3
Once the rate is set and the test is started, the switch
setting is ignored until the stop switch is pressed or a
limit switch is tripped.
Limit Switches – These switches are located on the
platform behind the water chamber.
Adjustment of these switches is made by loosening the
Phillips-head screws and moving the limit switch as-
sembly in the direction desired. The home position has
been set so that the load crossarm is in the middle of
the shear rings.
Note: The limit of travel of the drive shaft is dependent
on the limit switch settings. Do not operate the drive
motor with the water chamber disconnected because
this will make the limit switches inoperable.
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 LVDT 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 LVDT by raising or lowering the indicator
rod and holder so the tip of the LVDT 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 required weights to the weight
hanger. The consolidation result is read on the Digital
Readout Box.
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. Tare the shear load cell which is displayed on chan-
nel 1 of the digital readout box.
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. Tare the horizontal displacement LVDT on channel
2 of the readout box. To begin shear, switch the DI-
RECTION toggle switch to the left towards the LIMIT
light.
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. Load and Shear Displacement will be displayed
on channels 1 and 2 of the digital readout box and
transferred to an Excel le or the Direct Shear Data
Acquisition Software on the users connected com-
puter.
