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D-178

Installation/

Tensioning V-Drives

V-BELT DRIVES

Installing A Drive

Here are a few suggestions to keep in mind when installing

the drive:

1. Use a matched set of belts.

2. Clean oil and grease from the sheaves; remove any rust

or burrs from the sheave grooves.

3. Shorten the center distance of the drive until the belts

can be put on the sheaves without forcing.

4. Make sure that the sheaves are correctly aligned, that the

shafts are parallel, that there is clearance for the drive to

run and that the bearings have oil.

5. Work belts around in the groove by hand, so that the

slack of all belts is on the top, or slack of all belts is on

the bottom.

LIKE THIS:

(all slack at top)

OR LIKE THIS:

(all slack at bottom)

DO NOT APPLY THIS WAY:

(with slack at top and bottom)

Do not apply with the slack of some belts on the bottom

(see solid line) and the slack of others on the top (see

dotted line). Since V-belts will not slide in the groove,

belts thus applied will be injured when tightened for

operation.

Now tension the drive until only a slight bow appears on

the slack side of the belts when they are operating.

6. In a day or so, when the belts have had time to seat in

the grooves, re-tension the belts.

Tensioning The Drive

General Rules of Tensioning:

1. Ideal tension is the lowest tension at which the belt will

not slip under peak load conditions.

2. Check tension frequently during the ﬁrst 24-48 hours of

run-in operation.

3. Overtensioning shortens belt and bearing life.

4. Keep belts free from foreign material which may cause

slip.

5. Make V-drive inspection on a periodic basis. Tension

when slipping.

All V-belt drives should be guarded in such a manner as to

comply with the Williams-Steiger Occupational Safety and

Health Act and with all state and local laws and the American

National Standard Institute (ANSI) safety code.

Test The Tension

If you want to check the tension in a conventional V-belt

drive, use the procedure below:

1. Measure the span length, t.

2. At the center of the span (t) apply a force (perpen-

dicular to the span) large enough to deﬂect the belt

⁄64″ for every inch of span length. For example, the

deﬂection of a 100 inch span would be

100

⁄64 or 1

⁄16

inches.

3. Compare the force you have applied with the values

given in Table 12. If the force is between the values

for normal tension, and 1

⁄2 times normal tension, the

drive tension should be satisfactory. A force below

the value for normal tension indicates an under-

tensioned drive. If the force exceeds the value for 1

⁄2

times normal tension, the drive is tighter than it

needs to be. A new drive can be tightened initially to

two times normal tension to allow for the normal drop

in tension during run in.

Installation and Take-up Allowances

After calculating a center distance from a standard pitch

length, make provision for adjusting the center distance as

in Table 13, to allow for installation of the belts without injury,

for tensioning, and for maintenance of proper tension

throughout the life of the belt.

Force

Deﬂection

⁄64″ per

inch of span

, t

D177 - D192 3/28/03 4:23 PM Page 178

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