Page 234 - Analysis and Design of Machine Elements

Analysis and Design of Machine Elements
212
Steps Computation Results Units
4) Calculate the ratio of face width to tooth height
b/h
Module m = d /z = 64.363/19 mm
1
1t
1t
= 3.388 mm
Tooth height h = 2.25 m = 2.25 × 3.388 mm
1t
= 7.621 mm
The ratio of b/h = 64.363/7.621 = 8.445
K = 1.443
5) Calculate the load factor
−1
According to v = 3.23 m s , gear accuracy grade
7, from Eqs. (8.13)–(8.16), the dynamic factor is
found as K = l.10.
v
From Table 8.2, select transverse load factors K
Ha
= K = 1.0.
Fa
Select the application factor from Table 2.1 as
K = 1.0.
A
Determine the face load factor K from Table 8.3.

For accuracy grade 7 and a symmetrically sup-
ported pinion, substitute the relevant value
2
2
K = a + a (1 + a ) + a b
H 1 2 3 d d 4
2
2
=1.12 + 0.18(1 + 0.0×1 )×1 +2.3
×10 −4 ×64.363=1.314
From Eq. (8.18)
(b∕h) 2
N =
0 1 +(b∕h)+(b∕h) 2
8.445 2
= = 0.883
1 + 8.445 + 8.445 2
From Eq. (8.17)
K =(K ) N 0 = 1.314 0.883 = 1.27
F H
The load factor is then
K = K K K K H =1.0×1.10 × 1.0
v
A
H
×1.314 = 1.445
6) The modified pitch diameter by the actual load d = 66.671 mm
1
factor K can be obtained from Eq. (8.88) as
√ √
d = d 1t 3 K∕K = 64.363 × 3 1.445∕1.3
t
1
= 66.671mm
7) Compute module m
66.671
d 1
m = = = 3.509mm
z 1 19
4. Design by gear Using the design formula Eq. (8.29)
teeth bending m ≥ √ 2KT 1 2 ⋅ Y Fa Y Sa
3
strength d z 1 [ F ]
(1) Decide the 1) Select the endurance limit of the pinion and gear
allowable bending from Table 8.6.
stresses
Bending endurance limit of the pinion
Flim1 = 306 MPa
Bending endurance limit of the gear
Flim2 = 213 MPa
(continued)