Work Formulas
Many considerations and factors determine the selection of the best belts for the job. The following information will aid you in this process. Assistance is available for the asking.
Key to Symbols
B Sine of Angle of incline
C Center to Center distance (in inches)
D Diameter Drive Pulley (in inches)
d Diameter Tail Pulley (in inches)
E Effective Tension (in lbs.)
E1 Slack Side Tension (lbs.)
E2 Tight Side Tension (lbs.)
   
F Coefficient of Friction
(see Table No. 1)
G1 Load per sq. or cu. ft. (in lbs.)
G2 Load per Hour (in lbs.)
HP Horsepower
K Drive Factor (Table No. 2)
L Belt length (in inches)
   
M Belt weight
(overall length, not c/c)
P Product weight (in lbs.)
RPM Revolutions per Minute
S Speed Feet per minute (FPM)
T Operating Tension PIW (in lbs.)
W Belt Width (in inches)
Belt Length
When pulleys are approximately the same size:
L =
D + d
x 3.1416
+ 2C
2
When one pulley is much larger than the other is: (at least 3 or more times larger)
L =
D + d
x 3.1416 + 2C+
(D + d)2
2
4C
Belt Speed in
Feet Per Minute
S = D x RPM x .2618 x 1.021
MAXIMUM Product Weight
On Belt at any one time
When load is known per sq. foot:
P = G1 x C (in ft.) x W (in ft.)
 
When load is known by lbs. per hour:
P =
G2
x C (in ft.)
S x 60 (min.)
Horsepower to Drive
A Belt Conveyor
For LEVEL conveyors:
HP =
F x S x (P + M)
33,000
For INCLINED conveyors:
HP =
(P x B) + (P + M) x F x S
33,000
Effective Tension
(pull needed to move belt and load horizontally)
E = F x (P + M)
Slack Side Tension
(additional tension required to prevent sippage on drive pulley)
E1 = E x K
Tight Side Tension
(total tension ot move belt and load horizontally)
E = F x (P + M)
Operating Tension
(determines working strength of belt to handle job on per inch width basis)
T =
E2
W
TABLE #1
COEFFICIENT OF FRICTION
(Belt to slider bed or rollers)
Belt
Steel or Aluminum
Metal Rollers
F.S. Pulley Side
.30 to .35
.10 to .15
Bare Duck or BB Side
.20 to .25
.10 to .15
Cover on pulley side
.50 to .55
.10 to .15
TABLE #2
DRIVE FACTOR "K"
Belt Wrap On Drive Pulley
Screw Take-Up
Gravity or Weighted Take-Up
Bare
Lagged
Bare
Lagged
180°
1.6
1.0
.84
.50
220°
1.2
.6
.62
.35
240°
1.0
.5
.54
.30
Calculating length of a roll of belting -- How to calculate the approximate length of a roll of belting. Add together the diameter of the roll and the diameter of the hole in inches and divide the result by 2. Multiply by 3.14 and by the number of coils in the roll. This gives the length in inches. Divide by 12 and you will have the approximate number of feet in the roll.