Spokes "yielding" ?

In article <[email hidden]>,

still me said:

I've got a conceptual problem with this... I know head bolts on a car
engine yield as part of the final torquing process, but you tighten
them to serious levels with long wrenches and big threads.
Envisioning a measly spoke wrench getting enough tension on those
little threads to actually cause a spoke's metal to yield seems
somewhat difficult to believe.

That's not what takes spokes to yield. Read up on "stress relieving"
for bicycle spokes.

Quoted message said:

I'm not questioning that you could stretch a wire the size of a
spoke, but that you can get that kind of pressure with the interface
we have. Of course, that's a seat of the pants thought and not based
in science.

So, is there science to support this? Have people put spokes into a
scientific test environment, tightened them to reasonable specs such
as we can get with our fingers, and seen actual, measurable, metal
yield occur? Inquiring minds want to know!

Ah, let the flame war begin.

still me said:

I've got a conceptual problem with this... I know head bolts on a car
engine yield as part of the final torquing process, but you tighten
them to serious levels with long wrenches and big threads. Envisioning
a measly spoke wrench getting enough tension on those little threads
to actually cause a spoke's metal to yield seems somewhat difficult to
believe. I'm not questioning that you could stretch a wire the size of
a spoke, but that you can get that kind of pressure with the interface
we have. Of course, that's a seat of the pants thought and not based
in science.

They bend. You're right that torqueing up the nipple cannot provide
enough force to stretch a spoke.

Jobst has some figures I think in his book that have also been posted to
RBT about how much force it takes to yield a spoke by stretching it
along its length. Basically it's a hell of a lot.

But you can bend a spoke in your hands easily. The reason is leverage--
you apply a fairly small force at the point where you apply it but
there's a much higher force at the bend.

The spoke can bend a bit at the elbow under the action of
nipple-tightening.

Quoted message said:

So, is there science to support this? Have people put spokes into a
scientific test environment, tightened them to reasonable specs such
as we can get with our fingers, and seen actual, measurable, metal
yield occur? Inquiring minds want to know!

Just put a spoke into a hub, make it an outbound spoke, do it up to
normal tension, and take it out again. Compare it to an unused spoke,
and you may well see that its elbow angle has got a little bit more
acute.

still me said:

I've got a conceptual problem with this... I know head bolts on a car
engine yield as part of the final torquing process, but you tighten
them to serious levels with long wrenches and big threads. Envisioning
a measly spoke wrench getting enough tension on those little threads
to actually cause a spoke's metal to yield seems somewhat difficult to
believe. I'm not questioning that you could stretch a wire the size of
a spoke, but that you can get that kind of pressure with the interface
we have. Of course, that's a seat of the pants thought and not based
in science.

So, is there science to support this? Have people put spokes into a
scientific test environment, tightened them to reasonable specs such
as we can get with our fingers, and seen actual, measurable, metal
yield occur? Inquiring minds want to know!

Yes, Google it.

Ben C said:

The spoke can bend a bit at the elbow under the action of
nipple-tightening.

Ok... I've seen that. So we're talking about "unbending" of the elbow,
and perhaps a little bending of the flange, but not a "yield" along
the length, correct?

I can deal with that :-)

In article <[email hidden]>,

still me said:

Ben C said:

The spoke can bend a bit at the elbow under the action of
nipple-tightening.

Ok... I've seen that. So we're talking about "unbending" of the
elbow, and perhaps a little bending of the flange, but not a "yield"
along the length, correct?

That is my understanding. Jobst was talking about reducing the residual
stresses from putting that elbow into the spoke. It's rare for an
undamaged spoke to break at mid-span. They tend to break at the elbow
and at the first thread.

still me said:

I've got a conceptual problem with this... I know head bolts on a car
engine yield as part of the final torquing process,

not true. some do, some don't. "tty" or "torque to yield" are the type
you're referring to. their use is not universal.

Quoted message said:

but you tighten
them to serious levels with long wrenches and big threads. Envisioning
a measly spoke wrench getting enough tension on those little threads
to actually cause a spoke's metal to yield seems somewhat difficult to
believe. I'm not questioning that you could stretch a wire the size of
a spoke, but that you can get that kind of pressure with the interface
we have. Of course, that's a seat of the pants thought and not based
in science.

So, is there science to support this? Have people put spokes into a
scientific test environment, tightened them to reasonable specs such
as we can get with our fingers, and seen actual, measurable, metal
yield occur? Inquiring minds want to know!

go to dtswiss.com and look up the yield strengths for their spokes.
you're looking at 900-1400Nmm^-2. for a 2.0mm diameter spoke, that's
3.14mm^2 cross section at say 900Nmm^-2 = 2826N to yield. that's 633lbs
tension. typical wheel build spoke tension is ~1/3rd that. can you
figure things out from there?

still me said:

Ben C said:

The spoke can bend a bit at the elbow under the action of
nipple-tightening.

Ok... I've seen that. So we're talking about "unbending" of the elbow,

It could bend either way-- out a bit for an inbound spoke, in a bit for
an outbound one.

Quoted message said:

and perhaps a little bending of the flange, but not a "yield" along
the length, correct?

Correct. The elbow is what all the fuss is about and where the problems
tend to be which is why some manufacturers are pursuing the idea of
straight-pull spokes.

The hub flange doesn't exactly bend but the holes do usually yield on
aluminium hubs as you can see if you compare a used hub with a new one.

jim beam said:

still me said:

I've got a conceptual problem with this... I know head bolts on a car
engine yield as part of the final torquing process,

not true. some do, some don't. "tty" or "torque to yield" are the type
you're referring to. their use is not universal.

Yea... I was generalizing for discussion.

Quoted message said:

go to dtswiss.com and look up the yield strengths for their spokes.
you're looking at 900-1400Nmm^-2. for a 2.0mm diameter spoke, that's
3.14mm^2 cross section at say 900Nmm^-2 = 2826N to yield. that's 633lbs
tension. typical wheel build spoke tension is ~1/3rd that. can you
figure things out from there?

Yea, that was sort of my point. The physics were beyond me, but it
didn't pass the gut test.

Ben C said:

Correct. The elbow is what all the fuss is about and where the problems
tend to be which is why some manufacturers are pursuing the idea of
straight-pull spokes.

The hub flange doesn't exactly bend but the holes do usually yield on
aluminium hubs as you can see if you compare a used hub with a new one.

Yes, seen that too. Again, no scientific evidence here (why research
when my intuition can guide me!) but I always thought that was a road
load created issue. That is, a newly built wheel will not show this,
but a wheel that has had road loads imposed over years will.

I confess to never disassembling a newly tensioned wheel to see if it
had this issue. I'm usually happy that I can get them built and
straight. Perhaps someone else has done this before putting the wheel
on the road?

Ben C said:

still me said:

Ben C said:

The spoke can bend a bit at the elbow under the action of
nipple-tightening.

Ok... I've seen that. So we're talking about "unbending" of the elbow,

It could bend either way-- out a bit for an inbound spoke, in a bit for
an outbound one.

Quoted message said:

and perhaps a little bending of the flange, but not a "yield" along
the length, correct?

Correct. The elbow is what all the fuss is about and where the problems
tend to be which is why some manufacturers are pursuing the idea of
straight-pull spokes.

that's to fatigue not yield. fatigue occurs well below yield point.

Quoted message said:

The hub flange doesn't exactly bend but the holes do usually yield on
aluminium hubs as you can see if you compare a used hub with a new one.

still me said:

jim beam said:

still me said:

I've got a conceptual problem with this... I know head bolts on a car
engine yield as part of the final torquing process,

not true. some do, some don't. "tty" or "torque to yield" are the type
you're referring to. their use is not universal.

Yea... I was generalizing for discussion.

then you should say "some" head bolts. your statement was fully inclusive.

Quoted message said:

Quoted message said:

go to dtswiss.com and look up the yield strengths for their spokes.
you're looking at 900-1400Nmm^-2. for a 2.0mm diameter spoke, that's
3.14mm^2 cross section at say 900Nmm^-2 = 2826N to yield. that's 633lbs
tension. typical wheel build spoke tension is ~1/3rd that. can you
figure things out from there?

Yea, that was sort of my point. The physics were beyond me, but it
didn't pass the gut test.

still me said:

Ben C said:

Correct. The elbow is what all the fuss is about and where the problems
tend to be which is why some manufacturers are pursuing the idea of
straight-pull spokes.

The hub flange doesn't exactly bend but the holes do usually yield on
aluminium hubs as you can see if you compare a used hub with a new one.

Yes, seen that too. Again, no scientific evidence here (why research
when my intuition can guide me!) but I always thought that was a road
load created issue. That is, a newly built wheel will not show this,
but a wheel that has had road loads imposed over years will.

hub indentation occurs as the wheel is build and "stress relieved".

Quoted message said:

I confess to never disassembling a newly tensioned wheel to see if it
had this issue. I'm usually happy that I can get them built and
straight. Perhaps someone else has done this before putting the wheel
on the road?

yes. there is no discernible difference unless the wheel is slack
spoked and sliding wear occurs.

still me said:

I've got a conceptual problem with this... I know head bolts on a car
engine yield as part of the final torquing process, but you tighten
them to serious levels with long wrenches and big threads. Envisioning
a measly spoke wrench getting enough tension on those little threads
to actually cause a spoke's metal to yield seems somewhat difficult to
believe. I'm not questioning that you could stretch a wire the size of
a spoke, but that you can get that kind of pressure with the interface
we have. Of course, that's a seat of the pants thought and not based
in science

Could you believe that you could break a coat-hanger with your
fingers?

As Jobst has demonstrated in his book, spokes go from 1000N to 0N
once per wheel revolution. That constant cycling creates metal
fatigue at
the elbow. After some time... bing ... the fatigued spoke gives way.

It's not complicated, really.

Quoted message said:

Ben C said:

Correct. The elbow is what all the fuss is about and where the problems
tend to be which is why some manufacturers are pursuing the idea of
straight-pull spokes.
The hub flange doesn't exactly bend but the holes do usually yield on
aluminium hubs as you can see if you compare a used hub with a new one.

still me said:

Yes, seen that too. Again, no scientific evidence here (why research
when my intuition can guide me!) but I always thought that was a road
load created issue. That is, a newly built wheel will not show this,
but a wheel that has had road loads imposed over years will.

I confess to never disassembling a newly tensioned wheel to see if it
had this issue. I'm usually happy that I can get them built and
straight. Perhaps someone else has done this before putting the wheel
on the road?

Dimples at the edge of aluminum flange spoke piercings occur when the
wheel is tensioned.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

jim beam said:

still me said:

jim beam said:

still me wrote:
> I've got a conceptual problem with this... I know head bolts on a car
> engine yield as part of the final torquing process,
not true. some do, some don't. "tty" or "torque to yield" are the type
you're referring to. their use is not universal.

Yea... I was generalizing for discussion.

then you should say "some" head bolts. your statement was fully inclusive.

Maybe. We're not talking about cars here so it works as an example and
further detail is unnecessary.

Do you correct people face to face and start endless, pointless
arguments over trivial matters like this all the time - or just here
on the USEnet?

still me said:

jim beam said:

still me said:

On Wed, 18 Jul 2007 21:57:34 -0700, jim beam
<[email hidden]> wrote:

> still me wrote:
>> I've got a conceptual problem with this... I know head bolts on a car
>> engine yield as part of the final torquing process,
> not true. some do, some don't. "tty" or "torque to yield" are the type
> you're referring to. their use is not universal.
Yea... I was generalizing for discussion.

then you should say "some" head bolts. your statement was fully inclusive.

Maybe. We're not talking about cars here so it works as an example and
further detail is unnecessary.

Do you correct people face to face and start endless, pointless
arguments over trivial matters like this all the time - or just here
on the USEnet?

Welcome to our tolerant, friendly little group.

The deal with stress relieving spokes is that it's a form of mechanical
stress relief. In mechanical stress relief, by momentarily raising
stress above the static level, any *local* regions in the part that are
operating close to yield will yield and will be at a lower static level
once the operation is over. It's not the intent to yield the bulk of the
material, the additional stress is too low for that.

With a wheel, the local static stresses may be high from spoke forming
at the factory or the spoke being bent to conform to the flange. It
really doesn't matter, the fatigue load is a change in spoke tension, so
by momentarily increasing the tension you'll "micro-yield" any areas of
concern, however they came to be. If they aren't there, it won't hurt
anything.