lewis_factor¶
- property HelicalGear.lewis_factor: float | None
Factor used to compute stresses on the gear tooth.
It is a tabular value that in general depends on the number of gear teeth, the pressure angle and the helix angle. In this case, the considered pressure angle is always 20 degrees, so the Lewis factor depends only on the number of gear teeth
n_teethand thehelix_angle.Returns¶
floatFactor used to compute stresses on the gear tooth.
Notes
The Lewis factor is a tabular value that depends on the helical gear virtual number of teeth, which can be computed as:
\[z_v = \frac{z}{\cos^2 \beta_b \, \cos \beta}\]where:
\(z\) is the gear number of teeth
n_teeth,\(\beta\) is the gear
helix_angle,\(\beta_b\) is the gear base helix angle.
The gear base helix angle \(\beta_b\) can be computed as:
\[\beta_b = \tan^{-1} \left( \cos \alpha_t \, \cos \beta \right)\]where the \(\alpha_t\) is the gear transverse pressure angle, which can be computed as:
\[\alpha_t = \tan^{-1} \frac{\tan \alpha}{\cos \beta}\]where \(\alpha\) is the pressure angle of the gear, always equal to 20 degrees.
Lewis Factor Table¶
Number of teeth |
Lewis Factor |
|---|---|
10 |
0.201 |
11 |
0.226 |
12 |
0.245 |
13 |
0.264 |
14 |
0.276 |
15 |
0.289 |
16 |
0.295 |
17 |
0.302 |
18 |
0.308 |
19 |
0.314 |
20 |
0.320 |
21 |
0.325 |
22 |
0.330 |
24 |
0.337 |
26 |
0.344 |
28 |
0.352 |
30 |
0.358 |
32 |
0.364 |
34 |
0.370 |
36 |
0.377 |
38 |
0.383 |
40 |
0.389 |
43 |
0.394 |
45 |
0.399 |
50 |
0.408 |
55 |
0.415 |
60 |
0.421 |
65 |
0.425 |
70 |
0.429 |
75 |
0.433 |
80 |
0.436 |
90 |
0.442 |
100 |
0.446 |
150 |
0.458 |
200 |
0.463 |
300 |
0.471 |
400 |
0.478 |
500 |
0.484 |