37-1-615 Page 48
FIGURE 7-28
FIGURE 7-29
29 FINDING SMALLEST MINUS READING – FIGURE 7-28. Hold the gear under clockwise pressure to
maintain metal-to-metal contact. Rotate the shaft counterclockwise two complete revolutions with
a wrench. (Do not rotate by moving the gear.) If at any time the indicator hand moves to the plus
side, reset at zero, and again rotate two complete revolutions. Notice the place of the smallest
reading (this is smallest figure on the indicator dial). Continue rotation until the smallest reading is
again reached and reset the indicator at zero. This is the closest clearance of rotors in this
direction of rotation. If the indicator pointer flutters at any time during rotation, check for burrs or dirt
on the rotors or gear teeth.
30. FINDING SMALLEST PLUS READING - FIGURE 7-29. Hold the gear under counterclockwise
pressure to take up all slack, and rotate the rotor clockwise two complete revolutions with a
wrench. Note the place of the smallest plus reading, and continue rotation until the smallest reading
is again reached and stop. This is the point of minimum interlobe clearance.
31. SETTING THE INTERLOBE CLEARANCE - FIGURE 7-30. The interlobe clearance is divided with
2/3 on the discharge side and 1/3 on the suction side. Hold the gear from turning. Move the shaft
counterclockwise with a wrench just enough to obtain 1/3 of the indicator reading obtained in
Step 29.
EXAMPLE: The minimum plus reading in Step 29 is +.018; move the rotor until the indicator reads
+.012. This divides the interlobe clearance with 2/3 on the discharge and 1/3 on the suction side.
FIGURE 7-30
FIGURE 7-31
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