bending stiffness of spokes

I recently had a discussion with a guy at no-tubes.com about how round
spokes will increase the lateral stiffness of a wheel by up to 25%.
His claim was that a round spoke is stiffer in bending than a bladed
spoke of the same volume. Thus, especially with spokes that have very
low bracing angles, the bending stiffness of the spoke is a large
enough factor that you can feel the difference between a bladed spoke
and round spoke when you stress the wheel by hand using the press on
both sides of the rim while the hub axle is on the ground method.
While I definitly agree that a round spoke is stiffer in bending than
a bladed spoke I question wether or not it is significant enough to
feel or even measure a significant difference in lateral stiffness of
a wheel. It would stand to reason, though, that the bending stiffness
of a spoke would be more important on a hub with flanges that provide
a low bracing angle since the spoke length will change very little for
a given lateral deflection. I still question as to whether or not the
lateral stiffness of a wheel would change a significant amount though.
Has anyone done any calculations on the bending stiffness of a spoke?
I figured most spokes will see about 3 deg. (1/2" of lateral rim
movement on a 26" rim) of movement on a rear wheel. This is assuming
the non-drive flange is towards the center of the hub like American
Classic so we don't see spokes going slack. Thanks for your advice.

Steve Sauter

steve wrote:

I recently had a discussion with a guy at no-tubes.com about how round
spokes will increase the lateral stiffness of a wheel by up to 25%.

Nope. Spokes are loaded solely in tension or compression; they can't
support any significant bending loads. The factors that contribute to
wheel lateral stiffness, in approximate order of importance, are as
follows:

1) rim lateral stiffness
2) spoke bracing angle
3) spoke count
4) spoke gauge/cross-sectional area
5) axle stiffness
6) bearing stiffness

If you include for the possibility of non-steel spokes, then the
Young's modulus of the spoke material would fall at #3 or #4 on the
above list. But using spokes made out of anything other than steel
would be a mistake.

Spoke shape doesn't enter into it, except to the extent that it
reduces or increases spoke gauge equivalent.

Chalo

steve wrote:

I recently had a discussion with a guy at no-tubes.com about how round
spokes will increase the lateral stiffness of a wheel by up to 25%.

Nope. Spokes are loaded operationally solely in tension; they can't
support any significant bending loads. The factors that contribute to
wheel lateral stiffness, in approximate order of importance, are as
follows:

1) rim lateral stiffness
2) spoke bracing angle
3) spoke count
4) spoke gauge/cross-sectional area
5) axle stiffness
6) bearing stiffness

If you include for the possibility of non-steel spokes, then the
Young's modulus of the spoke material would fall at #3 or #4 on the
above list. But using spokes made out of anything other than steel
would be a mistake.

Spoke shape doesn't enter into it, except to the extent that it
reduces or increases spoke gauge equivalent.

Chalo

On Dec 6, 12:14*am, Chalo wrote:
steve wrote:
I recently had a discussion with a guy at no-tubes.com about how round
spokes will increase the lateral stiffness of a wheel by up to 25%.

Nope. *Spokes are loaded operationally solely in tension; they can't
support any significant bending loads. *The factors that contribute to
wheel lateral stiffness, in approximate order of importance, are as
follows:

1) rim lateral stiffness
2) spoke bracing angle
3) spoke count
4) spoke gauge/cross-sectional area
5) axle stiffness
6) bearing stiffness

If you include for the possibility of non-steel spokes, then the
Young's modulus of the spoke material would fall at #3 or #4 on the
above list. *But using spokes made out of anything other than steel
would be a mistake.

Spoke shape doesn't enter into it, except to the extent that it
reduces or increases spoke gauge equivalent.

Chalo

I agree that spokes can't handle a significant bending load, but they
can handle some. It takes a lot more effort to bend 32 spokes than 1.
I am wondering if anyone has tested this or can figure out the bending
stiffness of a round spoke versus a bladed.

Steve Sauter

steve wrote:
I recently had a discussion with a guy at no-tubes.com about how round
spokes will increase the lateral stiffness of a wheel by up to 25%.
His claim was that a round spoke is stiffer in bending than a bladed
spoke of the same volume. Thus, especially with spokes that have very
low bracing angles, the bending stiffness of the spoke is a large
enough factor that you can feel the difference between a bladed spoke
and round spoke when you stress the wheel by hand using the press on
both sides of the rim while the hub axle is on the ground method.
While I definitly agree that a round spoke is stiffer in bending than
a bladed spoke I question wether or not it is significant enough to
feel or even measure a significant difference in lateral stiffness of
a wheel. It would stand to reason, though, that the bending stiffness
of a spoke would be more important on a hub with flanges that provide
a low bracing angle since the spoke length will change very little for
a given lateral deflection. I still question as to whether or not the
lateral stiffness of a wheel would change a significant amount though.
Has anyone done any calculations on the bending stiffness of a spoke?
I figured most spokes will see about 3 deg. (1/2" of lateral rim
movement on a 26" rim) of movement on a rear wheel. This is assuming
the non-drive flange is towards the center of the hub like American
Classic so we don't see spokes going slack. Thanks for your advice.

Steve Sauter

i think someone is confused about the word "bend". the only part of a
tensioned spoke that "bends" is the spoke elbow, if it's not a straight
pull spoke. thus, "bending" is not a contributor to stiffness.

the biggest factors in stiffness are the rim, and the spoke elasticity.

Chalo brought next idea :


Nope. Spokes are loaded solely in tension or compression; they can't
support any significant bending loads.

Imho they can't withstand any compression load as well....

Martin

In article ,
Martin Borsje wrote:

Chalo brought next idea :


Nope. Spokes are loaded solely in tension or compression; they
can't support any significant bending loads.

Imho they can't withstand any compression load as well....

Until they are built up into a pretensioned structure, e.g., a wheel at
full tension, that is true. But in the wheel, the spokes can support a
large compressive load.

In article
,
steve wrote:

On Dec 6, 12:14*am, Chalo wrote:
steve wrote:
I recently had a discussion with a guy at no-tubes.com about how
round spokes will increase the lateral stiffness of a wheel by up
to 25%.

Nope. *Spokes are loaded operationally solely in tension; they
can't support any significant bending loads. *The factors that
contribute to wheel lateral stiffness, in approximate order of
importance, are as follows:

1) rim lateral stiffness 2) spoke bracing angle 3) spoke count 4)
spoke gauge/cross-sectional area 5) axle stiffness 6) bearing
stiffness

If you include for the possibility of non-steel spokes, then the
Young's modulus of the spoke material would fall at #3 or #4 on the
above list. *But using spokes made out of anything other than steel
would be a mistake.

Spoke shape doesn't enter into it, except to the extent that it
reduces or increases spoke gauge equivalent.

Chalo

I agree that spokes can't handle a significant bending load, but they
can handle some. It takes a lot more effort to bend 32 spokes than 1.
I am wondering if anyone has tested this or can figure out the
bending stiffness of a round spoke versus a bladed.

Wouldn't be that hard. Take two wheels that are the same except for the
spokes, clamp them by the axles positioned horizontally, and hang a
weight on the rim 90 degrees from the rim joint. Measure the amount of
deflection. Luckily part of this has already been done! See examples
he

http://www.sheldonbrown.com/rinard/wheel/index.htm

Damon did not address bladed spokes specifically, but did address
differences in spoke thickness (scroll down to #7).

HTH!

Tim McNamara wrote:
In article
,
steve wrote:

On Dec 6, 12:14�am, Chalo wrote:
steve wrote:
I recently had a discussion with a guy at no-tubes.com about how
round spokes will increase the lateral stiffness of a wheel by up
to 25%.
Nope. �Spokes are loaded operationally solely in tension; they
can't support any significant bending loads. �The factors that
contribute to wheel lateral stiffness, in approximate order of
importance, are as follows:

1) rim lateral stiffness 2) spoke bracing angle 3) spoke count 4)
spoke gauge/cross-sectional area 5) axle stiffness 6) bearing
stiffness

If you include for the possibility of non-steel spokes, then the
Young's modulus of the spoke material would fall at #3 or #4 on the
above list. �But using spokes made out of anything other than steel
would be a mistake.

Spoke shape doesn't enter into it, except to the extent that it
reduces or increases spoke gauge equivalent.

Chalo
I agree that spokes can't handle a significant bending load, but they
can handle some. It takes a lot more effort to bend 32 spokes than 1.
I am wondering if anyone has tested this or can figure out the
bending stiffness of a round spoke versus a bladed.

Wouldn't be that hard. Take two wheels that are the same except for the
spokes, clamp them by the axles positioned horizontally, and hang a
weight on the rim 90 degrees from the rim joint. Measure the amount of
deflection. Luckily part of this has already been done! See examples
he

http://www.sheldonbrown.com/rinard/wheel/index.htm

Damon did not address bladed spokes specifically, but did address
differences in spoke thickness (scroll down to #7).

HTH!

oh timmy, you're such a retard. spoke elasticity is a function of cross
section area and length. if the cross section area is the same, it
makes no difference if the spoke is of flat, round, or banana cross-section.

Tim McNamara wrote:
In article ,
Martin Borsje wrote:

Chalo brought next idea :

Nope. Spokes are loaded solely in tension or compression; they
can't support any significant bending loads.
Imho they can't withstand any compression load as well....

Until they are built up into a pretensioned structure, e.g., a wheel at
full tension, that is true. But in the wheel, the spokes can support a
large compressive load.

only if the rim allows them to do so timmy. if your rim was made of
styrofoam, spokes wouldn't do ****.