Quoted message said:Michael Johnson said:Quoted message said:>> That's one spoke-squeezing (and why-we-have-crosses) theory I've
>> not heard of before. Why does a slight bend at the cross prevent
>> breaking due to fatigue?Quoted message said:Quoted message said:> According to Barnett, when the spokes don't have a slight bend,
> they are subjected to cycles of being bent against each other and
> released as they go through load/unload cycles. This constant
> flexing eventually results in material fatigue. This is the
> contention in the manual, at any rate.Quoted message said:Quoted message said:I think you'll find that spokes removed from a wheel show no kink
where they cross an interleaved opposing spoke, before or after
stress relieving. The two advantages of interleaving, something
most wheel builders do, is that spokes do not go entirely slack
when riding over rough road and a broken spoke doesn't not dangle
freely and foul the wheel regardless of which end fails.Quoted message said:I didn't say that the spokes developed a kink where they cross. What
I said was that they are constantly flexed, i.e. bowed then unbowed,
as they are loaded and unloaded. This bowing takes place along the
entire length of the spoke and results in fatigue at the elbow,
where the spoke typically breaks. Again, according to Barnett.If the spoke does not change shape, how does this method alter how the
spoke flexes in use, assuming it does so?
ever heard of elasticity?
Quoted message said:In contrast, I think you'll
find that the spokes run in an unchanging straight line to the ends
and that the slight deflection at interleaved spoke crossing moves so
slightly that it causes no perceptible sound as these points fret
against each other. In time this causes a notch in each spoke, one
that is noticeable when they are displaced past one another manually
and click back into the notch when released.
sound??? deliberate attempt to obfuscate. and this paragraph
contradicts your contention about "not changing shape".
Quoted message said:
Quoted message said:If you introduce a bend in the spoke, which Sheldon's method (and the
method in Barnett, which differs only in the implement used) actually
does, then the spoke is already in a bowed shape and doesn't flex as
much as it is loaded and unloaded, thereby reducing mechanical fatigue.I think you'll find that there is no permanent bend introduced by
these methods, the spokes being essentially as straight as they were
fresh out of the box. What changes is the elbow bend for outbound
spokes, mainly on the left side. Improving the spoke line is best
done directly and manually before the wheel has full tension, and it
doesn't have anything to do with spoke crossings.
there's no evidence that you /can/ "improve" the spoke line while at
full tension since you cannot overshoot. elasticity and yield require
that you overshoot.
Quoted message said:
Quoted message said:Your point about interleaving, while true enough, is a red herring.
Wat in particular do you mean in that respect?
oh, the irony of fisherman jobst!
Quoted message said:
Quoted message said:Quoted message said:> I cannot personally vouch for the truth of the assertion, I
> haven't seen the experimental data. It sounds plausible, however.
> Certainly more so than the idea that momentarily /increasing/ the
> tension on a spoke is going to relieve spoke wind-up.Quoted message said:Quoted message said:Its the adjacent spoke that becomes unloaded from this maneuver
that untwists, the same as when a wheel is pressed against the
floor on its axle. It is the slackening spoke that untwists.Quoted message said:So you're claiming that the rim flexes enough radially when you
squeeze some spokes to cause other spokes to go slack and unwind? I
would expect this effect to be minimal at best, especially compared
to pressing on the rim.When grasping pairs of spokes firmly, the rim moves radially inward
and partially relaxes adjacent spoke tension. As the spokes are
pulled together, they do not change length
oh yes they do. it's called elasticity.
Quoted message said:so something must move (by
the cosine of the angle).
yeah. see above.
Quoted message said:The only length change spokes is in
microns, locally at high concentrations.
1. that contradicts the above.
2. yield, what you're alluding to, is a presumption.
3. even if yield occurs, it's in regions of high residual stress close
to the neutral plane, not the regions from which fatigue is observed to
initiate, the regions farthest from neutral.
Quoted message said:These changes are immaterial
to wheel alignment while radial rim flexing remains in the elastic
zone unless the wheel is too tight.
but their foggy and imprecise presumption is essential to your ability
to "cure" and thus sell wheel books.
if that income stream is drying up, maybe you should sell a book on your
contributions to automotive design? but be careful with your facts on
that one jobst - there's a broader and better educated audience. might
cause problems in the presumption and concoction departments.