Question:
The crankarm method seems to be favored in this newsgroup, although all
the wheelbuilders i'm apprenticed to have never used it or heard of it.
They use either the 'grab 4 and squeeze really hard' method or put it on
the floor and stand on it in sections. Or they won't tell me what they
really do, I'm not always sure.
I just finished my rolf cert. build using their wine press method. (For
those not familiar, its a table with a round hole just smaller than the
rim diameter supporting the laced wheel, and the hub is pressed
laterally to the rim, with a torque wrench. Flip the wheel and do the
other side, etc.)
The 'overpriced wisconsin wheels' method was interesting,
...does anyone use this method for traditional 3x and higher spoke count
wheels? I have it around anyway, and it was pretty expensive for the
shop so I might as well use it.
...is it as effective or superior to other favorite methods from someone
using both methods on comparative wheels? It seems to be a more uniform
way to stress all the spokes evenly, if uniform stressing matters
...if you are, what tensions are you using for conventional wheels? Rolf
being 85 ft/lbs. I'm not looking for an exact number, just a range or
recommended starting point.
Answer:
I'm just poking fun at the Rolf wheels here, since they are made by
Trek. I'm just referring to the wine press again. I didn't coin the
phrase, but liked it when I first heard it. Rolf wheels have fairly
heavy rims to support the paired spoking and the stress cycles it is
subjected to to build it in the press (about five times). Opinions of
some is that they are neat looking but actually not that light for
$6-700 a set, hence the phrase.
Grabbing 4 and squeezing hard is the only way one can do this manually.
The other methods do little or nothing for the spokes. Pressing down
on the rim with the axle as opposing force, whether by standing on it
or pushing with the hands only serves to slacken the under side
spokes. It does not appreciably increaser tension on the upper side.
This does not adequately stress relieve the spokes. The box is useful
for tightening spokes because it unloads the under side spokes, but it
does not do a good job at stress relief. It helps for tightening flat
spokes that require such unloading while tensioning as do spokes in
wheels with so few spokes, because they must be more than twice as
tight as wheels with a full complement of 36. At such high tension,
spokes easily twist off from thread ramp and friction torque.
I take it the Wisconsin method to which you refer is the Rolfing box.
This does not do a good job. Besides, you can collapse a rim with it
if the wheel has more than 20 spokes because the increase in tension
is greater than the loss to the under side spokes. On the other hand
it is an alternate method and one that does some good. However, with
paired spokes, it seems that a special tool to squeeze these pairs
would be far more useful, simpler and less cumbersome.
Stress relieving requires that the spoke tension be increased
significantly, above their (if I have the term and concept right) plastic
deformation threshhold. This relieves internal stresses within the metal
of the spoke left over from manufacturing (drawing the spoke through wire
dies and bending the elbow), which in turn increases the service life of
the spoke.
Pushing the rim to one side, walking on the spokes, etc. does not
increase spoke tension significantly. It does reduce the tension on some
spokes which allows them to release their wind-up (twist) that occurred
while tightening them. Some satisfying pings are often heard when the
spoke is unloaded. But that's not stress relieving.
