Reliability
217
time factor is
t3rd = 0.93t
t is the actual gear box operating time
t2nd = 0.03t
tlst = 0.03t
0.01t
/reverse ----- 1.00t
The terms are substituted into the reliability equation to obtain the system
reliability developed in Table 4.3.
Rsystem = (R3rd)(Rznd(Rlst)(Rreverse)
715.248 ]
Rsystem = exp
10 6 hr t
Let Rsystem = 0.90 and take lne of both sides
715.248
-- t = -0.1054
106 hr
t = 147.3 hr continuous operation at rated power
Should lower extreme failure values be used, the hours would increase.
Note: Alone for 3rd gear
I 627"19147.3hr]=0.918
R3r d = exp - 106 h~
Lower failure values for just 3rd gear components
2(261 + 262) -- 2(0.072 + 0.25) = 0.644 not
(a) (b) bearings and seals
2c8 =
= 0.060 not 1.1 (h) jaw clutch
2G3 ~
= 0.087 not 4.3 (c) spur gears
2264 =
= 0.300 not 1.24 (d) shafting
Table 4.3 Summary of transmission 2s and a check on 2 sums
Components
3rd
2nd
1st
Reverse
E2s
Bearing seals 2(0.93)(139.5) 4(0.03)(139.5) 4(0.03)(139.5) 6(0.01)(139.5) 301.32
Jaw clutch
(0.93)(33)
None
None
None
30.69
Gear parts
None
2(0.03)(129) 2(0.03)(129) 3(0.01)(129) 19.35
Shafts
2(0.93)(18.6) 3(0.03)(18.6) 3(0.03)(18.6) 4(0.01)(18.6) 38.69
Shifting fork (0.93)(297.9) (0.03)(297.9) (0.03)(297.9) (0.01)(297.9) 297.9
Housing
(0.93)(27.3) (0.03)(27.3) (0.03)(27.3) (0.01)(27.3)
27.3
2sums
627.192
35.91
35.91
16.236
715.248