The document provides instructions for installing and tensioning V-belt drives. It describes disconnecting power, inspecting components, installing new belts, checking alignment, tensioning belts using various methods like the tension finder or tensiometer, and rechecking tension over time. Proper tensioning is important for long belt life and avoiding slippage or damage from too little or too much tension.

1. V-Belt Installation & Tensioning

2. V-Belt Installation Check List
1) Disconnect and lock out power source. Observe all safety procedures.
2) Remove belt guard
3) Loosen motor mounts
4) Shorten center distance
5) Remove old belts
6) Inspect belt wear patterns for possible troubleshooting
7) Inspect and clean drive elements-bearings, shafts, etc.
8) Inspect sheave grooves for wear - replace if necessary
9) Preliminary sheave alignment
10) Identify proper replacement belts
11) Install new belts
12) Tension belts
13) Final sheave alignment
14) Replace guard
15) Start drive (look & listen)
16) Re-tension after 24 hours

3. Safety First
• Be sure to review and
comply with all building
and safety codes
• Disconnect and lockout
the power supply

4. Inspect Drive Elements
• Inspect and replace faulty
or damaged machine
elements such as worn
bearings or bent shafts

5. Relieve Belt Tension
• Loosen the drive take-up
and move the sheaves
closer together to facilitate
the removal of the old
belts and to insure
installation of the new
belts without damage

6. Inspect Drive Elements
• Sheaves should be
cleaned of rust and foreign
material

7. Inspect Sheaves
• Sheave condition and
alignment are vital to V-
Belt life & performance
• Never install new belts
without a thorough
inspection of the sheaves
• Look for worn groove
sidewalls, shiny sheave
groove bottom, wobbling
sheaves and damaged
sheaves

8. Select Replacement Belts
• Never mix new and used belts
on a drive
• Never mix belts from more
than one manufacturer
• Always replace with the right
type of belt
• Always observe belt matching
limits

9. Installing New Belts
• Place the new belts on the
sheaves and be sure that the
slack of each belt is on the
same side
• Do not force the belts on the
sheaves by using a pry bar or
by rolling the sheaves

10. Check Sheave Alignment
• Sheave should be mounted
as close to bearing as
possible to reduce overhung
load on bearing
• The straight-edge should
make contact at two distinct
points along the outside
perimeter of both sheaves
• V-Belt sheave alignment
should be within a tolerance
of 1/16” per 12” of drive
center distance

11. Sheave Alignment
Proper Parallel Horizontal Vertical
(Off-Set) Angular Angular
(Pigeon-Toed)
1
2
3
4
There should
be no gaps
between the
sprocket and
straightedge
at 1-2-3-4
The straight-edge should make contact at four distinct
points along the outside perimeter of both sheaves.

12. V-Belt Tensioning
• Proper tensioning is the
single most important
factor necessary for long,
satisfactory operation
• Too little tension will result
in slippage, causing rapid
belt and sheave wear and
loss of productivity
• Too much tension can
result in excessive stress
on the belts, bearings and
shafts

13. V-Belt Tensioning
Tension-Finder
• A simple method to assure
proper tensioning
• Easy and Accurate
• For use on individual belts
or V-Bands
• Should not be used with
aramid or glass cord belts

14. V-Belt Tensioning
Using the Tension-Finder
• Step 1: Install belts
loosely on the drive
• Step 2: Apply enough
tension to take the slack
out of the belts

15. V-Belt Tensioning
Using the Tension-Finder
• Step 3: Scribe a line on
the belt using the Tension-
Finder as a square

16. V-Belt Tensioning
Using the Tension-Finder
• Step 4: Place the Start
Slot over the line

17. V-Belt Tensioning
Using the Tension-Finder
• Step 5: With the line in
the Start Slot, attach the
spring to the belt
• For cog belts, the best
place for the spring may
be in the cog

18. V-Belt Tensioning
Using the Tension-Finder
• Step 6: Scribe a line at the
spring end of the Tension-
Finder. Use this line as a
reference point in case the
spring slips off the belt

19. V-Belt Tensioning
Using the Tension-Finder
• Step 7: Determine the
required slot for your drive
from the table. Then
keeping the Tension-
Finder snug against the
clip, tighten the belt until
the line has moved to the
designated slot.

20. V-Belt Tensioning
Using the Tension-Finder
• Step 8: Remove Tension-
Finder hardware from the
belt, tighten mounting
bolts and replace belt
guards. You’re ready to
start the drive!
• Warning!! Remove all
Tension-Finder hardware
from the belt before
starting the drive.

21. V-Belt Tensioning
Special instructions for Cog Belts
• Place the spring in a
cog groove

22. V-Belt Tensioning
Special instructions for Cog Belts
• Put a dot in the start
slot. Be careful not to
catch the pen in the slot
so you don’t pull the tip
out of the pen.

23. V-Belt Tensioning
Special instructions for Cog Belts
• Scribe a line through
the dot. The line should
extend across the width
of the Tension-Finder.

24. V-Belt Tensioning
Recommended tensioning slots for Tension-Finder
The recommended slot numbers will provide an
adequate level of belt tension on average drives. If
more tension is required go to a higher slot number.
For less tension go to a lower slot number.

25. V-Belt Tensioning
Using the Spring Loaded Tensiometer
1. Measure the span length of
the drive. Set the large “O”
ring at 1/64” for each inch of belt
span. For example, set the
large “O” ring 1/4” for a span
length of 16”, at 1/2” for a span
length of 32”, at 1” for a span
length of 64” etc.

26. V-Belt Tensioning
Using the Spring Loaded Tensiometer
2. Set the small “O” ring at zero and
press down the Tensiometer at the
center of the belt span.
A. On a single belt drive, depress the
Tensiometer until the large “O” ring is
even with the bottom of a straight
edge placed on the outside rims of the
two sheaves.
B. On a multiple belt drive, depress
the Tensiometer until the large “O” ring
is even with the top of the next belt.
Measure each belt in the drive. and
take the average reading of all belt
tensions.

27. V-Belt Tensioning
Using the Spring Loaded Tensiometer
3. Remove the Tensiometer, and
observe that the small “O” ring has
moved from its original setting at
zero to the number of pounds
required to deflect the belt to the
extent noted above.
4. Check this reading against the
value of Pmin and Pmax calculated
in Step 4 of the “Formula Method”
or from the Table.

28. V-Belt Tensioning
Strand Deflection - Formula Method
Step 1. Measure span length (t) in inches as
shown or calculate as follows:
Where:
t = span length, in inches
C = center distance, in inches
D = large sheave pitch diameter, in inches
d = small sheave pitch diameter, in inches
This method is based on the fact that the force required to deflect a given
span length by a given amount is related to the tension in the belt.

29. V-Belt Tensioning
Strand Deflection - Formula Method
Step 2. Calculate the deflection distance by: t/64 = deflection. Note that the
deflection distance is always 1/64” per inch of span length (for example, a 32”
span length would require a deflection of 32/64 or 1/2 inch).
Step 3. Calculate the static strand tension (Ts) per belt by the following formula:
Design HP x K
Ts = + Tc
Q x S
Where: K = value from the table depending on value of D - d
C
Q = number of belts/ribs on drive
S = belt speed, feet per minute / 1000
Tc = add-on tension allowance for centrifugal force, from Table.
Note: The value of
Ts is for an
individual V-belt.

30. V-Belt Tensioning
Strand Deflection - Formula Method
Step 4.
Calculate the recommended minimum & maximum deflection forces (P), in pounds:
Ts + Y (1.5 x Ts) + Y
Pmin = Pmax =
16 16
Where:
Ts = Static strand tension (from Step 3)
Y = Constant from Table 30

31. V-Belt Tensioning
Strand Deflection - Formula Method
For drives using only one belt, and at least one shaft is free to turn, use
the following for the deflection forces (P):
Ts + tLr (1.5xTs) + tLY
Pmin = Pmax =
16 16
Where: t = span length, inches (from step 1)
L = belt pitch length, inches
Y = constant from Table

32. V-Belt Tensioning
STEP 5 Using a Tensiometer apply
force to ONE belt of the drive,
perpendicular to the span at its mid-point.
Measure the deflecting force being applied
when the belt has been deflected the
distance calculated in Step 2 (use an
adjacent belt as reference point; on single
belt drives, use straight edge or taut string
across sheaves). The measured force
should be between the values of Pmin and
Pmax calculated in Step 4. If the measured
force is outside these values, adjust center
distance to increase or reduce tension, and
repeat above procedure. On multiple belt
drives an average of readings on each belt
is recommended.

33. V-Belt Tensioning
NOTE: If new belts are being
installed for the first time, it is
permissible to tension as much as
1.33 x Pmax to allow for initial
stretch and seating in the grooves.
STEP 6
During the first 24 hours of
operation, it is advisable to repeat
the procedure in Step 5 at least
once.

34. V-Belt Tensioning
• Operate the drive for a few minutes to seat the belts in
the sheave grooves. Observe the operation of the drive
under the highest load condition (usually starting). A slight
bowing of the slack side of the drive indicates adequate
tension. If the slack side remains taut during the peak
load, the drive is too tight.
• Check the tension on a new drive several times during
the first 24 hours of operation, by observing the slack side
span.

35. V-Belt Tensioning
• Keep the drive free of foreign material which might cause
slippage or damage to the belt and sheave surfaces.
• If a V-Belt slips, it is too loose. Increase the tension by
increasing the center distance.
• Never apply belt dressing as this will damage the belt and
cause early failure.

36. V-Belt Tensioning
• Excessive tension can be
even more detrimental
than too little tension not
only on the belts but also
the bearings and shafts.
• Indicators of excessive
tensioning may be
repeated belt breakage,
excessive vibration,
overheated bearings,
whipping or bent shafts

37. V-Belt Tensioning
Elongation Method
• Because belt elongation is
related to the tension causing
it, tape-measured lengths,
both slack and tight, can be
used to obtain proper Vee-
Band tension.
• Note: The Tension-Finder
is based on the elongation
method.

38. V-Belt Tensioning
Elongation Method
STEP 1 Check sheaves to make sure they are properly
aligned and that the grooves are not excessively worn (they
should not be dished out more than 1/64”).
STEP 2 Decrease the center distance until the Vee-
Band(s) can be easily slipped into the sheave grooves.
Forcing the belts on can damage the load-carrying cords
and cause premature failure.
STEP 3 With the Vee-Band(s) still on the drive at no
tension, tape their outside circumference (slack O.C.).

39. V-Belt Tensioning
Elongation Method
NOTE: If you are tensioning a used belt, decrease the
center distance until there is no tension on it; then tape the
outside circumference.

40. V-Belt Tensioning
Elongation Method
STEP 4 Find the required static tension (Ts) per individual
strand (rib) using the formula:
Design HP x K
Ts = + Tc
Q x S
Where: K = value from table depending on D-d
C
Q = number of belts
S = belt speed, fpm/1000
Tc = add-on tension allowance for centrifugal force (See Table)

41. V-Belt Tensioning
Elongation Method
STEP 5 Find a range of recommended Static Strand
Tensions:
Lower value = Ts (from Step 4)
Upper value = 1.5 x Ts
STEP 6 Calculate minimum and maximum elongation band
lengths for use in tensioning drive:
a. From table, find length multipliers corresponding to the
lower and upper values of Ts in Step 5.
b. Multiply the slack O.C. found in Step 3 by the multipliers to
find the minimum and maximum elongated band lengths.

42. V-Belt Tensioning
Elongation Method
STEP 7 Increase the drive
center distance until a tape
measurement of the bands O.C.
is between the two values
calculated for elongated band
lengths in Step 6(b).
STEP 8 Re-tension as
required. A new Vee-Band may
lose tension rapidly during the
run-in period & will probably need
re-tensioning. A Vee-Band that
has been on a drive for some time
may also require re-tensioning
due to tension decay from normal
use and wear.

43. www.CarlisleBelts.com
www.c-rproducts.com
sales@c-rproducts.com
Tel: +44 1327 701030
Fax: +44 1327 701031
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