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The Basics of Wheel Alignment and Wheelbuilding
On Fri, 6 Aug 2004 07:35:16 +0100, "Trevor Jeffrey"
wrote: wrote in message ... On Fri, 6 Aug 2004 00:42:55 +1000, Weisse Luft wrote: . But you're saying that the variation of the spoke load is less. Is this a matter of both thick and thin spokes being tensioned to X pounds and the thick one going to 0 pounds of tension, a variation of X, while the more elastic thinner spoke doesn't drop as far--say to 10 lbs tension--and therefore has a smaller load range of X -10 instead of the full range of X. Presumably spokes last longer with this smaller load variation. I'm hoping that I've managed to figure out what you (and others) already understood, since it seems clearer than waving my hands and declaring that losing all tension is a bad thing. Steels tested for this, have not shown it to be evident. Reduction of magnitude of load variation may increase life of sample, but the increase of tension before applying load variation does not show benefits for component life. TJ Dear Trevor, Actually, I wrote that, not Weisse Luft. You may have misunderstood something here. As far as I know, both the butted spokes with the thinner midsection and the straight spokes would be tensioned to the same force of X pounds of tension. It's the increased elasticity of the thinner double-butted spoke that reduces the variation of tension. When the thicker and therefore less elastic straight spokes contract enough to go from X pounds to 0 pounds of tension, they have experienced the full range of possible tension variation. In the same situation, the thinner and therefore more elastic double-butted spokes start at the same X pounds of tension, but do not relax to 0 pounds of tension. Their range of variation is therefore smaller. Again, both kinds of spokes began at the same tension in the wheel. The difference is that the thick spokes will lose all tension well before the thin spokes do. Carl Fogel |
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#102
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The Basics of Wheel Alignment and Wheelbuilding
Trevor Jeffrey wrote:
Mark McMaster wrote in message ... Trevor Jeffrey wrote: Mark McMaster wrote in message ... As far as the role of the rim, it's main role is supply a continuously round surface to mount the tire, / INCORRECT The rim provides the rolling surface and the tyre reduces rolling resistace and provides grip to assist traction. I consider a tyre should also reduce jarring. How can you say that the rim provides the rolling surface, if the wheel doesn't roll on the surface of the rim? / I assure you it can. I have ridden a bare rim after tearing a tyre cased by wheel collapse (constructed as instructed in JB's book) during sprinting. It was the poor stability of this wheel made me want to investigate further on constructional techniques. I'm confused - how could your wheel collapse so badly that it tore the tire casing, and yet still be in good enough shape that you could ride on it? I've never seen a collapsed wheel tear a tire casing, although I suppose it could happen; I've never seen a collapsed wheel that would still roll. Also, you are entirely incorrect about the tire reducing rolling resistance - it increases the rolling resistance, not decreases it. / Robert Thompson and John Dunlop etc would disagree. Rolling resistance was not the issue that Thompson and Dunlop were trying to address. The thing that is interesting here is that you can not possibly have researched whether pneumatic tires reduce rolling resistance over solid wheels. If you had, you would have found numerous resources showing that the flexing of the pneumatic tire casing (and tread) increases the rolling resistance compared to a solid wheel. Here are a few: http://www.lafn.org/~dave/trans/energy/rail_energy.html http://www.channel4.com/science/micr...r/Science.html Why do you do this? Why do you make completely unverified assertions based on pre-conceptions and wild guesses, and then defend them as if they were absolute truths? You have offered absolutely no objective evidence to back up anything you claim. If tires decreased rolling resistance, railroad cars would roll on pneumatic tires instead of directly on their solid wheels./ Oh no they wouldn't. Oh yes they do. But where? I cannot recall. The railway carriage was in existence long before the invention of the pneumatic tyre. Wheels are large and the track is smooth and resilient. Notice the use of the word track, a carriage wheel has to track the line accurately at high speed under braking and acceleration in straight lines and around curves. This is acheived through special shaping of the wheel's tyre and the track. The track is cambered. Railway locomotives are heavy, the complications to use pneumatic tyres resilient enough for this application are great. It would be impossible to convert to a pnuematic tyred rail system. Impossible? No. Impractical? In some cases. Pneumatic tires for railroad wheels actually are in service in some locations: http://www.skytraincorp.com/wheels-maglev.htm http://encyclopedia.thefreedictionar...%20underground (Note, the second web site has a reference to the added rolling resistance caused by rubber tires as a disadvantage to their use on railroad wheels.) If you had looked at the analyses of spoke tension changes when a wheel is loaded more carefully, you would see that the summation of the spoke tensions _decrease_ when a wheel is loaded. In other words, there are large spoke tension decreases directly at the bottom of the wheel, and only very small spoke tension increases elsewhere around the rim. The total sum of the spoke tension increases is far less than the sum of the spoke tension decreases. Although there may be some increases in rim compression around parts of the wheel due to the small spoke tension increases, they are very small. This is complex, innaccurate and irrelevant. It is absurd that you wish to persuade that the spokes change tension to move the rim, the force on a loaded wheel is generally in directions so as to bring together rim and hub in the lower portion of the wheel. To suggest that the spokes act to move the rim is incongruous of an inanimate object. The point is stated above, the spokes transfer the load from the rim to the hub. I know not of which analysis you seem to think I have looked at. If it suggests that which you have indicated, it is worthless. It appears that you are suffering from cognitive dissonance. During discussions on wheel mechanics, you become agitated / I really don't. Don't make false accusations. Apparently you do. When I simply commented on the data (not the conclusions) of tests regarding spoke tension changes in loaded bicycle wheels, you claim they are "complex, inaccurate and irrelevant." The raw data is not complex, it is simply direct measurements of tension changes. It is not inaccurate, as they have been independently verified by several unrelated organizations. And if measurements of the distributions of forces in a wheel are irrelevant to how a wheel supports a load, then you must think it is done by magic instead. whenever the actual measured tension changes in a loaded wheel is pointed, because they don't jibe with your particular views. It is still uneccasary and irrelevant, you only bring it up to cause diversion. No, the ignoring direct data of wheel forces in determining how wheel works is a diversion from finding the truth. Again I ask - what objective evidence do you base your beliefs on? If you have no evidence to support your statements (and all other available evidence disputes it) you must be wrong. May I remind you, any reference I have made to wheel loading, assumes spokes which are not pre-tensioned. My method of wheelbuilding specifically aims to reduce pre-loading of the rim to the minimum required to prevent loss of lateral stability during service. As long as spokes do not become loose, lateral stability is maintained. I was not prepared for and did not want a discussion on load theory of the wheel as it depends upon components used and actual constructional technique. Please note that the heading of the thread is "The Basics of Wheel Alignment and Wheelbuilding" Ah, but the available evidence shows that the bottom spokes do lose tension when the wheel is loaded. How do guarantee that the spokes don't become completely slack, as you have said is required to maintain lateral stability, if the spokes are pre-tensioned? The changes in spoke tension in a loaded wheel have been analyzed and measured several times. They always lead to the same conclusions about how loads are distributed through out the wheel components. In case you need reminding (and it appears you do) of the spoke tension changes, here are a few links to some finite element analyses and direct measurements: http://www.achrn.demon.co.uk/astounding/ian/wheel/ http://www.rose-hulman.edu/~fine/FE2...ects/Hartz.pdf http://www.duke.edu/~hpgavin/papers/...heel-Paper.pdf http://groups.google.com/groups?q=sp...&hl=en&lr=&ie= UTF-8&c2coff=1&selm=34AE9E7E.3593%40usit.net&rnum=3 There are also other published tests and analyses not on the web. This is because this loading mode can apply a high load tangential to the rim./ You do not understand arches do you? Please ignore previous statement and ammend to " I see you've heard of arches." All serviceable loads directed through a wheel through the plane of that wheel will be restrained by the rim. This is because the rim acts as an arch and changes the direction of load through 90deg to travel along that arch. No, absolutely not. Neither an arch, nor any other static structure, can eliminate a force vector component. Newton's 3rd law states that every action has equal and opposite reaction. If a vertical force is applied to a structure, there must be an equal and opposite vertical force to support it. An arch can not make a vertical force horizontal. There may be an additional horizontal force generated (which again must have an equal and opposite force to support it), but an arch can not make any force vector disappear. This is basic freshman statics. I suggest you review a pertinent text book. of the rim to the front and back of the wheel. If this were so, then the loads would have to then be transferred (by compression) to the top 180 degree arch of rim. But if that were the case, in order to support this load on the top arch of the rim, you would see corresponding increases in tension in the spokes at the top of the wheel, supporting the arch. However, all the analyses and measurements have shown that the small spoke tension increases that do occur at the top aren't nearly enough to support the load. Looking at the analysis in the first web site cited above, out of the 1000 N load applied at the bottom of the wheel, The vertical components of all the top spokes combined are only 100 N (10%). Where is the rest of the load being supported? Look at the bottom of the wheel, and you can see tension decreases account for about 950 N (95%) of the load. (Further, you'll see that there are spoke tension increases below rim, of about 5% of the total load). The only conclusion that can be reached is that the rim does not act like a classic arch, and only transfer a small portion of the external load to the top of the wheel. So, your theory that a load on the wheel increases compression on the rim is clearly inconsistent with the actual data. Is the data relevant, is it shown that the spokes are adequately tensioned and not over-tensioned? By this I mean that the spokes will become loose when the service load is exceeded. I don't know what you mean by asking if "the spokes are adequately tensioned and not over-tensioned?". Spoke components are made from linearly elastic materials (metals) so as long as the spokes are adequately tensioned and do not completely slacken, nor exceed their elastic limit, the results are valid (and since there is little increase in tension in any spokes when the wheel is loaded, it is unlikely they will exceed their elastic limit.) Is it also shown that the spokes take a direct line and are not looped around each other. Unless these conditions are satisfied, it is improbable that the data would corespond to my wheel build. If you disagree, perhaps you may think it raises serious doubt. If you had actually looked at the data, you would see that wheels both radially laced, and with crossed (interlaced) spokes were examined. Again you are not doing your research. If there is little increase in the tension in the top spokes, there can be little increase in compression in the top half of the rim, which means that there is little rim compression transferred from the bottom half of the rim. Therefore, the load on a wheel is not transferred from the ground to the hub primarily by rim compression. You make an assumption based on pre-conceived ideas and measurements on others wheels. My statements hold true for a wheel not pre-tensioned. So how does the load transfer between tyre and spokes if not by compression? Faries? No, there are no assumptions. They are simply the logical conclusions based on the data and known laws of nature. The magnitudes of the spoke tension changes have been measured and calculated by many independent parties, who have all discovered What they set out to "discover" The aim to discover how a bicycle wheel actually supports a load. What are you trying to discover? the same patterns of load distribution. You can not simply dismiss the data, just because it doesn't match your ideas. If your theory can not account for the load distribution, your theory is wrong. Even if you do manage to concoct a some convoluted explanation to make your theory fit, that still doesn't make it correct. I'll remind you, my aim was to reduce the tensioning of spokes to the minimum required, and that this was acheivable throughthe pre-forming of the spoke at its crossing. How does pre-forming of the spokes at the crossing minimize the pre-tensioning? The spokes at the bottom of the wheel loose tension, regardless of the path they take from the hub to the rim. Occam's razor says that the simplest theory is the best - the theory that the external load is carried by the decreases in tension of a pre-tensioned wheel is simple, direct, and matches all the known data. It would not apply should the spokes be loose before loading, so does not apply to all tensile spoked wheels. To exclude some wheels because they are not up to some sort of arbitary tension is not a valid argument to support the theory that the wheel is supported by a decrease in tension. But if they are not up to adequate tension, then when the bottom spokes slacken with load, they fail your test of maintaining lateral stability. Therefore, any wheel which remains stable must be pre-tensioned, and any wheel that is pre-tensioned supports loads by decreases in tension. Your explanation on a pretensioned wheel is influential without resorting to the sites. I'll give it further thought. That is a poor approach. Your thoughts should be guided by the physical evidence, and not by what you assume the physical evidence should be based on your mental ramblings. I think this 95% shift may only occur in a grossly pre-tensioned wheel. My methods do not require gross pre-tensioning so how similar, measured results will be is questionable. Wheels are linearly elastic, so the decrease tension of the bottom spokes equal to 95% of the load will be the same regardless of the the initial tension in spokes. (This is required by Hooke's Law.) The fact still remains that lateral and radial stability along with reduced spoke failures can be attained by pre-forming the spokes at their crossing. Please elaborate. The forces inside the wheel caused not the external load can not be eliminated, only re-distributed. How does your pre-forming change the force distribution? Interestingly, you have laid out all the pieces on how wheels support a load, you just have to put them together. A load on a wheel causes a decrease in tension in the bottom spokes almost equal to the applied load. The bottom spokes must not completely slacken, or the wheel loses lateral support. Therefore, the spokes in the bottom wheel must have some pre-tension, to keep from slackening when a load is applied. Since the greater the applied load, the more tension is lost in the bottom spokes, higher loads require more spoke pre-tension. In other words, the strength of the wheel is directly related to the amount of static tension in the spokes. Of course, there are practical limits to how much static spoke tension a given wheel can stand, but in general, a tighter wheel is a stronger wheel. Mark McMaster |
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The Basics of Wheel Alignment and Wheelbuilding
Right on all accounts, Mark. The fact that all spoke failures I have seen, save one SPECIAL case, have been at the ends with NO measurable change in cross sectional area. The one special case was where a foreign object was wedged in between the failed spoke and the fork. This spoke has the classic ductile failure with necking to an eventual small cup and cone fracture. This failure analysis is highly indicative of cyclic fatigue, not over tension. While its possible to over tension a wheel (and I have done it experimentally), the resulting increase in tension does not increase the failure rate of the spokes. Because the wire spoked wheel is a pretensioned structure, the tension and count of the spokes must match the rim and the load. Here is the art of wheel building. I have a friend who had his designer wheels rebuilt with straight gauge spokes in lieu of DT Revolutions because of a spoke failure. This was recommended by the LBS, not the wheel's manufacturer. He has not been able to ride more than 50 miles without loss of tension and a retrue even though the spokes initially are at the limit of normal tensioning. Oh yes, these are a paired spoke wheels with a low count. More elastic spokes ARE the answer. -- Weisse Luft |
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The Basics of Wheel Alignment and Wheelbuilding
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The Basics of Wheel Alignment and Wheelbuilding
Mark McMaster wrote in message ... Rolling resistance was not the issue that Thompson and Dunlop were trying to address. So what issues? Patent spec. 10,990 10 June 1846 Robert William Thomson "The nature of my said Invention consists in the application of elastic bearings round the tires of the wheels of carriages, for the purpose of lessening the power required to draw the carriages, rendering their motion easier and diminishing the noise they make when in motion." Impossible? No. Impractical? In some cases. Pneumatic tires for railroad wheels actually are in service in some locations: As I said. (Note, the second web site has a reference to the added rolling resistance caused by rubber tires as a disadvantage to their use on railroad wheels.) That would be the rolling resistance over a typical railroad wheel running on a purpose designed track and has minimal relationship to a bicycle wheel which can run over soft ground. It appears that you are suffering from cognitive dissonance. During discussions on wheel mechanics, you become agitated / I really don't. Don't make false accusations. It is still uneccasary and irrelevant, you only bring it up to cause diversion. No, the ignoring direct data of wheel forces in determining how wheel works is a diversion from finding the truth. Again I ask - what objective evidence do you base your beliefs on? If you have no evidence to support your statements (and all other available evidence disputes it) you must be wrong. To say that force is transfered by the rim to the spokes to the hub was not something I thought needed explanation because the newsthread appeared to be about how to build a better wheel. Of which I put forward my explanation of how I managed it. You on the other hand persist in constantly going off topic on many different lines in an attempt to discredit my postings. Ah, but the available evidence shows that the bottom spokes do lose tension when the wheel is loaded. How do guarantee that the spokes don't become completely slack, as you have said is required to maintain lateral stability, if the spokes are pre-tensioned? This is a bit garbled. I hope the following answers the question that you think you were asking. I have stated that a wheel's spokes do not require pre-tensioning to function. I have stated a wheel's spokes require a modicum of tensioning during build, sufficient to prevent loose spokes under maximum load predicted by cornering and braking. I have also stated that the fear of a loose spoke is unfounded. the rim. This is because the rim acts as an arch and changes the direction of load through 90deg to travel along that arch. No, absolutely not. Neither an arch, nor any other static structure, can eliminate a force vector component. Newton's 3rd law states that every action has equal and opposite reaction. If a vertical force is applied to a structure, there must be an equal and opposite vertical force to support it. An arch can not make a vertical force horizontal. There may be an additional horizontal force generated (which again must have an equal and opposite force to support it), but an arch can not make any force vector disappear. This is basic freshman statics. I suggest you review a pertinent text book. And the load is transfered by the spokes is what I said, I did not go into detail because it depends on how much tension is in the spokes on the predominant manner on exactly the way the load is transferred. Plus it was not relevant for my method to acertain the precise load values at any one moment. It being sufficient to know that the rotating wheel produces cyclic variation in the spokes, so that a spoke and its 'pair' will have relative changes in tension as they rotate. It is the relative changes in tension which move the spoke crossing in an out so as to cause the fatigue failure at the hub. I don't know what you mean by asking if "the spokes are adequately tensioned and not over-tensioned?". Spoke components are made from linearly elastic materials (metals) so as long as the spokes are adequately tensioned and do not completely slacken, nor exceed their elastic limit, the results are valid (and since there is little increase in tension in any spokes when the wheel is loaded, it is unlikely they will exceed their elastic limit.) By over-tensioned, I mean that the tension within the spokes is liable to cause the rim to buckle due to excessive compression without adequate lateral support. Buckling is the usual failure of long slim members in compression, my method not only addresses the problem of fatigue failure at the spoke heads, it also improves lateral stability and reduces rim compression so allowing a more predictable wheel. Is it also shown that the spokes take a direct line and are not looped around each other. Unless these conditions are satisfied, it is improbable that the data would corespond to my wheel build. If you disagree, perhaps you may think it raises serious doubt. If you had actually looked at the data, you would see that wheels both radially laced, and with crossed (interlaced) spokes were examined. Again you are not doing your research. I stated I had not examined the wesite. I have done my research. Check the patent cited at the top of this posting. If there is little increase in the tension in the top spokes, there can be little increase in compression in the top half of the rim, which means that there is little rim compression transferred from the bottom half of the rim. Therefore, the load on a wheel is not transferred from the ground to the hub primarily by rim compression. You make an assumption based on pre-conceived ideas and measurements on others wheels. My statements hold true for a wheel not pre-tensioned. So how does the load transfer between tyre and spokes if not by compression? Faries? No, there are no assumptions. They are simply the logical conclusions based on the data and known laws of nature. So how is the load tranferred between tyre and spokes? The magnitudes of the spoke tension changes have been measured and calculated by many independent parties, who have all discovered What they set out to "discover" The aim to discover how a bicycle wheel actually supports a load. What are you trying to discover? How to make the most reliable wheel, of which I have given my account of my method and why it is better. Why do you persist in going off topic? How does pre-forming of the spokes at the crossing minimize the pre-tensioning? The spokes at the bottom of the wheel loose tension, regardless of the path they take from the hub to the rim. The pre-forming of the spokes reduces the frequency of fatigue failure at the hub. Without pre-forming the tension of the spokes required to matched the radial stability is much greater, resulting in excessive rim compression with the lateral instability that results. The It would not apply should the spokes be loose before loading, so does not apply to all tensile spoked wheels. To exclude some wheels because they are not up to some sort of arbitary tension is not a valid argument to support the theory that the wheel is supported by a decrease in tension. But if they are not up to adequate tension, then when the bottom spokes slacken with load, they fail your test of maintaining lateral stability. Therefore, any wheel which remains stable must be pre-tensioned, and any wheel that is pre-tensioned supports loads by decreases in tension. A theory on wheel support is incorrect if it excludes those specious wheels, which although servicable, would not be normally acceptable for service. To say the rim is restrained by the spokes satisfies all conditions of a tensile spoked wheel. When you say any wheel, you should stick to it. It is also erroneous for you to say "a pretensioned wheel supports loads by decreases in tension" when you know increases in tension over the top of the wheel take place. Your explanation on a pretensioned wheel is influential without resorting to the sites. I'll give it further thought. That is a poor approach. Your thoughts should be guided by the physical evidence, and not by what you assume the physical evidence should be based on your mental ramblings. I have not measured spoke tensile forces or rim compression as they are not at critical levels in my wheels due to the technique of wheelbuilding I advocate. The tensioning of spokes in others wheels is not relevant to my method. I have no intrest in wheelbuilding techniques that produce a wheel with demonstrable risk of failure. The unwarranted incessant contradiction of my postings is evident of your mental state however. I think this 95% shift may only occur in a grossly pre-tensioned wheel. My methods do not require gross pre-tensioning so how similar, measured results will be is questionable. Wheels are linearly elastic, so the decrease tension of the bottom spokes equal to 95% of the load will be the same regardless of the the initial tension in spokes. (This is required by Hooke's Law.) Hookes law applies to solids and does not apply when components are taken out of their elastic range, which is bounded by the limit of proportionality. I do not feel that Hookes law should necessarily be applied to a wheel due to the sliding movement evident from wear at the spoke crossing. The use of a tied and soldered wheel I may have found more acceptable. The crossing of spokes puts a bend in them, the relative varience in tension of a pair of spokes means that each spoke has behaviour approaching a damped spring. The crossing of the spokes generally reduces the loading and unloading rate of the spoke which is thought to effect fatigue progression. If all bottom spokes become loose when the load is applied, the top spokes wholy(100%) take the load, the bottom spokes are not functioning. But of course yours is a specious argument to support a specious wheel. The fact still remains that lateral and radial stability along with reduced spoke failures can be attained by pre-forming the spokes at their crossing. Please elaborate. The forces inside the wheel caused not the external load can not be eliminated, only re-distributed. How does your pre-forming change the force distribution? By making the kink at the crossing, the spoke takes the shortest possible route(with crossed spokes) between rim and hub. This enables it to better restrain the rim as tendancy for the rim to move out is countered more positively than by a spoke which is left without the correct shaping. Interestingly, you have laid out all the pieces on how wheels support a load, you just have to put them together. A load on a wheel causes a decrease in tension in the bottom spokes almost equal to the applied load. The bottom spokes must not completely slacken, or the wheel loses lateral support. Therefore, the spokes in the bottom wheel must have some pre-tension, to keep from slackening when a load is applied. Since the greater the applied load, the more tension is lost in the bottom spokes, higher loads require more spoke pre-tension. In other words, the strength of the wheel is directly related to the amount of static tension in the spokes. Of course, there are practical limits to how much static spoke tension a given wheel can stand, but in general, a tighter wheel is a stronger wheel. I did not say decrease in bottom spokes is nearly equal to the load. If I ever talk about spoke tensions in relation to the general support of how the wheel bears its load by force distribution as a whole, a call for vectors would be in order. I'll repeat again read the subject heading " The Basics of Wheel Alignment and Wheelbuilding", theory of how a wheel bears its load was not warranted, your off topic. Where I agree or disagree with you is not relevant to an improved wheelbuilding method. Trevor |
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The Basics of Wheel Alignment and Wheelbuilding
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The Basics of Wheel Alignment and Wheelbuilding
Trevor Jeffrey Wrote: Mark McMaster wrote in message ... Rolling resistance was not the issue that Thompson and Dunlop were trying to address. So what issues? Patent spec. 10,990 10 June 1846 Robert William Thomson "The nature of my said Invention consists in the application of elastic bearings round the tires of the wheels of carriages, for the purpose of lessening the power required to draw the carriages, rendering their motion easier and diminishing the noise they make when in motion." Impossible? No. Impractical? In some cases. Pneumatic tires for railroad wheels actually are in service in some locations: As I said. (Note, the second web site has a reference to the added rolling resistance caused by rubber tires as a disadvantage to their use on railroad wheels.) That would be the rolling resistance over a typical railroad wheel running on a purpose designed track and has minimal relationship to a bicycle wheel which can run over soft ground. It appears that you are suffering from cognitive dissonance. During discussions on wheel mechanics, you become agitated / I really don't. Don't make false accusations. It is still uneccasary and irrelevant, you only bring it up to cause diversion. No, the ignoring direct data of wheel forces in determining how wheel works is a diversion from finding the truth. Again I ask - what objective evidence do you base your beliefs on? If you have no evidence to support your statements (and all other available evidence disputes it) you must be wrong. To say that force is transfered by the rim to the spokes to the hub was not something I thought needed explanation because the newsthread appeared to be about how to build a better wheel. Of which I put forward my explanation of how I managed it. You on the other hand persist in constantly going off topic on many different lines in an attempt to discredit my postings. Ah, but the available evidence shows that the bottom spokes do lose tension when the wheel is loaded. How do guarantee that the spokes don't become completely slack, as you have said is required to maintain lateral stability, if the spokes are pre-tensioned? This is a bit garbled. I hope the following answers the question that you think you were asking. I have stated that a wheel's spokes do not require pre-tensioning to function. I have stated a wheel's spokes require a modicum of tensioning during build, sufficient to prevent loose spokes under maximum load predicted by cornering and braking. I have also stated that the fear of a loose spoke is unfounded. the rim. This is because the rim acts as an arch and changes the direction of load through 90deg to travel along that arch. No, absolutely not. Neither an arch, nor any other static structure, can eliminate a force vector component. Newton's 3rd law states that every action has equal and opposite reaction. If a vertical force is applied to a structure, there must be an equal and opposite vertical force to support it. An arch can not make a vertical force horizontal. There may be an additional horizontal force generated (which again must have an equal and opposite force to support it), but an arch can not make any force vector disappear. This is basic freshman statics. I suggest you review a pertinent text book. And the load is transfered by the spokes is what I said, I did not go into detail because it depends on how much tension is in the spokes on the predominant manner on exactly the way the load is transferred. Plus it was not relevant for my method to acertain the precise load values at any one moment. It being sufficient to know that the rotating wheel produces cyclic variation in the spokes, so that a spoke and its 'pair' will have relative changes in tension as they rotate. It is the relative changes in tension which move the spoke crossing in an out so as to cause the fatigue failure at the hub. I don't know what you mean by asking if "the spokes are adequately tensioned and not over-tensioned?". Spoke components are made from linearly elastic materials (metals) so as long as the spokes are adequately tensioned and do not completely slacken, nor exceed their elastic limit, the results are valid (and since there is little increase in tension in any spokes when the wheel is loaded, it is unlikely they will exceed their elastic limit.) By over-tensioned, I mean that the tension within the spokes is liable to cause the rim to buckle due to excessive compression without adequate lateral support. Buckling is the usual failure of long slim members in compression, my method not only addresses the problem of fatigue failure at the spoke heads, it also improves lateral stability and reduces rim compression so allowing a more predictable wheel. Is it also shown that the spokes take a direct line and are not looped around each other. Unless these conditions are satisfied, it is improbable that the data would corespond to my wheel build. If you disagree, perhaps you may think it raises serious doubt. If you had actually looked at the data, you would see that wheels both radially laced, and with crossed (interlaced) spokes were examined. Again you are not doing your research. I stated I had not examined the wesite. I have done my research. Check the patent cited at the top of this posting. If there is little increase in the tension in the top spokes, there can be little increase in compression in the top half of the rim, which means that there is little rim compression transferred from the bottom half of the rim. Therefore, the load on a wheel is not transferred from the ground to the hub primarily by rim compression. You make an assumption based on pre-conceived ideas and measurements on others wheels. My statements hold true for a wheel not pre-tensioned. So how does the load transfer between tyre and spokes if not by compression? Faries? No, there are no assumptions. They are simply the logical conclusions based on the data and known laws of nature. So how is the load tranferred between tyre and spokes? The magnitudes of the spoke tension changes have been measured and calculated by many independent parties, who have all discovered What they set out to "discover" The aim to discover how a bicycle wheel actually supports a load. What are you trying to discover? How to make the most reliable wheel, of which I have given my account of my method and why it is better. Why do you persist in going off topic? How does pre-forming of the spokes at the crossing minimize the pre-tensioning? The spokes at the bottom of the wheel loose tension, regardless of the path they take from the hub to the rim. The pre-forming of the spokes reduces the frequency of fatigue failure at the hub. Without pre-forming the tension of the spokes required to matched the radial stability is much greater, resulting in excessive rim compression with the lateral instability that results. The It would not apply should the spokes be loose before loading, so does not apply to all tensile spoked wheels. To exclude some wheels because they are not up to some sort of arbitary tension is not a valid argument to support the theory that the wheel is supported by a decrease in tension. But if they are not up to adequate tension, then when the bottom spokes slacken with load, they fail your test of maintaining lateral stability. Therefore, any wheel which remains stable must be pre-tensioned, and any wheel that is pre-tensioned supports loads by decreases in tension. A theory on wheel support is incorrect if it excludes those specious wheels, which although servicable, would not be normally acceptable for service. To say the rim is restrained by the spokes satisfies all conditions of a tensile spoked wheel. When you say any wheel, you should stick to it. It is also erroneous for you to say "a pretensioned wheel supports loads by decreases in tension" when you know increases in tension over the top of the wheel take place. Your explanation on a pretensioned wheel is influential without resorting to the sites. I'll give it further thought. That is a poor approach. Your thoughts should be guided by the physical evidence, and not by what you assume the physical evidence should be based on your mental ramblings. I have not measured spoke tensile forces or rim compression as they are not at critical levels in my wheels due to the technique of wheelbuilding I advocate. The tensioning of spokes in others wheels is not relevant to my method. I have no intrest in wheelbuilding techniques that produce a wheel with demonstrable risk of failure. The unwarranted incessant contradiction of my postings is evident of your mental state however. I think this 95% shift may only occur in a grossly pre-tensioned wheel. My methods do not require gross pre-tensioning so how similar, measured results will be is questionable. Wheels are linearly elastic, so the decrease tension of the bottom spokes equal to 95% of the load will be the same regardless of the the initial tension in spokes. (This is required by Hooke's Law.) Hookes law applies to solids and does not apply when components are taken out of their elastic range, which is bounded by the limit of proportionality. I do not feel that Hookes law should necessarily be applied to a wheel due to the sliding movement evident from wear at the spoke crossing. The use of a tied and soldered wheel I may have found more acceptable. The crossing of spokes puts a bend in them, the relative varience in tension of a pair of spokes means that each spoke has behaviour approaching a damped spring. The crossing of the spokes generally reduces the loading and unloading rate of the spoke which is thought to effect fatigue progression. If all bottom spokes become loose when the load is applied, the top spokes wholy(100%) take the load, the bottom spokes are not functioning. But of course yours is a specious argument to support a specious wheel. The fact still remains that lateral and radial stability along with reduced spoke failures can be attained by pre-forming the spokes at their crossing. Please elaborate. The forces inside the wheel caused not the external load can not be eliminated, only re-distributed. How does your pre-forming change the force distribution? By making the kink at the crossing, the spoke takes the shortest possible route(with crossed spokes) between rim and hub. This enables it to better restrain the rim as tendancy for the rim to move out is countered more positively than by a spoke which is left without the correct shaping. Interestingly, you have laid out all the pieces on how wheels support a load, you just have to put them together. A load on a wheel causes a decrease in tension in the bottom spokes almost equal to the applied load. The bottom spokes must not completely slacken, or the wheel loses lateral support. Therefore, the spokes in the bottom wheel must have some pre-tension, to keep from slackening when a load is applied. Since the greater the applied load, the more tension is lost in the bottom spokes, higher loads require more spoke pre-tension. In other words, the strength of the wheel is directly related to the amount of static tension in the spokes. Of course, there are practical limits to how much static spoke tension a given wheel can stand, but in general, a tighter wheel is a stronger wheel. I did not say decrease in bottom spokes is nearly equal to the load. If I ever talk about spoke tensions in relation to the general support of how the wheel bears its load by force distribution as a whole, a call for vectors would be in order. I'll repeat again read the subject heading " The Basics of Wheel Alignment and Wheelbuilding", theory of how a wheel bears its load was not warranted, your off topic. Where I agree or disagree with you is not relevant to an improved wheelbuilding method. Trevor Do I understand your method as putting a "kink" in each spoke at the exact crossing point, at the exact angle, and rotationally on the spoke in the exact position.... before the spokes are assembled into the wheel? How exactly do you do that? I am not arguing against the concept, just wondering how you go about accomplishing it. Further, it would be useful to know how you measure the benefit(s). It seems that there are many methods used and contrary statements made. Sapim says don't bend the spoke elbow from it's factory position. Bontrager Wheel Works and others seem to say that bending is not only OK but should be done to attain alignment with the hub flange. The only general agreement between the two most respected spoke manufacturers (DT & Sapim) is that the use of spoke head washers is of benefit. I have built about 950 wheels. I am still learning. I am always interested to learn how things can be done better... but I want substantiated proof. -- daveornee |
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The Basics of Wheel Alignment and Wheelbuilding
On Sun, 8 Aug 2004 04:23:46 +0100, "Trevor Jeffrey"
wrote: wrote in message ... On Fri, 6 Aug 2004 07:06:12 +0100, "Trevor Jeffrey" wrote: [snip] I have ridden a bare rim after tearing a tyre cased by wheel collapse (constructed as instructed in JB's book) during sprinting. It was the poor stability of this wheel made me want to investigate further on constructional techniques. [snip] Dear Trevor, Could you explain this a bit more? That is, what exactly does "wheel collapse" mean to you? It sounds catastrophic, since it caused a torn tire. Wheel buckled to lock up in frame pitching me to ground. Did you somehow repair this wheel and continue riding on it after removing the tire? Or was there a later experiment? tyre was torn where rim joint had twisted, tyre not repairable and was removed. rim wsa partially straightened in drainage grid and front brake pulled to one side as it could not be relaxed to a\llow for rim oscillations. I assume, perhaps incorrectly, that you built a wheel to the best of your ability to Jobst Brandt's suggestions and feel that it had "poor stability" because it collapsed, not that the wheel suffered from "poor stability" after it collapsed, was repaired, and was ridden with no tire. The wheel was constructed to the letter of the method suggested, it had poor lateral stability and it collapsed during sprinting, this is self evident. TJ Dear Trevor, So it was a front wheel that failed during sprinting? Front wheels are usually symmetrical and therefore considerably stronger than dished rear wheels. Front wheels typically bear less weight than rear wheels. To steer, front wheels are free to swivel, unlike rear wheels, which are fixed in the rear triangle. Sprinting doesn't usually involve braking or turning. So it doesn't seem likely that a front wheel with intact spokes collapsed from any unusual forces on its own. You don't mention any spoke damage, just a wheel collapse, but my guess would be that a fatigued spoke happened to break during a sprint (there are no unusual forces on a front wheel in that situation), the out-of-true wheel then jammed, and this jamming and the crash damaged the rim. If this is what happened, the "lateral stability" might be a matter of the number of spokes. Low-spoke-count wheels often cannot be trued enough to spin in the frame when one spoke breaks. Carl Fogel |
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The Basics of Wheel Alignment and Wheelbuilding
On Sun, 8 Aug 2004 07:27:05 +0100, "Trevor Jeffrey"
wrote: wrote in message ... On Fri, 6 Aug 2004 07:35:16 +0100, "Trevor Jeffrey" wrote: wrote in message ... On Fri, 6 Aug 2004 00:42:55 +1000, Weisse Luft wrote: . But you're saying that the variation of the spoke load is less. Is this a matter of both thick and thin spokes being tensioned to X pounds and the thick one going to 0 pounds of tension, a variation of X, while the more elastic thinner spoke doesn't drop as far--say to 10 lbs tension--and therefore has a smaller load range of X -10 instead of the full range of X. Presumably spokes last longer with this smaller load variation. I'm hoping that I've managed to figure out what you (and others) already understood, since it seems clearer than waving my hands and declaring that losing all tension is a bad thing. Steels tested for this, have not shown it to be evident. Reduction of magnitude of load variation may increase life of sample, but the increase of tension before applying load variation does not show benefits for component life. TJ Dear Trevor, Actually, I wrote that, not Weisse Luft. You may have misunderstood something here. As far as I know, both the butted spokes with the thinner midsection and the straight spokes would be tensioned to the same force of X pounds of tension. It's the increased elasticity of the thinner double-butted spoke that reduces the variation of tension. A wheel with infinitely thick spokes does not require pretensioning, so the thicker spoke requires less tension than the thinner spoked wheel. The materials elasticity does not change with section, I understand your usage to mean its more stretchy. When the thicker and therefore less elastic straight spokes contract enough to go from X pounds to 0 pounds of tension, they have experienced the full range of possible tension variation. A greater load would be required for the wheel with thicker spokes for them to become loose. In the same situation, the thinner and therefore more elastic double-butted spokes start at the same X pounds of tension, but do not relax to 0 pounds of tension. Their range of variation is therefore smaller. The situation is not the same because the thicker spokes make a stiffer wheel with less deformity for the same load. Again, both kinds of spokes began at the same tension in the wheel. The difference is that the thick spokes will lose all tension well before the thin spokes do. No, because the thicker spoke has greater resilience, the rim will deform less due to better constraint. The smaller rim deformation results in lower tension loss in the low spokes. Trevor Dear Trevor, I'm puzzled by a number of things that you write. What do you mean, for example, when you say that the thicker spoke has greater resilience? As I understand it, a thicker spoke shows less elastic deformation under the same tension as a thinner spoke. Carl Fogel |
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The Basics of Wheel Alignment and Wheelbuilding
The Brandt book says butted spokes stretch more in the middle and less at
the ends, resulting in less metal fatigue in these vulnerable areas. wrote in message ... On Sun, 8 Aug 2004 07:27:05 +0100, "Trevor Jeffrey" wrote: wrote in message ... On Fri, 6 Aug 2004 07:35:16 +0100, "Trevor Jeffrey" wrote: wrote in message ... On Fri, 6 Aug 2004 00:42:55 +1000, Weisse Luft wrote: . But you're saying that the variation of the spoke load is less. Is this a matter of both thick and thin spokes being tensioned to X pounds and the thick one going to 0 pounds of tension, a variation of X, while the more elastic thinner spoke doesn't drop as far--say to 10 lbs tension--and therefore has a smaller load range of X -10 instead of the full range of X. Presumably spokes last longer with this smaller load variation. I'm hoping that I've managed to figure out what you (and others) already understood, since it seems clearer than waving my hands and declaring that losing all tension is a bad thing. Steels tested for this, have not shown it to be evident. Reduction of magnitude of load variation may increase life of sample, but the increase of tension before applying load variation does not show benefits for component life. TJ Dear Trevor, Actually, I wrote that, not Weisse Luft. You may have misunderstood something here. As far as I know, both the butted spokes with the thinner midsection and the straight spokes would be tensioned to the same force of X pounds of tension. It's the increased elasticity of the thinner double-butted spoke that reduces the variation of tension. A wheel with infinitely thick spokes does not require pretensioning, so the thicker spoke requires less tension than the thinner spoked wheel. The materials elasticity does not change with section, I understand your usage to mean its more stretchy. When the thicker and therefore less elastic straight spokes contract enough to go from X pounds to 0 pounds of tension, they have experienced the full range of possible tension variation. A greater load would be required for the wheel with thicker spokes for them to become loose. In the same situation, the thinner and therefore more elastic double-butted spokes start at the same X pounds of tension, but do not relax to 0 pounds of tension. Their range of variation is therefore smaller. The situation is not the same because the thicker spokes make a stiffer wheel with less deformity for the same load. Again, both kinds of spokes began at the same tension in the wheel. The difference is that the thick spokes will lose all tension well before the thin spokes do. No, because the thicker spoke has greater resilience, the rim will deform less due to better constraint. The smaller rim deformation results in lower tension loss in the low spokes. Trevor Dear Trevor, I'm puzzled by a number of things that you write. What do you mean, for example, when you say that the thicker spoke has greater resilience? As I understand it, a thicker spoke shows less elastic deformation under the same tension as a thinner spoke. Carl Fogel |
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