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Second Year > Belts > Flashcards

Belts Flashcards

0
Q

Stretch

A

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

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1
Q

Pitch line

A
  • runs through the load carrying zone of the belt where the tensile members are located
  • it’s where you measure from
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2
Q

V belt Construction

A
  • 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
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3
Q

Transmit power from?

A
  • Friction between the sides of the belt and the sides of the sheave groove
  • tensile members from the driver to the driven pulley
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4
Q

Power depends on?

A

-Strength of the tensile members

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5
Q

Creep

A

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

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6
Q

Slip

A

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

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7
Q

Friction

A

-The grip between the belt and the pulley

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8
Q

Coefficient of friction

A

-Depends on the nature of the surfaces in contact

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9
Q

Tension on the belt

A

-Determines the force between the belt and the pulley

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10
Q

Gripping

A

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

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11
Q

What is a classical/standard series of belts?

A

A,B,C & D

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12
Q

Cogged “Raw” edge advantages?

A
  • greater flexibility and cooling

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

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13
Q

An ‘x’ after the classical series letter

A

-mean its “Cogged raw edge”

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14
Q

Banded Belts

A
  • the belts are constructed by joining two or more standard belts with a common backing
  • high speed
  • designed to solve belt whip, vibration &turnover
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15
Q

Double V

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

- used for serpentine drives

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16
Q

High Capacity

A
  • higher side walls of belts and sheaves giving greater tension
  • know 3/8 = 3V, 5/8 = 5V, 1” = 8V
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17
Q

High capacity belt designation

A

3/8 = 3V, 5/8 = 5V, 1” = 8V

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18
Q

Disadvantage of high capacity belts

A

-require higher tension which causes higher bearing loads

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19
Q

Fractional horsepower designation (light duty)

A
  • 2L, 3L, 4L & 5L

- generally used for less than 1 horsepower

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20
Q

Poly V or Micro V

A
  • Designation J,K,L & M
  • for high speed
  • shape is several v’s together
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21
Q

Open-ended Belting

A
  • can only carry 1/3 of the load of a corresponding endless belt
  • same code as ABCD but have a VO at the end
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22
Q

Link Belt

A
  • available with the same power ratings as classical v belts

- they do not like high RPM

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23
Q

Round belts

A
  • 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
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24
Q

Serpentine drives

A
  • When the belt or chain is weaving in and out of sprockets and using both sides of the chain or belt
  • think snakes
25
Q

Checking the sheave groove?

A
  • 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
Q

Max sheave misalignment

A

-1/16 inch per foot

27
Q

Max axial runout?

A

-.005

28
Q

Idler

A
  • 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
Q

When should you recheck tension on v belt.

A

-during the first 24-48 hours of operation

30
Q

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

A

-set it and forget it

31
Q

Synchronous Belts (positive drive or timing belt)

A
  • 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
Q

Advantages of synchronous belts

A
  • do not require re-tensioning
  • no lubrication needed
  • 98% efficient
  • very wide speed range 30,000 RPM
33
Q

Disadvantages of synchronous belts

A
  • not suitable for large shock loads

- require more accurate alignment than v belts

34
Q

Belt operation

A

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

35
Q

Arc of contact

A
  • v belts 120 degrees

- Synchronous 60 degrees or 6 teeth

36
Q

Types of synchronous belts

A
  • trapezoid
  • rounded
  • twin
  • helical offset
37
Q

Trapezoid

A

-flat sides

38
Q

Rounded tooth profile

A
  • replaces some of the sliding friction with rolling friction
  • stronger tooth profile then flat
39
Q

Twin toothed

A

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

40
Q

Helical Offset

A
  • highest power rating
  • lowest sound rating
  • very little backlash
41
Q

Synchronous codes

A
  • 22.5 L 075

- pitch length, tooth pitch, width

42
Q

A pulley

A

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

43
Q

A Sheave

A

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

44
Q

A sprocket

A

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

45
Q

Sprocket code

A

-16 L 075

Number of grooves, tooth pitch, width

46
Q

Code for poly v pulley

A

-6 L 48

Number of grooves, cross section, diameter

47
Q

Taper-Bored Hubs

A

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

48
Q

QD hub

A
  • Bushing is split on barrel and flange

- keyed on shaft

49
Q

Tapered bushing hub

A
  • Bushing is split only on barrel

- keyed on shaft and bushing

50
Q

Tapered loc hub

A

-bushing has no flange

51
Q

Pulley Diameter

A

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

52
Q

Poly V-belts pulley

A
  • have no crown on the driving surface

- has a number of circumferential grooves to grip and guide the belt

53
Q

Belt whip

A

-vibration in the vertical plane

54
Q

Automatic take-ups

A

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

55
Q

Quarter turn drive

A
  • Transmits power from a horizontal shaft to a vertical shaft
  • centrelines must be in line.
  • derate horsepower to 90% of normal rating
56
Q

Excessive vibration

A

-caused by misalignment or runout or long span

57
Q

Uneven sprocket tooth wear

A

-caused by misalignment

58
Q

Variable speed belt

A

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

59
Q

Chirps

A

-indicate dirt or dust in sheave grooves

Second Year (19 decks)

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