bicycle_disciple said:Werehatrack said:Werehatrack said:I would add to the observations above that the low-spoke-count wheels
have loading delta during rotation,
make that "higher loading delta during rotation relative to that
typical of a high-spoke-count wheel."
--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.
I do not understand. Please explain loading delta.
B.D
http://cozybeehvie.blogspot.com
Dear B.D.,
The greek delta letter is often used to indicate change in equations.
On a low spoke count wheel, the change in load may be greater.
That is, on a 36-spoke wheel, the bottom 5 spokes lose considerable
tension and then regain it. The total tension loss (or change or
delta) is spread over 5 spokes.
On an 18-spoke wheel, the same tension loss is spread over only 3
spokes, so the total tension loss _may_ be greater.
Unfortunately, we have only FEA's for 36-spoke wheels and don't know
what fewer spokes do. Here's an FEA for 36-spokes:
http://www.astounding.org.uk/ian/wheel/index.html
Ian's FEA suggests that the 5 spokes lose tension at roughly these
relative rates (67~69, 244~250, ~350):
/ / | \ \ 36-spoke wheel
-7 -25 -35 -25 -7 total ~99
But what happens to an 18-spoke wheel with the same load?
It could produce a much greater change in the middle spoke:
/ | \ 18 spokes?
-7 -85 -7 total ~99 much greater change
Or the same change:
/ | \ 18 spokes?
-32 -35 -32 total ~99 same change
Or even slight less change:
/ | \ 18 spokes?
-33 -33 -33 total ~99 slightly less change
The assumption is that the correct model tends toward the greater
change example, meaning that a low spoke-count wheel's spokes see a
greater delta or change in tension, from o to say 85 rather than just
from 0 to 35.
The greater the range of loading delta (spoke tension change), the
sooner the flange will fatigue and fail.
Cheers,
Carl Fogel
