AGMA 91FTM9 PDF

When naval ship propulsion gear teeth break, the affected teeth are "field dressed", so that the units can be put back into service. Then the gears are rerated to a lower rating and used reliably, at least until replacement elements become available. Using sketches or computers, an estimate is made of the instantaneous total length of contact as the damaged sections go through mesh with the results being used as a basis of rerating the unit. Consideration is given to end reliefs, the location of the damage on the helix and the nature of the field dressing, and actual material properties. The results of this analysis, together with analysis of the causes of the original failure, provide limits within which the unit can be operated with the same reliability as new.