Losing one spoke in an 18 spoke wheel... effect on lateral true.

I just built an 18 spoke front wheel using CX-Ray spokes and a Niobium
30 rim. I thought I'd try taking one spoke loose to see how much the
lateral deflection changed. The Niobium 30 is a 30mm deep aluminum rim
but it is relatively light... ~450g. The tension originally was 110kg
+-5kg, and it was true to a max variation of .25mm. After loosening
one spoke completely, the lateral deflection was a maximum of .20
inches (5.0mm). Though this is fairly large, it isn't enough to leave
me stranded... I can open my brakes enough so that it doesn't rub, and
keep riding. I thought it would be more, actually... I've heard some
stories...

I also took a spoke loose from another wheel I had handy. It has 32
spokes, a Velocity Aerohead rim (21mm deep, 410g), and Wheelsmith AE15
spokes tensioned to ~90kg (front wheel). The max lateral deflection
went to .12in (3.1mm). This is substantially less, but the difference
isn't as big as I thought it might be. Maybe the difference in the
stiffness of the rims is the reason. The Aerohead is fairly light and
flexible... the stiffness of the spokes is about the same for both
wheels.

BTW, if you'd like to try this on your own, it only takes a minute to
tighten up that one spoke when you are done.

On 23 Feb 2007 22:29:33 -0800, "Ron Ruff"
wrote:

I just built an 18 spoke front wheel using CX-Ray spokes and a Niobium
30 rim. I thought I'd try taking one spoke loose to see how much the
lateral deflection changed. The Niobium 30 is a 30mm deep aluminum rim
but it is relatively light... ~450g. The tension originally was 110kg
+-5kg, and it was true to a max variation of .25mm. After loosening
one spoke completely, the lateral deflection was a maximum of .20
inches (5.0mm). Though this is fairly large, it isn't enough to leave
me stranded... I can open my brakes enough so that it doesn't rub, and
keep riding. I thought it would be more, actually... I've heard some
stories...

I also took a spoke loose from another wheel I had handy. It has 32
spokes, a Velocity Aerohead rim (21mm deep, 410g), and Wheelsmith AE15
spokes tensioned to ~90kg (front wheel). The max lateral deflection
went to .12in (3.1mm). This is substantially less, but the difference
isn't as big as I thought it might be. Maybe the difference in the
stiffness of the rims is the reason. The Aerohead is fairly light and
flexible... the stiffness of the spokes is about the same for both
wheels.

BTW, if you'd like to try this on your own, it only takes a minute to
tighten up that one spoke when you are done.

Dear Ron,

Did you check the wheel after riding for a block or two, or just after
loosening the spoke?

Cheers,

Carl Fogel

On Feb 23, 11:40 pm, wrote:
Did you check the wheel after riding for a block or two, or just after
loosening the spoke?

Good question, Carl!... but I haven't even put a tire on it yet.

I wondered if the horror stories about a wheel breaking a spoke and
causing a crash, were because the wheel actually tacoed. I could have
tried stress-relieving via the "mavic method" when the spoke was out
to see if I could break something... but I didn't... and I don't think
I want to try it now either...

On Feb 24, 7:29 am, "Ron Ruff" wrote:
I just built an 18 spoke front wheel using CX-Ray spokes and a Niobium
30 rim. I thought I'd try taking one spoke loose to see how much the
lateral deflection changed. The Niobium 30 is a 30mm deep aluminum rim
but it is relatively light... ~450g. The tension originally was 110kg
+-5kg, and it was true to a max variation of .25mm. After loosening
one spoke completely, the lateral deflection was a maximum of .20
inches (5.0mm). Though this is fairly large, it isn't enough to leave
me stranded... I can open my brakes enough so that it doesn't rub, and
keep riding. I thought it would be more, actually... I've heard some
stories...

I also took a spoke loose from another wheel I had handy. It has 32
spokes, a Velocity Aerohead rim (21mm deep, 410g), and Wheelsmith AE15
spokes tensioned to ~90kg (front wheel). The max lateral deflection
went to .12in (3.1mm). This is substantially less, but the difference
isn't as big as I thought it might be. Maybe the difference in the
stiffness of the rims is the reason. The Aerohead is fairly light and
flexible... the stiffness of the spokes is about the same for both
wheels.

BTW, if you'd like to try this on your own, it only takes a minute to
tighten up that one spoke when you are done.

Are these 18 spokes evenly spaced? I used to have some cheapo 18 spoke
wheels that also had a funny spoke pattern. I think it was pairs, but
I am not sure. When spokes broke, the wheel went more than 5mm out of
true. The wheels had 30mm section rims. I'll bet spoke pattern (or
more specifically rim-hole distribution) has a lot to say here.

Joseph

"Ron Ruff" wrote in message
oups.com...
On Feb 23, 11:40 pm, wrote:
Did you check the wheel after riding for a block or two, or just after
loosening the spoke?

Good question, Carl!... but I haven't even put a tire on it yet.

I wondered if the horror stories about a wheel breaking a spoke and
causing a crash, were because the wheel actually tacoed. I could have
tried stress-relieving via the "mavic method" when the spoke was out
to see if I could break something... but I didn't... and I don't think
I want to try it now either...


With that few spokes, I would imagine there would be a large amount of rim
movement. The problem with so many modern wheels is they use a heavier rim
and fewer spokes to do the job. Less spokes means each one has to do more
work. I believe many of the RBT wheel sages have commented voluminously
about this in the past...

Bruce

"Ron Ruff" wrote in message
ups.com...
I just built an 18 spoke front wheel using CX-Ray spokes and a Niobium
30 rim. I thought I'd try taking one spoke loose to see how much the
lateral deflection changed. The Niobium 30 is a 30mm deep aluminum rim
but it is relatively light... ~450g. The tension originally was 110kg
+-5kg, and it was true to a max variation of .25mm. After loosening
one spoke completely, the lateral deflection was a maximum of .20
inches (5.0mm). Though this is fairly large, it isn't enough to leave
me stranded... I can open my brakes enough so that it doesn't rub, and
keep riding. I thought it would be more, actually... I've heard some
stories...

Here's the rub; when descending at high speed and you lose a spoke, can
you then open your brakes wide enough so the rim doesn't rub? This may
be a problem.


I also took a spoke loose from another wheel I had handy. It has 32
spokes, a Velocity Aerohead rim (21mm deep, 410g), and Wheelsmith AE15
spokes tensioned to ~90kg (front wheel). The max lateral deflection
went to .12in (3.1mm). This is substantially less, but the difference
isn't as big as I thought it might be. Maybe the difference in the
stiffness of the rims is the reason. The Aerohead is fairly light and
flexible... the stiffness of the spokes is about the same for both
wheels.

BTW, if you'd like to try this on your own, it only takes a minute to
tighten up that one spoke when you are done.

Phil H

On Feb 24, 2:44 am, "
wrote:
Are these 18 spokes evenly spaced?

Yes, they are evenly spaced, radial heads in.

On Feb 24, 8:22 am, "Phil Holman" piholmanc@yourservice wrote:
Here's the rub; when descending at high speed and you lose a spoke, can
you then open your brakes wide enough so the rim doesn't rub? This may
be a problem.

A little brake rub would just slow me down. If the wheel warped much
more though, the tire would start rubbing on the forks as well...

Ron Ruff Wrote:
On Feb 24, 8:22 am, "Phil Holman" piholmanc@yourservice wrote:
Here's the rub; when descending at high speed and you lose a spoke,
can
you then open your brakes wide enough so the rim doesn't rub? This
may
be a problem.

A little brake rub would just slow me down. If the wheel warped much
more though, the tire would start rubbing on the forks as well...
The broken spoke swinging around would tend to make me stop and undo it
from the nipples(assuming it broke at the elbow).
Stiffer deep section rims like the one you are using spread the loads
over a wider portion of the rim. The spoke support angle of radially
spoked wheel with heads in is the highest and stiffest obtainable with
the particular rim and hub.
You would have even less movement with stiffer spokes; like 14 g
spokes.
There are a lot of variables to selecting a particular build.
Dynamic loading of wheels is fairly complex. A single component
failure, such as a broken spoke, needs to be factored in when making
the selections. As the charts that Sapim gives indicate; CX-Ray has
the longest fatigue life of any othe Sapim's spokes. If you went from
18 to 36 spokes, as an example, I would expect the fatigue life of each
spoke to double.... if the dynamic wheel loads presented were the same.

I suspect that your comparison to the Velocity Aerohead 32 spoke wheel
has 3X spoke pattern; thus a smaller spoke support angle.

You can look at wheel stiffness examples and information:
http://www.sheldonbrown.com/rinard/wheel/index.htm
http://www.sheldonbrown.com/rinard/wheel/data.htm
to get some more static results from over 100 wheels that Damon Rinard
tested before he went off to work for Trek.


--
daveornee

In article . com,
"Ron Ruff" wrote:

On Feb 24, 8:22 am, "Phil Holman" piholmanc@yourservice wrote:
Here's the rub; when descending at high speed and you lose a spoke,
can you then open your brakes wide enough so the rim doesn't rub?
This may be a problem.

A little brake rub would just slow me down. If the wheel warped much
more though, the tire would start rubbing on the forks as well...

That's interesting. I wonder if the results would be the same with a
similar rear wheel.

I think you're right that the rim stiffness will have an effect on how
much the wheel goes out of true if a spoke breaks.