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Stop Switch – Momentary push button to stop the
motor.
Direction Switch – Momentary (spring loaded) switch.
After setting the desired shear rate, moving the switch
in the desired direction will initiate movement. This
switch will then become inactive until the stop button is
pressed, or a limit switch is activated. The left position
will move the water chamber to the left. It will continue
until the water chamber activates the limit switch. At
this time, the limit indicator light will be lit. The right
switch position will move the shear box to the right until
the home limit switch is made. See above note...
Home & Limit Indicators – Used to indicate the limit
of travel of the shear box.
Fuse – 4 amp SLO BLO fuse located in the cabinet
rear.
OPERATING INSTRUCTIONS
Read all operating instructions before performing a test
and refer to ASTM D3080 or AASHTO T 236 for com-
plete test procedures and calculations.
Set Up
1. Place the shear box into the water chamber and se-
cure the load cell shaft to the top of the shear box.
2. Tighten the two shear ring clamping knobs located
on the left side of the water chamber.
3. Install the counterbalance, Model HMA-735, if nec-
essary.
4. Tare the load cell by pressing the "Tare" button on
the digital readout.
5. Adjust the top cross arm and dial gauge so there is
1/8in gap between the cross arm and loading ball.
Align the cross arm pin so it is above the loading
ball. Make sure the cross arm is level.
6. Adjust the dial gauge by raising or lowering the in-
dicator rod and holder so the tip of the dial gauge is
resting on the cross arm pin.
Consolidation
The weight of the consolidation load arm with two up-
right rods lower cross arm and lower weight platform is
11.9lbs. The lever arm on the right side of the device
has been preset to a 10:1 ratio, select a consolida-
tion load and apply the requires weights to the weight
hanger. The consolidation result is read on the top dial
indicator.
Refer to ASTM D3080 for consolidation calculations.
Direct Shear
1. After consolidation phase is complete, add a small
seating shear load by adjusting the two knurled nuts
on the load cell support.
2. Adjust or zero the horizontal dial indicator.
3. Remove the two holding screws on the shear box
to separate the top and bottom sections. Adjust the
four adjusting screws on the shear box to set the
gap between the top and bottom of the shear box.
One full turn of these adjusting screws will give a
0.031in (0.78mm) gap.
4. Set the shear/strain rate with the thumbwheels on
the left side of the machine. Each number is set by
pushing the thumbwheel button, the rate is in inches
per minute (0001 = 0.0001 in/min).
5. To begin shear, switch the DIRECTION toggle switch
to the left towards the LIMIT light. Record shear
readings at the prescribed intervals.
6. The water chamber with shear box will continue to
move at the set rate until the limit switch is activated
or the STOP button is pressed.
7. At the test completion, switch the DIRECTION tog-
gle to the right towards the HOME light. Press the
stop button when Zero load is reached on the load
cell readout.
8. Remove the vertical load by removing the weights
from the Weight Hanger
9. The Shear Box can now be removed from the water
chamber and the sample can be inspected.
MAINTENANCE
Special care should be taken to see that the four roll-
er bearings between the water chamber and the base
slide track are properly cleaned and contain a slight
amount of oil during and after use. It is recommended
to cover the Direct Shear machine when not in use to
prevent dust buildup.
Empty the water chamber after each test to prevent soil
and sand buildup inside the chamber. The water can be
drained from the port, or the chamber can be removed
from the Direct Shear Machine for thorough cleaning.
ACCESSORIES
HMA-739 Shear Box Counterbalance
HMA-610 Direct/Residual Shear Data Acquisition
Software
3
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