Belts

Question 1

What is a V-belt

Answer 1

Has a wedged shaped cross section, transmits power by gripping a sides of a groove in a pulley

Question 2

What are some Advantages of V-belts

Answer 2

Most cost effective (compared to chains and gears) 
Reliable,
Don’t need lubrication,
Absorb shock
Quiet
Slip on overload to protect components

Question 3

What are some Limitations of V-belts

Answer 3

Most have fixed center distances
Minimum 120° arc contact,
Unsuitable first timing belts
Unsuitable for high temperatures
Not practice for high surface speeds because of dynamic balancing

Question 4

Where might you find a V-belt?

Answer 4

Pump, speed changer, conveyors, fans, engine accessory’s etc.

Question 5

How is a V-belt constructed

Answer 5

Tensile members on inside (consist of cords that carry load)
Compression material (transmits power between sheave and the tensile members and support cords)
Cover (protects internal parts from wear)

Question 6

How do v-belts transmit power?

Answer 6

Friction between sides of belt and sides of sheave groove. The tensile members from the driver to the driven pulley

Question 7

The amount of power a belt can transmit depends on what?

Answer 7

Strength of tensile members, the grip of the belt on pulley (arc contact, tension applied, coefficient of friction between belt and pulley )

Question 8

What is the Pitch line

Answer 8

Pitch line runs through the old carrying zone, of the belt where tensile members are located. Located as close to outside diameter of the sheave so wisest cross section of belt carries load.

Question 9

What is Stretch

Answer 9

Increase of belt over period of time

Question 10

What is creep?

Answer 10

Loss of driving speed due to lengthening and shortening of the belt. Causes by elasticity of the belt.

Question 11

What is slip? And what problems does it produce

Answer 11

Increasing the load with a give. Tension on the belt, the arc through which it creeps on the pulley increases. Slip produces a power loss between driver and driven, increases belt and sheave wear,

Question 12

What are the types of V belts?

Answer 12

A,B,(commonly used for single and multiple belt drives) and C,D,E(used in multiple drives only)

Question 13

Variations of the V-belts are what?

Answer 13

Clogged raw edge, banded, double V, and fractional horse power

Question 14

Belt drives are what kind of drive

Answer 14

Friction, they transmit by a belt pressed tightly onto a pulley

Question 15

What does the area of contact between belt and pulley surfaces depend on?

Answer 15

Belt width and arc of contact

Question 16

What does the arc contact depend on?

Answer 16

Center to center distance, pulley diameter,and the take up device used.

Question 17

What are 3 pulley surfaces

Answer 17

Flat, crowned(convex, highest point is at center) , and grooved (sheaves)

Question 18

What are the most Common belt materials

Answer 18

Cotton, leather, rubber, nylon or other synthetic materials

Question 19

How long of run in period should a new belt have

Answer 19

12-24 hours and then re tensioned

Question 20

What are flat belts?

Answer 20

Used in conveyers and drip p belts , drive members carry the forces to transmit power. Can be manufactured endless or as a reel stock.

Question 21

What are notched V-belts used for ?

Answer 21

Small sheave, short centre, hight speed drives. The notch helps cooling.

Question 22

What is a high capacity V-belt

Answer 22

Also called wedge, hi torque or narrow v belts. 3V 5V 8V. Meaning they are 3/8, 5/8/ and 8/8. They can transmit up to 3x as Mitch horse power in the same drive space.

Question 23

What is a light duty V-belt

Answer 23

Also called fraction so horsepower. 2L 3L 4L 5L. I dictated in 1/8 of a inch. Example 2L= 2/8 3L= 3/8. They have a neoprene cover for protection against weather-heat-chemicals.

Question 24

What is a double angle v belt?

Answer 24

Also called a HEX belt, absorb compression and tension forces.

Question 25

Where are wide V-belts used and what are they

Answer 25

Used in variable speed drives. A wide V-belt has cord drive members in a neoprene filler enclosed by fabric cover.

Question 26

What is a positive drive belt?

Answer 26

Also called Timingbelts, gear belts. They have teeth inside , mesh with similarly shaped teeth in the pulley. Have the same advantages as chain or gear, but quieter. Do not last long and can’t handle heavy loads.

Question 27

How do you determine the word that of a pulley.

Answer 27

Width of a new flat belt is determined by the width of the narrowest pulley. In general pulley face should be one inch wider when belt is up to 6” and two inches wider for anything over 6”

Question 28

How should belts be stored

Answer 28

Cool dry place, synthetic belts should be in a cool humid place but NOT. In contact with water