Lecture 12

Worm Gear Design

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Lecture 13 and Lecture 14

General Survey and Stresses in Belts

The belts are used to transmit power from one shaft to another

by means of pulleys. The power transmitted is depending upon the

following factors:

1. The velocity of the belt

2. The tension under which the belt is placed on the pulley

3. The arc of contact between the belt and the smaller pulley

4. The condition under which the belt is used.

The belt drive can be differentiated as follows:

1. According to type of belt: flat belt Fig (27/1), v-belt Fig (27/4),

and rope belt Fig (27/22).

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2. According to the belt layout: open, crossed, half-crossed, and

angular drives, Fig (27/1). Also, speed changing drives Fig

(27/8) to Fig (27/10), and Fig (27/4).

3. According to type of belt: flat belt Fig (27/1), v-belt Fig (27/4),

and rope belt Fig (27/22).

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4. According to the belt construction: leather belts with one, or

two or three plies, textile belts, steel belts and compound belts.

5. According to the belt joint: belts with mechanical joints, glued,

sewn, or endless belts, Fig (27/16).

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General Relationships:

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Angle of contact and Length of Belt: a) Open Drive: Dimensions for the belt drive of Fig (27/1a).

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b) Crossed Drive: Dimensions for the belt drive of Fig (27/1c).

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