Well, I learned today that all is not well in my model. I tried to apply the model with rim profile twist to an set of data that I took on a Real Design Supersphere wheel. The original model without twist or buckling did reasonably on this wheel. That model predicted the response to the single spoke perturbations and the truing algorithm trued up the wheel up nicely (>.15 mm in both directions). The wheel has fewer spokes and lower tension than the last wheel I reported that did very well with the model with twist. It seemed likely that this wheel would be have less effect from the buckling instability because tension was lower. I thought success was a foregone conclusion. Not so fast.
The short version of the story is that the new model of this wheel is unstable at a much lower tension than actually exists in the wheel. It becomes stable if I decrease the spoke tension or increase torsional stiffness beyond reasonable values. In further investigation, I also find that a symmetry that the wheel should possess (every forth spoke should have the same influence function) turns out not to be true for the new model. I think these are two separate problems, but maybe not.
I do not have time to work on the wheel right now. I must make some cabinets.
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