Wheel build problem

[blingybob]

Hey Please to meet you I'm a new user.

I've recently built a set of road wheels

Stan's alpha 340 rims with 253g set of hubs, sapim spokes and nipples (20/24) weighing about 1200g all in with tyres.

I've ridden them twice and both times i've took out a different spoke from the rear drive side of the wheel, its pulled the spoke out of the nipple, thread gone (I believe brass nipples not sure til tomz if they are alloy til I ask my wheel builder guy).

Cant understand why?

I'm now starting to think my weight is the reason I'm 85kg.

Any one got a suggestion

Considered glueing if i cant get stronger nipples.....weight loss not doable before you ask lol

Thanx Rob

[cny-man]

Your weight is nothing as a factor. Possible but unlikely the nipples/spokes are an incorrect match. How were spokes/nipples purchased and received?

[blingybob]

Hi I bought all of the parts myself but my wheel builder bought spokes and nipples directly from sapim I believe

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They came in same box I'm sure

[cny-man]

Seems to me it's the wheel builder's job to figure out the problem and solution.

[DaveM]

If they are brass nipples, I'd say they either have to be the wrong size or the spokes are too short (can you see any threads on the spoke where they meet the nipple?)

If they're allow nipples, could also be wrong size or maybe way over tensioned?

Either way, yeah, the wheel builder should be helping you. This is definitely a problem in the way the wheel was built.

And, no, don't glue your nipples...

[blingybob]

Hi
My wheelbui!dear has changed the lacing pattern on the drive side rear from straight to cross over and put new longer brass nipples instead for added strength. Think a ride will answer question, but will keep you posted

[DaveM]

Yikes. He built it with the drive side spokes radial? That's kind of a basic no-no.

[blingybob]

Hi

Can you let me know why thats a basic 'No' 'No' please?

The guy I use has been repairing my bikes since 1984 and has always been good to me and I have never had too complain.

I have had many sets of wheels built over the years, these the only ones with an issue.

I ride em' but let him fix em' if you know what I mean, but I don't want to break my neck!

Do you think he is trying to solve an unsolvable problem?

What your take on it?

Everything is new and compatable

Thanx

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Quick add on ref spoke comment from daveM bit before ref. size. thread etc. The spokes seem pretty ok too me ref threads etc. Nipples 12mm 14g although now he has replaced them with longer ones and due to relacing the spokes are obviously now longer to do the job

[DaveM]

Maybe there's been a change in thinking on this. But when I learned to build wheels, you always had to have drive side spokes at least 1 cross. The pedaling force comes in to the wheel through the hub. That rotational force then has to transfer out to the rim/tire/road through the spokes. With radial spokes, the twisting force of the hub moving relative to the rim puts a lot of extra stress on the radial spokes because they are lying exactly at 90 deg. to the orientation of the force. Since the spokes really only connect to the hub through tension, the hub actually has to rotate ahead of the rim a little until there a tiny amount of angle is created so the hub can pull the rim forward. This increases the tension and stress on the spokes to a large degree. The drive side rear also has more stress on it already on a multi-speed bike because these spokes has less dish (are more vertical) than the non-drive side to make room for the gear cluster. Even if it works, it would be a huge loss of durability for a very small weight savings.

I may be off on some of the technical aspects of this. Maybe one of the engineers on here can correct/improve my description.

It still sounds weird to me that you would have spokes pulling themselves out of the nipples completely. Usually spokes will break long before they just pull out threads. But this could be related to very light weight nipples or some other material issue.

There are a lot of different hub/spoke/rim configurations nowadays and maybe he used parts that account for this. But the fact that he's rebuilding it with crossed spokes makes it sound like he thinks this is a problem as well.

[blingybob]

Thanks for your input, how it stands now is ride it weekend and see. I'll try to post picture first tho
Thanx again

[nfmisso]

(07-17-2014, 02:58 AM)blingybob Wrote:  ....Can you let me know why thats a basic 'No' 'No' please?......

Dave's explanation is correct.

Radially laced spokes are not capable of transmitting torque from the hub to the rim.

Drive side spokes are intended to transmit the vast majority of the torque from the hub to the rim. Hubs are not the stiff in torsion and will deflect. If you have radial on the drive side, and cross on the non-drive side, the hub will deflect enough to rip the drive side spokes from their nipples and/or pull them out of the rim.

A more detailed answer requires an understanding of static analysis, free body diagrams, stress, strain, etc.