I have not done a structural analysis of a windmill but I know something about wind loading of buildings. I believe with some certainty that the extra weight of the mechanism up at the hub is pretty incidental comapred to the wind loads imposed on the structure. In fact I bet the wind load is so great that the extra weight can be ignored in the calculations.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.