V-Belt Drive Factors

Arc of contact correction Factors G & R

D-d C Arc of Contact* Factor G Factor R
0.00 180 1.00 1.000
0.10 174 0.99 0.999
0.20 169 0.97 0.995
0.30 163 0.96 0.989
0.40 157 0.94 0.980
0.50 151 0.93 0.968
0.60 145 0.91 0.954
0.70 139 0.89 0.937
0.80 133 0.87 0.917
0.90 127 0.85 0.893
1.00 120 0.82 0.866
1.10 113 0.80 0.835
1.20 106 0.77 0.800
1.30 99 0.73 0.760
1.40 91 0.70 0.714
1.50 83 0.65 0.661

*Small Sheave
D = Diameter of large sheave  d = Diameter of small sheave 
C - Center distance

Allowable Sheave Rim Speed

Sheave Material Rim Speed**
Cast Iron Steel 6,500
Ductile Iron 8,000
Steel 10,000

** Feet per Minute

NOTE:  Above rim speed values are  maximum for normal considerations. In some cases, these values maybe exceeded. Consult factory and include complete details of proposed application.

Bearing Load Calculations

To find actual bearing loads it is necessary to know machine components weights and values of all other forces contributing to the load. Sometimes it becomes desirable to know the bearing load imposed by the V-belt drive alone. This can be done if you know bearing spacing with respect to the sheave center and shaft load and apply to the formulas.

Overhung Sheave

Bearing Load Calculations

Load at B in pounds = Shaft Load x (a + b) / a
Load at A in pounds = Shaft Load x b / a
a and b = Spacing in inches

Sheave Between Bearings

Sheave Between Bearings

Load at D in pounds = Shaft Load x c / c + d
Load at C in pounds = Shaft Load x d / c + d
c and d = Spacing in inches

Short Cuts to Figuring Pump Drives

D = Diameter of Pump Sheave^
d = Diameter of Engine Sheave^
SPM = Strokes per Minute
RPM = Engine Speed in Revolutions per Minute
R = Gear Box Ratio
C = Shaft Center Distance^
^ Required values to determine belt length.

D = RPM x d / SPM x R
d = SPM  x R  x D / RPM
SPM = RPM  x d / R x D
RPM = SPM x R x D / d
R = RPM  x d / SPM x D
Belt Length = 2C + 1.57(D + d)+ (D—d) / 4C

Manufactured in the USA by G&G Manufacturing Company.