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Wheel building questions
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On Wed, 13 Oct 2004 23:53:04 +1000, big Pete
wrote: Wrote: On Wed, 13 Oct 2004 10:05:58 +1000, big Pete wrote: Wrote: On Tue, 12 Oct 2004 23:41:14 +1000, big Pete wrote: David L. Johnson Wrote: You probably have them already, but if not I recommend butted spokes. They make a more reliable wheel. I am a big guy (245 pounds last time I checked) will butted spokes make that big of a strength difference in the wheel? I did not buy the rim and spokes yet. I am thinking of a Sun double walled rim with eyelets that I can get for a good price. And the spokes are 14 gauge stainless steal (non butted) as stated in the my first post. I will Also try to make a dish stick. Looks like I am able to make it from the suggestions you guys have given me. Thank you all Pete Dear Pete, Both thick 14 gauge spokes and thin butted spokes with 14 gauge ends and a 15 gauge middle are more than strong enough to bear the loads--they break at the ends, not in the middle. Double-butted spokes keep the ends thick to try to reduce such breaks. Their advantage is that, being thinner for most of their length, they stretch more and therefore are less likely to lose all tension (a bad thing) as they roll under the hub. When the rim flattens ever so slightly against the pavement, the spoke above it loses tension. A thick straight spoke didn't stretch as far as a thin-center-section spoke, so the thick spoke loses all tension and rattles, going out of true and breaking more often and while the thin spoke can contract that much and still have tension, which makes it likely to last longer. Think of them as rubber bands at the same tension, neither of which is going to snap in the middle, but neither of which we want to go slack. The thinner rubber band enjoys a greater range of motion. Carl Fogel Dear Carl, You are going to have to enlighten me a bit more. I think I agree with your analogy. OK so the thinner band has a better range of motion. But that would imply that they will ware out faster because of the bigger range of motion they are going though. Dear Pete, You raise a good point, but the long thinner middle section of spokes doing the stretching simply doesn't wear out. That is, spokes don't break in the middle. They fatigue, crack, and fail at the elbow about nine times out of ten. The tenth spoke one breaks at the nipple. That's why the spokes are left thick (double-butted) at each end. Even a thin mid-section stainless steel spoke is so strong in tension that it isn't going to fail due to the normal stress cycle of losing and regaining tension as it rolls under the axle. As others have suggested in this thread, this is roughly what Jobst Brandt points out in "The Bicycle Wheel" when he recommends double-butted spokes. Paradoxically, a thinner mid-section spoke produces a more reliable wheel, not because it is stronger than a thicker spoke (it isn't), but because it is more than strong enough and its increased elasticity lets it function better at what spokes need to do, which is to maintain tension throughout the load range without going slack. The metallurgical side of this is that ferrous metals (steels) have the charming characteristic of being able to cycle indefinitely if the stress is low enough--they just won't fatigue and break. (The elbows and nipples break because stress is concentrated there and encouraged by various details like the bending, the threading, and so forth.) So the engineers can design a steel structure to last forever in terms of stress cycles if the stress is kept low enough. Non-ferrous metals like aluminum, titanium, and magnesium do not share this ruggedness. Given enough stress cycles, they fatigue, no matter how low the stress is. The engineers have to design non-ferrous structures to reduce the amount of stress in each cycle, reduce the cycles, or both--and still they can calculate when non-ferrous things should bust. Some theory holds that steels eventually do fatigue even at low stress cycling, but so much later that it's indefinite for practical purposes. But no theory that I know of predicts that a double-butted spoke will wear out in the middle--it will break at the elbow or nipple, but not as soon as a straight, thick spoke that is more prone to losing all tension if it rolls under a heavily loaded axle. For heavier loads, the usual solution is more spokes, not thicker spokes--36 spokes might increase to 48 spokes for many tandems and for truly heavy riders like Chalo Colina, who has about 135 pounds on lightweights like you and 185 pounds on delicate creatures like me. Carl Fogel Dear Carl, Thank you for the enlighten. I will look into double-butted spokes. I have not yet had too many problems with 36 spokes on a wheel ... The only spokes that brake on me are the ones from the wheel I got from the garbage (this wheel is on my pos commuter). I am also looking for the book you guys mentioned to me, right now though my library system. Is this book the "wheel builders bible"? I have never had a wheel with double-butted spokes does it make a difference in feel? Pete Dear Pete, Interlibrary loan should be able to get a copy of Jobst Brandt's "The Bicycle Wheel." If possible, specify the third edition. Here on rec.bicycles.tech, it's often referred to as the bible--and like any bible, it has passages that inflame controversy. For example, I remain agnostic about the spoke-squeezing stress-relief theory that's supposed to make spokes immortal, but even if turns out to be myth and lore, I can't see how it can hurt anything. Online, you can browse Sheldon Brown's detailed wheel-building page he http://www.sheldonbrown.com/wheelbuild.html It has colored diagrams, handy links to many terms, and a reference to Jobst's book--with a link to let you buy it online from Sheldon in Massachusetts, who can probably use some cheering up after the Yankees trounced Boston last night. As for any difference in feel between butted and unbutted spokes, I'd be astonished if anyone claimed to be able to tell the difference. While the increased elasticity of the thinner-middle-section spoke helps keep tension on the spoke as it rolls under the hub, the actual amount of stretching is tiny. The rubber of the tire deforms far more than the spoke changes length. When you look at diagrams showing how the rim flattens at the contact patch, there's usually a comment that the amount of distortion is greatly exaggerated--otherwise, you couldn't see the difference.) However, there might be one situation in which you could tell the difference in feel while riding double-butted spokes. When a wheel hits something hard enough to cause a spoke to lose all tension and go slack, there might be a faint but unpleasant rattle and then a click as the wheel continues rolling and tension is regained. (I've never noticed this, but vaguely recall people mentioning it here.) You'd get less of that with double-butted spokes. Otherwise, the increased stretchiness would be undetectable by a rider. Carl Fogel |
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On Wed, 13 Oct 2004 23:53:04 +1000, big Pete
wrote: Wrote: On Wed, 13 Oct 2004 10:05:58 +1000, big Pete wrote: Wrote: On Tue, 12 Oct 2004 23:41:14 +1000, big Pete wrote: David L. Johnson Wrote: You probably have them already, but if not I recommend butted spokes. They make a more reliable wheel. I am a big guy (245 pounds last time I checked) will butted spokes make that big of a strength difference in the wheel? I did not buy the rim and spokes yet. I am thinking of a Sun double walled rim with eyelets that I can get for a good price. And the spokes are 14 gauge stainless steal (non butted) as stated in the my first post. I will Also try to make a dish stick. Looks like I am able to make it from the suggestions you guys have given me. Thank you all Pete Dear Pete, Both thick 14 gauge spokes and thin butted spokes with 14 gauge ends and a 15 gauge middle are more than strong enough to bear the loads--they break at the ends, not in the middle. Double-butted spokes keep the ends thick to try to reduce such breaks. Their advantage is that, being thinner for most of their length, they stretch more and therefore are less likely to lose all tension (a bad thing) as they roll under the hub. When the rim flattens ever so slightly against the pavement, the spoke above it loses tension. A thick straight spoke didn't stretch as far as a thin-center-section spoke, so the thick spoke loses all tension and rattles, going out of true and breaking more often and while the thin spoke can contract that much and still have tension, which makes it likely to last longer. Think of them as rubber bands at the same tension, neither of which is going to snap in the middle, but neither of which we want to go slack. The thinner rubber band enjoys a greater range of motion. Carl Fogel Dear Carl, You are going to have to enlighten me a bit more. I think I agree with your analogy. OK so the thinner band has a better range of motion. But that would imply that they will ware out faster because of the bigger range of motion they are going though. Dear Pete, You raise a good point, but the long thinner middle section of spokes doing the stretching simply doesn't wear out. That is, spokes don't break in the middle. They fatigue, crack, and fail at the elbow about nine times out of ten. The tenth spoke one breaks at the nipple. That's why the spokes are left thick (double-butted) at each end. Even a thin mid-section stainless steel spoke is so strong in tension that it isn't going to fail due to the normal stress cycle of losing and regaining tension as it rolls under the axle. As others have suggested in this thread, this is roughly what Jobst Brandt points out in "The Bicycle Wheel" when he recommends double-butted spokes. Paradoxically, a thinner mid-section spoke produces a more reliable wheel, not because it is stronger than a thicker spoke (it isn't), but because it is more than strong enough and its increased elasticity lets it function better at what spokes need to do, which is to maintain tension throughout the load range without going slack. The metallurgical side of this is that ferrous metals (steels) have the charming characteristic of being able to cycle indefinitely if the stress is low enough--they just won't fatigue and break. (The elbows and nipples break because stress is concentrated there and encouraged by various details like the bending, the threading, and so forth.) So the engineers can design a steel structure to last forever in terms of stress cycles if the stress is kept low enough. Non-ferrous metals like aluminum, titanium, and magnesium do not share this ruggedness. Given enough stress cycles, they fatigue, no matter how low the stress is. The engineers have to design non-ferrous structures to reduce the amount of stress in each cycle, reduce the cycles, or both--and still they can calculate when non-ferrous things should bust. Some theory holds that steels eventually do fatigue even at low stress cycling, but so much later that it's indefinite for practical purposes. But no theory that I know of predicts that a double-butted spoke will wear out in the middle--it will break at the elbow or nipple, but not as soon as a straight, thick spoke that is more prone to losing all tension if it rolls under a heavily loaded axle. For heavier loads, the usual solution is more spokes, not thicker spokes--36 spokes might increase to 48 spokes for many tandems and for truly heavy riders like Chalo Colina, who has about 135 pounds on lightweights like you and 185 pounds on delicate creatures like me. Carl Fogel Dear Carl, Thank you for the enlighten. I will look into double-butted spokes. I have not yet had too many problems with 36 spokes on a wheel ... The only spokes that brake on me are the ones from the wheel I got from the garbage (this wheel is on my pos commuter). I am also looking for the book you guys mentioned to me, right now though my library system. Is this book the "wheel builders bible"? I have never had a wheel with double-butted spokes does it make a difference in feel? Pete Dear Pete, Interlibrary loan should be able to get a copy of Jobst Brandt's "The Bicycle Wheel." If possible, specify the third edition. Here on rec.bicycles.tech, it's often referred to as the bible--and like any bible, it has passages that inflame controversy. For example, I remain agnostic about the spoke-squeezing stress-relief theory that's supposed to make spokes immortal, but even if turns out to be myth and lore, I can't see how it can hurt anything. Online, you can browse Sheldon Brown's detailed wheel-building page he http://www.sheldonbrown.com/wheelbuild.html It has colored diagrams, handy links to many terms, and a reference to Jobst's book--with a link to let you buy it online from Sheldon in Massachusetts, who can probably use some cheering up after the Yankees trounced Boston last night. As for any difference in feel between butted and unbutted spokes, I'd be astonished if anyone claimed to be able to tell the difference. While the increased elasticity of the thinner-middle-section spoke helps keep tension on the spoke as it rolls under the hub, the actual amount of stretching is tiny. The rubber of the tire deforms far more than the spoke changes length. When you look at diagrams showing how the rim flattens at the contact patch, there's usually a comment that the amount of distortion is greatly exaggerated--otherwise, you couldn't see the difference.) However, there might be one situation in which you could tell the difference in feel while riding double-butted spokes. When a wheel hits something hard enough to cause a spoke to lose all tension and go slack, there might be a faint but unpleasant rattle and then a click as the wheel continues rolling and tension is regained. (I've never noticed this, but vaguely recall people mentioning it here.) You'd get less of that with double-butted spokes. Otherwise, the increased stretchiness would be undetectable by a rider. Carl Fogel |
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On Wed, 13 Oct 2004 13:12:36 -0600, wrote:
On Wed, 13 Oct 2004 23:53:04 +1000, big Pete wrote: Wrote: On Wed, 13 Oct 2004 10:05:58 +1000, big Pete wrote: Wrote: On Tue, 12 Oct 2004 23:41:14 +1000, big Pete wrote: David L. Johnson Wrote: You probably have them already, but if not I recommend butted spokes. They make a more reliable wheel. I am a big guy (245 pounds last time I checked) will butted spokes make that big of a strength difference in the wheel? I did not buy the rim and spokes yet. I am thinking of a Sun double walled rim with eyelets that I can get for a good price. And the spokes are 14 gauge stainless steal (non butted) as stated in the my first post. I will Also try to make a dish stick. Looks like I am able to make it from the suggestions you guys have given me. Thank you all Pete Dear Pete, Both thick 14 gauge spokes and thin butted spokes with 14 gauge ends and a 15 gauge middle are more than strong enough to bear the loads--they break at the ends, not in the middle. Double-butted spokes keep the ends thick to try to reduce such breaks. Their advantage is that, being thinner for most of their length, they stretch more and therefore are less likely to lose all tension (a bad thing) as they roll under the hub. When the rim flattens ever so slightly against the pavement, the spoke above it loses tension. A thick straight spoke didn't stretch as far as a thin-center-section spoke, so the thick spoke loses all tension and rattles, going out of true and breaking more often and while the thin spoke can contract that much and still have tension, which makes it likely to last longer. Think of them as rubber bands at the same tension, neither of which is going to snap in the middle, but neither of which we want to go slack. The thinner rubber band enjoys a greater range of motion. Carl Fogel Dear Carl, You are going to have to enlighten me a bit more. I think I agree with your analogy. OK so the thinner band has a better range of motion. But that would imply that they will ware out faster because of the bigger range of motion they are going though. Dear Pete, You raise a good point, but the long thinner middle section of spokes doing the stretching simply doesn't wear out. That is, spokes don't break in the middle. They fatigue, crack, and fail at the elbow about nine times out of ten. The tenth spoke one breaks at the nipple. That's why the spokes are left thick (double-butted) at each end. Even a thin mid-section stainless steel spoke is so strong in tension that it isn't going to fail due to the normal stress cycle of losing and regaining tension as it rolls under the axle. As others have suggested in this thread, this is roughly what Jobst Brandt points out in "The Bicycle Wheel" when he recommends double-butted spokes. Paradoxically, a thinner mid-section spoke produces a more reliable wheel, not because it is stronger than a thicker spoke (it isn't), but because it is more than strong enough and its increased elasticity lets it function better at what spokes need to do, which is to maintain tension throughout the load range without going slack. The metallurgical side of this is that ferrous metals (steels) have the charming characteristic of being able to cycle indefinitely if the stress is low enough--they just won't fatigue and break. (The elbows and nipples break because stress is concentrated there and encouraged by various details like the bending, the threading, and so forth.) So the engineers can design a steel structure to last forever in terms of stress cycles if the stress is kept low enough. Non-ferrous metals like aluminum, titanium, and magnesium do not share this ruggedness. Given enough stress cycles, they fatigue, no matter how low the stress is. The engineers have to design non-ferrous structures to reduce the amount of stress in each cycle, reduce the cycles, or both--and still they can calculate when non-ferrous things should bust. Some theory holds that steels eventually do fatigue even at low stress cycling, but so much later that it's indefinite for practical purposes. But no theory that I know of predicts that a double-butted spoke will wear out in the middle--it will break at the elbow or nipple, but not as soon as a straight, thick spoke that is more prone to losing all tension if it rolls under a heavily loaded axle. For heavier loads, the usual solution is more spokes, not thicker spokes--36 spokes might increase to 48 spokes for many tandems and for truly heavy riders like Chalo Colina, who has about 135 pounds on lightweights like you and 185 pounds on delicate creatures like me. Carl Fogel Dear Carl, Thank you for the enlighten. I will look into double-butted spokes. I have not yet had too many problems with 36 spokes on a wheel ... The only spokes that brake on me are the ones from the wheel I got from the garbage (this wheel is on my pos commuter). I am also looking for the book you guys mentioned to me, right now though my library system. Is this book the "wheel builders bible"? I have never had a wheel with double-butted spokes does it make a difference in feel? Pete Dear Pete, Interlibrary loan should be able to get a copy of Jobst Brandt's "The Bicycle Wheel." If possible, specify the third edition. Here on rec.bicycles.tech, it's often referred to as the bible--and like any bible, it has passages that inflame controversy. For example, I remain agnostic about the spoke-squeezing stress-relief theory that's supposed to make spokes immortal, but even if turns out to be myth and lore, I can't see how it can hurt anything. Online, you can browse Sheldon Brown's detailed wheel-building page he http://www.sheldonbrown.com/wheelbuild.html It has colored diagrams, handy links to many terms, and a reference to Jobst's book--with a link to let you buy it online from Sheldon in Massachusetts, who can probably use some cheering up after the Yankees trounced Boston last night. As for any difference in feel between butted and unbutted spokes, I'd be astonished if anyone claimed to be able to tell the difference. While the increased elasticity of the thinner-middle-section spoke helps keep tension on the spoke as it rolls under the hub, the actual amount of stretching is tiny. The rubber of the tire deforms far more than the spoke changes length. When you look at diagrams showing how the rim flattens at the contact patch, there's usually a comment that the amount of distortion is greatly exaggerated--otherwise, you couldn't see the difference.) I'd be surprised if there weren't a difference in feel. A bike wheel's a pretty resonant structure and resonances ARE easy to feel. Having said that I'll agree that there won't be a discernable difference in deformation under load. But a thinner spoke pulled to the same tension as a thicker one will resonate at a higher pitch. All of the shock and vibration from the road is transmitted through this resonant structure, I can't believe there won't be a difference in feel. Time for someone to buld up some matched wheelsets for testing and test ride them with a focus on road buzz and vibration, etc. Ron |
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On Wed, 13 Oct 2004 23:42:06 -0400, Ronsonic wrote:
On Wed, 13 Oct 2004 13:12:36 -0600, wrote: On Wed, 13 Oct 2004 23:53:04 +1000, big Pete wrote: Wrote: On Wed, 13 Oct 2004 10:05:58 +1000, big Pete wrote: Wrote: On Tue, 12 Oct 2004 23:41:14 +1000, big Pete wrote: David L. Johnson Wrote: You probably have them already, but if not I recommend butted spokes. They make a more reliable wheel. I am a big guy (245 pounds last time I checked) will butted spokes make that big of a strength difference in the wheel? I did not buy the rim and spokes yet. I am thinking of a Sun double walled rim with eyelets that I can get for a good price. And the spokes are 14 gauge stainless steal (non butted) as stated in the my first post. I will Also try to make a dish stick. Looks like I am able to make it from the suggestions you guys have given me. Thank you all Pete Dear Pete, Both thick 14 gauge spokes and thin butted spokes with 14 gauge ends and a 15 gauge middle are more than strong enough to bear the loads--they break at the ends, not in the middle. Double-butted spokes keep the ends thick to try to reduce such breaks. Their advantage is that, being thinner for most of their length, they stretch more and therefore are less likely to lose all tension (a bad thing) as they roll under the hub. When the rim flattens ever so slightly against the pavement, the spoke above it loses tension. A thick straight spoke didn't stretch as far as a thin-center-section spoke, so the thick spoke loses all tension and rattles, going out of true and breaking more often and while the thin spoke can contract that much and still have tension, which makes it likely to last longer. Think of them as rubber bands at the same tension, neither of which is going to snap in the middle, but neither of which we want to go slack. The thinner rubber band enjoys a greater range of motion. Carl Fogel Dear Carl, You are going to have to enlighten me a bit more. I think I agree with your analogy. OK so the thinner band has a better range of motion. But that would imply that they will ware out faster because of the bigger range of motion they are going though. Dear Pete, You raise a good point, but the long thinner middle section of spokes doing the stretching simply doesn't wear out. That is, spokes don't break in the middle. They fatigue, crack, and fail at the elbow about nine times out of ten. The tenth spoke one breaks at the nipple. That's why the spokes are left thick (double-butted) at each end. Even a thin mid-section stainless steel spoke is so strong in tension that it isn't going to fail due to the normal stress cycle of losing and regaining tension as it rolls under the axle. As others have suggested in this thread, this is roughly what Jobst Brandt points out in "The Bicycle Wheel" when he recommends double-butted spokes. Paradoxically, a thinner mid-section spoke produces a more reliable wheel, not because it is stronger than a thicker spoke (it isn't), but because it is more than strong enough and its increased elasticity lets it function better at what spokes need to do, which is to maintain tension throughout the load range without going slack. The metallurgical side of this is that ferrous metals (steels) have the charming characteristic of being able to cycle indefinitely if the stress is low enough--they just won't fatigue and break. (The elbows and nipples break because stress is concentrated there and encouraged by various details like the bending, the threading, and so forth.) So the engineers can design a steel structure to last forever in terms of stress cycles if the stress is kept low enough. Non-ferrous metals like aluminum, titanium, and magnesium do not share this ruggedness. Given enough stress cycles, they fatigue, no matter how low the stress is. The engineers have to design non-ferrous structures to reduce the amount of stress in each cycle, reduce the cycles, or both--and still they can calculate when non-ferrous things should bust. Some theory holds that steels eventually do fatigue even at low stress cycling, but so much later that it's indefinite for practical purposes. But no theory that I know of predicts that a double-butted spoke will wear out in the middle--it will break at the elbow or nipple, but not as soon as a straight, thick spoke that is more prone to losing all tension if it rolls under a heavily loaded axle. For heavier loads, the usual solution is more spokes, not thicker spokes--36 spokes might increase to 48 spokes for many tandems and for truly heavy riders like Chalo Colina, who has about 135 pounds on lightweights like you and 185 pounds on delicate creatures like me. Carl Fogel Dear Carl, Thank you for the enlighten. I will look into double-butted spokes. I have not yet had too many problems with 36 spokes on a wheel ... The only spokes that brake on me are the ones from the wheel I got from the garbage (this wheel is on my pos commuter). I am also looking for the book you guys mentioned to me, right now though my library system. Is this book the "wheel builders bible"? I have never had a wheel with double-butted spokes does it make a difference in feel? Pete Dear Pete, Interlibrary loan should be able to get a copy of Jobst Brandt's "The Bicycle Wheel." If possible, specify the third edition. Here on rec.bicycles.tech, it's often referred to as the bible--and like any bible, it has passages that inflame controversy. For example, I remain agnostic about the spoke-squeezing stress-relief theory that's supposed to make spokes immortal, but even if turns out to be myth and lore, I can't see how it can hurt anything. Online, you can browse Sheldon Brown's detailed wheel-building page he http://www.sheldonbrown.com/wheelbuild.html It has colored diagrams, handy links to many terms, and a reference to Jobst's book--with a link to let you buy it online from Sheldon in Massachusetts, who can probably use some cheering up after the Yankees trounced Boston last night. As for any difference in feel between butted and unbutted spokes, I'd be astonished if anyone claimed to be able to tell the difference. While the increased elasticity of the thinner-middle-section spoke helps keep tension on the spoke as it rolls under the hub, the actual amount of stretching is tiny. The rubber of the tire deforms far more than the spoke changes length. When you look at diagrams showing how the rim flattens at the contact patch, there's usually a comment that the amount of distortion is greatly exaggerated--otherwise, you couldn't see the difference.) I'd be surprised if there weren't a difference in feel. A bike wheel's a pretty resonant structure and resonances ARE easy to feel. Having said that I'll agree that there won't be a discernable difference in deformation under load. But a thinner spoke pulled to the same tension as a thicker one will resonate at a higher pitch. All of the shock and vibration from the road is transmitted through this resonant structure, I can't believe there won't be a difference in feel. Time for someone to buld up some matched wheelsets for testing and test ride them with a focus on road buzz and vibration, etc. Ron Dear Ron, I think that the usual problem of claims about "feel" is hard to overcome. No matter how resonant the structure of the metal spokes, hub, and rim may be, it's all damped by the inflated rubber tire. But you could be right. A faintly similar test would be to try to tell the difference between hitting a tire while blindfolded with the same hammer heads mounted on different rubber-covered shafts--wood, fiberglass, and steel. I know that carpenters believe in differences between the feel of such materials, but I don't know about whether they would claim to feel the difference with a resilient rubber tire on one end and a rubber grip on the other. Carl Fogel |
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On Wed, 13 Oct 2004 23:42:06 -0400, Ronsonic wrote:
On Wed, 13 Oct 2004 13:12:36 -0600, wrote: On Wed, 13 Oct 2004 23:53:04 +1000, big Pete wrote: Wrote: On Wed, 13 Oct 2004 10:05:58 +1000, big Pete wrote: Wrote: On Tue, 12 Oct 2004 23:41:14 +1000, big Pete wrote: David L. Johnson Wrote: You probably have them already, but if not I recommend butted spokes. They make a more reliable wheel. I am a big guy (245 pounds last time I checked) will butted spokes make that big of a strength difference in the wheel? I did not buy the rim and spokes yet. I am thinking of a Sun double walled rim with eyelets that I can get for a good price. And the spokes are 14 gauge stainless steal (non butted) as stated in the my first post. I will Also try to make a dish stick. Looks like I am able to make it from the suggestions you guys have given me. Thank you all Pete Dear Pete, Both thick 14 gauge spokes and thin butted spokes with 14 gauge ends and a 15 gauge middle are more than strong enough to bear the loads--they break at the ends, not in the middle. Double-butted spokes keep the ends thick to try to reduce such breaks. Their advantage is that, being thinner for most of their length, they stretch more and therefore are less likely to lose all tension (a bad thing) as they roll under the hub. When the rim flattens ever so slightly against the pavement, the spoke above it loses tension. A thick straight spoke didn't stretch as far as a thin-center-section spoke, so the thick spoke loses all tension and rattles, going out of true and breaking more often and while the thin spoke can contract that much and still have tension, which makes it likely to last longer. Think of them as rubber bands at the same tension, neither of which is going to snap in the middle, but neither of which we want to go slack. The thinner rubber band enjoys a greater range of motion. Carl Fogel Dear Carl, You are going to have to enlighten me a bit more. I think I agree with your analogy. OK so the thinner band has a better range of motion. But that would imply that they will ware out faster because of the bigger range of motion they are going though. Dear Pete, You raise a good point, but the long thinner middle section of spokes doing the stretching simply doesn't wear out. That is, spokes don't break in the middle. They fatigue, crack, and fail at the elbow about nine times out of ten. The tenth spoke one breaks at the nipple. That's why the spokes are left thick (double-butted) at each end. Even a thin mid-section stainless steel spoke is so strong in tension that it isn't going to fail due to the normal stress cycle of losing and regaining tension as it rolls under the axle. As others have suggested in this thread, this is roughly what Jobst Brandt points out in "The Bicycle Wheel" when he recommends double-butted spokes. Paradoxically, a thinner mid-section spoke produces a more reliable wheel, not because it is stronger than a thicker spoke (it isn't), but because it is more than strong enough and its increased elasticity lets it function better at what spokes need to do, which is to maintain tension throughout the load range without going slack. The metallurgical side of this is that ferrous metals (steels) have the charming characteristic of being able to cycle indefinitely if the stress is low enough--they just won't fatigue and break. (The elbows and nipples break because stress is concentrated there and encouraged by various details like the bending, the threading, and so forth.) So the engineers can design a steel structure to last forever in terms of stress cycles if the stress is kept low enough. Non-ferrous metals like aluminum, titanium, and magnesium do not share this ruggedness. Given enough stress cycles, they fatigue, no matter how low the stress is. The engineers have to design non-ferrous structures to reduce the amount of stress in each cycle, reduce the cycles, or both--and still they can calculate when non-ferrous things should bust. Some theory holds that steels eventually do fatigue even at low stress cycling, but so much later that it's indefinite for practical purposes. But no theory that I know of predicts that a double-butted spoke will wear out in the middle--it will break at the elbow or nipple, but not as soon as a straight, thick spoke that is more prone to losing all tension if it rolls under a heavily loaded axle. For heavier loads, the usual solution is more spokes, not thicker spokes--36 spokes might increase to 48 spokes for many tandems and for truly heavy riders like Chalo Colina, who has about 135 pounds on lightweights like you and 185 pounds on delicate creatures like me. Carl Fogel Dear Carl, Thank you for the enlighten. I will look into double-butted spokes. I have not yet had too many problems with 36 spokes on a wheel ... The only spokes that brake on me are the ones from the wheel I got from the garbage (this wheel is on my pos commuter). I am also looking for the book you guys mentioned to me, right now though my library system. Is this book the "wheel builders bible"? I have never had a wheel with double-butted spokes does it make a difference in feel? Pete Dear Pete, Interlibrary loan should be able to get a copy of Jobst Brandt's "The Bicycle Wheel." If possible, specify the third edition. Here on rec.bicycles.tech, it's often referred to as the bible--and like any bible, it has passages that inflame controversy. For example, I remain agnostic about the spoke-squeezing stress-relief theory that's supposed to make spokes immortal, but even if turns out to be myth and lore, I can't see how it can hurt anything. Online, you can browse Sheldon Brown's detailed wheel-building page he http://www.sheldonbrown.com/wheelbuild.html It has colored diagrams, handy links to many terms, and a reference to Jobst's book--with a link to let you buy it online from Sheldon in Massachusetts, who can probably use some cheering up after the Yankees trounced Boston last night. As for any difference in feel between butted and unbutted spokes, I'd be astonished if anyone claimed to be able to tell the difference. While the increased elasticity of the thinner-middle-section spoke helps keep tension on the spoke as it rolls under the hub, the actual amount of stretching is tiny. The rubber of the tire deforms far more than the spoke changes length. When you look at diagrams showing how the rim flattens at the contact patch, there's usually a comment that the amount of distortion is greatly exaggerated--otherwise, you couldn't see the difference.) I'd be surprised if there weren't a difference in feel. A bike wheel's a pretty resonant structure and resonances ARE easy to feel. Having said that I'll agree that there won't be a discernable difference in deformation under load. But a thinner spoke pulled to the same tension as a thicker one will resonate at a higher pitch. All of the shock and vibration from the road is transmitted through this resonant structure, I can't believe there won't be a difference in feel. Time for someone to buld up some matched wheelsets for testing and test ride them with a focus on road buzz and vibration, etc. Ron Dear Ron, I think that the usual problem of claims about "feel" is hard to overcome. No matter how resonant the structure of the metal spokes, hub, and rim may be, it's all damped by the inflated rubber tire. But you could be right. A faintly similar test would be to try to tell the difference between hitting a tire while blindfolded with the same hammer heads mounted on different rubber-covered shafts--wood, fiberglass, and steel. I know that carpenters believe in differences between the feel of such materials, but I don't know about whether they would claim to feel the difference with a resilient rubber tire on one end and a rubber grip on the other. Carl Fogel |
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