Home Page

TABLE 1.49 LEWIS FORM FACTOR, Y
 TOOTH FORM FACTOR LOAD NEAR THE PITCH POINT
Number of Teeth 14½o 20o Full Depth 20o Stub
14
15
16
17
18
19
20
22
24
26
28
30
34
38
43
50
60
75
100
150
300
Rack		 -
-
-
-
-
-
-
-
0.509
0.522
0.535
0.540
0.553
0.566
0.575
0.588
0.604
0.613
0.622
0.635
0.650
0.660		 -
-
-
0.512
0.521
0.534
0.544
0.559
0.572
0.588
0.597
0.606
0.628
0.651
0.672
0.694
0.713
0.735
0.757
0.779
0.801
0.823
 0.540
0.566
0.578
0.587
0.603
0.616
0.628
0.648
0.664
0.678
0.688
0.698
0.714
0.729
0.739
0.758
0.774
0.792
0.808
0.830
0.855
0.881

             Reprinted with the permission of E. I. DuPont de Nemours and Co.; see Ref. 8.

20.5.3 Surface Durability for Spur and Helical Gears —Excessive contact stresses can cause wear of the tooth surface and can be a limiting factor in the performance of a plastic gear. For spur gears which are not lubricated or (in some cases) only initially lubricated, both contact stress and bending stress should be checked, the smaller load being the limiting load.
For spur gears the Hertzian contact stress, 5,, in the elastic range is given by:

  
                             Next Page  Prev Page