| became _/ when an unused ss spoke was heated. Is torture unreliable where spokes are concerned? Why does the same 90-degree bend respond differently to heat in the different spokes? Someone on RBT ought to know what's going on. Is it carbon plated versus stainless steel? Different thicknesses? Used versus unused? Something else that I'm too ignorant to think of? Here are some before and after diagrams and pictures. On the left is the used, plated, carbon 2 mm spoke. On the right is the unused stainless steel 1.8 mm spoke. bent heated c s c s | | \ / carbon | | carbon \ / ________| | ________\ / vise| | vise| / ____|_____| ____|_____/ stainless stainless The bent spokes stick up || like this: http://server5.theimagehosting.com/i...inlessbent.jpg After heating, they splay apart \/ like this: http://server5.theimagehosting.com/i...inlessheated.j pg It's not an optical illusion. The pegboard and ruler are about a foot (snip) This is a classical example of bongification, a term I introduced to rbt many years ago. At the time, no one other wreck.bikers had even heard the word, to say nothing of actually comprehending. BB |
#4
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Odd spoke behavior
On Fri, 13 Oct 2006 08:53:24 -0700, jim beam
wrote: wrote: Never mind why, but I recently tortured some spokes. I bent them at their midspans, stuck them in a vise with their free ends pointing straight up, and applied a propane torch to the bends. None of the spokes stood up to torture. Old, used, 2 mm carbon spokes curled up when heated. This bend _| became _\ when an old used spoke was heated. But a new, unused, 1.8 mm stainless steel spoke uncurled when heated. This bend _| became _/ when an unused ss spoke was heated. Is torture unreliable where spokes are concerned? Why does the same 90-degree bend respond differently to heat in the different spokes? Someone on RBT ought to know what's going on. Is it carbon plated versus stainless steel? yes. Different thicknesses? to some degree. Used versus unused? no. Something else that I'm too ignorant to think of? Here are some before and after diagrams and pictures. On the left is the used, plated, carbon 2 mm spoke. On the right is the unused stainless steel 1.8 mm spoke. bent heated c s c s | | \ / carbon | | carbon \ / ________| | ________\ / vise| | vise| / ____|_____| ____|_____/ stainless stainless The bent spokes stick up || like this: http://server5.theimagehosting.com/i...inlessbent.jpg After heating, they splay apart \/ like this: http://server5.theimagehosting.com/i...lessheated.jpg It's not an optical illusion. The pegboard and ruler are about a foot past the yellow hammer handle, and the yellow hammer handle is about a foot past the spokes in the vise: camera spokes hammer ruler-on-pegboard Cheers, Carl Fogel i don't know the exact mechanism, but here are some thoughts: 1. residual stress. if there's a residual stress profile, as the material is heated towards yield [yield is temperature dependent as any blacksmith knows], then the portion that remains stressed can prevail in a tug-o-war over the portion that is not. 2. this is relatively simple situation with the stainless spoke as it remains in a largely austenitic phase both before and after heating. with a carbon steel however, heating will cause a phase transformation from ferritic to austenitic, two entirely different crystal structures, and i believe that will throw the cat among the pigeons regarding residual stress behavior - i don't know exactly how residual stress survives the phase change, if at all, and i don't know whether residual stress has any influence on exact temperature of transition, but i think you can be sure there is a thesis or two out there that will explain. what's really interesting carl is whether the pre-formed spoke elbows behave like this when heated. during manufacture, residual stress can be mechanically relieved by a small scale secondary operation that quickly follows the primary forming operation. if spokes leave the factory with residual stress, then your spoke elbows should evidence the same kinds of behavior when heated. if they leave the factory in a relieved condition, then they won't. Dear Jim, Both spokes start to bend almost as soon as the propane flame hits the bend, and keep bending in the same direction with more heat (curling up for the carbon, uncurling for the stainless steel). I've heated the straight section beyond the bend to a cheerful orange glow and then moved the glowing orange section slowly through the bend and into the straight section beyond. Checking spoke elbows was indeed my hope, but that would take very careful measurements and an understanding of why the hell obvious bends in the midspans curl or uncurl in different directions depending on whether they're used carbon 2 mm or unused 1.8 mm stainless. You can see in the pictures how little the angle of the 90-degree bend changes---the end of a 6-inch "needle" moves, but not dramatically. But there's no point in heating tiny spoke elbows when I haven't the faintest idea what monster 90 degree midspan bends are doing when I heat them. I expected that the bends might change to a different degree, due to different materials or different diameters, but I didn't expect the spokes to thumb their noses at me and curl and uncurl in completely different directions when I toasted their bends. It's a ridiculously simple test, so maybe other posters will try it and figure out something using different spokes. Just bend a spoke sideways, stick the spoke in a vise, and heat the bend with the flame from a soldering torch. The bending motion is visible, but it seems to go one way for carbon and the other way for stainless. If the spoke is heated enough, it loses so much of its strength that it becomes quite flexible, so sticking the free end straight up or down will reassure you that the heat is bending things, not gravity. Cheers, Carl Fogel |
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Odd spoke behavior
wrote:
On Fri, 13 Oct 2006 08:53:24 -0700, jim beam wrote: wrote: Never mind why, but I recently tortured some spokes. I bent them at their midspans, stuck them in a vise with their free ends pointing straight up, and applied a propane torch to the bends. None of the spokes stood up to torture. Old, used, 2 mm carbon spokes curled up when heated. This bend _| became _\ when an old used spoke was heated. But a new, unused, 1.8 mm stainless steel spoke uncurled when heated. This bend _| became _/ when an unused ss spoke was heated. Is torture unreliable where spokes are concerned? Why does the same 90-degree bend respond differently to heat in the different spokes? Someone on RBT ought to know what's going on. Is it carbon plated versus stainless steel? yes. Different thicknesses? to some degree. Used versus unused? no. Something else that I'm too ignorant to think of? Here are some before and after diagrams and pictures. On the left is the used, plated, carbon 2 mm spoke. On the right is the unused stainless steel 1.8 mm spoke. bent heated c s c s | | \ / carbon | | carbon \ / ________| | ________\ / vise| | vise| / ____|_____| ____|_____/ stainless stainless The bent spokes stick up || like this: http://server5.theimagehosting.com/i...inlessbent.jpg After heating, they splay apart \/ like this: http://server5.theimagehosting.com/i...lessheated.jpg It's not an optical illusion. The pegboard and ruler are about a foot past the yellow hammer handle, and the yellow hammer handle is about a foot past the spokes in the vise: camera spokes hammer ruler-on-pegboard Cheers, Carl Fogel i don't know the exact mechanism, but here are some thoughts: 1. residual stress. if there's a residual stress profile, as the material is heated towards yield [yield is temperature dependent as any blacksmith knows], then the portion that remains stressed can prevail in a tug-o-war over the portion that is not. 2. this is relatively simple situation with the stainless spoke as it remains in a largely austenitic phase both before and after heating. with a carbon steel however, heating will cause a phase transformation from ferritic to austenitic, two entirely different crystal structures, and i believe that will throw the cat among the pigeons regarding residual stress behavior - i don't know exactly how residual stress survives the phase change, if at all, and i don't know whether residual stress has any influence on exact temperature of transition, but i think you can be sure there is a thesis or two out there that will explain. what's really interesting carl is whether the pre-formed spoke elbows behave like this when heated. during manufacture, residual stress can be mechanically relieved by a small scale secondary operation that quickly follows the primary forming operation. if spokes leave the factory with residual stress, then your spoke elbows should evidence the same kinds of behavior when heated. if they leave the factory in a relieved condition, then they won't. Dear Jim, Both spokes start to bend almost as soon as the propane flame hits the bend, of course - you're imparting energy that allows dislocations and atoms to move about in their lattice. during the drawing process, wire stock is heated multiple times to soften and de-stress. and keep bending in the same direction with more heat (curling up for the carbon, uncurling for the stainless steel). to a degree. there's only so much stored energy. I've heated the straight section beyond the bend to a cheerful orange glow and then moved the glowing orange section slowly through the bend and into the straight section beyond. Checking spoke elbows was indeed my hope, but that would take very careful measurements and an understanding of why the hell obvious bends in the midspans curl or uncurl in different directions depending on whether they're used carbon 2 mm or unused 1.8 mm stainless. You can see in the pictures how little the angle of the 90-degree bend changes---the end of a 6-inch "needle" moves, but not dramatically. but you should be able to get a visual on the "before and after". But there's no point in heating tiny spoke elbows when I haven't the faintest idea what monster 90 degree midspan bends are doing when I heat them. why not? it's exactly the same principle. I expected that the bends might change to a different degree, due to different materials or different diameters, but I didn't expect the spokes to thumb their noses at me and curl and uncurl in completely different directions when I toasted their bends. It's a ridiculously simple test, so maybe other posters will try it and figure out something using different spokes. Just bend a spoke sideways, stick the spoke in a vise, and heat the bend with the flame from a soldering torch. The bending motion is visible, but it seems to go one way for carbon and the other way for stainless. If the spoke is heated enough, it loses so much of its strength that it becomes quite flexible, that's a function of both temperature and time. so sticking the free end straight up or down will reassure you that the heat is bending things, not gravity. Cheers, Carl Fogel |
#6
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Odd spoke behavior
On Oct 12, 10:20 pm, wrote: Never mind why, but I recently tortured some spokes. I bent them at their midspans, stuck them in a vise with their free ends pointing straight up, and applied a propane torch to the bends. None of the spokes stood up to torture. Old, used, 2 mm carbon spokes curled up when heated. This bend _| became _\ when an old used spoke was heated. But a new, unused, 1.8 mm stainless steel spoke uncurled when heated. This bend _| became _/ when an unused ss spoke was heated. Is torture unreliable where spokes are concerned? Why does the same 90-degree bend respond differently to heat in the different spokes? Someone on RBT ought to know what's going on. Is it carbon plated versus stainless steel? Different thicknesses? Used versus unused? Something else that I'm too ignorant to think of? Here are some before and after diagrams and pictures. On the left is the used, plated, carbon 2 mm spoke. On the right is the unused stainless steel 1.8 mm spoke. bent heated c s c s | | \ / carbon | | carbon \ / ________| | ________\ / vise| | vise| / ____|_____| ____|_____/ stainless stainless The bent spokes stick up || like this: http://server5.theimagehosting.com/i...rbonstainlessb... After heating, they splay apart \/ like this: http://server5.theimagehosting.com/i...rbonstainlessh... It's not an optical illusion. The pegboard and ruler are about a foot past the yellow hammer handle, and the yellow hammer handle is about a foot past the spokes in the vise: camera spokes hammer ruler-on-pegboard Cheers, Carl Fogel Dear Carl, Too many variables. To possibly eliminate some of these you should test (if you have them): New carbon spokes, 2.0mm and 1.8mm Used stainless spokes, 2.0mm and 1.8mm Not sure I understand why you wouldn't similarly test the bends at the spoke head. No offence, but do you have a day job? Best wishes, Nigel Grinter www.wellspokenwheels.com |
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Odd spoke behavior
On 14 Oct 2006 08:42:25 -0700, wrote:
On Oct 12, 10:20 pm, wrote: Never mind why, but I recently tortured some spokes. I bent them at their midspans, stuck them in a vise with their free ends pointing straight up, and applied a propane torch to the bends. None of the spokes stood up to torture. Old, used, 2 mm carbon spokes curled up when heated. This bend _| became _\ when an old used spoke was heated. But a new, unused, 1.8 mm stainless steel spoke uncurled when heated. This bend _| became _/ when an unused ss spoke was heated. Is torture unreliable where spokes are concerned? Why does the same 90-degree bend respond differently to heat in the different spokes? Someone on RBT ought to know what's going on. Is it carbon plated versus stainless steel? Different thicknesses? Used versus unused? Something else that I'm too ignorant to think of? Here are some before and after diagrams and pictures. On the left is the used, plated, carbon 2 mm spoke. On the right is the unused stainless steel 1.8 mm spoke. bent heated c s c s | | \ / carbon | | carbon \ / ________| | ________\ / vise| | vise| / ____|_____| ____|_____/ stainless stainless The bent spokes stick up || like this: http://server5.theimagehosting.com/i...rbonstainlessb... After heating, they splay apart \/ like this: http://server5.theimagehosting.com/i...rbonstainlessh... It's not an optical illusion. The pegboard and ruler are about a foot past the yellow hammer handle, and the yellow hammer handle is about a foot past the spokes in the vise: camera spokes hammer ruler-on-pegboard Cheers, Carl Fogel Dear Carl, Too many variables. To possibly eliminate some of these you should test (if you have them): New carbon spokes, 2.0mm and 1.8mm Used stainless spokes, 2.0mm and 1.8mm Not sure I understand why you wouldn't similarly test the bends at the spoke head. No offence, but do you have a day job? Best wishes, Nigel Grinter www.wellspokenwheels.com Dear Nigel, I was hoping that someone in our pack of well-educated engineers would know why used carbon 2 mm spokes curl up when their bends are heated, but unused 1.8 mm stainless steel spokes uncurl. Testing more spokes of different dimensions, brands, and history might show some other patterns, but it wouldn't tell me why the patterns are different. The reason that I tested giant 90 degree bends that I made myself with half a foot of spoke sticking out is that it's easy to see that much spoke actually moving right in front of your eyes and there's no question that the spoke has just been bent and not treated in any other way. Think about how disconcerting it would have been if two elbows curled and uncurled only as much as the angles in that picture. One "needle" is about 150 mm long. The other is about 3 mm long. Would you believe your measurements on a tiny spoke elbow? Or would you wonder if it was just too hard to measure? Your browser seems to truncate the picture links, so here they are again: http://server5.theimagehosting.com/i...inlessbent.jpg or http://tinyurl.com/y8lodt http://server5.theimagehosting.com/i...lessheated.jpg or http://tinyurl.com/tnrhw A quick check with a protractor program indicates that the carbon spoke curls up less than 2 degrees. In other words, I was checking first to see if anything at all happened on a large scale before I wasted any time trying to see if I could measure extremely small changes in tiny spoke elbows. And I'm not sure if the bending is caused by stresses being relieved or by some weird expansion that overwhelms any stress relief. Yes, I've got a day (and night) job. Luckily, it allows me enough time to bend two spokes with my forepaws, clamp them in a vise, wave a propane torch at them for less than ten seconds, and wonder what the hell is going on. No offence, but I take it that you haven't a clue, either. Maybe someone else on this technical newsgroup does. If not, I'll enjoy the vision of puzzled engineers trying to figure it out by toasting spokes. Cheers, Carl Fogel |
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Odd spoke behavior
On Sat, 14 Oct 2006 11:51:01 -0600, wrote:
On 14 Oct 2006 08:42:25 -0700, wrote: On Oct 12, 10:20 pm, wrote: Never mind why, but I recently tortured some spokes. I bent them at their midspans, stuck them in a vise with their free ends pointing straight up, and applied a propane torch to the bends. None of the spokes stood up to torture. Old, used, 2 mm carbon spokes curled up when heated. This bend _| became _\ when an old used spoke was heated. But a new, unused, 1.8 mm stainless steel spoke uncurled when heated. This bend _| became _/ when an unused ss spoke was heated. Is torture unreliable where spokes are concerned? Why does the same 90-degree bend respond differently to heat in the different spokes? Someone on RBT ought to know what's going on. Is it carbon plated versus stainless steel? Different thicknesses? Used versus unused? Something else that I'm too ignorant to think of? Here are some before and after diagrams and pictures. On the left is the used, plated, carbon 2 mm spoke. On the right is the unused stainless steel 1.8 mm spoke. bent heated c s c s | | \ / carbon | | carbon \ / ________| | ________\ / vise| | vise| / ____|_____| ____|_____/ stainless stainless The bent spokes stick up || like this: http://server5.theimagehosting.com/i...rbonstainlessb... After heating, they splay apart \/ like this: http://server5.theimagehosting.com/i...rbonstainlessh... It's not an optical illusion. The pegboard and ruler are about a foot past the yellow hammer handle, and the yellow hammer handle is about a foot past the spokes in the vise: camera spokes hammer ruler-on-pegboard Cheers, Carl Fogel Dear Carl, Too many variables. To possibly eliminate some of these you should test (if you have them): New carbon spokes, 2.0mm and 1.8mm Used stainless spokes, 2.0mm and 1.8mm Not sure I understand why you wouldn't similarly test the bends at the spoke head. No offence, but do you have a day job? Best wishes, Nigel Grinter www.wellspokenwheels.com Dear Nigel, I was hoping that someone in our pack of well-educated engineers would know why used carbon 2 mm spokes curl up when their bends are heated, but unused 1.8 mm stainless steel spokes uncurl. Testing more spokes of different dimensions, brands, and history might show some other patterns, but it wouldn't tell me why the patterns are different. The reason that I tested giant 90 degree bends that I made myself with half a foot of spoke sticking out is that it's easy to see that much spoke actually moving right in front of your eyes and there's no question that the spoke has just been bent and not treated in any other way. Think about how disconcerting it would have been if two elbows curled and uncurled only as much as the angles in that picture. One "needle" is about 150 mm long. The other is about 3 mm long. Would you believe your measurements on a tiny spoke elbow? Or would you wonder if it was just too hard to measure? Your browser seems to truncate the picture links, so here they are again: http://server5.theimagehosting.com/i...inlessbent.jpg or http://tinyurl.com/y8lodt http://server5.theimagehosting.com/i...lessheated.jpg or http://tinyurl.com/tnrhw A quick check with a protractor program indicates that the carbon spoke curls up less than 2 degrees. In other words, I was checking first to see if anything at all happened on a large scale before I wasted any time trying to see if I could measure extremely small changes in tiny spoke elbows. And I'm not sure if the bending is caused by stresses being relieved or by some weird expansion that overwhelms any stress relief. Yes, I've got a day (and night) job. Luckily, it allows me enough time to bend two spokes with my forepaws, clamp them in a vise, wave a propane torch at them for less than ten seconds, and wonder what the hell is going on. No offence, but I take it that you haven't a clue, either. Maybe someone else on this technical newsgroup does. If not, I'll enjoy the vision of puzzled engineers trying to figure it out by toasting spokes. Cheers, Carl Fogel After scribbling the reply above, I tested a 2.34 mm soft carbon spoke. Most of the time was spent digging the propane torch out and then untwisting the coat hang-- Er, preparing the 2.34 mm soft carbon spoke. A 90-degree bend was made in a straight section and the spoke was placed in a vise, sticking straight up. The rest of the spoke was straightened to provide about two feet of "needle" to show which way it moved. Toasting produced the expected result, namely the carbon spoke curled up a little more. I toasted a few more pieces, including the massive factory bends in the coat hang-- Er, in the spoke. They curled up very slightly, too. That took about 15 minutes, most of it wasted on setting up to check the change in small sections of the coat hang-- Er, in small sections of the spoke. Cheers, Carl Fogel |
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Odd spoke behavior
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#10
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Odd spoke behavior
On Sat, 14 Oct 2006 18:28:02 GMT, Joe Riel wrote:
writes: The reason that I tested giant 90 degree bends that I made myself with half a foot of spoke sticking out is that it's easy to see that much spoke actually moving right in front of your eyes and there's no question that the spoke has just been bent and not treated in any other way. What if you clamp the (swaged) head of the spoke in the vise, then heat the elbow. That way the long part of the spoke will serve as a suitable pointer. Any resulting movement isn't necessarily in the elbow, it could be in the head or head/vise interface, however, if there is no consistent movement than you should be able to conclude that the elbow doesn't move. Think about how disconcerting it would have been if two elbows curled and uncurled only as much as the angles in that picture. One "needle" is about 150 mm long. The other is about 3 mm long. Would you believe your measurements on a tiny spoke elbow? Or would you wonder if it was just too hard to measure? Dear Joe, The problem with clamping the hub end of the spoke is that it's so tiny and such a weird shape. Would any movement be due to the heating of the elbow bend only 3 mm away causing the swaged end to soften or expand and shift in the precarious grip of the vise? For that matter, the vise would be squashing the end of the spoke before any heat was applied. The button-elbow section is such a tiny area that clamping it in a vise might introduce new stresses. So my plan is to clamp the long part of the spoke in the vise, well away from the elbow, and take pictures against a cross-hatched background, before and after heating the end. If the change is only a degree or two, pictures are much more reassuring than just eyeballing things. But before I fuss around trying to take pictures of 1 degree bend changes in 3 mm sections, I want to check whether I'm looking at thermal stress relief or at some weird heat distortion that overwhelms any stress relief changes. Why does the used carbon plated 2 mm spoke curl up, but the unused stainless 1.8 mm spoke uncurls? There must be an explanation, but it's going to have to be a good one if the changes are due to stress relief. Of course, someone might spend five minutes duplicating my test and figure out that all spokes curl the same way if the test is done right. At this point, I'm almost hoping that someone will point out a really dumb mistake that I'm making. Now I'm going to toast another pair of bent spokes laid flat on a concrete floor--no vise or gravity involved to do anything weird. Cheers, Carl Fogel |
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