abt12
Mechanical
- Mar 27, 2015
- 6
I'm getting significant pushback from management and our vendor about the need for helical gears to have an axial/overlap contact ratio of greater than 1 for best performance. Our vendor says it won't help noise as long as the transverse ratio is over 1.5, and management doesn't want the longer packaging, but wants things as quiet as possible. We don't need the added width for strength or wear, but are already maxed on helical angle based on motor bearing life and as fine as we dare to get on pitch.
Unfortunately, I haven't found much supporting evidence for my assertion, except a lot of rules of thumb. Most of the research I've seen has been comparing the effect of higher contact ratios (1.25 vs 2+).
The only two pieces of supporting literature I've discovered so far are from Dudley's Handbook (5.1.13) - "... a certain amount of face width is required to get the benefit of helical-gear action. General experience indicates that it takes at least two axial pitches of face width to get full benefit from the overlapping action of helical teeth... if the face width is less than one axial pitch, the tooth action will be in between that of a spur gear and a true helical."
and Umezawa - "Clearly, choosing an overlap ratio over 1.0 lowers the vibration of a helical gear pair" (also see Fig. 1)
Am I correct here, or totally off base? Is there another good source of supporting evidence either way?
Unfortunately, I haven't found much supporting evidence for my assertion, except a lot of rules of thumb. Most of the research I've seen has been comparing the effect of higher contact ratios (1.25 vs 2+).
The only two pieces of supporting literature I've discovered so far are from Dudley's Handbook (5.1.13) - "... a certain amount of face width is required to get the benefit of helical-gear action. General experience indicates that it takes at least two axial pitches of face width to get full benefit from the overlapping action of helical teeth... if the face width is less than one axial pitch, the tooth action will be in between that of a spur gear and a true helical."
and Umezawa - "Clearly, choosing an overlap ratio over 1.0 lowers the vibration of a helical gear pair" (also see Fig. 1)
Am I correct here, or totally off base? Is there another good source of supporting evidence either way?