Breaking Spokes on 28H 2X wheel



J

Joel

Guest
I recently built a new wheel using a Shimano 6500 front hub and
Velocity Aerohead 28H rim laced 2X.
I have broken three spokes so far. I am sure the wheel is built
correctly and spokes have sufficient tension.
A friend suggested maybe the spokes were too tight. My understanding
is that it is impossible to apply enough tension to break spokes by
tension alone. I had a similar experience several years ago with the
same configuration except the spokes were revolutions instead of
regular DB. I beleive the problem has to do with the 2 X pattern and
the stress applied to the spokes where they cross over. I can see at
the cross over significant bowing of the spoke. I measured the
distance from the cross over to the spoke holes in the hub at 1.5
inches. I have a 28H 3X wheel that measures 2 inches and has much less
bowing. I also have a 28H 2X rear wheel that measures 1.75 inches and
have not broken any spokes on that one. I believe the soultion to this
front wheel is to use 3X.

Joel
 
A

Art Harris

Guest
Joel wrote:
> I recently built a new wheel using a Shimano 6500 front hub and
> Velocity Aerohead 28H rim laced 2X.
> I have broken three spokes so far. I am sure the wheel is built
> correctly and spokes have sufficient tension.
> A friend suggested maybe the spokes were too tight. My understanding
> is that it is impossible to apply enough tension to break spokes by
> tension alone.


Spokes break due to fatigue at locations where the stresses are near
the elastic limit. Where are the spokes breaking? At the elbows? Did
you stress relieve and improve the spoke line? What brand and gauge of
spokes?

Art Harris
 
B

Ben C

Guest
On 2007-02-21, Joel <[email protected]> wrote:
> I recently built a new wheel using a Shimano 6500 front hub and
> Velocity Aerohead 28H rim laced 2X.
> I have broken three spokes so far. I am sure the wheel is built
> correctly and spokes have sufficient tension.
> A friend suggested maybe the spokes were too tight. My understanding
> is that it is impossible to apply enough tension to break spokes by
> tension alone. I had a similar experience several years ago with the
> same configuration except the spokes were revolutions instead of
> regular DB. I beleive the problem has to do with the 2 X pattern and
> the stress applied to the spokes where they cross over. I can see at
> the cross over significant bowing of the spoke. I measured the
> distance from the cross over to the spoke holes in the hub at 1.5
> inches. I have a 28H 3X wheel that measures 2 inches and has much less
> bowing. I also have a 28H 2X rear wheel that measures 1.75 inches and
> have not broken any spokes on that one. I believe the soultion to this
> front wheel is to use 3X.


Where did they break?
 
J

Joel

Guest
The spokes are breaking near the elbow but in the straight section.
The spokes are new, it is not fatigue.
I did stress relieve the spokes like I always do.
I have since discovered that I have a another 28H 2X front wheel this
one with a Mavic rim.
The spokes on this wheel have very short butts about 1/2 inch long, so
the cross over occurs at the narrow diameter of the spoke.
On the problem wheel the butts are much long and the crossover occcurs
at the large diameter of the spoke.
I think this is significant in terms of how much bowing is occuring
due to the cross over.

Joel
 
P

Paul Kopit

Guest
On 21 Feb 2007 12:18:38 -0800, "Joel" <[email protected]> wrote:

>I recently built a new wheel using a Shimano 6500 front hub and
>Velocity Aerohead 28H rim laced 2X.
>I have broken three spokes so far. I am sure the wheel is built
>correctly and spokes have sufficient tension.


I've built that same wheel several times 2x just as you did. I've
used 2.0/1.8, 1.8 straight, and 2.0/1.5. I recall the spoke length as
192 mm. I build to 100 kgF. I've never broken a spoke in the front.
I weight ~200 lbs and ride on less than pristine roads.

When there is a bit of tension, I bang the spokes down to the flange
with a rubber hammer. I don't do any special stress relieving. Toward
the final tensioning of the wheel, I overturn the spokes almost a full
turn before returning to ¼ turn. I usually use DT spokes but have had
good luck with Wheelsmith too.
 
J

Joel

Guest
Yep I use 191 or 192 mm.
What kind of tensiometer are you using, I'm thinking I should get one
but they can be expensive.
I use a screw driver handle to push the spokes against the hub flange
and also were they cross over (from Jobst's book)
I wonder why I have had the problem twice. Im pretty sure the problem
will go away with 3X.

Joel
 
J

jim beam

Guest
Art Harris wrote:
> Joel wrote:
>> I recently built a new wheel using a Shimano 6500 front hub and
>> Velocity Aerohead 28H rim laced 2X.
>> I have broken three spokes so far. I am sure the wheel is built
>> correctly and spokes have sufficient tension.
>> A friend suggested maybe the spokes were too tight. My understanding
>> is that it is impossible to apply enough tension to break spokes by
>> tension alone.

>
> Spokes break due to fatigue at locations where the stresses are near
> the elastic limit.


often repeated mistake - fatigue happens well below the elastic limit.
that's why it's fatigue and not yielding.

> Where are the spokes breaking? At the elbows? Did
> you stress relieve and improve the spoke line? What brand and gauge of
> spokes?
>
> Art Harris
>
>
>
 
J

jim beam

Guest
Joel wrote:
> I recently built a new wheel using a Shimano 6500 front hub and
> Velocity Aerohead 28H rim laced 2X.
> I have broken three spokes so far. I am sure the wheel is built
> correctly and spokes have sufficient tension.
> A friend suggested maybe the spokes were too tight. My understanding
> is that it is impossible to apply enough tension to break spokes by
> tension alone. I had a similar experience several years ago with the
> same configuration except the spokes were revolutions instead of
> regular DB. I beleive the problem has to do with the 2 X pattern and
> the stress applied to the spokes where they cross over. I can see at
> the cross over significant bowing of the spoke. I measured the
> distance from the cross over to the spoke holes in the hub at 1.5
> inches. I have a 28H 3X wheel that measures 2 inches and has much less
> bowing. I also have a 28H 2X rear wheel that measures 1.75 inches and
> have not broken any spokes on that one. I believe the soultion to this
> front wheel is to use 3X.
>
> Joel
>

where are the spokes breaking?
 
Q

Qui si parla Campagnolo

Guest
On Feb 21, 1:18 pm, "Joel" <[email protected]> wrote:
> I recently built a new wheel using a Shimano 6500 front hub and
> Velocity Aerohead 28H rim laced 2X.
> I have broken three spokes so far. I am sure the wheel is built
> correctly and spokes have sufficient tension.
> A friend suggested maybe the spokes were too tight. My understanding
> is that it is impossible to apply enough tension to break spokes by
> tension alone. I had a similar experience several years ago with the
> same configuration except the spokes were revolutions instead of
> regular DB. I beleive the problem has to do with the 2 X pattern and
> the stress applied to the spokes where they cross over. I can see at
> the cross over significant bowing of the spoke. I measured the
> distance from the cross over to the spoke holes in the hub at 1.5
> inches. I have a 28H 3X wheel that measures 2 inches and has much less
> bowing. I also have a 28H 2X rear wheel that measures 1.75 inches and
> have not broken any spokes on that one. I believe the soultion to this
> front wheel is to use 3X.
>
> Joel


I'm gonna guess that the tension was not high enough, makes for spoke
flex and like a metal hanger that you bend back-forth, makes for
broken spokes. How do you know that the wqheel had 'sufficient'
tension.
 
J

Joel

Guest
I don't have a way to measure it, but I have built probably a dozen
wheels that have no problems and spokes on this wheel are as tight or
tighter than all of those wheels. Also I was riding with a group when
one of the spokes broke and we compared my wheel to others and the
spokes where tighter than everybody elses which prompted the comment,
your spokes are too tight thats why they are breaking.

Can anybody here accept the fact that with fewer crosses in the
pattern, the cross over occurs closer to the hub flange which causes
increased bowing of the spokes. This combined with higher spoke
tension which is translated by the bowing into a force that is not
tension is what is breaking the spokes. Actually lower spoke tension
in this case could prevent or reduce the breaking.

Joel
 
S

steve

Guest
On Feb 22, 11:49 am, "Joel" <[email protected]> wrote:
> I don't have a way to measure it, but I have built probably a dozen
> wheels that have no problems and spokes on this wheel are as tight or
> tighter than all of those wheels. Also I was riding with a group when
> one of the spokes broke and we compared my wheel to others and the
> spokes where tighter than everybody elses which prompted the comment,
> your spokes are too tight thats why they are breaking.
>
> Can anybody here accept the fact that with fewer crosses in the
> pattern, the cross over occurs closer to the hub flange which causes
> increased bowing of the spokes. This combined with higher spoke
> tension which is translated by the bowing into a force that is not
> tension is what is breaking the spokes. Actually lower spoke tension
> in this case could prevent or reduce the breaking.
>
> Joel


Joel,
If anything, the increased bowing would decrease the tension at the
elbow. Since your spoke is not in line with the force vector, there is
now an x and y component to your force. There could be a number of
facters that could explain why your spokes broke but it is unlikely
that 2x or high tension is the cause of this. If you still have the
broken spokes it might help to look at the break. If there is no
necking and it lookes like the two broken ends could fit back together
then they broke from fatigue. You can also tell whether the crack
started at the outside of the spoke or the inside by looking at the
break. Generally spokes that break from fatigue will have a clean
fracture until the last little section of spoke. When a spoke
fatigues it starts to fracture at its high stress area or defect area
and contiues to fracture through the spoke until there is just a small
amount of spoke left that isn't fractured. At this point that little
bit of spoke that is still left can't handle the force so it stretches
and breaks from to much force, not from fatigue. This section of the
spoke will look different than the rest of the break and is on the
opposite side of were the fracture started.

Steve Sauter
 
K

Kinky Cowboy

Guest
On 22 Feb 2007 08:49:08 -0800, "Joel" <[email protected]> wrote:

>
>Can anybody here accept the fact that with fewer crosses in the
>pattern, the cross over occurs closer to the hub flange which causes
>increased bowing of the spokes. This combined with higher spoke
>tension which is translated by the bowing into a force that is not
>tension is what is breaking the spokes. Actually lower spoke tension
>in this case could prevent or reduce the breaking.
>


Unless I have entirely the wrong picture in my head, you could test
this hypothesis by building the same wheel but NOT interlacing the
spokes. Given that my 20 spoke 2X Mavic Ellipse is proving pretty bomb
proof without the benefit of interlacing, I shouldn't worry too much
about this mild deviation from the Book

I doubt that the bend at the crossover is a factor, but it is at least
a factor which can be eliminated. You'd need to ensure that the spokes
on this new non-interlaced build were from exactly the same batch as
the failing ones

Kinky Cowboy*

*Batteries not included
May contain traces of nuts
Your milage may vary
 
J

Joel

Guest
On Feb 22, 11:00 am, Kinky Cowboy <[email protected]> wrote:
> On 22 Feb 2007 08:49:08 -0800, "Joel" <[email protected]> wrote:
>
>
>
> >Can anybody here accept the fact that with fewer crosses in the
> >pattern, the cross over occurs closer to the hub flange which causes
> >increased bowing of the spokes. This combined with higher spoke
> >tension which is translated by the bowing into a force that is not
> >tension is what is breaking the spokes. Actually lower spoke tension
> >in this case could prevent or reduce the breaking.

>
> Unless I have entirely the wrong picture in my head, you could test
> this hypothesis by building the same wheel but NOT interlacing the
> spokes. Given that my 20 spoke 2X Mavic Ellipse is proving pretty bomb
> proof without the benefit of interlacing, I shouldn't worry too much
> about this mild deviation from the Book
>
> I doubt that the bend at the crossover is a factor, but it is at least
> a factor which can be eliminated. You'd need to ensure that the spokes
> on this new non-interlaced build were from exactly the same batch as
> the failing ones
>
> Kinky Cowboy*
>
> *Batteries not included
> May contain traces of nuts
> Your milage may vary


I had that same thought, but I dont have enough new spokes left. I
could reuse the spokes that are on the wheel but I am afraid they
might be on the verge of failing like the three that broke.
 
J

Joel

Guest
Steve,

It is the force components other than tension that you mention that
might be resonsible for breaking the spokes. It is like you are
pulling on the spoke at an angle rather than straight in line. I don't
have the other side of the broken spoke but it looks like you
described. A clean break with a small protrusion on one side. When I
think of fatigue I think of a wheel that has been riden for many
hours, not just a few hours. So if the cause is not 2X and not high
tension then what? Defective spokes?

Joel
 
Q

Qui si parla Campagnolo

Guest
On Feb 22, 9:49 am, "Joel" <[email protected]> wrote:
> I don't have a way to measure it, but I have built probably a dozen
> wheels that have no problems and spokes on this wheel are as tight or
> tighter than all of those wheels. Also I was riding with a group when
> one of the spokes broke and we compared my wheel to others and the
> spokes where tighter than everybody elses which prompted the comment,
> your spokes are too tight thats why they are breaking.


Rims will taco way before high tension will break spokes.
>
> Can anybody here accept the fact that with fewer crosses in the
> pattern, the cross over occurs closer to the hub flange which causes
> increased bowing of the spokes. This combined with higher spoke
> tension which is translated by the bowing into a force that is not
> tension is what is breaking the spokes.


See above, Tough to say w/o measuring the spokes, but...replace the
spokes, reduce the tension, go ride and see what happens.
Actually lower spoke tension
> in this case could prevent or reduce the breaking.
>
> Joel