Ron Ruff said:
On Apr 23, 10:28 pm, daveornee <daveornee.2pj...@no-
mx.forums.cyclingforums.com> wrote:
> I demonstrated a 5% lateral stiffness difference in changing from 14 g
> to 14/15 DB spokes in an otherwise identical build. In that particular
> comparison the lateral deflection difference was .07 mm at a 25 pound
> lateral deflection load.
I'm curious about your test setup. Have you tested many wheels? I've
been trying to test a few, but my "rig" is not very stiff. On the
other hand I'm getting bigger differences than that. It seems to me
from calculations and experiments that most of the lateral stiffness
is provided by the spokes, and there is ~23% difference in stiffness
between those spokes (2.0 vs 1.8mm). Between 1.8mm and 1.5mm there is
~44% difference.
When my uncle owned a machine shop I used his milling machine base + a couple of fixtures he milled for me to insure that the locknuts would not move when the wheel was laterally loaded. The setup was almost identical to Damon Rinard's setup when he had access to the machine shop at University of California - San Diego.
My fixtures were made from CrMo steel and I used a vinyl coated 1/8" steel cable looped over the rim to hold the 25 pound weight. I intended to test a bunch of wheels, but my time and shop time became obstacles.
Yes, the spokes themselves have a contribution to the lateral stiffness, but the rim, hub, and how the spokes are laced also contribute to how the wheel responds to lateral loading. I also had plans to see how various wheel configurations respond in radial loading.... and then in combination of radial and lateral loading. Again, my time and my uncle's patience/machine shop avaialbility became obstacles I could not overcome.
Check out what Damon says and measures on his site:
"7. How does spoke gauge affect stiffness?
Thicker spokes make a wheel stiffer, if all else is equal. A typical 32 spoke wheel built with 2.0mm spokes is about 11% stiffer than a similar wheel built with 2.0-1.45mm swaged spokes.
Compare the deflection of two wheels: numbers 39 and 47. Wheel 39 is built with 2.0-1.45mm swaged spokes, but wheel 47 is built with 2.0mm straight gauge spokes. Hub dimensions are effectively identical, spoke count is the same and the rims are the same make and model, so the only structural difference is the spoke gauge.
Result? The wheel with thinner spokes deflected 0.051" (1.30mm) in font and 0.067"1.70mm) in the rear, but the wheel with thicker spokes deflected less: only 0.046" (1.17mm) and 0.055" (1.40mm) for front and rear, respectively. That's an 11% increase in stiffness for the thicker spoked wheels.
Interestingly, wheel stiffness depends on more than just spoke thickness; the rim and other factors also contribute, so only part of the increase in raw spoke stiffness shows up in measured wheel stiffness. The thicker spoke by itself is nearly twice as stiff axially as the thinner spoke!"
From:
http://www.sheldonbrown.com/rinard/wheel/index.htm
Item #7
and data table at:
http://www.sheldonbrown.com/rinard/wheel/data.htm
I did a few tests by only changing one variable, such as spoke guage, to get the details of what goes on there. I varied hubs, such as changing from Shimano Ultegra to Phil Wood.... but I also had to use slightly shorter spokes with the PW hubs. My tests are old and my uncle has since sold his shop and retired to play golf.
David Ornee, Western Springs, IL