Originally Posted by 46x17
THink of force being applied to spoke tugging on both ends.
Think of straight spokes vs. DB ones.
Which one will stretch more and where?
Right the DB one will stretch more! Where? In the skinny section!
Does that equal less stress at the ends?
Yes, because the skinny middle section absorbs some of it.
I have to disagree with that last sentence. Assuming that the cross-sectional areas at the ends of both spokes are identical, the stresses at the ends must also be identical when subjected to the same forces. Actually, the tensile stress in the middle portion of a 14/15 ga spoke will be about 23% higher than that of the 14 ga spoke, given the same forces at the ends.
I think we need to forget about the spoke as an individual element, and look at the wheel as a system. I believe that the enhanced durability of the DB spoked wheel is due to its inherent ability to transfer loads to adjacent spokes better than the SG spoked wheel, thus preventing any one spoke from being overloaded repeatedly.