FOR MODELS: JGW, JGR AND JGJ SECTION 5 - MAINTENANCE
PAGE 5 - 22 1/01
Piston Rod Run Out
Check piston rod run out after installing a new unit, after relocating a unit or after any main-
tenance that could affect rod run out.
Verify that the crosshead guides are properly shimmed to level. Refer to “Procedure For Set-
ting and Aligning” on page 2-1. Verify that the crossheads are in direct contact with the bot-
tom guide. A 0.0015 inches (0.04 mm) feeler stock should not be able to be inserted more
than 1/2 inches (13 mm) at all four corners of the crosshead.
Position the dial indicator
1
stem against the piston rod, close to the packing case. Set the
indicator to zero with the piston toward the crank end. Readings are to be taken in both the
vertical and horizontal directions. When measuring vertical rod moment, upward movement
will be recorded as positive, downward movement will be recorded as negative. When mea-
suring horizontal rod movement, rod movement toward the auxiliary end of the frame, will be
recorded as a positive reading, movement toward the drive end of the frame will be recorded
as a negative reading. Copy Table 5-3 to record readings. Bar over crankshaft by hand and
record readings at mid-stroke and with piston at the head end.
Compare readings to Table 5-4.
If a vertical reading is greater than the maximum acceptable reading, the following proce-
dure is used to determine acceptability: With the piston at the head end, use feeler gages to
determine clearance at the top of the piston. On wear band pistons this clearance is over the
band. Feeler top clearance is divided by ()) 2 and then the following amount is subtracted:
(-)0.003 inches (0.08 mm) for JGJ Models and (-)0.004 inches (0.10 mm) for JGW & JGR
Models. Place a feeler of this calculated thickness under the bottom of the piston. Place the
feeler under the wear band on wear band pistons. This feeler should be long enough to stay
1. Use a 0.0001 inches (0.001 mm) increment dial indicator.
TABLE 5-3: PISTON ROD RUN OUT
THROW NUMBER: 1 2 3 4 5 6
VERTICAL
Piston @ CE000000
Mid-Stroke
Piston @ HE
HORIZONAL
Piston @ CE000000
Mid-Stroke
Piston @ HE
TABLE 5-4: MAXIMUM ACCEPTABLE PISTON ROD RUN OUT READINGS
DIRECTION
JGW & JGR JGJ
INCHES (
mm) INCHES (mm)
Vertical 0.0015 (0.038) 0.0010 (0.025)
Horizontal 0.0010 (0.025) 0.0005 (0.013)
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