Help Calculating AGMA Pitting Geometry Factor
Help Calculating AGMA Pitting Geometry Factor
(OP)
I'm using AGMA 908-B89 and trying to calculate "I" for a pair of external spur gears. I can't seem to match the "I" calculation from Equation 4.1 with the values published in the tables in Paragraph 7.
For example, 20 deg pressure angle, 0 deg helix angle, equal addendum Np=21, Ng=135. I get I=0.139 using Equation 4.1, but the tables show I=0.118.
I tried to figure it out from Appendix A, but I'm stuck. The value of "I" I get from equation 4.1 is exactly equal to the value of Cc from equation A.13.
Can anyone help explain what I might be missing?
For example, 20 deg pressure angle, 0 deg helix angle, equal addendum Np=21, Ng=135. I get I=0.139 using Equation 4.1, but the tables show I=0.118.
I tried to figure it out from Appendix A, but I'm stuck. The value of "I" I get from equation 4.1 is exactly equal to the value of Cc from equation A.13.
Can anyone help explain what I might be missing?





RE: Help Calculating AGMA Pitting Geometry Factor
RE: Help Calculating AGMA Pitting Geometry Factor
dimensions: (Cr, Ro1, Ro2) per the second paragraph of section 3. BASIC GEAR GEOMETRY
This would then give these as:
Cr = 78
Ro1 = 11.5
Ro2 = 68.5
Rb1 = 9.866
Rb2 = 63.429
using these would calculate
Rm1 = 10.5
p1 = 2.955
p2 = 23.722
Using these would yield a value of 0.118 for the I factor
Hope this helps
Chris
RE: Help Calculating AGMA Pitting Geometry Factor
When I corrected the formula for rho(1), I got the correct pitting resistance factor without non-dimensionalizing the variables.
Attached is the corrected calculation.