New wheelset: should bearings still be adjusted?

I think a little spinning with fine abrasive

aaaaaaaaaaaaaaaaa

? speculation is best left to finding the BM !issue, digesting the contents.

Tweaking was generally compulsive, yesterday. Today tweaking is specialized or store bought.

T/F ?

'like' who grinds their heads ?

On 14/02/14 04:22, Frank Krygowski wrote:
On Thursday, February 13, 2014 1:34:39 AM UTC-5, JoeRiel wrote:
Frank Krygowski writes:


Let's look at the other end of the problem. The length (radius) of the
QR lever is about 2". If it swings through a 90 degree angle, that gives
an input travel distance of 3.14 inches. 50 pounds is not at all an extreme
grip strength. 50 lb * 3.14 in = 157 inch pounds of input work. For
conservation of work (or energy) the output work of skewer force * skewer
distance should be the same, assuming negligible friction losses. Using
that 0.025" output travel I mentioned, I get 6283 pounds output force.


The applied force, though, isn't constant, but increases with the angle.

That's true. And the cam probably isn't linear. I was just trying to get
a rough idea.

Sort of an aside: My calculations above (Force input * distance input =
force output * distance output) are an expression of conservation of energy
(or conservation of work). Naturally, they're valid only if there are no
friction losses, and we know the cam has significant friction. And there's
the hidden assumption of constant mechanical advantage through the range of
motion. So it's merely a rough calculation.

For linkage mechanisms (like Vise Grips locking pliers, some robotics
grippers I've worked with, etc.) the action is very non-linear; IOW the
mechanical advantage varies greatly, and is often highest at (or close to)
the configuration at which contact occurs. For those situations with
varying mechanical advantage, an alternate approach is to calculate forces
based on conservation of _power_, defined as P=F*velocity. So it becomes
Fi * Vi = Fo * Vo. But to use this, one doesn't actually measure any
velocities; one uses kinematics principles to get the ratio of input to
output velocities at the condition of interest. (There are fairly
simple graphic ways to do this for linkages.) The computed ratio of
velocities is the (inverse) ratio of forces.

I haven't tried this technique with cams; it would require details of
the cam profile. But it does point out that varying geometry makes things
more complicated.


The mechanical advantage has to change significantly, as far as I can
see, because the QR lever acts as an over centre latch. A bit like the
eccentric cams on a compound bow. The closing force must go through a
maxima before becoming less toward the fully closed position. If not,
the cam would spring open as you ride down the road, if it held at all
due to friction.

--
JS

yes !

tell us, were there other QR attempts before Campangnolo ?