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Old 09-21-06, 09:32 AM   #1
Little Darwin
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Non-Interlaced Spokes a Problem?

I have had a question bubbling under the surface for a while... I built some wheels in my youth, before I even heard about interlacing. They were 26 x 1 3/8 36 hole 3 cross without interlacing. I seem to have had something in common with Raleigh, which I just read used to do the same thing.

I rode those wheels for a few years on the roads and some moderately rough trails without a problem. And, as a rider in my youth, I had a propensity for bending and breaking axles and even a frame or two, so I was not easy on equipment...

Everything I have read so far on wheel building said to interlace, but none said why...

Is there a real reason for interlacing, or is it another residual based on "that's the way it is done" from those that came before? Are interlaced rims stiffer? Are they stronger? Is it easier to replace spokes?

If it is important, then how do radially spoked wheels compensate for the reduced rigidity or strength?

I will be rebuilding some wheels this winter for the first time in 30+ years, so I am curious about this. I will probably just lace the way the wheels are currently laced, but I would like to know why!

Thank you for "listening"
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Old 09-21-06, 10:15 AM   #2
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I don't have my "bible" (Jobst Brand's The Bicycle Wheel here at the office, and he has a pretty detailed explanation as to why it's worth doing. The basic logic is that forces are spread out among the spokes better with interlacing, and I believe this also makes the wheels stiffer side-to-side.
But you're right, it's probably not totally necessary with modern good-quality spokes that are unlikely to break. Radial spokes are harder on the hub flange, but it's not because they're interlaced but rather because the spoke pulls directly away from the hub instead of tangent to the flange.

If you're going to build wheels, you may as well interlace them - real benefits do exist. But I agree with you that it's not completely necessary. It's just a no-cost way to get some benefits.
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Old 09-21-06, 10:37 AM   #3
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Yeah, interlacing adds very little if anything to the wheel-strength. It might equalize tension somewhat between two spokes, but that's it. It doesn't affect tension that much even . Feel how much force it takes to bend one spoke over the other when you're building the wheel and you'll see that it doesn't contribute much to lateral-stiffness either. In the end, it's really the spoke-tension and the included-angle of the spokes that determine the forces on the rim.

Sheldon Brown's site has some data-tables of wheel-stiffnesses of various builds. You'll find that the stiffest wheels are radial (hard on the hub-flanges though). And there was one case where two identical wheels where built, but one with the spokes on the inside and one on the outside of the flanges. Obviously, the one that spaced the spokes further apart yielded a laterally-stiffer wheel...
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Old 09-21-06, 01:44 PM   #4
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It also gives the spoke a better line to the rim.
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Old 09-21-06, 02:04 PM   #5
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Quote:
Originally Posted by DiabloScott
It also gives the spoke a better line to the rim.
I'm not an engineer (I don't even play one on TV), but I have noticed the following in two wheel builds, one interlaced, the other not, using the same hubs and rims: The interlaced wheels were easier to true, and tend to stay true better.

I suspect that, where you are alternating the "sidedness" of the spoke heads, that interlacing gives the spokes closer to the same angle going into the nipple/rim, making the truing process more consistent.

Then again, I might be full of it.

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Old 09-21-06, 02:34 PM   #6
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This is interesting.

I was talking to a guy at the local LBS yesterday about interlacing.

I'm currently planning on building up a 3 leading - 3 trailing wheel just for a fun project.
He recommended against it, due to its lack of lateral rigidity.
I thought that was weird, as its basically 3 cross.

Then I went home and thought about interlacing the leading and trailing spokes.
There seems to be a few ways to do it (I had to draw them out), but ideally I'd want each to interlace only once.

The way I plan on building the wheel though, some will have to be interlaced more than once.

For the record, the LBS guy said to go with Crowsfoot..
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Old 09-21-06, 03:49 PM   #7
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+1 on Jobst Brandt's book as a reference. It's a wealth of wheel physics information.
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Old 09-21-06, 10:05 PM   #8
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I've wondered openly about the "strength" of a radial lacing vs tangental lacing (spokes leave the hub at a right angle). There seems to be no common answer on strength.

What is agreed upon however is that you should not use radial lacing for wheels which experience torque at the hub. This includes ANY rear wheel and ANY disc brake wheel. On a radial spoked wheels, torqueing the hub results in a shearing force across the length the spokes. This is aspect of a spoke that is the weakest. This is easily verified by bending a spoke in half.

Tangental lacing allows the torquing forces to be express axially along the length of the spoke. Take a spoke by each end and try to stretch it like taffy. I gaurantee you cannot do it. This is the strong tensile strength of the spoke.

Some people will advocate a half radial lacing on hub torqueing wheel using the reasoning that one side of the spokes is for the torquing side, and the other is for the "rim brake" side. I cannot believe this as a hub is a rigid body and all forces expressed on one flange will also be expressed on the other. No doubt there is some imperceptible amount of twist across the hub body. But I cannot believe this would alleviate the torquing expressed across the spokes.

So basically the ONLY acceptable application for a radially spoked wheel is a front wheel with rim brakes. No dsc brakes, no drum brakes!!!!

Personally I believe a tangental wheel is less prone to tacoing as when you strike an object, the movement of the rim inwards at the contact point is partially OPPOSED by the tension of the spoke that leaves the rim at an angle. When struck
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Old 09-21-06, 10:50 PM   #9
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Quote:
Originally Posted by lyledriver
ůsnip
I'm currently planning on building up a 3 leading - 3 trailing wheel just for a fun project.
He recommended against it, due to its lack of lateral rigidity.
I thought that was weird, as its basically 3 cross.
snipů
I built a 3-leading/3-trailing wheel recently, but gave up on it as I'd based the wheel on a small-flanged hub, and that pattern only really works on a hub with large flanges; my attempt looked awful and although was laced correctly, I think it might have been more successful using smaller gauge spokes. One advantage is that for that particular hub/rim combination, the spoke length is the same as that for a 3x pattern.

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Old 09-21-06, 11:35 PM   #10
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Originally Posted by Al1943
+1 on Jobst Brandt's book as a reference. It's a wealth of wheel physics information.
That's not as a reference for writing style or usage, right? -1 on JB's writing. I have a theory he trumpets his educational pedigree to disguise his obtuse, pedestrian* writing.

*pun intended .
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Old 09-22-06, 06:35 AM   #11
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If you hit a really big bump, the danger is that one or two of the spokes at the bottom will go slack, potentially leading to a catastrophic failure. If the spokes are interlaced, they will have tension applied to them by their interlace-mates, giving them just a little more tension leeway before going slack. When the bump passes, the spokes return to normal tension and all is well.
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Old 09-22-06, 02:10 PM   #12
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Quote:
Originally Posted by willtsmith_nwi
I cannot believe this as a hub is a rigid body and all forces expressed on one flange will also be expressed on the other. No doubt there is some imperceptible amount of twist across the hub body. But I cannot believe this would alleviate the torquing expressed across the spokes.
Nothing in this world is rigid, everything is flexible (to varying degrees). You'd be surprised how little flexibility is necessary to significantly reduce stress. A small diameter hub shell (old Campag, etc) passes perhaps 10% torque to the off-side flange. Larger diameter shells, like most disc brake hubs, pass a higher percentage through. It never reaches 50% though.
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Old 09-22-06, 02:49 PM   #13
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Originally Posted by LWaB
A small diameter hub shell (old Campag, etc) passes perhaps 10% torque to the off-side flange. Larger diameter shells, like most disc brake hubs, pass a higher percentage through. It never reaches 50% though.
Really ... ? How do you explain hubs laced radially on the drive side and crossed on the non-drive side? They seem to work just fine.
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Old 09-22-06, 06:07 PM   #14
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Originally Posted by DiabloScott
Really ... ? How do you explain hubs laced radially on the drive side and crossed on the non-drive side? They seem to work just fine.
The drive side is winding up under pedaling, allowing torque transfer on both sides. This should tell you that wind-up isn't a huge problem. After all, most penny farthings are radially spoked and survive reasonably well, although metal fatigue gets noticeable after the first 100 years or so.

Nowadays, this set-up is used on large diameter hub shells, reducing wind-up.

By the way, to those people worrying about spokes temporarily completely detensioning under impact, you need to tighten your spokes.
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Old 09-22-06, 06:55 PM   #15
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Quote:
Originally Posted by LWaB
The drive side is winding up under pedaling, allowing torque transfer on both sides.
Well, there's just enough wind up to transfer almost all the torque through the hub to the non drive side; there's not enough wind up on the radial side to have much of a spoke angle relative to the rim.



Some pennyfarthing wheels are radially laced but the spokes are so much longer, and there are so many more of them that the little bit of wind up does get the job done - plus you're applying torque to both sides of the hub.
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Old 09-22-06, 07:16 PM   #16
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It seems we basically agree DiabloScott.

With high spoke tensions (as on drive-side spokes), you don't need much of an angle to transfer torque.

The majority of PFs are radially spoked, with some bikes tangentially spoked. Longer spokes don't help, reducing spoke angle but there are more spokes and higher flanges involved. Seeing as only one pedal is pushed at a time, the hub itself experiences wind-up alternately in each direction.
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Old 09-22-06, 10:27 PM   #17
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Quote:
Originally Posted by LWaB
It seems we basically agree DiabloScott.
Yes we do, thank you for being civil.


Quote:
Originally Posted by LWaB
With high spoke tensions (as on drive-side spokes), you don't need much of an angle to transfer torque.
If that were true, it wouldn't matter how you laced the non-drive side.

Quote:
Originally Posted by LWaB
The majority of PFs are radially spoked, with some bikes tangentially spoked. Longer spokes don't help, reducing spoke angle but there are more spokes and higher flanges involved. Seeing as only one pedal is pushed at a time, the hub itself experiences wind-up alternately in each direction.
Longer spokes can stretch more before they break. When you wind up a hub you are stretching the spokes. The reason you can't radially lace both sides of a 700c rear wheel is that most of the spokes on both sides would break because torque will be transferred through the <essentially rigid> hub shell.

Last edited by DiabloScott; 09-22-06 at 11:01 PM.
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Old 09-23-06, 01:47 AM   #18
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When I started as a mechanic, I built up a radial rear 700C wheel (just to be different). Apart from feeling a little soggy when sprinting, it was OK until a flange broke (drive side, of course). Things you do when you are young and stupid.

It seems that several BMXs currently run radial spoking front and rear.
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Old 09-24-06, 02:39 PM   #19
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hehe ... he said "rigid"

Quote:
Originally Posted by LWaB
Nothing in this world is rigid, everything is flexible (to varying degrees). You'd be surprised how little flexibility is necessary to significantly reduce stress. A small diameter hub shell (old Campag, etc) passes perhaps 10% torque to the off-side flange. Larger diameter shells, like most disc brake hubs, pass a higher percentage through. It never reaches 50% though.
Yes, I agree that the word "rigid" has artificial constraints placed upon it. And I do believe that I did say that the hub will twist to an imperceptible degree. You would be right to point out that human perception may have nothing to do with the problem.

However, I will point out that the one flange cannot move without the other coming along. This topic sounds a bit like applying a load to the bottom of a hanging rope and expecting there to be some difference in tension from one side to another. Tension affects a body uniformly. The variable bit is the how much different parts stretch.

In any case, I'd be interested to hear from a mechanical engineer or read a scientific paper on this. A simple way to test the issue would be to attach tensionometers to say 4 pulling spokes at regular intervals on both sides of the hub than apply torque to a wheel fixed in place and see how the spokes load. If drive side does indeed experience 90% greater tension change than the non-drive side than I will have no choice then to believe it.

Quote:
Originally Posted by LWaB
When I started as a mechanic, I built up a radial rear 700C wheel (just to be different). Apart from feeling a little soggy when sprinting, it was OK until a flange broke (drive side, of course). Things you do when you are young and stupid.

It seems that several BMXs currently run radial spoking front and rear.
Thats the part I forgot to mention. Hubs flanges are stronger tangentally with respect the hub then radially. There is just plain more material in that direction. I wouldn't expect a BMX spoke to fail anyway since they typically have a high spoke count to a 20" diameter.
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Old 09-25-06, 02:43 AM   #20
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Quote:
Originally Posted by willtsmith_nwi
However, I will point out that the one flange cannot move without the other coming along. This topic sounds a bit like applying a load to the bottom of a hanging rope and expecting there to be some difference in tension from one side to another. Tension affects a body uniformly. The variable bit is the how much different parts stretch.
Correct, apply some tension to one end of a rope (or a rubber band) and fix the other end and you will measure the same tension at both ends. On the other hand, you will get movement of one end relative to the other (stretching). Differential movement can be a result of tension, compression or, for a hub, mostly torsion.

Have a look at the back of Jobst Brandt's book for differential movement of rear hub flanges and resulting spoke tension changes..
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