Re: Sapim CX-Ray spoke question



ITS bROWN'S IDEA!

an extra long shank is a plus-it'll clear the hub leaving the more
delicate (yecch) thin spoke shaft clear of hub wear, more giving in
the torque rod spec.
 
J

jim beam

Guest
[email protected] wrote:
> ITS bROWN'S IDEA!
>
> an extra long shank is a plus-it'll clear the hub leaving the more
> delicate (yecch) thin spoke shaft clear of hub wear, more giving in
> the torque rod spec.
>

but spokes don't break in the shaft, they break in the elbow due to
bending. and the longer the shank, the more the bending moment, outside
of an appropriately flanged hub of course.
 
B

Ben C

Guest
On 2007-04-24, [email protected] <[email protected]> wrote:
> ITS bROWN'S IDEA!
>
> an extra long shank is a plus-it'll clear the hub leaving the more
> delicate (yecch) thin spoke shaft clear of hub wear, more giving in
> the torque rod spec.


I'm fairly sure you don't want an extra long shank.

As jim explained, it will bend backwards and forwards at the elbow as
you ride and quickly break from fatigue. As far as I know Jobst would
not disagree with the essence of this either.

Where does Brown explain the benefit of a long shank?

And how does this torque rod theory work? A torque rod in my
understanding is a torsion bar. You twist it and it wants to twist back
so you can use it as a spring. The suspension on the early Renault 5 and
I think also the VW Beetle used torsion bars where other cars use coil
springs.

But in a wheel, the only time the spokes twist like that is by mistake
during the build. We call it "windup". It's important to get the windup
out after the build or avoid getting it in during; but when the wheel's
in use the spokes don't twist.

Ideally they just go loose-tight-loose-tight along their axis as you
ride along. They can handle that fine since the axial tension is far
from yield. That's why straight-pull spokes will last (practically)
forever, and also elbow spokes if you can get the elbow as flat as you
can to the flange.

Having a thinner middle section is said to reduce flex at the elbow
since the middle can bend more instead. That's a good thing, and may
mitigate the problems of having an excessively long shank. But a shank
too long for the hub thickness is always basically a bad thing.
 
On Apr 24, 12:45 am, jim beam <[email protected]> wrote:
> [email protected] wrote:
> > ITS bROWN'S IDEA!

>
> > an extra long shank is a plus-it'll clear the hub leaving the more
> > delicate (yecch) thin spoke shaft clear of hub wear, more giving in
> > the torque rod spec.

>
> but spokes don't break in the shaft, they break in the elbow due to
> bending. and the longer the shank, the more the bending moment, outside
> of an appropriately flanged hub of course.


IN THEORY, the torque rod design spec 'eliminates' elbow/hub bending
wear AND with installation wax/teflon lubrication on and in the spoke
holes, elbow wear becomes inconsequential.
 
J

jim beam

Guest
[email protected] wrote:
> On Apr 24, 12:45 am, jim beam <[email protected]> wrote:
>> [email protected] wrote:
>>> ITS bROWN'S IDEA!
>>> an extra long shank is a plus-it'll clear the hub leaving the more
>>> delicate (yecch) thin spoke shaft clear of hub wear, more giving in
>>> the torque rod spec.

>> but spokes don't break in the shaft, they break in the elbow due to
>> bending. and the longer the shank, the more the bending moment, outside
>> of an appropriately flanged hub of course.

>
> IN THEORY, the torque rod design spec 'eliminates' elbow/hub bending
> wear AND with installation wax/teflon lubrication on and in the spoke
> holes, elbow wear becomes inconsequential.
>

what is this "elbow wear" of which you speak? it's not fatigue, the
means by which they fail.
 
the questions appears to rest with newton but finish in practicality.
are spokes 30% lighter than Alpines string enough to take occasional
abuse like the occasional squirrel or shcok cord?