Chexjc said:will reusing spokes compromise the strength of the wheel? AND - will
eventually switching from the 12g spokes to the 14g SS spokes
compromise the rim at all?
The short answer is spokes can be reused if they aren't damaged without
compromising anything. I've got a mountain-bike wheel I've replaced the
rim on twice that is still on the same set of spokes.
The long answer is a little more complex. When you take apart the old
wheel, it is important to evenly release the tension on the spokes
(say, one turn at a time) so that you don't deform the rim in the
process. When you build up the new wheel, the -wheel- will be just as
strong as if you used new spokes, provided you tension the spokes
properly. However, the -individual spokes-, if not installed properly,
may fail prematurely from fatigue.
A spoke in a wheel doesn't follow a straight line; it has a set of
bends near the hub, a bend where it crosses the spokes that face the
other direction, and a small bend where it goes into the nipple. A good
wheel builder, using a few different techniques, pre-bends (or
strain-relieves) the spokes, so that they are in the same shape absent
the tension as they are with the tension. If you don't do this, as the
wheel rotates in use, the spokes are like a paperclip being bend
back-and-forth, and eventually work-harden and fail. In a properly
built wheel the spokes don't fatigue in this manner -- actually, if I
get normal service life out of a rim without any spoke breakage due to
fatigue, I *prefer* to reuse the spokes when replacing the rim. Since
they didn't fail, I take that as proof that they didn't fatigue and
were property strain-relieved. Why would I want to start over and take
my chance on a new set?
Spokes can always be reused if the wheel is build rebuilt with the same
type hub and rim, and provided you keep the spokes in the same position
(left inner, left outer, right inner, right outer). Changing the rim
type usually isn't a big issue, but changing the hub flange shape could
be. If you must reuse spokes in this situation, you may want to
evaluate how different the shape might be and whether it would be
possible to straighten them prior to lacing the wheel. Properly
strain-relieving will be important.
If you totally ignore the bends in the spokes, reinstall them randomly,
and don't strain-relieve, worst case is that the spokes suffer from
premature fatigue and break one-by-one. Breaking of a single spoke
shouldn't damage the rim. Properly tensioned, even if not property
strain-relieved, the reused spokes will resist a "potato-chip" type
failure of the entire wheel as well as properly tensioned new spokes.
You could re-drill the unicycle.com hub for the wider spokes, but
you'll need to property bevel the edges of the new holes. 12g spokes
are 2.5mm diameter; I'd guess you'd want a 2.7mm hole, or about a #36
drill bit. Beveling the edges is left as an exercise to the reader. If
you later wanted to rebuild the wheel with 14g spokes, you'd need to
replace the hub as well.
--
adelman
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