Grenzen der Getriebe-Entwicklung, bedingt durch die Freßgefahr des Zahnwerkstoffes

Summary

In all cases where they seek to reach the goal of utmost compactness and lightness, gear designers will tend to approach the only really insurmountable limit, that set by tooth breakage, as closely as they judge safe and economically justified. But other phenomena, of which pitting and scuffing are considered the most important, have often caused designers to keep off this limit, and thus from their goal, farther than they or the users of gears found acceptable.

Owing to differences in the influences of gear size and rotational speed on the power transmissible from the standpoints of, respectively, tooth breakage, pitting, and scuffing, a “critical size” can be assigned to any series of gears, all of the same type, lubricated with the same oil, and subjected to the same variability of operating conditions, but all of different sizes. “Critical size” is defined as that size, characteristic of the series concerned, beyond which scuffing will occur at powers transmitted that are smaller than the smaller of the two powers transmissible from the standpoints of, respectively, tooth breakage and pitting.

It follows that, unless a sufficiently powerful Extreme Pressure (anti-scuffing) oil is used, gear designers will, whenever the critical size holding good for mineral oil is to be exceeded, in the aforementioned cases, be prevented from attaining the utmost compactness and lightness inherent in the given series of gears from the standpoint of tooth breakage.