Maybe check the 300 page wheelbuild ing thread instead of perpetuating an off topic thread with no purpose.
The correct answer is "NO you cannot triplet lace a 16" wheel and there's no reason to ever do so"
Help triplet lacing a Shimano Alfine hub?!
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bm0p700f
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Wheel stiffness is a function of the both bracing angles not just one. The question has been answered and not understood that is the fustration.
Also saying wheel stiffnes varies from one side to the other is misleading. The load required to detension the spokes is different on both sides. That is a whole lot different to saying the stiffness on the NDS is less than the DS. That is what is mistaken, I have tried and obviously failed to explain stiffness and loads on spokes are different things and should be confused. The best article I have seen written on this is here. I suggest you read it.
http://www.rouesartisanales.com/article-23159755.html
As the NDS flange is moved wheels stiffness increases, that should be the case for both sides as moving the rim to the left means the DS spokes are stretched a bit and they have a certain stiffness to resist that change in length, they also pull on the rim to restore back to centre. The question is flawed that the problem.
If that explains it better tell Orfintho.
Also saying wheel stiffnes varies from one side to the other is misleading. The load required to detension the spokes is different on both sides. That is a whole lot different to saying the stiffness on the NDS is less than the DS. That is what is mistaken, I have tried and obviously failed to explain stiffness and loads on spokes are different things and should be confused. The best article I have seen written on this is here. I suggest you read it.
http://www.rouesartisanales.com/article-23159755.html
As the NDS flange is moved wheels stiffness increases, that should be the case for both sides as moving the rim to the left means the DS spokes are stretched a bit and they have a certain stiffness to resist that change in length, they also pull on the rim to restore back to centre. The question is flawed that the problem.
If that explains it better tell Orfintho.
Interessting reading, but not a single word about our problem. (Only the fact, that the immense lateral stiffness of realy deep rims, leads to brake pads rubbing at rims.)
As the NDS flange is moved wheels stiffness increases, that should be the case for both sides as moving the rim to the left means the DS spokes are stretched a bit and they have a certain stiffness to resist that change in length, they also pull on the rim to restore back to centre. The question is flawed that the problem.
The wheel is balanced. And it stays balanced, independent of the NDS flange position.
Say you want to move the NDS flange and keep DS tension and rim position stable. Then you have to change spoke tension at NDS too. You have to do so, as long as the lateral force wich comes from the NDS spokes is equal to the lateral force coming from DS spokes again. In short: The farther the NDS flange away from the middle, the lower the tension.
If you decrease NDS tension too much, the rim will move to the left and the situation at DS changes. The bracing angle at DS changes to allow the rim to move, and therfore the lateral component of the DS tension changes too. This happens "as long as" the wheel is balanced again.
Code: Select all
Tnds = Tension NDS.
Tds = Tension Drive side.
sin(AlphaNDS)^2 * Tnds = sin(AlphaDS)^2 * Tds
This means:
the lateral forces on NDS = the lateral forces on DS
If you change AlphaNDS and want to keep the DS stable (wich is the case we discuss here), then you have to change Tnds too. The amount depends on the change of sin(AlphaNDS)^2.
If you change the positon of the rim by adding more tension to NDS, you also change AlphaNDS and AlphaDS (maybe Tds and Tnds too).
A spoke stretches with the tension applied, not with the postion of the rim.
Spokes don't stretch or destretch (does the word exist?) with the tension of the other sides spokes.
That means:
- Lateral stiffness is equal for both sides. This is supported by Sheldons experiment described in his article at #4.
- Changing the NDS flange (without changing anything at DS) does not change lateral stiffness, as the lateral forces are balanced.
I would change my mind, if someone could show, that the radial components of spoke tension would have an impact on lateral stiffness.
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bm0p700f
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"That means:
- Lateral stiffness is equal for both sides. This is supported by Sheldons experiment described in his article at #4. - correct
- Changing the NDS flange (without changing anything at DS) does not change lateral stiffness, as the lateral forces are balanced. - worng
You are also correct in your statement as the NDS flange moves out spoke tension on that side decreases.
Spokes do stretch when loaded.
LAteral stiffness is a function of both the NDS and DS bracing angle, spoke stiffness, spoke count and rim stiffness that is it. Spoke tension has nothing to do with it. If you build wheels it is very apparant that even a few mm difference on the NDS flange to centre of hub spacing has a big impact on stiffness. You can feel it when stressing a wheel. Take for example the old power tap hub with spacing of 32mm/177 and a novatec F172 hub with spacing of 38/18mm. While the old power tap hub hage 70mm PCD on the flanges that does not improve the NDS bracing angle enough and the result is a 28H hub on a stiff archetype rim with sapim race spokes is quite flexible and it quite easy to de tension the NDS spokes with side loads (put the hub on a black of wood and push). Build the same rim in 28H with the same spokes on the novatec hub and it is very stiff to the point you cannot detension the NDS spoke. Detensioning the NDS spokes though will happen on any wheel if the side load is high enough, the stiffer the wheel the more load is needed to displace the rim by one unit (say mm).
Stiffness = load/displacement. So the ammount of lateral displacement for a given load is determined by the wheels lateral stiffness. It does not mean however that the lateral stiffness of a wheel has anything to with loads placed on the wheel. Similarly the spoke has a stiffness in turn effect the overal lateral, radial and torsional stiffness on the wheel. Once again the stiffness of the spoke is not dependant on the tension in the spoke. The young's modulus (a measure of how stiff a material is) is 193 GPa, this is the same if the spoke is loaded or not. Actually if the spoke is loaded beyond the elastic limit this modulus does change but thats another matter.
Old shimano hub especially the 7 speed one give very good NDS and DS bracing angles with 45mm PCD and 37/22mm flange to centre spacings. DT Swiss road hubs anf old power tap hubs have appaling NDS bracing angle which is important to be as high as it can be.
You are still confusing forces and stiffness I think until you unwind that one you will not see what is happening in a wheels. Regardless of the hub dimensions. The lateral forces in any wheel are balanced. They have to be or the rim would move by itself. Radial components of spoke tesnion have nothing to do with this. In fact spoke tension has nothing to do with stiffness. This I think is the confusion you have.
- Lateral stiffness is equal for both sides. This is supported by Sheldons experiment described in his article at #4. - correct
- Changing the NDS flange (without changing anything at DS) does not change lateral stiffness, as the lateral forces are balanced. - worng
You are also correct in your statement as the NDS flange moves out spoke tension on that side decreases.
Spokes do stretch when loaded.
LAteral stiffness is a function of both the NDS and DS bracing angle, spoke stiffness, spoke count and rim stiffness that is it. Spoke tension has nothing to do with it. If you build wheels it is very apparant that even a few mm difference on the NDS flange to centre of hub spacing has a big impact on stiffness. You can feel it when stressing a wheel. Take for example the old power tap hub with spacing of 32mm/177 and a novatec F172 hub with spacing of 38/18mm. While the old power tap hub hage 70mm PCD on the flanges that does not improve the NDS bracing angle enough and the result is a 28H hub on a stiff archetype rim with sapim race spokes is quite flexible and it quite easy to de tension the NDS spokes with side loads (put the hub on a black of wood and push). Build the same rim in 28H with the same spokes on the novatec hub and it is very stiff to the point you cannot detension the NDS spoke. Detensioning the NDS spokes though will happen on any wheel if the side load is high enough, the stiffer the wheel the more load is needed to displace the rim by one unit (say mm).
Stiffness = load/displacement. So the ammount of lateral displacement for a given load is determined by the wheels lateral stiffness. It does not mean however that the lateral stiffness of a wheel has anything to with loads placed on the wheel. Similarly the spoke has a stiffness in turn effect the overal lateral, radial and torsional stiffness on the wheel. Once again the stiffness of the spoke is not dependant on the tension in the spoke. The young's modulus (a measure of how stiff a material is) is 193 GPa, this is the same if the spoke is loaded or not. Actually if the spoke is loaded beyond the elastic limit this modulus does change but thats another matter.
Old shimano hub especially the 7 speed one give very good NDS and DS bracing angles with 45mm PCD and 37/22mm flange to centre spacings. DT Swiss road hubs anf old power tap hubs have appaling NDS bracing angle which is important to be as high as it can be.
You are still confusing forces and stiffness I think until you unwind that one you will not see what is happening in a wheels. Regardless of the hub dimensions. The lateral forces in any wheel are balanced. They have to be or the rim would move by itself. Radial components of spoke tesnion have nothing to do with this. In fact spoke tension has nothing to do with stiffness. This I think is the confusion you have.
bm0p700f wrote:Also saying wheel stiffnes varies from one side to the other is misleading. The load required to detension the spokes is different on both sides. That is a whole lot different to saying the stiffness on the NDS is less than the DS.
That is a great distinction, thank you for making it so clear. As we all know, upon detensioning under large side loads, stiffness goes to s**t. The fact that that the ease of dimensioning most certainly varies directionally, could lead one to believe that the stiffness varies, but deflection under sub critical loads could be exactly the same and you wouldn't know it without a great test jig.
It almost begs further discussion on how thinner gauge spokes on the NDS would play into moving that critical turning point outward vs. the loss in subcritical stiffness...but I'll keep that one for another time and the proper thread!
