0
Q
Stretch
A
-means the increase in length of the belt over the period of time that it’s in service
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
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
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
4
Q
Power depends on?
A
-Strength of the tensile members
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
6
Q
Slip
A
-When you increase the load and the arc of creep extends all the way around the pulley
7
Q
Friction
A
-The grip between the belt and the pulley
8
Q
Coefficient of friction
A
-Depends on the nature of the surfaces in contact
9
Q
Tension on the belt
A
-Determines the force between the belt and the pulley
10
Q
Gripping
A
-On sides of both the sheave and belt, never the bottom
11
Q
What is a classical/standard series of belts?
A
A,B,C & D
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
13
Q
An ‘x’ after the classical series letter
A
-mean its “Cogged raw edge”
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
15
Q
Double V
A
- ‘hexagonal’ designated with AA, BB,CC & DD
- used for serpentine drives
16
Q
High Capacity
A
- higher side walls of belts and sheaves giving greater tension
- know 3/8 = 3V, 5/8 = 5V, 1” = 8V
17
Q
High capacity belt designation
A
3/8 = 3V, 5/8 = 5V, 1” = 8V
18
Q
Disadvantage of high capacity belts
A
-require higher tension which causes higher bearing loads
19
Q
Fractional horsepower designation (light duty)
A
- 2L, 3L, 4L & 5L
- generally used for less than 1 horsepower
20
Q
Poly V or Micro V
A
- Designation J,K,L & M
- for high speed
- shape is several v’s together
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
22
Q
Link Belt
A
- available with the same power ratings as classical v belts
- they do not like high RPM
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
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
Second Year
flashcards
Decks in class (19)
# Cards
-
Welding23
-
Compressors - Cylinders26
-
Compressors - Valves18
-
Compressors - Fundementals47
-
Bearings - Plain43
-
Bearings - Anti Friction31
-
Compressor Crosshead & Distance Pieces, crankshaft & frame30
-
Math11
-
Lubrication41
-
Bearing Misc.26
-
Cross Dial/Rim & Face21
-
Belts60
-
Couplings53
-
Chains47
-
Shafts & Fits17
-
Clutches37
-
Gears85
-
NDT23
-
Gaskets & Piping19
