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Pulleys and Belting. - In the following formulas for length of belting,

l= length of belt in feet a = diameter of larger pulley in inches b= diameter of smaller pulley in inches d = = distance between centers in feet

d

OPEN BELT PULLEYS SAME SIZE

1. For open belt where the difference in the diameters of the pulleys is not great,

l=.13(a+b) + 2 d EXAMPLE 1. Two 16-inch pulleys, 10 ft. between centers, are connected by an open belt. What is its length ? Here

a= 16 in., b = 16 in., and d = 10 ft. Then

I=.13(16 + 16) + 2 (10)

= .13(32) + 20 = 4.16 + 20 = 24.16 ft. EXAMPLE 2. Two pulleys, 24 in. and 20 in. in diameter, are 18 ft. between centers. What length of belting is necessary to connect them?

d

OPEN BELT PULLEYS DIFFERING SLIGHTLY IN SIZE

Here Then

a= 24 in., b = 20 in., and d = 18 ft.
1=.13 (24 + 20)+ 36

.13(44) + 36 = 41.7 ft.

Exercise

1. The distance between the centers of two 24-in. pulleys is

What must be the length of the connecting belt? 2. Two pulleys belted together are 20 in. in diameter. The distance between their centers is 22 ft. What is the length of the belt?

3. Two pulleys, the distance between whose centers is 14 ft., are 18 in. in diameter. If the pulleys are both replaced by 22-in. pulleys, how much must the belt be lengthened ?

4. What length of belting is required to connect two pulleys, 24 in. and 22 in. in diameter, the distance between whose centers is 20 ft. ?

5. Two pulleys have their centers 18 ft. apart; their diameters are 26 in. and 24 in. What length of belt is required to connect them ?

6. If the pulleys in Ex. 5 are replaced by 22-in. pulleys, what change must be made in the length of the belt?

d

CROSSED BELT

II. For crossed belt, or for open belt where the difference in the diameters is great,

l=.14 (a + b) + 2d EXAMPLE 1. What length of crossed belt is required to connect two 16-inch pulleys, 12 ft. between centers ?

l=.14 (16+16) + 2 (12)

= .14 (32) + 24 = 4.5 + 24 = 28.5 ft. EXAMPLE 2. What length of open belt is required to connect two pulleys of diameters 16 in. and 8 in. with centers 10 ft. apart?

l=.14 (16 + 8) + 2(10)
=.14 (24) + 20 = 3.4 + 20 = 23.4 ft.

Exercise

1. Two pulleys are 16 ft. between centers. The pulleys are 24 in. and 12 in. in diameter. What length of belt is required ?

2. The distance between the centers of a 28-in. pulley and an 18-in. one is 18 ft. What length of belt is required ?

3. Two pulleys 30 in. and 18 in. in diameter, are 16 ft. between centers. If the 30-in, pulley is replaced by a 28-in. one, how much must the belt be shortened ?

4. The distance between centers of two 22-in. pulleys is 20 ft. How long must the connecting belt be if crossed ?

5. Two pulleys connected by crossed belting are 20 in. in diameter. The distance between centers is 24 ft. What length of belt is required ?

6. Two 16-in. pulleys whose distance between centers is 18 ft. are connected by crossed belting. If the pulleys are both replaced by 20-in, pulleys, how much must the belt be lengthened ?

7. What is the length of the connecting crossed belt if the distance between centers is 22 ft. and the pulleys are 24 in, and 18 in. in diameter ?

8. The distance between the centers of a 28-in. pulley and an 18-in. one is 20 ft. How much more belting will be required if crossed than if not crossed ?

9. Two pulleys connected by crossed belting are 30 in. and 16 in. in diameter. Their distance between centers is 16 ft. If the 16-in. pulley is replaced by a 12-in. one, how much must the belt be lengthened?

10. In the preceding exercise, if the pulleys are replaced by two 18-in. ones, what change will be necessary in the length of the belt ?

LENGTH OF BELTING IN A COIL

1 length of belting, in feet
d = diameter of roll, in inches
e= diameter of eye, in inches
n = number of turns in the coil

1= .13 n(d + e)

EXAMPLE. The diameter of a coil of belting is 19 in., the diameter of the eye is 5 in., and the number of turns is 14. Determine the length of belting in the coil.

1=.13(14)(19 + 5)

=.13(14)(24)= 44 ft.

Exercise

1. How many feet of belting in a coil of 30 turns whose diameter is 21 in. and whose eye is 6 in. ?

2. How much belting in a roll of 41 coils, 2 ft. in diameter, with a 9-in. eye?

3. What is the length of belting in a solid roll of 40 coils, 2 ft. in diameter ?

4. At 30 cents per running foot, what is the cost of a roll of belting of 16 turns, with outside diameter 2 ft., inside diameter 20 in. ?

The length of rope, wire, hose, etc., wound on a reel is given by the formula :

1=.13 nt(a + e) where

n = no. of coils side by side
t = no. of layers in coil
a = diameter over all
e= diameter of shank of reel

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