LINEAR VIBRATION
TESTING AND ADJUSTING
Balance Procedure
The following correction procedure applied to 1st order
vibration motion.
1.
The crankshaft must assume the same position
each time a balance adjustment is made. To assure
this identical location is assumed, position flywheel
to top dead center (TDC) of Number 1 cylinder. A
chalk mark or scribe across flywheel and coupling
plates will provide an easy reference during the
balancing operation.
2. Remove bolts holding generator coupling plates to
flywheel. Rotate generator rotor with plates
attached 90° clockwise while flywheel remains at
Number 1 TDC. Replace coupling plate bolts and
retest for vibration.
3. If vibration remains, again position flywheel at TDC
Number 1 cylinder, index generator rotor another
90 clockwise (total 1800), and retest.
4. If necessary, repeat Step 3 by rotating another 90°
clockwise.
5. Position coupling assembly relative to flywheel where
least amount of vibration occurred. If magnitude of
vibration remains unacceptable, add weight of 2 oz
(56.70 g) under any single coupling plate to flywheel
bolt. Flat washers can be used for this purpose.
Bolt must be sufficiently long to maintain at least 1
1/4 times the bolt diameter of thread engagement.
6. Observe vibration level and relocate weight 90
quadrant to identify where minimum vibration occurs.
7. Add additional weight at point of minimum vibration
identified in Step 6 until vibration level is no longer
diminished. In no case should more than 5 oz
(141.75 g) be added under any one bolt.
8. If vibration levels are still unacceptable, a local
vibration control specialist should be consulted.
LINEAR VIBRATION GUIDELINES
The following graph is for use with analyzed linear
vibration
motion.
The
graph
tables
apply
to
measurements made an the basic engine structure and
generator frame. It is not for component vibration.
Figure 8
Line A is to be as a guideline for units as installed, either
with or without mounting isolators. If the linear vibration
motion is at higher levels, vibration complaints may
occur from personnel discomfort and perhaps some
premature parts service.
Line B is the vibration motion limit expected on a bare
engine,
i.e.,
with
all
crankshaft-driven
equipment
removed, and the engine mounted on isolating mounts
where the mounted engine natural frequency is less than
one-half the exciting frequency.
107
