Main Question or Discussion Point
In a two stage reduction gearbox is it possible to have more teeth on the gear pair (helical-parallel axis) of the 2nd stage? I ran through a specification for gear sizes and Im wondering if this is ok.
true. but then the whole designs based on constraints which can vary very much from application to application. since the op didnt specify any constraints, i only assumed a set of constraints.The assumption that the input and output shafts are aligned (a reverted train) is an unnecessary design hindrance that can drive the cost up and is not justified except in very special cases where the layout requires this. It is rarely done as a matter of routine.
true again, but the size should be minimized anyways(weight, inertia, space etc). surely undercutting is the deciding factor for minimum number of teeth.It is certainly permissible to have a different ratio in one pair versus the other pair; this is the norm. It is important to assure that neither pair involves a pinion with less than the minimum number of teeth to avoid undercutting.
In "the real world" you are given a basic set of criteria (variations are a certainty):how should we go about finding the true minimum Dr.D?(i am not being sarcastic)
duh Dr.D., I misread your post, i thought you were suggesting the true minimum based upon optimization of all the constraints.While it is never good practice to grossly oversize, it is also rarely worthwhile to truly minimize in the strictly mathematical sense. Even in aerospace work, where weight is at a premium, this is almost never done. Instead, people use good sense and use the smallest, lightest parts that are practical without seeking a true minimum.