On Sun, 15 Oct 2006 21:36:22 -0700, Dan
wrote:

Andy Froncioni wrote:
I'll make a jig and start measuring the
deflection on the dial gauge with known weights on the spoke.


Might not work very well since the ends of the spoke won't be held in
position like they would when assembled in a wheel. The wheel keeps the
ends aligned and parallel.

For round spokes, the reading should be about the same for the same
cross-sectional area. The area is proportional to the diameter squared:

From their charts:
http://www.dtswiss.com/data/files/MA...1202133804.pdf
A 1.8 spoke at 1000N is 1.77, 1.77/(1.8^2) = .546
A 2.0 spoke at 1000N is 2.19, 2.19/(2.0^2) = .547
a 2.34 spoke at 1000N is 3.00, 3.00/(2.34^2) = .548

Seems to increase slightly with spoke diameter so the bending stiffness
has something to do with it.

a flat spoke (or smaller diameter spoke) will have a lower bending
stiffness (moment of inertia) and therefore a lower reading. By
calculating cross sectional area and moment of inertia for various
spokes in their table it might be possible to empirically solve for any
spoke moment of inertia, area and tension.

Moment of inertia for a round: I = (pi)(diam^4)/64
For a rectangle: I = (width)(thickness^3)/12

I have not investigated this before so I am interested to hear what
others say.

Dan

Dear Dan,

You can investigate the effect of cross-section on a bicycle spoke
tension gauge by visiting a motorcycle shop.

Here's a picture of a bicycle spoke and a motorcycle spoke:

http://home.comcast.net/~carlfogel/download/spokes.jpg

The bicycle spoke is a typical 2 mm.

The motorcycle spoke is considered flimsy and is single-butted at the
hub end, 4.0 mm x 3.5 mm.

It gives an impressive tension reading when stuck loose in the jaws of
a tension gauge whose post-width and spring-force are designed for
bicycle spokes--the tension gauge's spring will be held back by the
bending resistance of the untensioned motorcycle spoke.

Cheers,

Carl Fogel