Humboldt H-3220A Benkelman Beam - Manual (Page 4)

Adjust the stop screw (#34), turning it in a clockwise direction, so the
indicator does not bottom out when it’s in the up position. This point is
reached when the indicator reading does not move while the operator is
turning the stop screw.
4. After adjustment, turn the stop screw (Fig. 1, #34) in a clockwise direction,
until approximately .004 of movement is registered on the indicator. Now
tighten the lock nut against the frame. Recheck the adjustment, making
sure the indicator is not bottomed out when the frame beam is moved to the
extreme top of its travel. (When using a dial indicator turn the stop screw
(Fig. 1, #34) in a clockwise direction, until approximately two divisions
of pointer movement are shown on the dial indicator.)
5. Turn the thumb wheel (Fig. 1, #45) until the bottom of the leveling screw
(Fig. 1, #49) is about 1-½" below the bottom of the frame.
6. Moving the Benkelman Beam to a smooth, hard, level floor, extend the
beams to their full length, locking them into position with the locking studs.
7. Note the relative position of the front follower tip (Fig. 1, #18) and the
dial indicator pointer. If the front follower tip is not on the floor, loosen the
lock nuts (#25) and screw the front leveling feet into their supports until the
indicator is about in its mid range. Making sure the two leveling feet are an
equal distance from the bottom of the frame, use the lock nuts to lock them
in place. The indicator is now in its correct location, protected from bottom-
ing damage.
8. Before carrying the Benkelman Beam with its beam extended, it is
suggested that the operator remove the dial indicator from the indicator
collet. This practice will prevent any shock movement, prolonging the
accuracy and performance of the dial indicator.
Operation
A. Place the unit 4.5 feet (1.37 m) behind the point of the pavement to be
tested. Insert the probe beam between the dual tires of the vehicle,
centering it so the tip of the probe rests on the test point.
B. Turn on the vibrator system and adjust the position of the rear support
(Fig. 1, #45) so the dial indicator is set to zero. Lock the rear support in
place with its locking screw (Fig. 1, #3). If additional adjustment is necessary,
it can be done by repositioning the height of the front legs. Zero the digital
indicator or note the dial indicator reading.
C. Drive the test vehicle forward at the test speed, recording the maximum
dial indicator reading as the vehicle advances.
D. After the vehicle has stopped (approximately 25 feet or 7.62 m in front of the
test point), record the final dial indicator reading.
E. Turn off the vibrator system.