V-Belt Drive Factors

Arc of contact correction 

Factors G & R

Allowable Sheave 

Rim Speed 

D-d
C
Arc of
Contact*
Factor
G
Factor
R
.00
.10
.20
.30
.40
.50
.60
.70
180
174
169
163
157
151
145
139
1.00
.99
.97
.96
.94
.93
.91
.89
1.000
.999
.995
.989
.980
.968
.954
.937
D-d
C
Arc of
Contact*
Factor
G
Factor
R
.80
.90
1.00
1.10
1.20
1.30
1.40
1.50
133
127
120
113
106
99
91
83
.87
.85
.82
.80
.77
.73
.70
.65
.917
.893
.866
.835
.800
.760
.714
.661
Sheave
Material
Rim
Speed**
Cast Iron
Ductile Iron
Steel
6,500
8,000
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.
 *Small Sheave  *Small Sheave

D = Diameter of large sheave  d = Diameter of small sheave 

C - Center distance

 
 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  SHEAVE BETWEEN BEARINGS 

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

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