Chapter 5 - Belt Drives

Question 1

Belt Definition

Answer 1

Transmit torque and motion by using sheaves.

Question 2

3 main criteria of Belt:

Answer 2

Friction
Tension
Arc of contact

Question 3

Arc of Contact

Answer 3

Wrap Angle.
Smaller angles transmit less power than the bigger angle.
Efficient wrap angle is between 165 & 180.

Question 4

Friction

Answer 4

Coefficient of friction determins amount of tension required to transmit torque and speed.

Question 5

Factors that affect friction:

Answer 5

Material Choice
Surface Roughness
Contaminants
Tension force

Question 6

Tension

Answer 6

If tension is not maintained then the life of the belt is greatly reduced.
Not enough tension causes slip, and too much tension puts excessive loads on bearings.

Question 7

Two types of tension

Answer 7

Tight Side Tension

Slack Side Tension

Question 8

Belt Struction Sections:

Answer 8

Tension Section
Compression Section
Tensile Cords
Cover/Top Fabric

Question 9

Tension Section

Answer 9

Upper section that carries the tensile forces.

Question 10

Compression Section

Answer 10

Made of rubber or rubberized fabric that supports the tensile member and exerts a wedging force against the pulley groove.

Question 11

Tensile Cords

Answer 11

Main load carrying element of the belt dirves and generally made out of synthetic fiber twisted cords.

Question 12

Cover/Top Fabric

Answer 12

Prevents the belt from environmental factors and wear/tear.

Question 13

Types of Belts:

Answer 13

Flat Belt
V-belt
Synchronous Belt

Question 14

Flat Belt

Answer 14

Simple flat belt used in agriculture and conveyor systems.

Question 15

V-belt

Answer 15

Most commonly used belt.

Cheap, great HP range, high and low speeds, very diverse types.

Question 16

Synchronous Belt

Answer 16

Allows for input and output shafts to be precisely matched.

Also called “Timing Belts.”

Question 17

Advantages of V-belts

Answer 17

Less maintenance.
Less Belt Space.
99% efficiency.
Rugged and nature strong.
Smooth Starting.
Dampen vibration and quiet.
No lubrication and clean.

Question 18

Types of V-belts

Answer 18

Classic (Agricultural)
Narrow
Light Duty
Double (Hexagonal)
Cogged, Raw-Edge
Joined (Banded)
V-Ribbed

Question 19

Classic Agricultural Nomenclature

Answer 19

Ex: A30
A = 1/2 X 5/16
B = 21/32 X 3/8
C = 7/8 X 17/32
D = 1 1/4 X 3/4

Question 20

Narrow V-Belt Nomenclature

Answer 20

Ex: 3V450 (3/8” width, 45” outside length)
3V = 3/8 X 5/16
5V = 5/8 X 17/32
8v = 8/8 X 7/8

Question 21

Light Duty Belt Nomenclature

Answer 21

Ex: 5L500 (21/32 width, 50” outside length)
3L = 3/8 X 7/32
4L = 4/8 X 5/16
5L = 21/32 X 3/8

Question 22

Double V-belt Nomenclature

Answer 22

Ex: AA230 (3/2” width, 45” outside length)

Same as Classic V-belt, but AA, BB, and CC.

Question 23

Cogged V-belt Nomenclature

Answer 23

Ex: 3VX120 (3V belt with 12” outside length)

Same as classic or narrow V-Belt, but add an X after the A or 3V.

Question 24

Joined Belts Nomenclature

Answer 24

Ex: 2-5VX1250 (consists of 2 5VX’s with a length of 125”)

Same as other belts but add a #- to the front.

Question 25

V-Ribbed Belt Nomenclature

Answer 25

Ex: 540L6 (54" ouside length, 6 ribs)
H = .063 X .12
J = .092 X .14
K = .140 X .165
L = .185 X .38
M = .37 X .51

Question 26

Sychronous Belt Nomenclature

Answer 26

MXL (mini extra light) = .08"
XL (extra light) = .2"
L (light)= .375"
H (heavy) = .5"
XH (extra heavy)= .875"
XXH (double extra heavy) = 1.25"

Question 27

Dual-Sided Synchronous Belt Nomenclature

Answer 27

Just like Sychronous belt but put a D in front

Question 28

Curvilinear-Tooth Belts

Answer 28

A synchronous belt but teeth are curved instead of trapezoidal, Pitches are 5, 8, 14, and 20mm.

Question 29

Belt Materials

Answer 29

Leather
Cotton or Fabric
Rubber
Balata

Question 30

Belt Drive Problems:

Answer 30

Improper Drive Maintenance
Environmental factors
Improper belt or pulley installation
Poor drive design
Defective drive components
Improper belt storage or handling