Reliability
221
PROBLEM 4.6
A propulsion system with four boilers, a two propeller outputs with
shafting, reduction gears, and two turbines have steam supplied with
two arrangements:
(a) One-boiler MTTF of 350,000 hr providing half-speed with three
boilers on standby.
(b) Two boilers in series providing cruise speed with the other two in
series on standby.
Find the reliability of both conditions and the over haul time if R(t) = 0.95
a criterion. Find the reliability in cruise speed if remaining boilers are not in
series standby but are used separately as standbys on the individual boilers
in operation.
PROBLEM 4.7
The cross section shown in Problem 4.7 gives an indication of parts in a hand
held power saw. Find the reliability
of the saw with the information in
Appendix D. Roughly estimate the time for the reliability
to equal 0.90.
[Note: This is a crude estimate.]
PROBLEM 4.8
Variable speed pulley patent drawings Problem 4.8 shows the pulley in two
extreme positions. Estimate the reliability
from information in Appendix
D and find the time when R(t)= 0.90.
~ Spindle~ Rubberboot ~-~.
~ Counterbalancemoveswithequaland
,~ ¯
~_ ~ ]1
i
opposite inertial force to spindle.
.~ ~.~ ".
Blades are available
for a variety of
different materials. Lever adjusts shoe for
depth-of-cut control.
to Z i~uO stroKes/mln
Prima~ wobble p~ate attaches to spindle.
/
and counterbalance to axial
Secondaw wobble plate attaches to counterbalance,
movement only.
Prob 4.7. Super Sawall cross section (Permission of Milwaukee Electric Tool
Corp. Brookfield, WI)