Fatigue Tests of Airplane Generator Brackets With Special Reference to Failure of Screw Fastenings

Fatigue tests on forged-steel airplane-generator brackets of different proportions are described. It was found that in many cases the limiting factor in the strength of the assembly was not that of the bracket itself but rather that of the screw fastenings used to hold the bracket to the generator frame. The fatigue strength of these screw fastenings is largely dependent on the rigidity (or thickness) of the bracket rim, since a flexible rim allows a high variable stress to be set up. Methods, which appear to yield reasonable results for design purposes, are given for calculating screw stresses as well as spoke and rim stresses in brackets of this type.