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Flashcards in Belts Deck (60):
0

Pitch line

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

1

Stretch

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

2

V belt Construction

-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

3

Transmit power from?

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

4

Power depends on?

-Strength of the tensile members

5

Creep

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

6

Slip

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

7

Friction

-The grip between the belt and the pulley

8

Coefficient of friction

-Depends on the nature of the surfaces in contact

9

Tension on the belt

-Determines the force between the belt and the pulley

10

Gripping

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

11

What is a classical/standard series of belts?

A,B,C & D

12

Cogged "Raw" edge advantages?

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

13

An 'x' after the classical series letter

-mean its "Cogged raw edge"

14

Banded Belts

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

15

Double V

-'hexagonal' designated with AA, BB,CC & DD
-used for serpentine drives

16

High Capacity

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

17

High capacity belt designation

3/8 = 3V, 5/8 = 5V, 1" = 8V

18

Disadvantage of high capacity belts

-require higher tension which causes higher bearing loads

19

Fractional horsepower designation (light duty)

-2L, 3L, 4L & 5L
-generally used for less than 1 horsepower

20

Poly V or Micro V

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

21

Open-ended Belting

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

22

Link Belt

-available with the same power ratings as classical v belts
-they do not like high RPM

23

Round belts

-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

24

Serpentine drives

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

25

Checking the sheave groove?

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

26

Max sheave misalignment

-1/16 inch per foot

27

Max axial runout?

-.005

28

Idler

-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

29

When should you recheck tension on v belt.

-during the first 24-48 hours of operation

30

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

-set it and forget it

31

Synchronous Belts (positive drive or timing belt)

-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

32

Advantages of synchronous belts

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

33

Disadvantages of synchronous belts

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

34

Belt operation

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

35

Arc of contact

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

36

Types of synchronous belts

-trapezoid
-rounded
-twin
-helical offset

37

Trapezoid

-flat sides

38

Rounded tooth profile

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

39

Twin toothed

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

40

Helical Offset

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

41

Synchronous codes

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

42

A pulley

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

43

A Sheave

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

44

A sprocket

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

45

Sprocket code

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

46

Code for poly v pulley

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

47

Taper-Bored Hubs

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

48

QD hub

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

49

Tapered bushing hub

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

50

Tapered loc hub

-bushing has no flange

51

Pulley Diameter

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

52

Poly V-belts pulley

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

53

Belt whip

-vibration in the vertical plane

54

Automatic take-ups

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

55

Quarter turn drive

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

56

Excessive vibration

-caused by misalignment or runout or long span

57

Uneven sprocket tooth wear

-caused by misalignment

58

Variable speed belt

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

59

Chirps

-indicate dirt or dust in sheave grooves