Section 17 Strength and Durability of Gears - SDP/SI

ELEMENTS OF METRIC GEAR TECHNOLOGY
Correction Factor C
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
– 0.3 – 0.2 – 0.1 0 0.1 0.2 0.3
Axial Shift Factor, K
Fig. 17-7 Correction Factor for Axial Shift, C
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Should the bevel gear pair not have any axial shift, then the coefficient C is 1, as per
Figure 17-7. The tooth profile factor, Y F , per Equation (17-31) is simply the Y FO . This value is
from Figure 17-8 or 17-9, depending upon whether it is a straight or spiral bevel gear pair.
The graph entry parameter values are per Equation (17-32).
Y F = Y FO (17-31)
z
⎫
z v = ––––––––––
cos δ cos 3 β m ⎪ ⎬ (17-32)
h a – h a0
⎪
x = ––––––
m
⎪
⎭
where: h a = Addendum at outer end (mm)
h a0 = Addendum of standard form (mm)
m = Radial module (mm)
The axial shift factor, K, is computed from the formula:
1 2 (h a – h a0 ) tan α
K = ––– n
{s – 0.5 πm – ––––––––––––––} (17-33)
m
cos β m
Metric
0 10
I
R
T
1
2
3
4
5
6
7
8
9
10
11
17.3.3.C Load Distribution Factor, Y ε
Load distribution factor is the reciprocal of radial contact ratio.
1
Y ε = ––– (17-34)
ε α
The radial contact ratio for a straight bevel gear mesh is:
⎫
2
√(R va1 – R 2 2 2 vb1 ) + √(R va2 – R vb2 ) – (R v1 + R v2 ) sin α
ε α = ––––––––––––––––––––––––––––––––––––––––
πm cos α
⎪ ⎪⎪
And the radial contact ratio for spiral bevel gear is: ⎬ (17-35)
2
√(R va1 – R 2 2 2 vb1 ) + √(R va2 – R vb2 ) – (R v1 + R v2 ) sin α t
ε α = –––––––––––––––––––––––––––––––––––––––– ⎪
πm cos α t
⎭
T-173
12
13
14
15
A