Page 37 - ABS150Mutipurpose(1)

Belt Tensioning Instructions
Timing Belt
HTB, Standard and Metric timing belts should be installed to
fit pulleys snugly, neither too tight nor too loose. The belt’s
positive grip eliminates the need for high initial tension.
When a belt is installed with a snug but not overly tight fit,
longer belt life, less bearing wear and more quiet operation
will result. Overtight belts can cause early failure and should
be avoided. With high torque a loose belt may “jump teeth”
upon startup. If such occurs, the tension should be increased
gradually until satisfactory operation is achieved.
To properly tension a timing belt, place belt on pulleys and
adjust takeup until the belt teeth mesh securely with the pul-
ley grooves. Measure belt span “t”. Then tighten belt so that
it deflects 1/64-inch for every inch of belt span when a force
as specified in the table below is applied to the top of the
belt. For belts wider than two inches, a metal or wooden
strip 3/4 to 1-inch wide should be placed across the belt
between it and the tester to prevent distortion.
The following range of deflection forces are normally ade-
quate for drive installation. Actual installation tension
required depends on peak loads, system rigidity, number of
teeth in mesh, etc.
Timing Belt Tensioning Deflection Force Table
HTB 8MM
(8mm)
HTB 14MM
(14mm)
MXL
(.080-in.)
XL
(1/5-in.)
L
(3/8-in.)
H
(1/2-in.)
XH
(7/8-in.)
XXH
(1-1/4-in.)
20mm
30mm
50mm
85mm
40mm
55mm
85mm
115mm
170mm
1/8-inch
3/16-inch
1/4-inch
5/16-inch
1/4-inch
5/16-inch
3/8-inch
1/2-inch
3/4-inch
1-inch
3/4-inch
1-inch
1-1/2-inch
2-inch
3-inch
2-inch
3-inch
4-inch
2-inch
3-inch
4-inch
5-inch
2 to 4 lbs
3 to 6 lbs
7 to 11 lbs
11 to 19 lbs
5 to 11 lbs
8 to 17 lbs
14 to 27 lbs
20 to 40 lbs
30 to 60 lbs
1 oz
1 - 1-1/2 oz
2 oz
2 - 2-1/2 oz
2-1/2 oz
3 oz
3-1/2 oz
7 oz
11 oz
1 lb
2 lbs
2-1/2 lbs
4 lbs
5-1/2 lbs
8-1/2 lbs
7-1/2 lbs
11-1/2 lbs
16-1/2 lbs
9 lbs
14 lbs
20 lbs
26 lbs
Belt Width Deflection Force Belt Pitch
Multi-Rib Belt Deflection Force Table
J
J
J
L
L
L
M
M
M
1.32-1.67
1.77-2.20
2.36-2.95
2.95-3.74
3.94-4.92
5.20-6.69
7.09-8.82
9.29-11.81
12.40-15.75
0.4
0.5
0.6
1.7
2.1
2.5
6.4
7.7
8.8
Belt Cross Section Small Sheave
Diameter Range
Force “F”
Lbs. Per rib
V-Belt & Multi-Rib Series
V-belt tensioning adjustment can be made using a tension
gauge or other type spring scale, using the following pro-
cedure. After seating the belts in the groove and adjusting
center distance so as to take up slack in the belts, further
increase the tension until only a slight bow on the slack
side is apparent while the drive is operating under load.
Stop the drive, and using the gage, measure the force nec-
essary to depress one of the center belts 1/64-inch for
every inch of belt span (see sketch below). For example, a
deflection for a 50-inch belt span is 50/64ths, or 25/32-
inch. The amount of force required to deflect the belt
should compare with the deflection forces noted in the
chart below. Also notice for V-belts the deflection forces
vary from the initial “run-in” values which are greater
(reflecting higher run-in tensioning) to the “normal” values
for after the run-in period.
Measure the span length “t” as shown in the sketch above.
Standard V-Belt Tensioning Deflection
Force Table
Belt
Cross-
Section
A
AX
B
BX
C
CX
D
E
3V
3VX
5V
5VX
8V
Smaller Pulley
Diameter Range
(in.)
3.0-3.6
3.8-4.8
5.0-7.0
3.0-3.6
3.8-4.8
5.0-7.0
3.4-4.2
4.4-5.2
5.4-9.4
3.4-4.2
4.4-5.2
5.4-9.4
7.0-9.0
9.5-16.0
7.0-9.0
9.5-16.0
12.0-16.0
18.0-22.0
21.6-27.0
3.40-4.20
4.20-10.6
2.20-3.65
4.12-10.6
7.10-10.9
11.8-16.0
4.40-10.9
11.8-16.0
12.5-17.0
18.0-22.4
Run-in
(lbs.)
3-3/8
4-1/4
5-1/8
4-1/8
5
6
4
6
7-1/8
5-1/4
7-1/8
9
11-1/4
15-3/4
13-1/2
17-1/2
24-1/2
33
48
6
7
7
8
16
20
18
22
36
40
Normal
(lbs.)
2-1/4
2-7/8
3-3/8
2-3/4
3-1/4
4
2-5/8
4
5-1/4
3-1/2
4-3/4
6
7-1/2
10-1/2
9
11-3/4
16-1/2
22
32
4
5
5
6
8-12
10-15
10-14
12-18
18-27
20-30
Deflection Force
37
Belt Tensioning In
structions
Span Length
t
Deflection 1/64” per inch of span
Force at
center of
span
See Pg 7 for Tiger Values
Insides:JB-7 Broc. Revise 8/16/05 6/20/07 8:48 AM Page 35