Chapter14-Belt and Chain Drives

Ex1-pg306

In [1]:
import math

print('MACHINE DESIGN \n Timothy H. Wentzell, P.E. \n EXAMPLE-14.1 Page No.306\n');

##Torque on small pulley
hp=2.;
n=2450.;
T=63000.*hp/n;

print'%s %.2f %s '%('\n Torque on small pulley = ',T,' in-lb.');
r=6/2.;
Fd=T/r;

##Front force
Fb=10.;
Ff=Fd+Fb;

print'%s %.2f %s '%('\n Front force = ',Ff,' lb.');

##Force pulling the shafts
Ft=Ff+Fb

print'%s %.2f %s '%('\n Force pulling the shafts = ',Ft,' lb.');

##Surface speed
D=2.*r;
Vm=math.pi*D*n/12.;

print'%s %.2f %s '%('\n Surface speed = ',Vm,' ft/min.');

##Ratio
D2=10.;
Mw=D2/D;

print'%s %.2f %s '%('\n Ratio = ',Mw,'');

##Output speed
no=n/Mw;

print'%s %.2f %s '%('\n Output speed = ',no,' rpm.');

##Note-There is an error in the answer given in textbook

MACHINE DESIGN 
 Timothy H. Wentzell, P.E. 
 EXAMPLE-14.1 Page No.306


 Torque on small pulley =  51.43  in-lb. 

 Front force =  27.14  lb. 

 Force pulling the shafts =  37.14  lb. 

 Surface speed =  3848.45  ft/min. 

 Ratio =  1.67  

 Output speed =  1470.00  rpm.

Ex2-pg310

In [2]:
import math

print('MACHINE DESIGN \n Timothy H. Wentzell, P.E. \n EXAMPLE-14.2 Page No.310\n');

##Length of belt
C=19.;
D1=4.;
D2=6.;

L1=2.*C+1.57*(D1+D2)+(D2-D1)**2./(4.*C);

##Assuming a 54-inch belt is available
L=54.;

print'%s %.2f %s '%('\n Length of belt = ',L,' in.');

##Centerline distance
B=4.*L-6.28*(D2+D1);

C=(B+math.sqrt(B**2.-32.*(D2-D1)**2))/16.;

print'%s %.2f %s '%('\n Centerline distance = ',C,' in.');

##Ratio
Mw=D2/D1;

print'%s %.2f %s '%('\n Ratio = ',Mw,'');

##Surface speed
n=1800.;
Vm=math.pi*D1*n/12.;

print'%s %.2f %s '%('\n Surface speed =',Vm,' ft/min.');

##Angle of contact

theta=180.-2*(180./math.pi)*math.asin((D2-D1)/(2.*C));

print'%s %.2f %s '%('\n Angle of contact = ',theta,' deg.');

MACHINE DESIGN 
 Timothy H. Wentzell, P.E. 
 EXAMPLE-14.2 Page No.310


 Length of belt =  54.00  in. 

 Centerline distance =  19.12  in. 

 Ratio =  1.50  

 Surface speed = 1884.96  ft/min. 

 Angle of contact =  174.01  deg.

Ex3-pg315

In [3]:
import math

print('MACHINE DESIGN \n Timothy H. Wentzell, P.E. \n EXAMPLE-14.3 Page No.315\n');

##Power rating of belt
P1=27.+2.98;
SF=1.5;
P=P1/SF;
P=round(P);

print'%s %.2f %s '%('\n Power rating = ',P,' hp.');

##Length of belt
C=20.;
D1=8.;
D2=16.;
L1=2.*C+1.57*(D1+D2)+(D2-D1)**2/(4.*C);

##Use an 80-inch belt
L=80.;

print'%s %.2f %s '%('\n Length of belt = ',L,' in.');

MACHINE DESIGN 
 Timothy H. Wentzell, P.E. 
 EXAMPLE-14.3 Page No.315


 Power rating =  20.00  hp. 

 Length of belt =  80.00  in.

Ex4-pg321

In [4]:
import math

print('MACHINE DESIGN \n Timothy H. Wentzell, P.E. \n EXAMPLE-14.4 Page No.321\n');

P=5.31;

print'%s %.2f %s '%('\n Horsepower rating = ',P,' hp.');

Nti=12.;
N1=1800.;
N2=900.;

##Output sprocket
Nto=(N1/N2)*Nti;

print'%s %.2f %s '%('\n Number of tooth on output sprocket = ',Nto,'');

##Surface speed
Pc=0.5;
D1=Pc*Nti/math.pi;
n=1800.;
Vm=math.pi*D1*n/12.;

print'%s %.2f %s '%('\n Surface speed = ',Vm,' ft/min.');

print('\n Type of lubrication - Bath or disc lubrication');

##Length of chain
C=10.;
D2=Pc*Nto/math.pi;

L1=2*C+1.57*(D1+D2)+(D2-D1)**2/(4.*C);

##Use 29 or 30 inch chain

L=30.;

print'%s %.2f %s '%('\n Length of chain = ',L,' in.');

hp=5.31;

T=63000.*hp/n;

F=2.*T/D1;

print'%s %.2f %s '%('\n Force in chain = ',F,' lb.');

##Comparism with ultimate strength 3700 lb - not a valid comparison because of speed etc.

MACHINE DESIGN 
 Timothy H. Wentzell, P.E. 
 EXAMPLE-14.4 Page No.321


 Horsepower rating =  5.31  hp. 

 Number of tooth on output sprocket =  24.00  

 Surface speed =  900.00  ft/min. 

 Type of lubrication - Bath or disc lubrication

 Length of chain =  30.00  in. 

 Force in chain =  194.62  lb.