Humboldt H-2792 Hi-Low Detector - Manual (Page 2)

General Information
The Hi-Low Detector is a device used for detecting and marking the points on a roadway
surface that deviates from the desired level of grade. It is a precision-made straightedge,
for checking both concrete and blacktop slabs. Basically, the machine consists of an
I-beam body 10 to 16 feet long with riding wheels at the ends and a detector wheel
at the middle, so that the machine can be steered on the surface. The detector wheel,
located at the middle of the machine, detects any vertical deviation of the surface from a
straight line between the supporting wheels at the ends of the machine.
The vertical deviations are shown by a movable pointer over a visible scale. Markings can
be made on the surface using a special dye kept in a reservoir and release valve control
mechanism. The timing and location of the marking can be controlled through a cable at
the operator’s handle.
The Hi-Low Detector is shipped completely assembled except for attaching the
operator’s handle, rear steering rod, and dye release cable.
Assembly
1. Attached the handle and steering rod to the I-beam body.
2. Run the loose end of the dye marker cable through the guide bracket so that 7/16"
(11mm) of cable wire extends beyond the bracket.
3. After tightening the bracket, adjust the push collar on the end of the cable wire so
that it clears the control valve lever by 1/32" (0.8mm).
4. With this setting, the push collar should fully open the control valve when the dye
release lever on the handle is actuated.
5. Connect the rear steering rod to the front wheel assembly. This will enable the front
wheels to turn about 20° to the right or left.
Components
1. Front Wheel Lock: The front wheel can be locked in a straightforward position by
turning the spring actuated locking rod off the holding peg. With this rod in the
down or locked position, the front wheel is non-steerable as required when the
Hi-Low Detector is used for aligning forms.
2. Tire Scrapers: An adjustable tire scraper is mounted in front of each wheel and
preset to clear the wheel by approximately 1/32" (0.8mm). These scrapers prevent
mud and dirt from accumulating on the rubber-tired wheel, which would result in
inaccurate readings. After long periods of use, it may be necessary to reset these
tire scrapers to 1/32" (0.8mm) clearance on each wheel.
3. Aerosol-Spray Dye Marking System: Irregular surfaces are marked by aerosol-spray
dye. Upon receiving the visual indicator signals, the operator depresses a button on
the steering handle that controls the marking-dye discharge valve. Bright orange
dye sprays onto the irregular surface from a replaceable aerosol can that is mounted
directly beside the indicator wheel. A series of long, parallel dye streaks laid
down by repeated passes on the uneven area vividly marks high and low spots for
correction. Use of the non-clogging aerosol can for dye discharge eliminates mixing,
permits precision marking, and prevents waste.
Accessories/Replacement Parts
H-2790B Bell/Buzzer indicator SYSTEM. Powered by a 6-volt battery
H-2790D Replacement aerosol dye. Cartoon of 12, 12 oz. (340g) spray cans.