spoke squeezing test
carl...@comcast.net
new 700c 32-spoke rear wheel, box rim, eyelets, sockets
2.0-1.8mm-2.0mm stainless steel spokes laced x3
ceiling rope holds up drive-side-horizontal spoke at midspan.
weights hang from midspan of parallel spoke above it
http://home.comcast.net/~carlfogel/download/squeeze1_setup.jpg
clamp squeezes opposite non-drive-side parallel spoke pair
clamp tension increased from 0 by 1/3 turns of vise grip adjuster
http://home.comcast.net/~carlfogel/download/squeeze1_clamp.jpg
measure with Park tension gauge held level
one post on 2.0mm section, other post on 1.8mm section
this required tests to calibrate
http://home.comcast.net/~carlfogel/download/squeeze1_calibrate.jpg
http://home.comcast.net/~carlfogel/download/squeeze1_calibrate.txt
tension
tension tension change
squeeze Park Mark upper lower upper lower upper lower
weight upper lower spoke spoke spoke spoke spoke spoke
lbs spoke spoke kgf kgf lbs lbs lbs lbs
--- ---------- ---------- ---------- ----------
-u- -l- -u- -l- -u- -l- -u- -l-
0 22.5 20.8 108.6 91.1 238.9 200.5 n/a n/a
5 22.5 21.0 108.6 93.0 238.9 204.6 0.0 4.1
10 22.2 21.0 105.6 93.0 232.3 204.6 -6.6 4.1
15 22.3 21.2 106.6 95.1 234.5 209.3 -4.4 8.8
20 22.7 21.5 110.6 98.3 243.3 216.3 4.4 15.8
25 22.9 21.9 112.6 102.5 247.7 225.6 8.8 25.1
30 23.1 22.4 115.3 107.6 253.7 236.7 14.8 36.3
35 23.5 22.8 122.3 111.6 269.1 245.5 30.1 45.1
40 23.9 22.9 129.3 112.6 284.4 247.7 45.5 47.3
45 23.9 23.0 129.3 113.6 284.4 249.9 45.5 49.5
50 24.0 23.5 131.0 122.3 288.2 269.1 49.3 68.6
55 24.2 23.9 133.8 129.3 294.3 284.4 55.4 83.9
60 24.6 24.0 139.3 131.0 306.4 288.2 67.5 87.7
65 24.9 24.1 143.4 132.4 315.5 291.2 76.6 90.8
70 25.0 24.6 144.8 139.3 318.6 306.4 79.6 106.0
75 25.1 24.8 146.4 142.0 322.1 312.5 83.2 112.0
80 25.2 24.8 148.0 142.0 325.7 312.5 86.8 112.0
85 25.2 25.0 148.0 144.8 325.7 318.6 86.8 118.1
90 25.5 25.0 152.9 144.8 336.4 318.6 97.5 118.1
95 25.6 25.1 154.5 146.4 339.9 322.1 101.0 121.7
100 25.8 25.2 157.8 148.0 347.1 325.7 108.2 125.2
http://home.comcast.net/~carlfogel/download/squeeze1_tension_absolute.jpg
http://home.comcast.net/~carlfogel/download/squeeze1_tension_relative.jpg
as in earlier tests . . .
tension dropped at first on the higher-initial-tension spoke
tension rose far faster on the lower-initial-tension spoke
higher tension spoke gained less tension
but ended up at higher tension
at 30 lbs squeeze, the higher-tension spoke rose only 15 lbs
calculations ignoring rim stiffness predict up to 10 times as much
at 60 lbs squeeze, tension had risen only 60-80 lbs for both
during test, alarming spoke bending beyond 60 lbs
after test, very faint bend visible in spoke
different results might be obtained from . . .
a different rim (thicker, different eyelets or sockets)
different spokes (straight 2.0mm, 36 instead of 32))
different initial tensions for all spokes
more closely matched initial tensions
some questions . . .
what leads to lower than expected tension increases?
test differs from two-handed squeezing?
test mis-measuring?
low initial spoke tension?
rim twisting due to offset of squeezed pairs?
flimsy rim?
how hard can you actually squeeze 8-9 times in a row?
some estimates are only 30-50 lbs
brace base of thumb on railing or edge of table
curl fingers around rope tied to known weight
try to raise weight an inch off floor 8-9 times
one hand likely to be weaker
how evenly tensioned are your spokes?
tone not likely to be as accurate as tension gauge
most models assume ideally even tension
how high is your spoke tension?
only a tension gauge can tell you
how would would a symmetrical front wheel behave?
drive-side spokes best candidates for testing
usually highest tension, most likely to fail
how much do wheels vary in reaction to spoke-squeezing?
only testing different wheels will show what happens
little more than a tension gauge is needed
what happens to tension on other spokes around wheel?
surprising results in earlier tests
Cheers,
Carl Fogel
Peter Cole
> squeeze parallel drive-side spokes and measure their tension
> as in earlier tests . . .
> at 30 lbs squeeze, the higher-tension spoke rose only 15 lbs
> calculations ignoring rim stiffness predict up to 10 times as much
Squeezing a pair of spokes of unequal initial tension will cause the
uneven gain in tension you see because of coupling through rim deflection.
> some questions . . .
>
> what leads to lower than expected tension increases?
> test differs from two-handed squeezing?
> test mis-measuring?
> low initial spoke tension?
> rim twisting due to offset of squeezed pairs?
> flimsy rim?
Flexible rims and low initial tension will cause less tension increase
for a given amount of squeeze. Whether that's "less than expected"
depends on your expectations. It's certainly predictable with knowledge
of spoke and rim parameters and initial tension.
I think you're chasing phenomena that aren't there. Just tension the
wheel fully, squeeze hard and go ride.
carl...@comcast.net
<peter...@comcast.net> wrote:
[snip]
>I think you're chasing phenomena that aren't there.
[snip]
Dear Peter,
A bit of a Freudian slip?
Cheers,
Carl Fogel
Jay S. Hill
Dear Monseigneur Fogel, Margrave of Brandenburg &. &. &. by His very
humble and obedient servant, Jayboy, scribe of His Most Serene Highness
the Reigning Prince of Americus,
Are you chasing Freudian slips that aren't there?
With obedient bowing and back-stepping from your resplendent chambers,
Jay