Spoke tension meter

Dave vt? writes:

I think both of the JB's are actually in agreement in this
matter. One JB calls it residual stress that is relieved, the
other calls it bedding in.

I don't believe so. Bedding in implies plastic deformation of the
hub, not of the spoke. Furthermore, I think you'll find "jim beam"
will claim that residual stress caused by spoke manufacture can't
be relieved by spoke squeezing.

You say: "Bedding in implies plastic deformation of the hub, not of
the spoke." I think bedding in implies plastic deformation of the
spoke/hub interface. Both the hub and the spoke can give a little in
that relationship.

"Bedding in" requires yielding. The spoke cross section will not
yield from bearing against aluminum. You can bend the wire but that
is not "bedding in", that's bending and forming line of the wire, also
known for producing residual stress. Bedding is in this context has
been used solely to describe the plastic deformation of the flange
where the spoke bears on aluminum. Hence the term does not apply in
the sense that you seem to propose.

Joe Riel writes:

I need a value for the radial stiffness of a wheel. Previously I
extracted values from the finite element data in "The Bicycle
Wheel". Alas, no mention is given of the spoke diameter used in the
simulation. In the "Torsional Stiffness of Spoking" table, a
diameter of 1.6mm is used. Maybe that is the value used for the
simulation. Does a later edition have more information?

No, and it wasn't intended to do other than to show typical wheel
response to loads. However, radial stiffness is directly related to
the compression (in stress analysis terms) of the four or so spokes
that change length under load. You can come up with that for typical
spokes of your choice. As you see, the number of spokes makes a
difference as well.

On Tue, 28 Jun 2005 00:59:19 GMT, Joe Riel
wrote:



Carl, Jobst, or anyone,

I need a value for the radial stiffness of a wheel. Previously I
extracted values from the finite element data in "The Bicycle Wheel".
Alas, no mention is given of the spoke diameter used in the
simulation. In the "Torsional Stiffness of Spoking" table,
a diameter of 1.6mm is used. Maybe that is the value used for the
simulation. Does a later edition have more information?


Joe

Dear Joe,

Here's an online FEA of a bicycle wheel similar to Jobst's:

http://www.astounding.org.uk/ian/wheel/index.html

It uses a spoke diameter of 2 mm. There's a link to the Perl
script that creates the model.

There's also a link to how it can be used to examine loads
in the rim.

And there's a link to some comparisons with analyses by
Professor Gavin and Andrew Hartz, showing that one used 1.83
mm spokes and the other seemed implausible, giving only an
area.

The link to the comparisons mentions a few other analyses of
bicycle wheels, too.

Carl Fogel

Joe Riel wrote:
Carl, Jobst, or anyone,

I need a value for the radial stiffness of a wheel. Previously I
extracted values from the finite element data in "The Bicycle Wheel".
Alas, no mention is given of the spoke diameter used in the
simulation. In the "Torsional Stiffness of Spoking" table,
a diameter of 1.6mm is used. Maybe that is the value used for the
simulation. Does a later edition have more information?


Joe

How about Francois Grignon's data?
http://www.sheldonbrown.com/rinard/wheel/grignon.htm

Details are at the link above, but here are the radial stiffnesses:

Wheel Radial stiffness(lb/in)
Shamal 12 HPW 12 600
Zipp 540 20 200
Mavic Cosmic Expert 13 500
Cane Creek Crono 8800
Specialized tri-spoke 8400
Campagnolo 32 spokes 13 500
Mavic 36 spokes 20 200

On Thu, 16 Jun 2005 15:27:32 -0700, "Jay Beattie"
wrote:

Boston snob! Get the giant Wurlitzer with the monkey stop -- you
know, where the little monky bangs the cymbals. That's a crowd
pleaser and a must-have for any bicycle shop. You can even get
the optional tire inflater stop. -- E. Power Beattie.

The organ in a local church here has a stop (among a few dozen) that makes
the Star Of Bethlehem turn circles, normally used only on Christmases.

Jasper

On Wed, 15 Jun 2005 22:36:40 +0000 (UTC),
(Luns Tee) wrote:

While we're at it.. please explain how insufficient spoke
tension causes spoke breakage. Inadequate tension produces an inferior
wheel, certainly, but the failure of low spoke tension is that spokes
go slack under load, allowing spoke nipples to rattle loose and the
wheel to then go out of true. Spoke breakage is not part of this, even
if it was more common at the time. But so were bell bottom pants.

I don't know *how* it works, but it's clear that it *does* work.

Jasper