On Wed, 19 Apr 2006 20:02:06 -0400, "Phil,
Squid-in-Training" <[email hidden]>
Quoted message said:Quoted message said:On Wed, 19 Apr 2006 01:29:08 -0400, "Phil,
Squid-in-Training" <[email hidden]>
Quoted message said:A customer's cheap, newish track wheel came in with a broken spoke.
I replaced the spoke and tensioned everything up all around. Very
smooth, almost no-resistance tensioning was experienced except for
the one replaced spoke (a DT). The rest were un-head-stamped
stainless 2.0. I kept tensioning until I realized that I was going
to be running out of spoke thread soon, and the tension was still
low! The one DT was very obviously tightening far more than the
others.
Has anyone noticed cheap spokes yielding instead of tensioning?
Dear Phil,
Could whoever built this "cheap, newish track wheel" have
simply used spokes that were too long and never really had
much tension on the wheel in the first place?
Tension should increase as the spokes are turned, regardless of how long the
spokes are. I did two full turns with almost no increase in tension,
whereas the one DT tightened up appreciably in 1/2 a turn. I had to skip it
on each rotation of the wheel during truing because it would actualy pull on
the rim instead of yielding.
Quoted message said:You could compare their length, elbow, and threaded section
to the DT spoke that works.
Heh... not on shop time... plus he was waiting for it.
Quoted message said:Wheel-builders use too-long spokes more often than factories
buy wildly defective raw wire.
How do you know?
Dear Phil,
With too-long spokes, you simply run out of spoke thread.
With too-long elbows, the elbow straightens and yields.
Both situations involve a wheel that was badly built before
it broke a spoke and puzzled you.
As for the relative rates badly chosen spoke lengths versus
wildlty defective steel spokes, you can compare the number
of posts on RBT.
Numerous posters on RBT have admitted to making mistakes
about calculating spoke lengths for hub-rim combinations,
but there are very few posts about 2mm stainless steel
spokes mysteriously yielding without raising tension.
If the 35 original stainless steel spokes were yielding
instead increasing appreciably in tension, then it sounds as
if you were pulling stainless steel spokes apart like taffy
with less than 60 pounds of force.
But 2mm stainless steel spokes typically take over 600
pounds of force to yield, ten times as much. As described,
we could apparently pull these odd spokes apart with our
bare hands.
Another possible explanation is that the nipples were
actually the culprit and were slowly stripping. For a while,
this would look like yielding spokes.
Again, there are far more complaints about no-good spoke
nipples on RBT than about 2mm stainless steel spokes turning
into rubber bands.
But maybe the materials people on RBT can tell us that there
really are ways to reduce the yield strength of stainless
steel 90%. I'd love to find out about a weird steel-making
process, alloy, or corrosive agent that turns steel into
licorice.
Cheers,
Carl Fogel
