Bicycle Mechanics - Mixed wheel lacing question

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View Full Version : Mixed wheel lacing question

Metaluna
06-14-08, 05:21 AM
I've been looking at building a new rear wheel (based on a 36h Centaur hub and DeepV rim), and have been looking at lacing methods that claim to address the spoke tension imbalance caused by the large dish of the Campy 10sp hubs.

I've been reading Robert Torre's wheel lacing pages (http://www.geocities.com/spokeanwheel/lacingsr.htm), specifically the one where he talks about 2X/3X mixed lacing, and I'm confused about something. On other parts of his website, he discusses more radical mixed lacings such as half radial and half-crow's-foot. With those lacings, the premise seems to be that the closer to radial the spoking pattern is, the more lateral strength the wheel will have. With this in mind, he talks about lacing the drive side with the radial or half-crow's-foot pattern, and the non-drive side with a conventional crossing pattern such as 2x. The idea is that, for a given spoke tension, the radial spokes will have a stronger lateral "pull" to the drive side, allowing you to dial in a higher tension on the non-drive side to keep the rim centered, which should in turn help keep the spokes from flexing and loosening on the n.d.s.

I'm a bit nervous about using any radial spokes at all on a low-flange hub, especially at my weight (255#), so as a compromise, I was thinking about trying a 2x/3x mixed pattern. With the previous discussion in mind, it seems to me that a 2x pattern will have slightly higher lateral strength since the spokes come off the hub at a more radial angle, and thus would be appropriate for the drive side to balance a 3x lacing on the non-drive side. However, on this (http://www.geocities.com/spokeanwheel/lacingsr.htm#23) page he pretty clearly states that the wheel should be laced 2x non-drive/3x drive, which seems backwards to me. The diagram seems to bear this out, as you can see that the position of a theoretical 3x-laced spoke on the n.d.s. seems to leave the hub at a more perpendicular angle to the axle, and therefore will have less lateral pull on the rim for a given spoke tension (again, this should be a good thing on the n.d.s., since it means you need more tension to balance the d.s.). So is my analysis incorrect, or are there other factors in play that cause this "backwards" lacing to work out better than the one I proposed?

My current rear wheel is a Mavic CXP33 laced 3x both sides with DT 14/15 spokes, and despite my best efforts at keeping consistent tension (using a tensiometer), I still have spokes loosening up on me on the left side every 1000mi or so. Right now I have the drive side at some insanely high tension like 170kgf, and the wheel dish is still a couple of mm off to the left (IIRC, the n.d.s spokes are in the neighborhood of 80ish kgf at the moment). Anything lower than that and the left side spokes have to be uncomfortably loose. One thing I may try is just replacing the CXP33 with a DeepV, keeping the same hub, and redoing the 3x lacing. I'm beginning to suspect that the CXP33 may be a bit warped and therefore requires some uneven tension to true it up. That also allows me to reuse my nice Record rear hub.

bubbagrannygear
06-14-08, 07:04 AM
So is my analysis incorrect, or are there other factors in play that cause this "backwards" lacing to work out better than the one I proposed?

I believe there are other factors in play. Think in terms, that tangential spoking is more able to resisit braking and pulling forces than radial and therefore more affected by them. Since the non drive spokes are under less tension than the drive, when pulling or breaking forces are applied to tangentialy laced non drive spokes, their tension reduces to the point where there is nothing to keep the nipples from backing off. If they are radially laced they will not "see" the breaking or pulling forces to the same extent, and therefore won't experience the same reduction in tension.

Since 2X is closer to radial than 3X, you want the 3X on the drive and the 2X on the non-drive. (also I share your hesitancy about going completely radial on the hub you mention).

eddy m
06-14-08, 07:32 AM
The simplest way to equalize the strain in each side is to use a lighter gauge spoke on the non-drive side. Use straight gauge in the right and double butted on the left, or double butted in the right and even lighter gauge on the left. If you are building them yourself, straight gauge will be easier to tension because they resist wind up better than lighter spokes. Laced it all 3X, you will not notice the difference between 2X an 3X, but it will be a little stronger torsionally, or you could make the drive side 2X to make that side a little stiffer laterally. The drive side is less stiff laterally because the flange is so close to the center line.
Try respoking your current wheels with very light spokes on the left side before you build up a complete wheel. You will see I am right.

em

dabac
06-14-08, 07:38 AM
Whew, that was a long post. I'll try to address some of your questions:
1) A "conservatively" built wheel (ie high spoke count 2X, 3X good components etc) is so strong that very few people (if any) really have seen enough wheels ridden to destruction under comparable circumstances to be able to say clearly what the consequenses of a certain build/lacing technique will have on riding characteristics and durability.
There are a lot strong opinions out there, but once you put different(but still comparable) wheels to repeatable lab tests the differences actually registered are often marginal.
2) the theoretical differences between 3X and 2X are small indeed. Proving that the difference in durability of two human-built, human-ridden wheels would depend on one being 3X and the other 2X would be highly questionable.
3) a half-radial rear, whether its DS or NDS offers a chance to improve the spoke angle and tension balance a little if you lace NDS heads-out or DS heads-in.
If you're using a rear hub with a chunky hub spindle you'll get all the torque transfer you'll ever need, so that's not always an issue.
Hubs with narrow hub spindles CAN be snapped during cruel and unusual tinkering sessions, so they might be less suited for a radial DS.
Bottom line is that the increase in tension balance offered by a half radial is measured in a few %, so don't expect too much from it.
4) That someone would be able to detect a significant improvement from a crow's foot lace seems highly improbable, although the theory is reasonably sound.
5) A far easier way to get a more durable wheel (if you're breaking NDS spokes) is to compensate for dish by using different spoke diameters. Damon Rinards spocalc tells you the left/right tension ratio for a given hub/rim combo, based on that you can calculate what spokes to use. Last rear I built would have ended up very near evenly balanced if I'd gone for 2mm DS spokes and 1,5mm NDS spokes. There's more tension compensation to be had by mixing spoke diameters than by mixing lacing patterns.
For instance, cross section area of a 2 mm spoke is 3,14 mm2, and 1,77mm2 for a 1,5 mm spoke. So if your NDS tension is half of your DS you'd end up with a fairly decent balance in terms of cross sectional load by using 2mm DS spokes and 1,5 mm NDS spokes.

eddy m
06-14-08, 08:25 AM
I've been reading Robert Torre's wheel lacing pages (http://www.geocities.com/spokeanwheel/lacingsr.htm), specifically the one where he talks about 2X/3X mixed lacing, and I'm confused about something.

I just checked out that page, and he makes several claims based only on his own analysis, without testing his conclusions experimentally. Unfortunately, his analysis is wrong. HE has partial free body diagrams of wheels which he believes show equal spoke tensions whenever the actual spoke lengths are equal. In fact, in order to have equal tension, the angle between the spoke and the plane of the rim need to be equal. The length of the spoke has not much to do with it. If I had better graphics, I would draw the correct free body diagram.
I would disregard everything on that site.

em

Ex Pres
06-14-08, 08:20 PM
Might want to PM waterrockets (sp?) he has been doing some interesting real world experimentation himself with mixed cross lacings. If I were you I might try 4X/2X just for fun.

Metaluna
06-16-08, 05:59 AM
Thanks to everyone for the feedback. I think I'm going to try dabac and eddy m's suggestion of 3-cross lacing with 2.0mm straight gauge spokes on the drive side (and 2.0/1.8 on the nds). I'm not sure I understand why the spoke tensions would be any different than using double-butted spokes on both sides, since the angles and forces should all be the same in the static situation, but perhaps the dynamic loads are different with the less stretchy straight gauge on the drive side (e.g. the hub will twist less when pedaling, so there will be less load transmitted to the nds spokes, so less flexing there)

In any event, this would be an easy and relatively cheap experiment that I could do on my existing hub and rim without notching up a new hub shell with an experimental lacing pattern. Also, this wheel has had enough miles (4000+) and re-truings on it that a spoke replacement wouldn't be the worst thing in the world anyway.

One mistake I think I made on this wheel was to lube the spoke threads on both sides, which may have contributed to the loosening problem. When I rebuild it I'll try leaving the nds threads dry and only lube the drive side (I use 90w gear oil as per Jobst Brandt), though opinions are always welcome.

dabac
06-16-08, 06:56 AM
I'm not sure I understand why the spoke tensions would be any different than using double-butted spokes on both sides,
Basically that's because we're trying to discuss fairly specific engineering issues using everyday language - and we're losing detail in the process.

In reality there are (at least)two different "tensions" that a spoke has to deal with:
1) the force by which the spoke is pulling the rim towards the hub.
2) the force experienced by the spoke's cross section.

Suppose you have same dia spokes on DS and NDS, 100 kg DS tension and 50 kg NDS tension. This means that force by cross section will be half in the NDS spokes as compared to DS spokes.
Now, if you were to replace the NDS spoke with one that only had half the cross section area, then the force by cross section would be the same for both spokes - even if one side is only seeing half the pull.

Why is this good you wonder?
Well, it's because the force by cross section has a lot to do with a spoke going slack or not. A higher force by cross section will help preventing the spoke from going slack, which will protect it against breakage through fatigue.

PNB
08-13-08, 06:40 AM
Think in terms, that tangential spoking is more able to resisit braking and pulling forces ...

Sorry for the intrusion - I´m just starting learning how to lace wheels.

But I don´t believe that spokes would/should resist any force due to braking.
Otherwise won´t be possible to lace a front wheel radial.
During braking, forces are applied to the rim and there is no torque among this and the hub.

So my understanding.

Edit:

Ups!
Unless you talk of disk brakes, then sure.
I Forgot them ...

waterrockets
08-13-08, 07:11 AM
Thanks to everyone for the feedback. I think I'm going to try dabac and eddy m's suggestion of 3-cross lacing with 2.0mm straight gauge spokes on the drive side (and 2.0/1.8 on the nds).

The gauge of the DS spokes is not going to affect the NDS spokes' durability. There may be the tiniest of effects due to the rim being a bit stiffer on the DS, but it wouldn't impact durability at all.

So, I think that a wheel with 2.0/1.8/2.0 NDS with a straight gauge DS is actually less durable than just 2.0/1.8/2.0 on both sides.

If you are going to try to eliminate fatigue on the NDS by controlling spoke gauge, just go thinner on the NDS, and carry on as you normally would for the DS.

I wouldn't recommend a straight gauge DS spoke unless you have some serious lateral stiffness issues (in which case I recommend a higher hub flange too). A 2.0/1.8/2.0 DS spoke will be more durable than straight gauge because it has to stretch further to reach tension. This means that displacing forces to the rim will be less likely to have enough movement to completely de-tension a given spoke. Also, cyclic forces don't change the tension as much with a thinner spoke, so there is less fatigue.

On the NDS, I'd recommend 2.0/1.5/2.0. This will enable them to stretch more at their lower tension, and offer the same benefits as thinner spokes on the DS.

Metaluna
08-13-08, 07:35 AM
Sorry for the intrusion - I´m just starting learning how to lace wheels.

But I don´t believe that spokes would/should resist any force due to braking.
Otherwise won´t be possible to lace a front wheel radial.
During braking, forces are applied to the rim and there is no torque among this and the hub.

So my understanding.

But ultimately the braking force has to be transmitted to the hub somehow, because this is where the force opposing the forward motion of the bike is applied (unless it's transmitted through the brake/fork crown). Obviously radial front wheels don't collapse when you touch the brakes, so presumably the spokes manage to transmit the braking force somehow, I'm just not sure how to analyze the forces.

Metaluna
08-13-08, 07:41 AM
The gauge of the DS spokes is not going to affect the NDS spokes' durability. There may be the tiniest of effects due to the rim being a bit stiffer on the DS, but it wouldn't impact durability at all.

[...]

On the NDS, I'd recommend 2.0/1.5/2.0. This will enable them to stretch more at their lower tension, and offer the same benefits as thinner spokes on the DS.

Hmm...I actually have two nearly identical rear wheels to play with (same rim, same spoke count, and nearly the same hub). Maybe I'll try rebuilding one of them with 2.0/1.5 and 2.0/1.8 spokes as you suggest and see if I notice any difference in durability compared to the other one, which has the straight gauge spokes on the DS.

waterrockets
08-13-08, 07:54 AM
But ultimately the braking force has to be transmitted to the hub somehow, because this is where the force opposing the forward motion of the bike is applied (unless it's transmitted through the brake/fork crown). Obviously radial front wheels don't collapse when you touch the brakes, so presumably the spokes manage to transmit the braking force somehow, I'm just not sure how to analyze the forces.

Braking forces are radial. The hub is trying to move forward, the inertia of the bike and rider are pushing it. The brake applies tangential force to the rim, but the hub isn't trying to twist against it, it's just trying to go forward. So, all the braking force pulls on the hub radially, from the back.

dabac
08-13-08, 08:29 AM
The gauge of the DS spokes is not going to affect the NDS spokes' durability. .

But it will. To get good durability you want each unit of cross section area on both DS and NDS side to carry the same load. Often you get a good match by using 1.8 mm DS and 1.5 mm NDS.
The difference in area is about 70% and the diff in load tend to be about 70% too.
Using 2.0 mm DS and 1.8 mm NDS will give another ratio when comparing areas, but if that ratio is a better match to the tension difference between DS and NDS for that hub/rim combo then it's a better choice.

PNB
08-13-08, 08:32 AM
Braking forces are radial. The hub is trying to move forward, the inertia of the bike and rider are pushing it. The brake applies tangential force to the rim, but the hub isn't trying to twist against it, it's just trying to go forward. So, all the braking force pulls on the hub radially, from the back.

I was about to post the same but you were faster.
During braking the hub would pull the spokes which lie behind, but only radially.

08-13-08, 08:36 AM
^^^^^
As long as this is not done on a disc brake equipped wheel.

eddy m
08-13-08, 10:03 AM
... To get good durability you want each unit of cross section area on both DS and NDS side to carry the same load. Often you get a good match by using 1.8 mm DS and 1.5 mm NDS.
The difference in area is about 70% and the diff in load tend to be about 70% too.
Using 2.0 mm DS and 1.8 mm NDS will give another ratio when comparing areas, but if that ratio is a better match to the tension difference between DS and NDS for that hub/rim combo then it's a better choice.
I'm not sure you need to match spoke stress as you need to keep the stresses well belo the yield stress. If both sides are equally stressed, but close to yield, you won't have a very reliable wheel. If the difference in tension is only 30%, same size spokes work on both sides. You could add a little lightness by going smaller on the NDS, but you won't add much durability, assuming both sides are in the range.
The last wheel I built was a Campy 9s, which has about 45% of tension on the NDS. I used 2 mm straight gauge and 2/1.8/2 on the NDS. If I had it to do over, I would use double butted both sides, but I was thinking that the it would be easier to control twisting with straight gauge, and straight gauge would increase the lateral stiffness and stability.

em

eddy m
08-13-08, 10:22 AM
The gauge of the DS spokes is not going to affect the NDS spokes' durability. There may be the tiniest of effects due to the rim being a bit stiffer on the DS, but it wouldn't impact durability at all.

So, I think that a wheel with 2.0/1.8/2.0 NDS with a straight gauge DS is actually less durable than just 2.0/1.8/2.0 on both sides.

If you are going to try to eliminate fatigue on the NDS by controlling spoke gauge, just go thinner on the NDS, and carry on as you normally would for the DS.

I wouldn't recommend a straight gauge DS spoke unless you have some serious lateral stiffness issues (in which case I recommend a higher hub flange too). A 2.0/1.8/2.0 DS spoke will be more durable than straight gauge because it has to stretch further to reach tension. This means that displacing forces to the rim will be less likely to have enough movement to completely de-tension a given spoke. Also, cyclic forces don't change the tension as much with a thinner spoke, so there is less fatigue.

On the NDS, I'd recommend 2.0/1.5/2.0. This will enable them to stretch more at their lower tension, and offer the same benefits as thinner spokes on the DS.
I think you are right that a wheel with straight gauge spoke is less durable, but the cross-section of a 2mm spoke is 25% greater than a 1.8mm spoke. That might add some lateral stability, which outweighs some loss of durability, at least for me.
I don't use 2.0/1.5/2.0 either. I think they are too heavily cold worked. At one time (when 36 spoke wheels were standard), 1/8/1.6/1.8 spokes were readily available. they were just as strong, lighter and cheaper than 2/1.5/2.
Finally, i not convinced spokes go slack frequently enough to cause fatigue failures. The cyclic change in tension is a function of the load on the wheel as it rolls, not the gauge of the spoke. With a straight gauge spoke, the change in tension causes elongation over the whole length of the spoke, right up to and at least part way around the elbow. Some parts of the elbow are near yield (especially if the spokes have not been properly stress relieves), and that leads to fatigue failure. With a double butted spoke. almost all the elongation occurs in the narrow section, so while the tension and stress at the elbow changes just as much under cyclic loads, there is far less elongation at the elbow or threads, and therefore less fatigue failure. That's explanation I've heard for the use of bolts with narrow midsections on cylinder heads, and I think the same explanation applies to bicycle spokes.

em

waterrockets
08-13-08, 01:08 PM
I think you are right that a wheel with straight gauge spoke is less durable, but the cross-section of a 2mm spoke is 25% greater than a 1.8mm spoke. That might add some lateral stability, which outweighs some loss of durability, at least for me.
I don't use 2.0/1.5/2.0 either. I think they are too heavily cold worked. At one time (when 36 spoke wheels were standard), 1/8/1.6/1.8 spokes were readily available. they were just as strong, lighter and cheaper than 2/1.5/2.
Finally, i not convinced spokes go slack frequently enough to cause fatigue failures. The cyclic change in tension is a function of the load on the wheel as it rolls, not the gauge of the spoke. With a straight gauge spoke, the change in tension causes elongation over the whole length of the spoke, right up to and at least part way around the elbow. Some parts of the elbow are near yield (especially if the spokes have not been properly stress relieves), and that leads to fatigue failure. With a double butted spoke. almost all the elongation occurs in the narrow section, so while the tension and stress at the elbow changes just as much under cyclic loads, there is far less elongation at the elbow or threads, and therefore less fatigue failure. That's explanation I've heard for the use of bolts with narrow midsections on cylinder heads, and I think the same explanation applies to bicycle spokes.

em

Yeah, I just used Wheelsmith 2.0/1.7/2.0 on both sides of my PowerTap build :thumb:

I'm not sure about fatigue on a spoke that doesn't go slack. I haven't had a spoke fatigue since I learned how important even tension was (4 years ago now?), but I used to break the DS trailing (I think) spokes at the elbow first. And, I know that my DS spokes weren't going slack from cyclic loads.

So, I'm not a metallurgist... can spokes fatigue just from tension variation, when the elbow remains static? I guess it's just "theoretically" static, so there will actually be some movement even if it remains under tension. Steel is supposed to be able to bend a small amount an infinite number of times without fatigue though...

tkm433
08-13-08, 02:36 PM
Beiing that you stated you are at 255 I would stick with staright gauge spokes! 3x both sides and use spoke prep.
If you are having to adjsut tension evry 1000 miles or so it could be due to many factors. One you are a big guy and the biycle parts are designed for that 135lbs to 175lbs pro rider weight and not us bigger guys.

Now ask yourself would you use double-butted spokes and anything less than 3x spoke pattern on a loaded touring bike and expect the wheel to last 1000 miles? So why would you want to do it on a road bike wheel that is required to hold a 255lbs man who most likely wants to get up and sprint and ride hard. The touring bike has dead weight and the rider is just trying to get from point A to point B while you are most liley getting out of the saddle push it hard and more or less riding the hell out of it so whay gamble on some cool looking spoke pattern.

I would build your rear wheel with 14gauge DT or Wheelsmith non butted spokes, brass nipples and spoke prep and a good old common and trusted 3x pattern.

dabac
08-13-08, 03:05 PM
I'm not sure you need to match spoke stress as you need to keep the stresses well below the yield stress. There's rarely any trouble at that end, even at fairly low spoke count wheels.

If both sides are equally stressed, but close to yield, you won't have a very reliable wheel. But you shouldn't need to go there.

If the difference in tension is only 30%, same size spokes work on both sides. You could add a little lightness by going smaller on the NDS, but you won't add much durability, ..

You could use the same spokes but different would be better. Suppose you're running 100 kg on the DS and 70 on the NDS, and that every spoke sees a tension reduction of 15 kg when it passes under the hub. That tension reduction is proportionally significantly smaller for the DS (15/100)than for the NDS(15/70).
Sure, with a good build and an average weight rider it'll still work, but but a thinner NDS spoke OR a thicker DS spoke would theoretically have offered better durability.

..The last wheel I built ..has about 45% of tension on the NDS.

I'd definitely have gone for straight gauge DS and 2.0-1.5-2.0 NDS and maybe even a half-radial for something like that. You'd need fairly high spoke tensions to keep the NDS variations at acceptable levels for such a build.

DannoXYZ
08-13-08, 03:24 PM
You could use the same spokes but different would be better. Suppose you're running 100 kg on the DS and 70 on the NDS, and that every spoke sees a tension reduction of 15 kg when it passes under the hub. That tension reduction is proportionally significantly smaller for the DS (15/100)than for the NDS(15/70).
Sure, with a good build and an average weight rider it'll still work, but but a thinner NDS spoke OR a thicker DS spoke would theoretically have offered better durability.I think what you're aiming at here implicitly is the amount of stretch in a spoke. Combining tension with cross-section will give you the amount of stretch in a spoke (from Young's Modulus). With lower tension, using a smaller cross-section will give you more stretch. If you can increase the stretch of the NDS to match that of the DS, then you may have an optimum situation of wheel-strength along with spoke-durability.

Yield-strength of 2.0mm spokes is around 200 kg. Spoke hardly ever fail from exceeding yield or ultimate-strengths unless someone sticks their foot through your wheel. There are two factors of "strength" and durability that most wheels endure:

1. Fatigue life pretty much applies mainly to spokes. Unless you've got certain Mavic rims, your rims will pretty much never crack from fatigue; perhaps wear out on the braking-surfaces, but certainly not fatigue. Fatigue on the spokes is the most when they undergo large tension-changes, especially if they lose ALL tension, such as in a stock wheel that's undertensioned. Fatigue failures typically always happen at the spoke-head where it bends. Fatigue is propagation of microscopic cracks and when they meet, the part separates into two. Tell-tale signs of fatigue-failure is when both halves of the part can be re-assembled and it fits perfectly (no deformation). For highest fatigue-resistance in the spokes, tension them towards the high-end of the rim's operating range. Obviously for rear-wheels, you'd do this for the drive-side and adjust the NDS for correct dishing.

2. Wheel "strength" or durability is the resistance to going out of true. This is mostly in the lateral axial-direction as the wheel is super-strong radially. On major factor in causing wheels to go out of true is low-tension and spoke-nipple rattling. Even on wheels with high-tension, hitting sharp impacts like pot-holes or speed-bumps can deform the contact-patch enough to un-tension the spokes at the bottom completely. The nipples can then wiggle loose and cause the wheel to go out of true. I've found that a thread-locker like spoke-prep or blue Loctite makes a huge difference in keeping a wheel true longer.

Interestingly enough, double-butted spokes results in a wheel that's "stronger", more durable and doesn't go out of true as quickly as straight-gauge spokes. That's because for the exact same tension, the DB spokes will stretch more and allow the rim to deform more before they allow the nipples to rattle.

The other variable here is the triangle angle between the spokes and the hub-flanges. Large-flange and wide-flange hubs give a larger included angle and larger portion of the spoke's tension goes to resisting lateral-deflection at the hubs. Look up Damon Rinard's wheel-strength test-data and you'll find two wheels with identical hubs/rims/spokes. The only difference is that they have radial-lacing with one on the inside of the flange and the other outside the flange. Obviously the wheel with the spokes on the outside of the flange (with larger included angle to rim) is stiffer; in fact, it was the stiffest wheel in the test.

But you have balance wheel-durability with hub lifespan as well. If you build radial on a thin flange, who cares if you've got a really stiff strong wheel with spokes that won't fatigue if the flange breaks in 6-months? It's all about balancing multiple variables and many times, these variables contradict one another. Increasing strength in one part may decrease it in another. A classic contrast here is balancing spoke-strength versus wheel-strength. Thicker straight-gauge spokes may result in spokes that never break, but the wheel won't stay as straight and true as one built form thinner DB spokes. You have to juggle the variables and find the best mix for your particular application.

VenturaCyclist
08-13-08, 03:44 PM
Over the decades I’ve built a lot of wheels and I’ve folded (figure 8) a few wheels. It has been a long time since I’ve had one fold. Now I build all my wheels three cross, carbon steel spokes, straight gage in the pulling direction. Pulling being the direction the spokes pull the wheel around when you step on the pedals. On the non pulling spokes I use two cross, carbon steel, straight gage. These 2x spokes would tend to compress a little when you step on the pedals whereas the other 3x spokes would tend to tension a little. On the other side of the hub where the gears are not I use all 4x, stainless steel, double butted. For instance on the last wheel I built I used half 12”, one fourth 11¾” and one fourth 11½”.

I’ve been lacing wheels this way for thousands and thousands of years and I have yet to have one fold or break any spokes. Gaging spoke tension by hand the spokes feels very even. Every spoke on the left side of the hub feels to be tensioned the same amount as every spoke on the right. All the spokes are tensioned like symetrical front wheel spokes.

From my experience I would say that you do not want to mix 4x, 3x and 1x or radial lacing. I know it doesn’t sound right but you do want the spokes to be almost all the same length.

dabac
08-13-08, 03:50 PM
Finally, i not convinced spokes go slack frequently enough to cause fatigue failures.
Well, that would depend on spoke tension, spoke count, rider weight, rider strength, and ride surface condition. For a well tensioned wheel and average weight rider spokes don't go slack. Other circumstances - they do.

.. The cyclic change in tension is a function of the load on the wheel as it rolls, not the gauge of the spoke. But tension over cross sectional surface area IS directly related to spoke gauge, and with DS and NDS of same dia but at different tension then the lower tensioned one will see a much bigger tension change proportionally.

.. That's explanation I've heard for the use of bolts with narrow midsections on cylinder heads, ..
The key to avoiding fatigue failure is to keep fasteners under tension. And not any old tension, but a tension so high that the cyclic load variations becomes no more than a proportionally small part of the combined tension. For a given load a thinner fastener is more elastic than a thicker one. That means it can absorb dimensional changes and still remain under tension better than a thicker fastener.

dabac
08-13-08, 03:53 PM
I think what you're aiming at here implicitly is the amount of stretch in a spoke. Combining tension with cross-section will give you the amount of stretch in a spoke (from Young's Modulus). With lower tension, using a smaller cross-section will give you more stretch. If you can increase the stretch of the NDS to match that of the DS, then you may have an optimum situation of wheel-strength along with spoke-durability.

Exactly!

eddy m
08-14-08, 07:59 AM
Over the decades I’ve built a lot of wheels and I’ve folded (figure 8) a few wheels. It has been a long time since I’ve had one fold. Now I build all my wheels three cross, carbon steel spokes, straight gage in the pulling direction. Pulling being the direction the spokes pull the wheel around when you step on the pedals. On the non pulling spokes I use two cross, carbon steel, straight gage. These 2x spokes would tend to compress a little when you step on the pedals whereas the other 3x spokes would tend to tension a little. On the other side of the hub where the gears are not I use all 4x, stainless steel, double butted. For instance on the last wheel I built I used half 12”, one fourth 11¾” and one fourth 11½”.

I’ve been lacing wheels this way for thousands and thousands of years and I have yet to have one fold or break any spokes. Gaging spoke tension by hand the spokes feels very even. Every spoke on the left side of the hub feels to be tensioned the same amount as every spoke on the right. All the spokes are tensioned like symetrical front wheel spokes.

From my experience I would say that you do not want to mix 4x, 3x and 1x or radial lacing. I know it doesn’t sound right but you do want the spokes to be almost all the same length.
That's an interesting way to lace a wheel. It seems to me that the 2X leading spokes must have more tension then the 3X trailing spokes. If the leading spokes compress under pedaling loads, and the trailing spokes stretch, that should make both stronger. That's a simple enough problem to solve that I might work on it before my next set of wheels. I'm not sure why lace 4X on the non-drive side. It seems to me that most hubs transfer a lot of torque across to the opposite side. The NDS is generally weaker, and if the 3X-2X combination makes it stronger it would be more important on the non-drive side.
I doubt that you equalize tension much between the 2 sides by using different patterns. Maybe the drive side trailing spokes are a little looser and that has some effect, but otherwise there's not too much you can do with the spoke pattern to equalize tension.

em

08-14-08, 08:24 AM
http://www.duke.edu/~hpgavin/papers/HPGavin-Wheel-Paper.pdf

For those who wish further reading on the matter.

dabac
08-14-08, 02:15 PM
Part of the "problem" when discussing different wheel builds is that if everything is "average" (spoke count, tension, rider weight, bike load, ride surface conditions, spoke tension, stress relief, ride distance....) then most wheels will have such huge margins against failures that just everything goes.
It's first when you begin to move away from the recommendations on one area or more that stuff starts breaking.

My beater bikes are pretty much a long lists of "don'ts", and they still keep rolling:
- Unlaceing, straightening and relaceing a tacoed rim? Still going strong
- reuseing hub in another lace pattern? No problem
- reuseing spokes? tedious, but no ticket to disaster
- mixing SS and galvanized spokes? Sure doesn't look as if the wheel cared.
- Spokes with threads still showing? ugly as sin, but doesn't appear significant otherwise

And the list goes on...

I see it as an interesting intellectual challenge to try to figure out the "best" wheel, or to build something working out of whatever I have laying around.
But I'm not the least surprised when someone comes along and swears blind on the usefulness and reliability of what would be considered a less-than-ideal configuration otherwise - most rider/ride combos have no trouble overcoming one or two adverse factors.

waterrockets
08-14-08, 02:55 PM
otherwise there's not too much you can do with the spoke pattern to equalize tension.

Well, there is triplet lacing, which will likely go so far as to end up favoring the NDS spokes...

http://www.all3sports.com/imageserver/images_big/FLC7RZR.jpg

dabac
08-15-08, 02:15 AM
Well, there is triplet lacing,
But that pretty much requires rims drilled for that purpose, which rather limits the selection.

Soil_Sampler
08-15-08, 05:15 AM
2to1