Dear Neil, to "supersize me" (MEW 283) had many pitfalls! The post-mortem on the breaks brings back memories of an agricultural problem that may give an answer? A 2"Dia solid roll shaft would break for no initially obvious reason. Close inspection after several had snapped showed an interesting pattern of rings getting bigger from one point, where a tiny mark caused by a hammer blow on assembly acted as a stress raiser! In use the shaft adopted a curve between the two bearings (about 10' or 3m apart). At any one time the front of the shaft was in compression whilst the rear was in tension, effectively bending the shaft back and forth with every rotation! The tiny indentation starts the crack that then runs straight through the shaft until it breaks.
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