Spoke wisdom

open topic, for anything cycling related.

Re: Spoke wisdom

Postby human909 » Mon Oct 01, 2012 11:45 am

Reman wrote:Spokes have almost all the strength in tensile/compressive directions and very little in shear and bending directions


Thats not strictly true. Spokes like any long thin steel wire/rod have very hight tensile strength and negligible axial compression strength and bending stiffness. Shear strength should be approximately similar to tensile strength.

Reman wrote:Low tension causes these shearing and bending forces, usually around the hub flange where most spoke breakages occur.

Not really. Low tension causes unloading and loading of the spoke which then rubs, bends and fatigues. Its the fatigue that is the problem not the bending or shearing which is SIGNIFICANTLY lower that would cause breakage.
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by BNA » Tue Oct 02, 2012 12:43 pm

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Re: Spoke wisdom

Postby Reman » Tue Oct 02, 2012 12:43 pm

human909 wrote:
Reman wrote:Spokes have almost all the strength in tensile/compressive directions and very little in shear and bending directions


Thats not strictly true. Spokes like any long thin steel wire/rod have very hight tensile strength and negligible axial compression strength and bending stiffness. Shear strength should be approximately similar to tensile strength.


Shear strength of spokes is half that of tensile strength, now this is far more than the resistance to bending but still not the same.

human909 wrote:
Reman wrote:Low tension causes these shearing and bending forces, usually around the hub flange where most spoke breakages occur.

Not really. Low tension causes unloading and loading of the spoke which then rubs, bends and fatigues. Its the fatigue that is the problem not the bending or shearing which is SIGNIFICANTLY lower that would cause breakage.


Fatigue caused by the bending and shearing...
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Re: Spoke wisdom

Postby chriscole » Tue Oct 02, 2012 7:17 pm

Mulger bill wrote:Disc and rear hubs must have a cross lacing on at least one side to prevent the rotary forces imposed by the drive/braking collapsing the wheel.

It is not strictly necessary to have the crossing on the drive/brake side but if it isn't then the hub shell must be strong enough to handle the assymetric forces involved.



Thanks for that. Best / most concise answer to my actual question thus far. :-)
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