Building a 20 spokes powertap wheel?
- Thread starter loaasvold
- Start date
Check out the DT Swiss webpage, which states the Aerolite and Aerocomp are DB bladed spokes. They also make other straight-gauge bladed spokes, eg Aerospeed. Calculating the areas of the Aerolight spokes based on the dimensions (2.0 mm ends/ 2.3 x 0.9 mm blades) you see these started as butted spokes. The straight-gauge New Aero's have the same 2.0 butt ends but a 3.3 x 1.1mm blade section).....and a weight of 437 g. The listed weight of the Aerolights is 278 g, just slightly less than the Revolutions, which are 2.0/1.5/2.0 round butted (14/17/14).
Yep, my wheels which cracked had 32 spokes, 14 ga st, but were cheaper rims. First one was the old Matrix ISO rim, built by Colo Cyclist. Spoke tension seemed high to me, and they never went out of true. Probably lasted 4-5K miles tops before rear spoke started pulling through.
I would be surprised if a CC wheel was not built to proper tension (although I am a high-tension preferred kind of rider). I never rode a Matrix rim...no eyelets IIRC?
Second failure was on a plain Mavic box rim, MA-40 I think, which was built by a good LBS builder. The rim failed not right at the spoke hole, but cracked at the sidewall corner. Went 12-15K miles before failure. (didn't keep good records then).
If you bomb potholes and RR tracks like I do...heheh! I have a pair of old MA rims, but never laced them up. I did ride a boatload of Monthlery's and Super Champ Arc en Ciel's with no issues...and Fiamme right down to the 280 gram flyweights.
I will admit to cracking a Campy Sigma or Omega rim, but those things were damned brittle...precip aged, solution heat treated wonders. And like I said, I abused the hell out of them. I got tagged by a car one time and the rim ended up in four shattered sections. No bending...just breaking. Even the Campy's of those series I put in the 'not so good' category.
Right when eyelets started being deleted to save a few grams and alloys got harder, the cracking started to become a more common problem.
I would be surprised if a CC wheel was not built to proper tension (although I am a high-tension preferred kind of rider). I never rode a Matrix rim...no eyelets IIRC?
Second failure was on a plain Mavic box rim, MA-40 I think, which was built by a good LBS builder. The rim failed not right at the spoke hole, but cracked at the sidewall corner. Went 12-15K miles before failure. (didn't keep good records then).
If you bomb potholes and RR tracks like I do...heheh! I have a pair of old MA rims, but never laced them up. I did ride a boatload of Monthlery's and Super Champ Arc en Ciel's with no issues...and Fiamme right down to the 280 gram flyweights.
I will admit to cracking a Campy Sigma or Omega rim, but those things were damned brittle...precip aged, solution heat treated wonders. And like I said, I abused the hell out of them. I got tagged by a car one time and the rim ended up in four shattered sections. No bending...just breaking. Even the Campy's of those series I put in the 'not so good' category.
Right when eyelets started being deleted to save a few grams and alloys got harder, the cracking started to become a more common problem.
Well, it certainly seems odd that the master of insults is complaining about someone else making an observation which YOU take as an insult ...
- of course, I am delighted that you have all but confirmed that you apparently believe in "Global Warming" despite Global temperatures having apparently NOT gone up for the past 12+ years otherwise you would probably not consider dismissal of fore mentioned Koolaid drinkers to be an insult of said individuals
Despite YOUR pretending to know, FYI, the particular bridge failure was due to side winds which were apparently not accounted for ...
- OR, are you saying that the engineering WAS NOT based on the so-called "science" of the known interactions of the materials with which the bridge was constructed? You know, steel cable stretches, etc. because it is not a brittle (or, stiff) material due to the impurities of alloying with carbon/etc. ...
AND, where it PROBABLY (but, hey, maybe not!?!) applies to bicycle wheels is in the front end shimmy which some people encounter on fast descents ... undoubtedly (PRESUMING the fork & headset are in good working order, of course), changing to a wheel which has less lateral flex will mitigate-or-PERMANENTLY-eliminate the problem.
That is, in addition to side winds OR uneven road surfaces, an out-of-true front-or-rear wheel can induce a unwanted shimmy, too ... and, the more "elastic" double-butted spokes could certainly exacerbate any shimmy.
HARMONICS can be a factor in ANY scale.
Wow. You are all over the place with your claims and arguments. First, your position is so fragile that you have to argue unrelated points to distract the discussion. An example is your Pavlov like drooling over the global warming issue. Sorry, Al, this isn't the forum for that discussion, and judging by what you do say and your of slurs in saying it, you're not equipped for that discussion at all. Further you logic has failed you. My not dismissing global warming is not proof of anything except that I'm not engaging you in that topic. I won't in this forum. I never said that wind wasn't factor in the Tacoma Narrows bridge failure. I said is was the result of design failure, the failure to anticipate things. As for the actual physical causes, there were several that were at work. Note that there is still disagreement among engineers as to why it failed. First, wind did not cause the failure, although vortex shedding did contribute. The vortex shedding was not the result of turbulence on a static bridge but was the result of the torsionally oscillating bridge, i.e. the bridge would gain a high enough angle of attack to shed vortices. The wind did not provide a force on the bridge large enough to cause the torsional oscillations. The bridge's aspect ratio--width over length--was too small, and the bridge was a very flexible bridge. As with all structures, there is an effective spring constant for the structure, both longitudinally, laterally, and torsionally. The bridge was oscillating at a rate such that when it lifted thru torsion the magnitude of the "lift" and the angular velocity of a lifting section happened to be coincident with the direction of the force applied by the wind. Note that the bridge did not fail because the wind and subsequent oscillations struck a harmonic. When a harmonic is hit, the harmonic frequency matches the frequency of the driving force. What the Tacoma bridge was doing was oscillating at frequency different than the stimuli that initiated the oscillation. I think I'm pretty up on harmonics since it is a critical component of my field and was the reason a lab I worked in tested jet engine parts, rocket parts, and ISS parts to identify harmonic frequencies. It's kind of important as you don't want an such devices failing because of the undamped and increasing motion caused by said harmonic. Let me reinforce an idea: engineering is based on science, but it wasn't the science that failed in the Tacoma Narrows. It was a failure in design, and a failure of the engineers. Wheels are a possible contributing factor to the generation of bike shimmy. I never said they weren't. The usual cause of shimmy is the rider's position on the bike, and it's a simple fact that all bikes will shimmy under the right conditions. Stiff wheels cannot permanently prevent shimmy. Like touching one or both knees to the top tube, scooting back in the saddle, and making sure the headset isn't too tight, all wheel stiffness does is change the natural frequency of the bike system. FWIW, the harmonics of concern in shimmy are the torsional harmonics. While less stiff wheels, may contribute to the onset of shimmy, there is no criteria for what is acceptably stiff. I, like many other riders, have descended mountains at a high speed with wheels laced with butted spokes. There is no indication or generalization that indicates wheels laced with butted spokes are bad. Interestingly, the strength of spokes--the origin of your argument--is not a factor in shimmy, so that makes shimmy another one of your red herrings. It appears that when you can't prove a point, you try to shift the topic as evidenced by your forays into global warming, the Tacoma Narrows bridge, and shimmy.alfeng said:
Wow...all that to say the wind caused the failure.
Of course the engineering and design was in error...just as Alf stated. Unaccounted wind loading.
Per wiki:
Historically, the name "Tacoma Narrows Bridge" has applied to the original bridge nicknamed "Galloping Gertie" which opened in July 1940 but collapsed due to aeroelastic flutter four months later, as well as the replacement of the original bridge which opened in 1950 and still stands today as the westbound lanes of the present-day twin bridge complex.
The first Tacoma Narrows Bridge opened to traffic on July 1, 1940. Its main span collapsed into the Tacoma Narrows four months later on November 7, 1940, at 11:00 AM (Pacific time) due to a physical phenomenon known as aeroelastic flutter caused by a 42 mph (68 km/h) wind.
Better stick to trying to prove wind does not affect the travel of sound. Or DB aero spokes. Or T&S spokes. Or just...not.
Of course the engineering and design was in error...just as Alf stated. Unaccounted wind loading.
Per wiki:
Historically, the name "Tacoma Narrows Bridge" has applied to the original bridge nicknamed "Galloping Gertie" which opened in July 1940 but collapsed due to aeroelastic flutter four months later, as well as the replacement of the original bridge which opened in 1950 and still stands today as the westbound lanes of the present-day twin bridge complex.
The first Tacoma Narrows Bridge opened to traffic on July 1, 1940. Its main span collapsed into the Tacoma Narrows four months later on November 7, 1940, at 11:00 AM (Pacific time) due to a physical phenomenon known as aeroelastic flutter caused by a 42 mph (68 km/h) wind.
Better stick to trying to prove wind does not affect the travel of sound. Or DB aero spokes. Or T&S spokes. Or just...not.
Well, I don't disagree with the plausibility of lacing a wheel with double-butted spokes potentially affecting the life of a rim ...
Whether someone believes that it is a compromise to have a wheel which flexes more than one that does not is in the eye of the beholder ...
- IMO, it is a potential compromise to how well a wheel may adversely affect how a wheel will respond and/or handle in the worst-case-scenario(s) which may be encountered ... a compromise which 'I' prefer to live without
FWIW. IMO, the Park Tool "conversion table" graphically provides why double-butted spokes are a serious compromise for a bicycle wheel:
With almost all other tensiometers, the Kgf is read on a dial or a scale.
I believe that the commonly accepted tension is in the 95-to-105 Kgf range.
If you look at the equivalent "deflection" for a 15g spoke and a 14g spoke you will see that the deflection is considerably different -- 21 vs. 23.5 -- not a noodle, but (in lay terms) certainly not as taut ...
Which suggests to ME that the rim can be more readily deflected from its centerline with a wheel laced with a 14-15-14 double-butted spoke when compared with a wheel laced with a straight 14g spoke.
I don't want to say that we should think of a rim as being a sacrificial part of the drivetrain, but rims should be expected to wear out from various reasons. So, if a rider feels that a comparatively flexy wheel is "okay" because they think that it extends the life of the wheel then that is their choice; but, IMO, potential rim life is a poor compromise over diminishing theoretical (at least, in my mind!) handling.
BTW. I suspect that the tension on your rear wheels which were laced with straight gauge spokes which cracked around the nipple holes may have been tensioned to too high a Kgf, particularly if the spoke holes which failed were the ones associated with the driveside spokes of the rear wheel ...
There are a lot of so-called "professional" wheelbuilders whom I suspect are not all that good at what they do ...
Here are two examples of what I refer to as rims which both have a Damascus'd brake surface ...
When a rim (particularly, a front rim!) is THAT heavily Damascus'd then it is, IMO, the sign of a improperly crafted wheel.
Wheel stiffness is not a function of spoke tension, except in the case where a spoke looses all tension as it passes near and through the angle subtending the contact patch. Stiffness is a function of spoke cross-sectional area and rim stiffness. The things associated with wheel stiffness are objective, theory based, and empirically provable.That's all there is to that topic. How much stiffness a customer wants in a wheel, is nearly entirely a function of personal preference, as is what the wheel builder feels is correct. As always, personal preference is not empirical and cannot be quantified via calculation. Personal preference is entirely subjective.
Alf, thanks for the answer. And I follow your example on the Park Tool table. A spoke with a smaller cross section will have more deflection under a given bending or tensile load. The area of the 1.8mm dia center section is 81% of the area of a 2.0mm spoke, so the strain or stretch to a given added tensile load would be 1/.81 or 23% greater. But I fail to see how this means building a wheel with 15 ga spokes, or 14/15 db spokes is any kind of "serious compromise".
Assume you're talking about a compromise in lateral stiffness, not wheel life. Since I've ridden wheels with both 14 ga and db spokes and never noticed a difference in ride or handling due to the difference in lateral stiffness, suppose we just disagree here. My current wheels, DT Swiss 1450's, are built with 14/17 ga "aerolite" spokes. They seem to ride and handle great for me. I can imagine a strong sprinter might want something stiffer, but on flat sprints up to my top speed (35 mph or so), I don't notice a problem with flex.
Those rims do look bad. Have never heard the term "Damascus'd", but I have seen rims with that kind of wear on the braking surface. Actually, a buddy's wheels look like that ....he got them with an ebay "bargain" bike. Agree that would indicate a wheel built with too much tension.
Assume you're talking about a compromise in lateral stiffness, not wheel life. Since I've ridden wheels with both 14 ga and db spokes and never noticed a difference in ride or handling due to the difference in lateral stiffness, suppose we just disagree here. My current wheels, DT Swiss 1450's, are built with 14/17 ga "aerolite" spokes. They seem to ride and handle great for me. I can imagine a strong sprinter might want something stiffer, but on flat sprints up to my top speed (35 mph or so), I don't notice a problem with flex.
Those rims do look bad. Have never heard the term "Damascus'd", but I have seen rims with that kind of wear on the braking surface. Actually, a buddy's wheels look like that ....he got them with an ebay "bargain" bike. Agree that would indicate a wheel built with too much tension.
Well, I guess that reading the chart is a matter interpretation ...
Just to clarify, if ~100 Kgf is the desired tension, then ...
- at ~100 Kgf a 14-15-14 double-butted spoke has approximately the same deflection as a 14g spoke at only 76 Kgf ...
- and, at ~100 Kgf your 17g ([COLOR= rgb(255, 140, 0)]¿1.6mm?[/COLOR]) cross sections have the equivalent deflection of a 14g at a meager [COLOR= rgb(255, 0, 0)]59 Kgf[/COLOR] ...
Loose (aka "flexy") & too loose, IMO ... at least, on paper.
DAMASCUS'D. You may-or-may-not have previously seen a Damascus Steel Blade without knowing THAT was what it was called ...
- on a Damascus Steel blade the steel is folded & forged MANY times
- the forging theoretically removes the "impurities" in the steel
- the more folding-and-forging, the more layers
- the layers become visible when the blade is shaped and honed
- the more layers, the better (as in "less brittle") the blade ... in theory, at least
- regardless, on a steel blade, the visual effect is rather striking
The variation in the rim's braking surface of a poorly crafted wheel is particularly visible with an older, anodized rim whose brake surface has not been machined ...
IMO, those distinguishable layers echo the layering of a Damascus Steel Blade to me ...
Referring to the particular type of brake surface wear as "Damascus'd" is to use an imperfect label ...
But, heck, it's MY euphemism to describe THAT type of uneven braking surface ...
- use it if if makes sense as a shorthand description ...
- don't adopt it if it doesn't
Rinse. Shampoo. Repeat. Increasing spoke tension does not increase wheel stiffness so long as spokes are not slack. Spoke tension varies directly with the effective cross sectional area (which is calculated from the effective spring constant). Proof:
alf, I did read the chart as you meant, could see that you selected the 100 kgf point for both the 2.0 and 1.8 mm spokes. I replied in terms of the diameter of the spoke, because it's only the cross-sectional area that matters, not the tension. The gauge numbers are looking at the bending, or beam deflection of the spoke. That does vary with tension, like a taut string level-line with a level hanging in the center. As a result, for measuring actual spoke tension, deflecting the spoke with a gauge is a proxy. But spokes aren't loaded this way on the wheel, they of course see straight tension loads from rider weight, bumps in the road, standing climbing, sprinting, etc.
The reason that preload tension doesn't affect stiffness is that the stress/strain curve for steel is generally linear in the operating region, up to the yield point.....ie, the modulus of elasticity is constant. You can look up a generic stress/strain curve for mild steels and see the straight line up to the yield point where the spoke turns to taffy and then breaks. So, if the modulus is constant, that means for every kgf added to the spoke, say by pushing the rim sideways, the spoke stretches the same amount, whether the tension is set at 60 kgf or 100 kgf. Sure, the looser spoke will deflect more when pushed by hand or gauge from the middle, but that just isn't the same as a end load, and it means nothing to the stiffness of the wheel.
Since the modulus is basically the same for all steel spokes, only the cross-sectional area of the spoke really matters, apart from the stiffness of the rim and number of spokes. This is what alienator has been saying almost forever here.
The reason that preload tension doesn't affect stiffness is that the stress/strain curve for steel is generally linear in the operating region, up to the yield point.....ie, the modulus of elasticity is constant. You can look up a generic stress/strain curve for mild steels and see the straight line up to the yield point where the spoke turns to taffy and then breaks. So, if the modulus is constant, that means for every kgf added to the spoke, say by pushing the rim sideways, the spoke stretches the same amount, whether the tension is set at 60 kgf or 100 kgf. Sure, the looser spoke will deflect more when pushed by hand or gauge from the middle, but that just isn't the same as a end load, and it means nothing to the stiffness of the wheel.
Since the modulus is basically the same for all steel spokes, only the cross-sectional area of the spoke really matters, apart from the stiffness of the rim and number of spokes. This is what alienator has been saying almost forever here.
Interesting ... alienator may-or-may-not have been expressing the same thing, but he is so inarticulate that he has failed to convey what was in his mind in a meaningful way ... Think about how meaningless the chart he recently posted in this thread is ... There is NO indication what tension the chart producer felt was at "full tension"
- at 125kgf, a few full turns of the nipples would change nothing (a sustainable, but ill advised tension).
- at 100kgf, it could matter
- then the myth of a smaller cross section being more elastic is an absurd reason to choose DB spokes unless it is for weight or appearance
- and if the myth is true that a DB spoke is more elastic then it follows that the RIM can be deflected further -- either manually in a stand or when riding -- when the spokes go through their elastic phases (for want of a better term) and the rim temporarily ovalizes
- the easiest test would be to make a front-or-rear wheel OUT OF TRUE by 1/16" (or, more!?!) before a descent to simulate a possible deflection to see at what speed it may-or-may-not become a factor ... 20mph, okay, maybe not ... 30mph, possibly ... 40mph , probably.
- IS EVERYONE RIDING AT LESS THAN 15mph?!?
To illustrate what dhk2 and I have said, let's have an example. See the attachment. [ATTACHMENT=345]Tension.pdf (117k. pdf file)[/ATTACHMENT] Note that I just noticed I left off the minus sign for the final result for each x2-x1. It doesn't matter as the answer is still the same.
alf, basically agree you don't need to pay extra for DB spokes. I had a couple of rear wheels rebuilt by LBS over the years, and went with straight 14 ga. spokes. Recall one of the builders said he preferred to work with the straight ga, as there was less windup when bringing them up to tension. If you don't care about saving grams, nothing wrong with straight gauge at all. And fully agree they do result in a wheel that's stiffer laterally.....but it's because of that larger cross-section, not because they can carry higher tensile loads or resist bending better.
Concerning cornering lateral loads on wheels and tires, it's an issue for trikes and cars, but not for two-wheeled vehicles because we corner by leaning. The force generated in a steady-state turn is strictly a function of lean-angle on the bike, with the force vector pushing back from the ground thru the center line of the mass on the bike. As long as the rider keeps centered over the saddle, the total force of gravity and cornering loads comes up right through the center of the wheel, so no lateral load on the wheel. Agree if we cornered flat like a car or trike, the lateral loads would be a huge problem to wimpy wheels.
Because there are no significant lateral loads on the wheels while cornering, my skinny-spoked climbing wheels do just fine on high-speed twisty descents. They do need to be strong enough to handle the additional cornering loads however. In an extreme limit turn on a road bike with good race tires on perfect pavement, say a 45 deg lean is possible with safety. That's 1G of cornering force, which results in a vector load of the square root of 2 (1.41) times the bike/rider weight. So, in that extreme turn, the bike/rider puts 41% more "weight" on the tires and wheels.
Concerning cornering lateral loads on wheels and tires, it's an issue for trikes and cars, but not for two-wheeled vehicles because we corner by leaning. The force generated in a steady-state turn is strictly a function of lean-angle on the bike, with the force vector pushing back from the ground thru the center line of the mass on the bike. As long as the rider keeps centered over the saddle, the total force of gravity and cornering loads comes up right through the center of the wheel, so no lateral load on the wheel. Agree if we cornered flat like a car or trike, the lateral loads would be a huge problem to wimpy wheels.
Because there are no significant lateral loads on the wheels while cornering, my skinny-spoked climbing wheels do just fine on high-speed twisty descents. They do need to be strong enough to handle the additional cornering loads however. In an extreme limit turn on a road bike with good race tires on perfect pavement, say a 45 deg lean is possible with safety. That's 1G of cornering force, which results in a vector load of the square root of 2 (1.41) times the bike/rider weight. So, in that extreme turn, the bike/rider puts 41% more "weight" on the tires and wheels.
It's clear you don't understand the theory. It's evidenced in the the false assumptions you make. The test Sheldon brown did three weeks after the first test is independent of the first test, yet it confirms the results of the first test that show that changing spoke tension does not change lateral stiffness. Stiffness is the effective spring constant and tells you what force is needed to either stretch or compress an object, or it tells you how much an object is compressed or stretched if a given force is applied. the relationship between force and displacement is a linear relationship throughout the elastic region of that curve, i.e. the region throughout which stretching or compressing do not cause permanent deformation. The curve become non-linear when it enters the plastic region, the region in which stretching or compressing leaves a permanent deformation. The tire being mounted or not doesn't say anything about the spoke tension having no impact on wheel stiffness. Likewise it doesn't matter if it was the back wheel or the front wheel. Read the pdf. The appropriate equations are simple to understand. Your introduction of the Keeling curve is another attempt to change direction and avoid the topic at hand. Likewise, it's another useless attempt to inject politics into a topic which apolitical. It doesn't build any credibility for you. Sheldon Brown's curve, as presented, is perfectly appropriate. It shows that in two different tests, the nature of the effect of spoke tension on wheel stiffness (which when divided into a lateral force, gives the stretch of a given spoke. The procedure was simple: loosen nipples one turn, apply load, and measure deflection. Repeat. Continue until spokes start to go slack (points 9 and 10 in each test). The time between the two tests if of no significance at all, so long as the spokes were not slack. It's obvious from the plots that the spokes were not slack after three weeks. The higher gauge spoke/smaller diameter spoke having less stiffness says nothing about whether it's wise to buy and use such a spoke. To have that mean something would require establishing an objective baseline for what is appropriate stiffness for a wheel. No such baseline exists. It's entirely dependent on what a builder and/or the rider think is appropriate. If you don't like such spokes, that's your personal preference, not a matter of theory or empirical truth. As has been repeated at least twice so far in this thread, although without counting I actually think it might be three times......spoke diameter does effect stiffness. So what? Again, there is no absolute definition of how much lateral deflection, i.e. wheel stiffness, is appropriate. More to the point, there is no empirical conclusion that double butted spokes or smaller diameter spokes are bad. Your point about loads applied by squeezing spokes, deflecting the rim by hand, or the dynamic loads on a wheel of a rider riding through at turn at a given speed, is no point at all. So long as a spokes are tensioned so that they don't go slack and don't enter the plastic region of their stress strain curves, it doesn't matter how the load is applied. You've also ignored the statements of others about doing high speed descents on double butted spokes, some less than 15 gauge in size. A wheel out of true absolutely does not simulate a lateral displacement due to load. A lateral displacement due to load, remains stationary, i.e. at the contact patch. A wheel out of true changes the mass distribution of the wheel and thus the moment of inertia and its location. In other words, it slightly changes the balance on the wheel. As such the moment of inertia orbits the axle's rotational axis, creating a cyclic loading of the wheel. Shimmy, the harmonic rotational torsion of the frame, will happen on every single bike at a given speed, no matter how true the wheels are since wheel trueness is only one of a number of causes for shimmy. Coming to understand these points is good for any mechanic as it allows the mechanic to give a customer factual information, which is very good for the customer. Customers are not well served when given false information.alfeng said:
You clearly don't get how equations work, so go ahead, refuse to learn anything that might contradict the mythology that you hold dear and with which you infect your customers. I'm sure your peers at the Flat Earth Society meetings will be proud. For the record and since you are intellectually incapable of understanding, the equations in the pdf are perfectly correct. Each of the two scenarios, i.e. each the different starting tensions represents a a 5N transient impact as you might get from a bump, a small hole in the road, and etc. This represents what variables typically do: change. What they do is right there in the name, "variable", i.e. "changeable". Variables that don't change are called "constants." The constants in the given equations are identified. If you had taken or passed algebra, you'd have got that. My daughter got that in 7th grade, as did the rest of her class. Here's a link to the Wikipedia page that defines and describes variables. Give it a read. It might be enlightening.alfeng said:
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