Pulleys

Pulleys: - Pulleys are power transmitted from one shaft to another shaft with the help of belts or ropes. Pulleys may be made of cast iron, wrought iron, steel or wood depending upon the size and the conditions of the work.

Hub or boss, rim and web or arms, these are pulleys three integral parts.

Hub or boss is the inner portion of a pulley which encloses the shaft to which it is keyed.

Rim is the outer portion on which the belt comes.

Web or arms connect the rim and hub.

Types of Pulleys:-

1.       Solid cast iron pulley: - Solid cast iron pulley is one piece casting. Small size pulley which diameter is smaller than200mm, solid web is provided to connect the outer rim with the boss. Larger pulley arms of elliptical straight or curved. Advantages of curved arms can yield under the stresses rather than breaking.

2.       Split pulley: - Split pulleys are made in two halves from cast iron. This is held on the shaft by bolts. This is used to where the ends of the shafts are not available.

3.       Fast and loose pulleys: - Loose pulley is free to rotate about the shaft while fast pulley is keyed to the shaft. The two pulleys are generally in same size.

4.       Built-up pulley: - Built-up pulley is a split type pulley. The ends of mild steel arms are shrunk into the hub at the time of casting.

5.       Stepped or speed cone pulleys: - Stepped or speed cone pulleys are used to for running the driven shaft at different speed for a constant speed of the driver. Two speed cone pulleys are mounted on two shafts. By placing the belt on the different steps in different speed of the driven shaft can be obtained while the driver shaft runs at constant speed. To reduce the weight this is made hollow.

6.       Rope and V-belt pulleys:-  Rope and V-belt pulleys are the rope  provided with grooves on the rim to hold the rope or V-belt. The shape and size of groove depends upon the rope or belt used.

Classified of Engineering Materials

Metals are exists naturally in the earth.

(i)                  Ferrous Materials:- The metals which contain iron, called ferrous Materials

(ii)                Non- ferrous Materials: - The metals which do not contain iron, called non- ferrous Materials.

            Example of non- ferrous Metals is copper, zinc, tin, aluminum, nickel, lead etc.

   

           Ferrous Materials are classified below

1.       Pig iron: - It is the first product in the process of converting iron ore. It is produce in blast furnace. Pig iron is refined in a cupola, cast iron is produced. Pig iron is put in puddling furnace, wrought iron is produced. If Pig iron is refined in furnace steel is produce.

2.       Cast iron: - Pig iron is refined in a cupola, cast iron is produced. Cast iron is brittle and grey colour. It contains carbon more than 2%. Cast iron can be cast into a desired shape in a sand mold.

3.       Wrought iron: - Pig iron is put in puddling furnace, wrought iron is produced. Wrought iron is never cast. It possesses high ductility and high resistance towards corrosion. All shaping is accomplished by pressing, forging or hammering.

4.       Steel: - Steel is an alloy of iron. If Pig iron is refined in furnace such as Bessemer converter, electric furnaces, Open –Hearth furnaces etc, steel is produce. It contains carbon less than 1.7%.