The Basics of Wheel Alignment and Wheelbuilding

On Sun, 01 Aug 2004 19:03:14 -0700, jim beam
wrote:

his "stress relief" theory on the other hand is entirely subjective,

Can you suggest some ways such a theory might be tested?

jim beam wrote:
Mark McMaster wrote:

jim beam wrote:

wrote:


snip

Spoke-squeezing is an intriguingly mysterious subject to
research. I remain agnostic, wavering one way and the other,
but haven't seen any experimental data or analyses involving
bicycle spokes. If you have the 3rd edition, perhaps you
could peek at the Wiedemer stuff and give me your thoughts
on it?




you may also want to consider this question:

q: elevator safety certification requires loading the cab to double
it's "safe working load". this is to test the wire ropes that
suspend it. the reason is that fracture mechanics predict that this
process will typically reveal by failure any latent flaws. but, if
we extend spoke squeezing theory, wouldn't this overload procedure
also prevent fatigue of elevator cables?

a: no. elevator cables still fatigue and need regular testing,
inspection & replacement.



This proves nothing one way or the other about the affects of
squeezing spokes to reduce residual stress. There is no question that
reducing residual (tensile) stresses can increase fatigue life. There
is also no question that spokes (or elevator cables) will still
fatigue if the cyclic load is high enough (i.e. above the endurance
limit). The question is whether squeezing the spokes provides any
significant beneficial reduction in residual stress, or increases the
endurance limit.

Mark McMaster



ah, this explains everything! stainless steel has been developed that
has an endurance limit! and it's used in bicycle spokes!!!

no. this is one of the fundamental flaws of "the book". it cites
material behavior for mild steel, which /does/ have an endurance limit,
and then presumes to describe behavior in stanless steel, which does
not. just exactly how this lends credibility to a revolutionary means
of eliminating metal fatigue is something i have yet to come to terms with.

Ah, as usual, you dodge the question rather than addressing
it. Whether or not a material has a true endurance limit or
not doesn't change the question of whether momentarily
overloading the spokes can reduce residual stress and/or
increase fatigue life, which is central to the argument.
But then, you appear to be far more interested in being a
contrarian than to actually knowing what is going on.

That momentarily overloading the spokes results in increased
spoke life has been reported by many sources. Not just here
in the RBT newsgroup but by others as well, both inside and
outside the industry. For example, here is the Bontrager
wheel manual which shows how their "wheel stressor" is used
to momentarily overload the spokes:

http://www.bontrager.com/workshop/do...eel_manual.pdf

So, just what is the mechanism that causes the spokes to have
improved fatigue life after momentarily overloading them?
If you
do not believe that Brandt is correct about relieving residual
stresses in the spokes, than what other explanation do you
propose?

And about stainless steel having an endurance limit:
Whether any material has a true and absolute endurance limit
is often debated. However, under a common usage of the term
(fatigue strength at 10^7 cycles is a common definition),
the types of stainless steel used in spokes does have an
endurance limit (but then, you probably knew that). We can
dispose of that red herring.

Here are some data on some stainless steels of the type used
in spokes (for example, Wheelsmith uses 304, DT uses 18-8),
including their endurance limits:

http://www.hghouston.com/ss_cwp.html
http://www.band-it-idex.com/pdfs/sta...el/302_305.pdf
http://www.askzn.co.za/tech/tech_grade_304.htm


Mark McMaster

Trevor Jeffrey wrote:
Tim McNamara wrote in message ...


oil. My spoke nipples do not unwind in use, despite being 215 lbs and
riding 32 spoke wheels 6,000 to 7,000 miles a year. The reason for
this is not using something to glue the nipples and spokes together,
but using adeqate tension in the first place. Stuff like linseed oil
and Spoke Prep just covers for a badly built wheel.

Hmmm, this conversation seems like old times.


The use of any oil will assist in the prevention of a nipple shaking
loose, a drying oil just happens to be the most successful in this
application, i.e. a wheel not overtensioned. The wheel construction is how
I describe and not what you ride. Your conversation is repeated because you
do not appear to take on board what I have wrote. Adequate tension is
accomplished when the wheel remains laterally stable under load. Further
tension unnecessarily reduces the available load capacity of the rim and so
of the wheel.

Sorry, it doesn't work this way. Because the spokes are far
stiffer than the rim, very little of the load is supported
by the rim at all when the wheel is loaded - at least not
until the spokes go slack. But then the wheel losses the
lateral stability you seek, so asking the rim to support the
load is a poor idea.

Mark McMaster

On Sun, 01 Aug 2004 21:45:24 -0500, dianne_1234
wrote:

On Sun, 01 Aug 2004 19:03:14 -0700, jim beam
wrote:

his "stress relief" theory on the other hand is entirely subjective,

Can you suggest some ways such a theory might be tested?

Dear Dianne,

One way would be to take before and after pictures that
either do or do not show microscopic changes in a squeezed
spoke.

(My understanding of such matters is so feeble that I should
add that "microscopic" may need to be replaced by "x-ray
diffraction" or even more exciting technologies involving
terms like "lattice" and "crystal" and "scanning
microscope"--or possibly "bi-focals.")

Unfortunately, this requires more than just swiping a spoke
across the bar-code reader at the grocery store, so I've
stopped holding my breath while waiting for such evidence to
appear.

Another test would be to find an industry in which a very
similar process has been developed and tested. The obvious
place to look would be spoked motorcycle wheels, or even the
spoked wheels of obsolete British sports cars. There might
be a paper detailing testing of spoke stress-relief lurking
out there somewhere. (If none can be found, this is not
proof that the theory is wrong--spokes in other applications
might be so over-engineered that stress-relief is pointless,
or the wheels elsewhere might just be badly built.)

A practical test would involve taking several brands of
modern spokes and subjecting batches of them to some Rube
Goldberg machine that mimics the rapid reduction of
otherwise steady tension in a rolling bicycle wheel for
millions of cycles. If the stress-relieved batch outlasted
the unsqueezed batch, it would settle the matter.

Because the subject is of little interest outside
rec.bicycles.tech, expensive and serious testing beyond
anecdote is unlikely. Perhaps someone will find a peer
reviewed paper on spokes (as opposed to related but arguably
different matters), but I expect that it would have turned
up by now if such a study existed.

(Again, the absence of a study is not proof for or against
the theory--and the Wiedemer citation that I assume appears
in the 3rd edition of "The Bicycle Wheel" might be
specifically on spokes. I take comfort in the fact that I'm
apparently not the only member of rec.bicycles.tech too
cheap to buy the newer edition.)

A less expensive (and less conclusive) test would be to find
a large group of dedicated bicyclists unaware of the spoke
squeezing theory and find out how often their spokes break.
The only group that I can think of that might fit this
description would be the Keirin racers of Japan, but it
wouldn't surprise me if they've thoughtlessly heard of the
stress-relief theory and ruined themselves as a control
group.

In any case, we could only compare such a group to a very
small, self-selected group here on rec.bicycles.tech. A
double-blind study is hard to arrange when there's little
interest and the testing is expected to take a long time.

One test that occurred to me is to find out what the spoke
squeezing theory predicts will happen to unsqueezed spokes.
Obviously, unsqueezed spokes are supposed to fatigue and
fail sooner than apparently immortal squeezed spokes, but
how much sooner? That is, given 72 spokes on a pair of
wheels built as similarly as possible, except for the spoke
squeezing, how many will break in each set of wheels in ten,
twenty, fifty, or a hundred thousand miles of similar
riding?

I haven't seen any such predictions, but making them might
help put the debate in perspective. My impression is that
those who doubt the theory would predict no significant
difference in spoke failure rates.

I have no idea what kind of failure rates would be predicted
for unsqueezed spokes by spoke-squeezing proponents, but it
would be fascinating to see what kind of predictions would
be made and how they would be supported.

Time to see how my troop of monkeys is doing on duplicating
the First Folio.

Carl Fogel

Mark McMaster Wrote:[color=blue]
jim beam wrote:


So, just what is the mechanism that causes the spokes to have
improved fatigue life after momentarily overloading them?
If you
do not believe that Brandt is correct about relieving residual
stresses in the spokes, than what other explanation do you
propose?

And about stainless steel having an endurance limit:
Whether any material has a true and absolute endurance limit
is often debated. However, under a common usage of the term
(fatigue strength at 10^7 cycles is a common definition),
the types of stainless steel used in spokes does have an
endurance limit (but then, you probably knew that). We can
dispose of that red herring.

Here are some data on some stainless steels of the type used
in spokes (for example, Wheelsmith uses 304, DT uses 18-8),
including their endurance limits:

http://www.hghouston.com/ss_cwp.html
http://www.band-it-idex.com/pdfs/sta...el/302_305.pdf
http://www.askzn.co.za/tech/tech_grade_304.htm


Mark McMaster


The 300 series of stainless steels are 18-8 stainless steels with
slight modifications between the different numbers. Since the 300
series is an AISI designation, European and other areas are not obliged
to call them with this designation.

These stainless steels are all austenitic, meaning they have no
ferromagnetic properties in their annealed state. Plastic deformation
changes this structure to partially ferritic structure making highly
cold worked stainless steels (with some exceptions like 316, a
molybdenum modification of 18-8) slightly magnetic. In addition, this
crystaline change greatly increases the yield strength and is HIGHLY
ansitropic in its effects.

The overstressing procedure forces changes in the elbow, causing it to
conform to the flange hole AND causing deformation of the flange hole
itself. Because of this, the stresses of the bend is now spread over a
longer range of the bend. Cyclic loading consistent with riding is now
operating this joint in a purely elastic range rather than exposing
tiny areas of the bend to very high stresses over very small areas.

This is no different than some pressure vessel codes (notably French, I
forget the code) that hydrostatically test pressure vessels at much
higher pressures than the design. This is termed "auto frettage" and
confers much higher cyclic life to the vessel.


--
Weisse Luft

On Mon, 02 Aug 2004 03:28:58 GMT, Mark McMaster
wrote:

jim beam wrote:
Mark McMaster wrote:

jim beam wrote:

wrote:


snip

Spoke-squeezing is an intriguingly mysterious subject to
research. I remain agnostic, wavering one way and the other,
but haven't seen any experimental data or analyses involving
bicycle spokes. If you have the 3rd edition, perhaps you
could peek at the Wiedemer stuff and give me your thoughts
on it?




you may also want to consider this question:

q: elevator safety certification requires loading the cab to double
it's "safe working load". this is to test the wire ropes that
suspend it. the reason is that fracture mechanics predict that this
process will typically reveal by failure any latent flaws. but, if
we extend spoke squeezing theory, wouldn't this overload procedure
also prevent fatigue of elevator cables?

a: no. elevator cables still fatigue and need regular testing,
inspection & replacement.



This proves nothing one way or the other about the affects of
squeezing spokes to reduce residual stress. There is no question that
reducing residual (tensile) stresses can increase fatigue life. There
is also no question that spokes (or elevator cables) will still
fatigue if the cyclic load is high enough (i.e. above the endurance
limit). The question is whether squeezing the spokes provides any
significant beneficial reduction in residual stress, or increases the
endurance limit.

Mark McMaster



ah, this explains everything! stainless steel has been developed that
has an endurance limit! and it's used in bicycle spokes!!!

no. this is one of the fundamental flaws of "the book". it cites
material behavior for mild steel, which /does/ have an endurance limit,
and then presumes to describe behavior in stanless steel, which does
not. just exactly how this lends credibility to a revolutionary means
of eliminating metal fatigue is something i have yet to come to terms with.

Ah, as usual, you dodge the question rather than addressing
it. Whether or not a material has a true endurance limit or
not doesn't change the question of whether momentarily
overloading the spokes can reduce residual stress and/or
increase fatigue life, which is central to the argument.
But then, you appear to be far more interested in being a
contrarian than to actually knowing what is going on.

That momentarily overloading the spokes results in increased
spoke life has been reported by many sources. Not just here
in the RBT newsgroup but by others as well, both inside and
outside the industry. For example, here is the Bontrager
wheel manual which shows how their "wheel stressor" is used
to momentarily overload the spokes:

http://www.bontrager.com/workshop/do...eel_manual.pdf

So, just what is the mechanism that causes the spokes to have
improved fatigue life after momentarily overloading them?
If you
do not believe that Brandt is correct about relieving residual
stresses in the spokes, than what other explanation do you
propose?

And about stainless steel having an endurance limit:
Whether any material has a true and absolute endurance limit
is often debated. However, under a common usage of the term
(fatigue strength at 10^7 cycles is a common definition),
the types of stainless steel used in spokes does have an
endurance limit (but then, you probably knew that). We can
dispose of that red herring.

Here are some data on some stainless steels of the type used
in spokes (for example, Wheelsmith uses 304, DT uses 18-8),
including their endurance limits:

http://www.hghouston.com/ss_cwp.html
http://www.band-it-idex.com/pdfs/sta...el/302_305.pdf
http://www.askzn.co.za/tech/tech_grade_304.htm


Mark McMaster


Dear Mark,

I'm pleased to see the Bontrager stressor tool, which does
indeed show a serious attempt to calibrate how much the
spokes are being stretched. Thanks for the link.

Being hopelessly contrarian even when wavering on the fence,
however, I have to ask if that same link proves that Jobst
is mistaken about paired spokes being antiquated nonsense?
That is, yes, they make a very nice tool for stretching
spokes, but the question is what the effect is of stretching
spokes, not how precisely it can be done.

That people have reported increased spoke life is true, but
the question is whether their reporting is accurate. They
may be quite right, but they may also be replicating the
tying and soldering reports that Jobst's testing demolished.

Do you know of any formal studies showing that squeezed or
stretched spokes enjoy a longer life? I'm sure that
Bontrager believes it, just as I'm sure that Jobst and
others believe it.

Unfortunately, it's a difficult matter to resolve either way
because any physical change in an actual spoke would
probably be on such a microscopic level that it would very
expensive to photograph and any statistically significant
testing might be frighteningly tedious.

Again, the lack of testing is not evidence that the theory
is wrong, just an indication of how beastly difficult it may
be: "The fatigue resistance of spokes was not tested for
lack of suitable equipment." --"The Bicycle Wheel," 2nd
edition, Part III, "Equations and Tests"

It's worth pointing out that those who deny the spoke
squeezing theory seem to be in the same boat in that their
testing is at least as anecdotal, leaving laymen like me to
admire all the fury and theory and to incline to agree with
whichever post I read last.

I suspect that the spokes don't care how much we abuse each
other and that they simply fatigue in a pattern that I
haven't yet seen documented. Some day, if I'm lucky, someone
will rub my nose in a knock-down, indisputable study, crow
about how the testing proves that their arguments were
correct, sneer at my wishy-washiness, and win my Fury
RoadMaster as a prize.

Carl Fogel

On Mon, 2 Aug 2004 13:58:26 +1000, Weisse Luft
wrote:

[snip metallurgy]

The overstressing procedure forces changes in the elbow, causing it to
conform to the flange hole AND causing deformation of the flange hole
itself. Because of this, the stresses of the bend is now spread over a
longer range of the bend. Cyclic loading consistent with riding is now
operating this joint in a purely elastic range rather than exposing
tiny areas of the bend to very high stresses over very small areas.

This is no different than some pressure vessel codes (notably French, I
forget the code) that hydrostatically test pressure vessels at much
higher pressures than the design. This is termed "auto frettage" and
confers much higher cyclic life to the vessel.

Dear Weisse,

Forgive my layman's summary of what seems rather clear, but
I want to be sure that I'm following you.

You agree with the spoke-squeezing side of the debate that
overstressing significantly increases spoke life, but you
believe that it has nothing to do with internal stress
relief and is instead a matter of a better mechanical mating
of the spoke elbow with the hub hole that spreads the load
out and greatly reduces the stress?

If so, would magnified before and after pictures of the hub
hole show a difference?

I have a vague notion that you've mentioned scuba equipment
in passing. Is that what you have in mind when you speak of
pressure vessels? I'm hoping to wander off into "auto
frettage," but can't figure out how it resembles the spoke
hole and elbow situation.

Thanks,

Carl Fogel

Tim McNamara wrote:
The type of guttersniping you indulge in does not advance the
discussion one whit. Over the years we've had recurrent posters with
the gunslinger mentality who come into town aiming to knock off the
big guy. You seem to be just another one of this species. I suspect
that many of those posters have been the same person hiding behind
different personae, due to consistencies in writing style and
conceptual framework. You don't raise chickens, by any chance?

Er, we already know that "jim beam" is a sock puppet for "tux lover", a
persona retired when it acquired too much of a reputation as a nut case.

That cannot be far away for "jim beam", since as far as I can see if
Brandt posted that wheels are round and spokes are thin it would net
another dose of froth.
--
David Damerell Distortion Field!

Mark McMaster wrote in message ...
Sorry, it doesn't work this way. Because the spokes are far
stiffer than the rim, very little of the load is supported
by the rim at all when the wheel is loaded - at least not
until the spokes go slack. But then the wheel losses the
lateral stability you seek, so asking the rim to support the
load is a poor idea.

To what you are referring does not work I cannot make out. The spokes
are tensile members so need to be resistive to stretch and the rim is a
compressive member so needs to be resistive to squash. One is the complete
opposite of the other. The two are not comparable to each other. Aluminium
is good in compression but not in tension, this is the way of the world,
aluminium rims and steel spokes. If the rim did not support the load it
would not need to be there. It either does or it does not, extraneous items
are most usually omitted on a human powered vehicle. Rims are essential
part of the wheel and bear all the load. What else could possible transmit
the force between tyre and spokes?
TJ

Mark McMaster wrote in message ...
So, just what is the mechanism that causes the spokes to have
improved fatigue life after momentarily overloading them?

Shaping the spoke at the crossing point reduces lateral movement at the
crossing causing angular displacement at the hub with the resultant early
spoke failure due to fatigue. Overtensioning the spokes goes someway to
achieving this unintentionally.

TJ