BELTS

Question 1

Length of Flat Belts, L

Answer 1

2C + 1.57(D2-D1) + [(D2-D2)^2/4C]

Question 2

Arc of Contact of Flat Belts,θ

Answer 2

π +/- 2arcsin [(R-r)/C]
π +/- [(D2-D1)/C] rad

+ sign for larger pully
- sign for smaller pulley
R for radius of larger pulley
r for radius of smaller pulley
D2 = diameter of smaller pulley
D1 = diameter of smaller pulley
C = center distance

Question 3

Length for crossed belt, L

Answer 3

2C + 1.57(D2+D1)+[(D2+D1)^2/4C]

Question 4

Arc of contact of crossed belt, θ

Answer 4

π + 2arcsin [(R+r)/C) rad

Question 5

Speed Ratio

Answer 5

D1N1=D2N2

Speed Ratio = N1/N2

Question 6

Tension in Belts

Answer 6

F1/F2 = e^(f*θ)
Provided that F1>F2

Question 7

Working Stress of belts, Sw

Answer 7

F1/bt

b = belt width
Working stress of leather belts = 300psi

Question 8

Tension in Belts considering centrifugal tension

Answer 8

(F1-Fc)/(F2-Fc) = e^(fθ)

Fc = centrifugal tension
Fc = (12ρbtv^2)/g in lbs

ρ = density of belt
b = belt width, in
t = belt thickness, in
v = belt velocity, ft/sec
=πDN
g = 32.2 ft/sec^2

Question 9

Net Belt pull (tangential force on pulley), F

Answer 9

F1-F2

Question 10

Power Transmitted in terms of T and P

Answer 10

T = F*r = (F1-F2)r
P = 2πTN

Question 11

Power transmitted in terms of belt velocity

Answer 11

HP = (F1-F2)v/550
kW = (F1-F2)v

v = belt velocity
= πDN, ft/sec or m/s

Question 12

Power Transmitted in terms of RPM

Answer 12

HP = TN/63,000
kW = 2πTN/60

where:
T = (F1-F2)r, ft-lb or kN-m
N = belt speed, RPM