Ron Ruff Wrote:
> On May 10, 6:36*am, "joseph.santanie...@[EMAIL PROTECTED]
"
> <joseph.santanie...@[EMAIL PROTECTED]
> wrote:
> > If that is the case, it doesn't matter which side the spokes are on.
> > Any "pull" spoke transfers torque to the rim, whichever side it is
> on.
> > So then it would make sense to have radial on the DS, not the NDS.
> > That way the shorter spoke and resulting angle helps make up for the
> > more inboard placement of the DS flange.
>
> It would help a little... but think about what you've done to the NDS
> spokes. Instead of 19mm and 36mm spacing, you'd get maybe 21mm and
> 36mm (just guessing). If you put 120kg in the DS, then the NDS would
> be 70kg... and these are the only spokes transfering torque. Combine a
> high torque load with the radial and side loads, and it won't take
> much to make the pu****ng spokes go slack.
>
> > This is totally unscientific and anecdotal, but I just took my light
> > wheels (28h, 2x DS, radial NDS, narrow AC hub flanges) for a short
> > test, and did some purposefully agressive side to side sprints. It
> > seems the wheel only have the occasional flop when I lean the bike
> to
> > the right, and the rims feels like it flexes in toward the NDS.
>
> You are very perceptive! This is the side that will buckle first,
> since the NDS tension is lower and the spokes are at more of an angle.
> You can demonstrate this easily by taking the wheel out and pressing
> on the edges of the rim, while the axle rests on a solid surface. The
> wheel will "boing" with lower force when you press towards the NDS.
>
> > The
> > flanges mean there is essentially no dish, so the only real
> difference
> > between each side is spoke length and thus angle. The rim does not
> > seem to flop toward the DS. That makes sense because the NDS is
> radial
> > and is in better position to resist.
>
> There is dish. Probably ~19mm DS and 28mm NDS. This is the main
> difference. Oddly, if the spacing (dish) was greater, you'd think the
> lateral stability situation would get worse... but it actually
> improves. A narrow spacing improves the tension balance, but this is
> only an issue if you have spokes going slack from radial loads... for
> all other loads it makes things worse. Narrow flanges reduce the
> lateral stiffness a lot, since this goes up exponentially with bracing
> angle, and they also reduce the load required to make the wheel
> buckle.
I agree with Ron Ruff. Whatever way you finally decide to build them,
make sure to stabilize the build and check spoke tensions often for at
least the first 100 miles to make sure that everything stays where you
put them... or at least gets back there.
I don't see any benefit for 3X on a 28 spoke wheel.
The wider set flanges and thicker hub mid section of the 7800 Dura Ace
hubs make them stiffer in all dimensions.
Your 50 mm high rims also help stiffness in three ways:
the rims themselves due to the rim height
the spoke sup****t angle is greater
the spoke length is shorter
Each contribution may be small, but it is measurable and in the
direction of increased stiffness.
--
daveornee
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