FORMULAS - Mulhern Belting for Conveyor Belts, Agricultural Belts, Rubber Fabrication and Industrial Belting

Belt Length

When pulleys are approximately the same size:

L=	D + d	x 3.1416 + 2C
	2

When one pulley is much larger than other (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

Effective Tension
(pull needed to move belt and load horizontally) E = F x (P + M)

Slack Side Tension
(addition tension required to prevent slippage on pulley drive) E1 = E x K

Maximum Product Weight on Belt at any one time

When load is known per square foot:

P + G1 x C (in feet) x W (in feet)

When load is known by lbs. per hour:

P =	G2	x C (in feet)
	S x 60 (minutes)

Horsepower to Drive a Conveyor Belt

HP=	For Level Conveyors: F x S x (P + M)
	33,000

HP=	For Level Conveyors: F x S x (P + M)
	33,000

Tight Side Tension
(total tension to move belt and load horizontally) E2 = E + E1

Operating Tension
(determines working strength of belt to handle job on per inch width basis)

T =	E2
	W

Calculating 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 the coils in the role. This gives you the length in inches. Divide by 12 and you will have the approximate number of fee in the roll.

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 #1 below)
G1 - Load per sq. or cu. ft. (in lbs.)
G2 - Load per Hour (in lbs.)

HP - Horsepower
K - Drive factor (table #2) below)
L - Belt length (in inches)
M - Belt Weight (overall length, not c/c)
P - Product weight (in lbs.)
RPM - Revolutions per minute
S - Speed per minute
T - Operating tension PIW (in lbs.)
W - Belt width (in inches)

TABLE #2 - DRIVE FACTOR K
Screw Belt Wrap on Drive Pulley	Gravity or Take-up		Weighted Take- up
Screw Belt Wrap on Drive Pulley	Bare	Lagged	Bare	Lagged
180º	1.6	1.0	.84	.5
220º	1.2	.6	.62	.35
240º	1.0	.5	.54	.3

TABLE #1 - COEFFICIENT OF FRICTION (belt to slider bed or rollers)
Belt	Steel or Aluminum	Metal Rollers
FS 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