Fig. 447.—Wrong way to run a belt. The pull should not come on the top side, because, with slack at bottom there is a tendency to slip.
The horse power transmitted per inch is
4,000 × 2 = 8 1,000 accordingly, the width of belt required to transmit 50 horse power is
50 ÷ 8 = 6.25, say 6".
For 4,000 ft. per minute belt speed, the distance in inches travelled by the belt per revolution of the pulley.
4,000 x 12 = 50.31 inches 954 This is equal to the circumference of the pulley, and the corresponding diameter is
50.31 = 16.1, say 16 inches. π
| 4,000 | × 2 = 8 |
| 1,000 |
| 4,000 x 12 | = 50.31 inches |
| 954 |
| 50.31 | = 16.1, say 16 inches. |
| π |
Ques. What is the proper speed for a belt?
Ans. From 3,000 to 5,000 feet per minute, depending on conditions.
Points Relating to Belts.
1. The amount of power that a belt of given size can transmit is not a very definite quantity. The rule just given is conservative and will give an amply large belt for ordinary conditions.
2. A belt should make a straight run through the air and over the pulleys without wabbling; it should maintain an even and perfect contact with that part of the pulley with which it comes in contact. In order to do this it should be kept soft, pliable, and have no abrasions or rough places.
