Belts Flashcards
____________ have a wedge shaped cross section.
V-belts
How do V-belts transmit power?
by gripping the sides of a groove in a pulley
What is the most cost effective means of power transmission:
A) V-belts
B) Gears
C) Chains
A) V-belts
True or false:
While V-belts are considered the most cost effective means of power transmission, they are also considered to be unreliable.
false;
they are considered highly reliable
True or false:
V-belts are able to absorb shock.
true
True or false:
The construction of V-belts allows for the belt to slip on overload.
true
Do V-belts require lubrication?
no;
- lubrication actually degrades the V-belts gripping ability
V-belts have a minimum of ______º arc of contact.
120º
Are V-belts suitable for positive drive engagements?
no;
they slip on overload, so they’re not good for positive drive applications
Can V-belts be used in areas of high ambient temperature?
no;
they degrade when exposed to high temperatures
True or false:
V-belts are not practical for high surface speeds because of problems with dynamic balancing.
true
What part of a V-belt construction consists of cords that carry the load?
the tensile members
What is the pitch line of a V-belt?
the pitch line is where the tensile members of the belt are located
With a V-belt, the _______________ material transmits the power between the sheave and the tensile member and supports the cords.
compression
True or false:
The compression material of a V-belt is often fibre-filled to provide transverse rigidity.
true
On a V-belt construction, what purpose does the cover serve?
it protects the internal parts from wear and the environment
How does a V-belt transmit power?
through friction between the sides of the belt and the sleeve transmitted to the tensile members of the V-belt
The amount of power a V-belt can transmit depends on what 2 things?
- strength of the tensile members
- grip of the belt on the pulley
What 3 things effect the grip of a V-belt on a pulley?
- arc of contact
- tension applied to the belt
- coefficient of friction between the belt and pulley
As it concerns belts, what is creep?
a change in belt speed from the tight side to the slack side
- the loss of driving speed due to the lengthening and shortening of the belt as it cycles from the tight side to the slack side
What effect does an increase in load have on creep?
the arc around the pulley through which creep occurs increases with load
What is the result of creep (not excessive)?
a slight belt flap on the return side
True or false:
The flutter or flapping of a belt is normal.
true
What happens when the load and tension on a V-belt are increased to the point where the arc of creep extends all the way round the pulley?
the belt will slip
What 4 negative effects does creep have on a V-belt arrangement?
- loss of power between driver and driven pulleys
- increased wear on belt and sheaves
- additional heat (belt degradation)
- excessive vibration
True or false:
The gripping action of a V-belt is entirely on the sides of the belt and the sides of the sheave groove in which it is wedged.
true
True or false:
A V-belt can touch the bottom of the sheave groove.
false;
- if the V-belt touches the bottom of the sheave the sheave is excessively worn
What is the most widely used series of V-belt?
the classical or standard series
What are the designations of classical or standard V-belts?
A, B, C, D, and E
What is another name for multiple series V-belts?
classical or standard series
What type of V-belt has the highest tolerance for poor operating conditions?
classical or standard series
What type of V-belt would be selected for an application where maintenance is infrequent?
classical or standard series
True or false:
The classical series V-belt has the most reliability for unusual drives (reverse bend, clutching, and quarter turn).
true
True or false:
An advantage of a classical series V-belt is that the cover wraps completely around the belt to provide protection on all sides of the belt.
true
What 4 types of V-belt were developed from the classical series V-belt?
- cogged raw edge
- banded (joined classical belts)
- double V
- fractional HP
What belt code designation identifies a cogged raw edge V-belt?
X = cogged raw edge
- AX, BX, CX, etc.
True or false:
The cogs on cogged raw edged belts allow for greater flexibility and enhanced airflow, resulting in a cooler operation when compared to a standard series V-belt.
true
What effect do the cogs on cogged raw edged belts have on the belt bend radius?
the cogs allow the belt to make tighter bends
Which V-belt would have a smaller bend radius: a cogged raw edged belt or a classical series?
cogged raw edge;
- the cogs allow for a tighter bend radius
Which V-belt fits the sheaves more accurately: a cogged raw edged belt or a classical series?
cogged raw edge
- Which V-belt is more efficient in terms of power transmission, weight, and space: a cogged raw edged belt or a standard belt?
- Why is this?
- cogged raw edge
- the higher coefficient of friction results in a smaller belt vs. a standard series
Can a cogged raw edged V-belt be used on clutching drives, drives that are subject to shock loads or drive with changing centre distances?
no
True or false:
A cogged raw edged V-belt cannot be subjected to reverse bending.
true
True or false:
A cogged raw edged V-belt can be used in applications where some slip is required.
false;
they cannot be subject to slip
What is the cause of the limitations of cogged raw edged V-belts?
the aggressive mature of the grip of the belt
What are banded V-belts?
belts constructed by jointed two or more standard belts with a common backing
What other names are banded belts known under?
Power-band and joined classical belts
What 3 problems were joined classical belts developed to solve?
- belt vibration
- belt whip
- belt turnover
Why is sheave alignment critical with banded belts?
banded belts have less ability to flex sideways than individual belts
True or false:
Banded belts have more power transmission ability when compared to the same number of individual belts.
false;
they have the same power transmission as the same number of individual belts
True or false:
Banded belts require more maintenance than individual V-belts.
true
What are the designations of banded belts?
B, C, D
- same as the classical seres belts
What types of belts would be designated AA, BB, and CC?
double V-belt
What is a hexagonal belt?
a double V-belt
This type of belt is a double-sided standard series V-belt.
a double V-belt
True or false:
Double V-belts are capable of transmitting power on both sides in serpentine drives
true
What type of V-belt is designated 2L, 3L, 4L, or 5L?
fractional HP V-belts
True or false:
Fractional HP V-belts are generally used for drives of less than 1 HP, but some OEM’s offer them up to 17 HP.
true
True or false:
Fractional HP belts can go very fast.
true
When a new standard series V-belt is installed on a sheave, how far down in the sheave groove should the top of the belt sit?
The top of the belt should be proud to the top of the sheave
What types of V-belts are designated 3V, 5V, and 8V?
high capacity V-belts
What are narrow V-belts?
the same as high capacity V-belts
What designations are used for high capacity V-belts?
3V, 5V, and 8V
What designations would be used with hexagonal belts?
AA, BB, and CC
What designations would be used for a fractional HP V-belt?
2L, 3L, 4L, and 5L
What design characteristic of a narrow V-belt increases its capacity?
the narrow wedge design provides more support for the tensile members
What are the 2 main advantages of high capacity V-belts when compared to classical series belts?
- compact
- higher power capacity
True or false:
High capacity V-belts are under tensioned if they are tensioned according to the same feel as classical V-belts.
true
What are the 2 main limitations of narrow V-belts?
- require higher tension = higher loading on bearings
- increased sheave wear in dusty and abrasive environments (due to higher side wall loading)
True or false:
Alignment and cleanliness are not important for high capacity belt drives.
false;
they are important
What is the top width of a 3V high capacity belt?
3V = 3/8”
- 1/8” x 3
What is the top width of a 5V high capacity belt?
5V = 5/8”
- 1/8” x 5
What is the top width of a 8V high capacity belt?
8V = 1”
- 1/8” x 8
True or false:
Worn sheaves affect the performance of joined high capacity belts more than classical banded belts.
true
What are the designations of poly V-belts?
J, K, L, and M
- also H for small sheaves and miniature drives
What are V-ribbed belts?
the same as poly V-belts
This type of flat belts are thin and have a ribbed driving face that runs in a grooved pulley with a well supported tensile member.
Poly V-belt
With a poly V-belt, are the tensile members outside the pulley grooves, or inside of them?
outside
- the tensile members are on top of the pulley vs narrow V-belt which would be in the pulley groove
True or false:
Poly V-belts do not perform well on small diameter pulleys.
false;
they perform well on small diameter pulleys
True or false:
V-ribbed belts are ideal for high speed ratios where there is a large difference between the driver and driven pulley diameters.
true
True or false:
Poly V-belts can be used with reverse bends or serpentine drives.
true
- found most often on automobiles as the timing belt
Why are poly V-belts ideal for high speed applications?
because their light weight and thin cross section
- heavier = more mass moving around = slower speeds
True or false:
Poly V-belts have a longer belt and sheave life due to equalized loading.
true
What are the 2 main limitations of poly V-belts?
- require special sheaves and high tension
- alignment is more critical
What 3 pieces of information do Poly V-belt codes contain?
- length
- section
- number of ribs
180J6 = 180” x J size x 6 ribs
What types of belts are used where speed changes are needed?
variable speed belts
This types of belt runs in sheaves with specially designed sides.
variable speed belt
What are the sides of variable speed sheaves called?
flanges
The sheaves used on variable speed drives move axially, so when the axial space is at its smallest, the driven pulley turns the ____________ (quickest/slowest).
slowest
- this is the smallest space between the flanges, not the smallest diameter
When the flanges of a variable speed belt sheave move apart, the belt moves down to a smaller diameter towards the centre. What effect would this have on speed?
sheave ∅ ↓ = speed ↑
When the flanges of a variable speed belt sheave move together, the belt moves outward to a larger diameter. What effect would this have on speed?
sheave ∅ ↑ = speed ↓
What do the first 2 digits of a variable speed belt designation represent?
the top width, in 1/16”
12 = 12 x 1/16” = 12/16” = 3/4”
12 would be a 3/4” wide belt
What do the 3rd and 4th digits of a variable speed belt designation represent?
the groove angle
What do the last 3 digits of variable speed belt designation represent?
the pitch length of the belt
255 = 25.5”
What is the main advantage of a variable speed belt drive systems?
economical way of providing infinitely variable speed
What are the 2 main limitations of variable speed belt drive systems?
- require special sheaves
- not practical for very large HP
- What precaution must be taken when adjusting the speed of a variable speed belt drive system?
- What can happen if this precaution is not observed?
- the belts must be turning before adjusting the speed
- the adjustment mechanism could be broken
What are two types of belts that can be cut to any length and fastened together?
- open ended belts
- link belts
What designations are used for open ended belts?
same cross section letter as standard belts (A, B, C, D, or E), but with VO after the letter.
What designation indicates an open ended belt?
VO
What is the main limitation of an open ended belt?
it can only carry 1/3 of the load that a corresponding endless belt could carry
What are the 2 main advantages of a link belt?
- can be used as an emergency replacement for endless belts
- available with the same power rating as classical V-belts of the same cross section
What are the 3 main limitations of link belts?
- more vibration
- cannot be used with back idlers
- cannot be used with endless belts
What do the two numbers in a round belt designation indicate?
1st # = diameter, in 1/16” of an inch
2nd # = length
- 5 x 33 ⟶ 5 x 1/16” = 5/16” ∅ x 33” length
Identify the length and diameter of a round belt labelled 4 x 365.
4 ⟶ belt ∅ ⟶ 4 x 1/16” = 4/16” = 1/4” ∅
365 ⟶ length ⟶ 36.5”
True or false:
Round belts are suitable for quarter turn drives.
true
True or false:
Round belts are not suitable for serpentine drives.
false
True or false:
Round belts can be supplied as open-ended to allow for custom lengths to be cut and spliced.
true
What is the main limitation of a round belt?
light duty, fractional HP only
True or false:
The codes on most belts in North America are standardized by the Rubber Manufacturers Association (RMA).
true
What does the letter designate on an RMA belt designation code?
the shape and size of the cross section
What do the numbers that follow the letter designation on an RMA belt designation code stand for?
the length of the belt in inches
- the last digit of the length number is a decimal of an inch (255 = 25.5”)
What 2 issues do dirt and deposits cause on belts and sheaves?
- Wear - degradation through abrasion and corrosion
- Vibration - imbalance which causes vibration
What are the two main reasons to inspect sheaves during cleanup?
- to check for possible cracks, especially around the hub
- check for dynamic balance
True or false:
X on belts indicates a cogged raw edge on both imperial and metric belts.
true
Where is belt length measured?
at the pitch line
What are the 2 ways to perform a wear check on belts and sheaves?
- sheave groove gauge
- check wear with a new belt
What causes a belt to swell?
excessive exposure to oil or grease
What effect does belt swell have on a belt?
the belt becomes soft, and the bottom envelope seam will “open up”
What do cut bottom and sidewalls indicate on a V-belt?
that the belt was pried overs the sheave during installation
What 2 things does fitting a belt involve?
- aligning the sheaves
- tensioning the belts
True or false:
Aligning the sheaves reduces vibration and extends belt life.
true
What is the maximum allowable misalignment of a V-belt?
1/16” offset per foot
With a belt and sheave arrangement, any runout that exceeds ________” should be corrected.
0.005”
- very difficult to achieve
What can happen when using tapered adapter bushings to mount sheaves and the bolts are not evenly tightened?
excessive runout
True or false:
Belts must be tight enough not to slip under normal operating conditions, but they must not be so tight as to create unnecessary load on the bearings during normal operation.
true
What causes evenly spaced deep bottom cracks on a belt?
a substandard backside idler
How is deflection for belt tensioning checked on banded belts?
with a special deflection gauge that contacts the entire width of the belt
Why is the elongation method usually used to check the tension of banded belts?
the high forces required to check with the specialized deflection gauge
What is the elongation method for checking belt tension with banded belts?
uses an elongation table with a number (length multiplier) that indicates how long the belt should be under proper tension
Where can idler pulleys be located on belts?
either inside or outside the belt strands
Idlers are often added to belt systems for what 3 reasons?
- increase belt tension
- increase arc of contact
- prevent belt whip
Should idlers be used on reversing drives?
no
When an outside idler is used to tension a belt, what type of pulley should be used for the idler?
a flat pulley at least 1.5 times the ∅ of the smaller pulley
When using an outside pulley to increase the arc of contact on a belt system, how should it be positioned?
as close as possible to the smaller sheave
After increasing the arc of contact, what is another reason to located an idler pulley as close as possible to the smaller sheave of a belt system?
to aid with tracking of the belt
- smaller ∅ = drive sheave, and the belt will wander on the flat side of the idler pulley; having it far away from the large one reduces the angle of misalignment
- On which span should idler pulleys be located?
- Why is this?
- the slack span
- it takes much less force to tension the slack span than drive span
Because an outside idler puts a backward bend on the belt, it leads to premature ____________ of the belt.
cracking
What effect does an inside idler have on the arc of contact of a belt?
it reduces it
True or false:
Even though an inside idler reduces the arc of contact of belts, if an adequate arc of contact is maintained, an inside idler is more reliable than an outside idler.
true
- no premature cracking due to bending the belt backwards
Why is a grooved pulley used on inside idlers?
better tracking
Where should an inside grooved idler be located?
on the slack side, at a point in the span that produces equal arcs of contact on the sheaves
Where should an inside flat idler be located?
away from the sheave the belt it is travelling towards to prevent unequal arcs of contact
What are contact idlers used for?
to counteract belt whip produced by long spans or shock loads
What is belt whip?
belt vibration in the vertical span
- this is where the belt is vibrating up and down
What are contact idlers also known as?
kiss idlers
How should outside kiss idlers be mounted in a pulley system?
located 1/3 of the span distance from the large pulley on the slack span
Should a kiss idler be set so that it creates a back bend in the belt?
no;
it should just “kiss” the top of the belt
What does an automatic take-up on a belt system consist of?
a spring on a movable mount or on an idler
What function does an automatic take-up perform in a belt system?
it maintains belt tension
- What effect does an automatic take-up have on a belt?
- How is the above achieved?
- it increases the life of the belt
- by providing uniform tension throughout the life of the belt (compensates for stretch)
True or false:
When tensioning belts, you have achieved the approximate tension when the belt springs back after being bump at mid-span.
true
If when bumped at mid-span and the belt does not spring back, its tension is too ___________ (tight/loose).
loose
If when bumped at mid-span and the belt feels like a solid board, it is too ____________ (tight/loose).
tight
Why is it a good idea to rotate the sheaves of a belts before checking the tension of said belt?
to ensure that belt is properly seating the sheave grooves
When installing belts, can new belts and old belts be used together on the same sheaves?
no
How long after initial installation should belt tension be rechecked?
during the first 24 to 48 hours
With belts, what is a quarter turn drive?
when power is transmitted from a horizontal shaft to a vertical shaft
What is the maximum speed ratio of a quarter turn belt drive?
2.5:1
- When using a quarter turn drive belt arrangement, the centre distance must be at least:
- Why is this distance required?
- 5.5 times the sum of the large sheave ∅ plus its face width (thickness)
- to ensure that the angle at which the belt enters the sheave is not too great
When using a quarter turn belt drive, where must the centreline of the horizontal shaft be located in relation to the vertical sheave?
it must be above the centreline of the vertical sheave
When using a quarter turn belt arrangement, the HP rating of the belt should be derated to ______%.
90%
What is the greatest concern when running a quarter turn belt drive arrangement?
ensure the angle at which the belt enters the sheave groove on the tight side is kept to a minimum
- this prevents the belts from flipping over the edges of the sheaves
With a belt system, start up checks should be repeated after how long after the initial start up?
24 to 48 hours
With a belt system, squealing sounds or the smell of burning rubber indicate:
a loose belt
With a belt system, flapping belts on the tight strand indicate:
misalignment
With a belt system, bearings running hotter than they did before the belt change indicate:
too much tension on the belts
With a belt system, increased amperage draw on an electric drive after the belt change indicates:
too much tension on the belts
With a belt system, excessive vibration can be caused by:
misalignment or runout
What should be used to clean a running belt?
brushes
- avoid entanglement
When tensioning a belt to compensate for stretch, how much tension should be added to the belt?
just enough to stop the slip
What could be the cause of slip if tensioning the belts do not eliminate it?
the belts and/or the sheaves grooves are worn
True or false:
Belt dressing should be used only as a last resort to avoid a machine outage at a critical time.
true
With a belt system, what is the cause of chirps?
dirt or dust in the sheave grooves or on the side of the belts
With V-belts, what is ride-out?
how high up on the sheave the belt rides
- as the sheave wears, the ride-out will decrease
What does squealing in a belt at start up or near maximum load indicate?
insufficient tension
If properly tensioned, what can a squealing belt indicate?
overload
What does belt whip on the tight span indicate on a belt drive system?
insufficient tension
What can be a cause of belts snaking?
runout or wobble on the sheaves
What is the maximum ambient temperature that normal belts should operate at?
60℃
If stored according to RMA recommendations, how long should belts last on the shelf?
8 years
What 4 things must be observed when storing belts according to RMA’s recommendations?
- protect from moisture and high temps
- store in original packaging and out of direct sunlight
- do not bend or hang on a diameter less than the smallest recommend pulley
- relax the tension on belts left on equipment that is to be idle for long periods of time
What type of belt would be used where there can be no slip?
synchronous belts
Positive drive belts and timing belts are names for:
synchronous belts
This type of belt must be run in special pulleys called sprockets.
synchronous belts
This type of belt is a flat belt with moulded teeth that engage with a special pulley called a sprocket.
a synchronous belt
Synchronous belts last about _____ times longer than chain drives.
3 times
- minimum, may last longer
- Which type of belt requires more tension: a classical V-belt or a synchronous drive?
- Why is this?
- synchronous drive
- rely on mechanical engagement vs. coefficient of friction
Do synchronous belts require re-tensioning after start up?
no;
- they need never be re-tensioned
Do synchronous belts require lubrication?
no
Synchronous belts are ______% efficient.
98%
True or false:
Synchronous belts are compact, have a wide speed range (up to 30,000 RPM), have wide power ratings (up to 1200 HP), and run quietly.
true
True or false:
Synchronous belts are virtually maintenance free
true
What are 2 disadvantages of synchronous belts?
- not great for high shock loads
- do not provide overload protection (no slip
On which type of belt is alignment more critical: V-belts or synchronous belts?
synchronous belts
Which type of belt is more sensitive to dirt: V-belts or synchronous belts?
synchronous belts
Do synchronous belts track or train well?
no
What happens to synchronous belts when things go wrong?
they break
What are the tensile members of synchronous belts usually made from?
twisted fibreglass cords
What are the 2 main advantages of using twisted fibreglass cords in synchronous belts?
- minimal stretch
- holds its tension because the fibres do not stretch
True or false:
Unlike gear teeth, the sprocket teeth of synchronous belts engage to the full depth of the grooves between the belt teeth with no root clearance
true
How do synchronous belts transmit power?
the positive engagement between the teeth on the belt and the teeth on the sprocket
True or false:
Synchronous belts will wander, even with accurately aligned sprockets.
true
What needs to be included on the sprockets of synchronous belts to combat wander?
flanges
What is the minimum number of flanges that needs to be included on sprockets on synchronous belts?
2 flanges
- they can be on the same sprocket, or on opposite sides of two sprockets
On other than vertical drives, why must there only be 2 flanges on sprockets that drive synchronous belts?
if more then 2 are used, the belt will climb up one flange and cut itself up
What is the minimum arc of contact of a synchronous belt?
at least 60º and a minimum of 6 teeth
What is ratcheting when it comes to synchronous belts?
teeth climbing out of engagement due to insufficient arc of contact/number of teeth engaged
This type of synchronous belt design has teeth with flat sides.
trapezoidal teeth
What are the 2 types of rounded tooth design found on synchronous belts?
- Rounded
- Parabolic (involute)
When it comes to synchronous belts, which design has the stronger tooth form: trapezoidal or rounded?
rounded
When it comes to synchronous belts, which design has the more energy efficient tooth design: trapezoidal or rounded?
rounded
What is the pitch of a timing belt?
the distance from one tooth to the correspond point on the next tooth
What is the tooth pitch distance of an L tooth pitch on a timing belt?
3/8”
What do the first 3 numbers on a synchronous belt code represent?
pitch length, in inches
225 = 22.5”
What does the letter after the pitch length number represent on a synchronous belt code?
the tooth pitch
L = 3/8”
What do the 3 numbers after the tooth pitch letter represent on a synchronous belt code?
the width, in inches
075 = 0.75” or 3/4”
What type of belts do normal synchronous belt codes not apply to?
Eagle belts, also known as helical offset tooth design belts
True or false:
Tension timing belts enough to remove any slack from the unloaded span to ensure the teeth do not ratchet at startup
true
True or false:
Tension synchronous belts until they are just snug enough to remove any clearance between the outside diameter of the sprocket teeth and the grooves between the belt teeth.
true
What effect does the herringbone tooth pater on Eagle synchronous belts have on dirt?
its throws the dirt away from the mesh point of the belt, making it better at handling dirt
What are the 3 parts of a pulley used in industrial machinery?
- rim
- web
- hub
What are the 3 different design for the material that supports the rim on the hub of a pulley?
- web
- block
- arm
What are 3 things that happen when a sub-minimum diameter sheave is selected to run with a belt?
- excessive bending stress in the under cord
- higher belt tensions
- run with higher temperatures
What do the first 2 numbers on a synchronous belt sprocket code designate?
the number of grooves on the sprocket
- treat these like teeth on a gear for ratio calculations
What does the letter that comes after the first two digits on a synchronous belt sprocket code designate?
the tooth pitch
What do the 3 numbers that come after the letter designation indicate on a synchronous belt sprocket code?
the width in inches
075 = 0.75” or 3/4”
True or false:
Poly V-belt pulleys are similar to flat belt pulleys, except that there is no crown on the driving surface.
true
What does the first number of a poly V-belt pulley code indicate?
the number of grooves
What does the letter that comes after the first number in a poly V-belt code indicate?
the cross section
What do the last two digits of a poly V-belt pulley code indicate?
the diameter of the pulley in inches
48 = 4.8”
True or false:
With V-belt drive sheaves, the three groove angles (34º, 36º, and 38º) depend on the radius of the sheave.
true
What are the 3 V-belt sheave groove angles?
34º, 36º, and 38º
With a V-belt sheave, the groove width is specified by the width:
at the outside diameter of the pulley
- the very top of the pulley
True or false:
The groove width at the outside diameter of a V-belt sheave is used to determine the belt width.
true
True or false:
The outside diameter of a V-belt sheave is used when determine the belt length.
true
Can you interchange bushing on V-belt sheaves?
no
This type of sheave bushing is slit through the barrel and flange and has no key in the OD of the barrel.
QD bushing
Which type of synchronous belt is used in serpentine arrangements?
twin toothed belts
Identify the following type of belt:
Standard wrapped V-belt
Identify the following type of belt:
Cogged raw edged V-belt
Identify the following type of belt:
Banded belts
Identify the following type of belt:
Double V-belt
Identify the following type of V-belt:
Fractional HP V-belt
Identify the the following V-belt code:
3V355
3 ⟶ top width ⟶ 1/8” x 3 = 3/8”
V ⟶ high capacity belt
355 ⟶ length = 35.5”
Identify the following type of belt:
Variable speed belt
Identify the following belt code:
1228V255
Variable speed belt
Identify the following type of belt:
Open ended belt
Identify the following type of belt:
Link belts
Identify the following type of belt:
Round belt
Identify the cause of this damage on a V-belt:
Swell;
The belt has been exposed to excessive oil or grease resulting in the belt swelling, and the bottom envelope seam opening up.
Identify the cause of the damage on this V-belt:
Caused by the belt being rolled onto the sheave
Identify the cause of the damage on this V-belt:
Back tension
Identify the following type of synchronous belt:
Twin toothed belt
Identify the following parts of this synchronous belt code:
225L075
225 = pitch length 22.5”
L = tooth pitch L
075 = width 0.75” or 3/4”
Identify the following information on a synchronous belt sprocket:
16L075
16 = number of grooves on the sprocket
L = tooth pitch L
075 = width 0.75” or 3/4”
Identify the following information on a poly V-belt pulley code:
6L48
Identify the following information from a V-belt sheave code:
QD4/3V6.00
Belt _____________ is the loss of driving speed due to the lengthening and shortening of the belt as it cycles from the tight side to the slack side.
Creep
Identify the following information of a poly V-belt:
180J6
180 = length in inches = 180”
J = section size = J
6 = number of ribs = 6
Wide V-belt drives are energized to perform best at:
1:1 ratios
Which type of V-belt gives the best crosswise rigidity?
wide belt series
Why do V-belt drives have notches moulded into them on the narrow side?
to reduce the radius that they can wrap around
How do manufacturers of variable speed V-belt drives prevent fretting corrosion?
with special coatings on the pulleys
Mounting belt drives on a solid flat metal surface is important. Why?
the drives can become distorted if mounted on uneven surfaces
True or false:
The convex sides of PIV pulleys are machined to have male and female tooth profiles.
true
Hydraulic variable speed drives are _____________ (hydrodynamic/hydrostatic) in design.
hydrostatic
True or false:
In a closed loop, variable speed hydraulic drive, the motor return oil goes directly to the reservoir.
false;
- in a closed loop, the return directly feeds the motor
Leakage oil in a closed loop, variable speed hydraulic drive is replaced by what device?
a charge pump
Variable fill hydraulic drives use what device to remove oil from the unit while it is running?
a scoop tube
How is pressure applied to the discs within a wet disc drive?
with a hydraulic piston
What can happen during the overhaul of a wet disc hydraulic system if the discs are not matched marked and positioned properly during reassembly?
it can create a condition of dynamic unbalance
What damage can be caused to a V-belt by using a sheave with variable diameter selections?
Ply separation caused by substandard sheave diameter
- if the sheave is too small, the belt radius will be too tight, resulting in ply separation
True or false:
The effective sheave diameter in a variable speed arrangement dictates the speed of the drive
True
