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 Cormac Eason
Posted: 09/10/06 16:38:56 56
Message: Stress relieving is where you load the spokes way past their in-use tension level in order that the spoke will sit properly against the hub flange and against teh spokes it crosses. This means that the spokes will be in the position they'd eventually end up in after a few months use before the wheel is used at all (This eliminates the retensioning most people talk about needing with new wheels).

It also means that the localised very high stresses most importantly where the corner of the hub flange meets the bend in the spoke are reduced as the hub/spoke interface is plastically deformed slightly to create a bigger contact area between the spoke and hub and therefore a lower stress level as the spoke tension is distributed over a greater area. Most spokes have residual stress from the manufacturing process which can also contribute to very high stress in tiny areas of the spoke. Stress relieving forces these areas to deform plastically (They remain the shape they were bent to rather than springing back to their unloaded initial shape). Once a spoke with high local stress has been very heavily loaded and this load removed (So the spoke goes back to it's initial as built tension) it will have far less areas of localised high stress and therefore will be a lot less susceptible to the initiation of fatigue cracks, making it massively more durable.

I Generally use an old crank which I twist between the spokes nearer the rim from where they cross. This bends the spokes around eachother as well as massively increasing their tension, leaving the spoke making as short as possible a path from the hub the the rim (This means it's less likely to need retensioning after the wheel has been used for a while and the spokes settle into this shape anyway). I also press on the spokes where they come out of the outside of the hub flange to bend them against the hub flange for the same reason.
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