Belts

Question 0

Stretch

Answer 0

-means the increase in length of the belt over the period of time that it’s in service

Question 1

Pitch line

Answer 1

• runs through the load carrying zone of the belt where the tensile members are located
• it’s where you measure from

Question 2

V belt Construction

Answer 2

• Tensile members consist of cords that carry the load
• compression material transmits the power between the sheave, the tensile member and supports the load
• cover protects the internal parts

Question 3

Transmit power from?

Answer 3

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

Question 4

Power depends on?

Answer 4

-Strength of the tensile members

Question 5

Creep

Answer 5

-loss of driving speed due to the lengthening and shortening of the belt as it cycles from the slack side to the tight side

Question 6

Slip

Answer 6

-When you increase the load and the arc of creep extends all the way around the pulley

Question 7

Friction

Answer 7

-The grip between the belt and the pulley

Question 8

Coefficient of friction

Answer 8

-Depends on the nature of the surfaces in contact

Question 9

Tension on the belt

Answer 9

-Determines the force between the belt and the pulley

Question 10

Gripping

Answer 10

-On sides of both the sheave and belt, never the bottom

Question 11

What is a classical/standard series of belts?

Answer 11

A,B,C & D

Question 12

Cogged “Raw” edge advantages?

Answer 12

• greater flexibility and cooling

- the raw edges have a higher coefficient of friction than wrapped belts and can thus transmit more power

Question 13

An ‘x’ after the classical series letter

Answer 13

-mean its “Cogged raw edge”

Question 14

Banded Belts

Answer 14

• the belts are constructed by joining two or more standard belts with a common backing
• high speed
• designed to solve belt whip, vibration &turnover

Question 15

Double V

Answer 15

• ‘hexagonal’ designated with AA, BB,CC & DD

- used for serpentine drives

Question 16

High Capacity

Answer 16

• higher side walls of belts and sheaves giving greater tension
• know 3/8 = 3V, 5/8 = 5V, 1” = 8V

Question 17

High capacity belt designation

Answer 17

3/8 = 3V, 5/8 = 5V, 1” = 8V

Question 18

Disadvantage of high capacity belts

Answer 18

-require higher tension which causes higher bearing loads

Question 19

Fractional horsepower designation (light duty)

Answer 19

• 2L, 3L, 4L & 5L

- generally used for less than 1 horsepower

Question 20

Poly V or Micro V

Answer 20

• Designation J,K,L & M
• for high speed
• shape is several v’s together

Question 21

Open-ended Belting

Answer 21

• can only carry 1/3 of the load of a corresponding endless belt
• same code as ABCD but have a VO at the end

Question 22

Link Belt

Answer 22

• available with the same power ratings as classical v belts

- they do not like high RPM

Question 23

Round belts

Answer 23

• rely on surface area contact
• for quarter turn drives & serpentine drives, low power cause no grab
• code gives diameter in 1/16 so 5 x 33 would by 5/16 diameter

Question 24

Serpentine drives

Answer 24

- When the belt or chain is weaving in and out of sprockets and using both sides of the chain or belt - think snakes

Question 25

Checking the sheave groove?

Answer 25

- a gauge or new belt. Both should be level with the top of the sheave - belt should never touch the bottom of the sheave

Question 26

Max sheave misalignment

Answer 26

-1/16 inch per foot

Question 27

Max axial runout?

Answer 27

-.005

Question 28

Idler

Answer 28

- Increase belt tension - Increase the arc of contact (move idler to equal contact) - Prevent whip - allows goes on the loose side - 1/3 of the span distance

Question 29

When should you recheck tension on v belt.

Answer 29

-during the first 24-48 hours of operation

Question 30

What's the rule for readjusting the tension on a synchronous belt?

Answer 30

-set it and forget it

Question 31

Synchronous Belts (positive drive or timing belt)

Answer 31

- Output shaft must be synchronized with the input shaft - flat belt with moulded teeth that engage in special toothed sprockets - for positive drive, high speed

Question 32

Advantages of synchronous belts

Answer 32

- do not require re-tensioning - no lubrication needed - 98% efficient - very wide speed range 30,000 RPM

Question 33

Disadvantages of synchronous belts

Answer 33

- not suitable for large shock loads | - require more accurate alignment than v belts

Question 34

Belt operation

Answer 34

-the depend on positive engagement of the teeth on the belt with the teeth on the sprocket

Question 35

Arc of contact

Answer 35

- v belts 120 degrees | - Synchronous 60 degrees or 6 teeth

Question 36

Types of synchronous belts

Answer 36

- trapezoid - rounded - twin - helical offset

Question 37

Trapezoid

Answer 37

-flat sides

Question 38

Rounded tooth profile

Answer 38

- replaces some of the sliding friction with rolling friction - stronger tooth profile then flat

Question 39

Twin toothed

Answer 39

-have teeth on both sides of the belt, making more compact and efficient.

Question 40

Helical Offset

Answer 40

- highest power rating - lowest sound rating - very little backlash

Question 41

Synchronous codes

Answer 41

- 22.5 L 075 | - pitch length, tooth pitch, width

Question 42

A pulley

Answer 42

-a wheel used to transmit power from its rim to a belt

Question 43

A Sheave

Answer 43

-a pulley with a groove that runs around the circumference of the rim

Question 44

A sprocket

Answer 44

-A special form of flat belt pulley that has grooves across its face to match the teeth in a synchronous drive belt

Question 45

Sprocket code

Answer 45

-16 L 075 | Number of grooves, tooth pitch, width

Question 46

Code for poly v pulley

Answer 46

-6 L 48 | Number of grooves, cross section, diameter

Question 47

Taper-Bored Hubs

Answer 47

-the key may be eliminated on very high speed drives for more accurate dynamic balancing.

Question 48

QD hub

Answer 48

- Bushing is split on barrel and flange | - keyed on shaft

Question 49

Tapered bushing hub

Answer 49

- Bushing is split only on barrel | - keyed on shaft and bushing

Question 50

Tapered loc hub

Answer 50

-bushing has no flange

Question 51

Pulley Diameter

Answer 51

-avoid sub-minimum diameter sheaves as they cause excessive bending stresses in the undercord, higher belt tensions and higher temperatures

Question 52

Poly V-belts pulley

Answer 52

- have no crown on the driving surface | - has a number of circumferential grooves to grip and guide the belt

Question 53

Belt whip

Answer 53

-vibration in the vertical plane

Question 54

Automatic take-ups

Answer 54

-a spring on a moveable motor mount or an idler to maintain belt tension

Question 55

Quarter turn drive

Answer 55

- Transmits power from a horizontal shaft to a vertical shaft - centrelines must be in line. - derate horsepower to 90% of normal rating

Question 56

Excessive vibration

Answer 56

-caused by misalignment or runout or long span

Question 57

Uneven sprocket tooth wear

Answer 57

-caused by misalignment

Question 58

Variable speed belt

Answer 58

-notches and ribs on underbelly -reduced side angle to move up and down in Flanges as the separate

Question 59

Chirps

Answer 59

-indicate dirt or dust in sheave grooves