Ch:24 Rope drive

exa 24-1 - Page 635

In [1]:
from __future__ import division
from math import sqrt, pi, exp, sin, asin
P=150000#
m=0.4#
D=1.8#
d=0.6#
C=4.2#
V=15#
Fc=m*V**2#
BL=44.81*10**3#
FOS=35#
F1=BL/FOS#
theta=pi-(2*asin((D-d)/(2*C)))#
beta=22.5*pi/180#
u=0.13#
x=u*theta/sin(beta)#
F2=(F1-Fc)/exp(x)#
n=P/((F1-F2)*V)#
n=13#
print "n is %0.0f    "%(n)#

n is 13

exa 24-2 - Page 635

In [2]:
from math import sqrt, pi
W=1000#
m=0.498#
BL=78#
d=12#
Am=0.39*d**2#
dw=sqrt(Am*4/(6*19*pi))#
Ew=74.4*10**3#
Ds=56*d#
sigb=Ew*dw/Ds#
Wb=sigb*pi*(d**2)/4*10**-3#
l=20#
Ws=m*l#
a=1.2#
Wa=a*(W/2+Ws)*10**-3#
#Let the static load be Ps
Ps=(W/2+Ws)*9.81*10**-3#
#let the effective load  be Peff
Peff=Ps+Wb+Wa#
FOS1=BL/Peff#
FOS2=BL/(5+0.612)#
print " annual FOS is %0.2f    "%(FOS1)#
print "\n FOS neglecting bending load is %0.1f    "%(FOS2)#

 annual FOS is 5.02    

 FOS neglecting bending load is 13.9

exa 24-3 - Page 636

In [3]:
d=12#
sigut=1960#
Pb=0.0025*sigut#
Ds=480#
F=Pb*d*Ds/2#
W=F*2*10**-3#
print "W is %0.3f kN   "%(W)#

W is 28.224 kN

exa 24-4 - Page 637

In [4]:
from math import sqrt, pi
sigut=1770#
Pb=0.0018*sigut#
W=4000#
a=2.5/2#
Ws=90*0.5#
Wa=(W+Ws)*a/9.81#
Weff=W+Wa#
d=sqrt(Weff*2/(23*Pb))#
d=12#
print "d is %0.0f mm   "%(d)#

d is 12 mm