should decrease as the boom is raised to its safe operat-
transducer is to be calibrated for "zero" error at a 500
boom angle. Rig the machine with a single part of line
and put on a load approximately equal to maximum
If the percent capacity meter at any time goes
single line load, unless this exceeds the rating plate. If
above 100%, the bell should ring.
the load exceeds the rating plate, use a load just below
(10) Unlock the pendulum on the angle
that given on the rating plate. To calibrate the
transducer, remove the cover from the transducer box,
transducer for zero error at 500, the correct load radius
and check that it swings freely through 90. The angle
must be calculated as follows (see fig. 8-6).
(a) Determine the boo(m length c(n the machine.
determined and the spot marked on the ground,
(b) See figure 8-6 to determine the distance
recheck the level of the machine, raise the boom, pick
from the center of rotation to the center of the boom
up the load and boom the center of the load exactly over
foot pins (boom offset).
the spot marked on the ground. This will put the boom
(c) Determine the sheave radius by measuring
at a 50 angle.
from the center of the sheave pin out to the end of the
(11) Make the following adjustment while the
engine is running. Remove the cable from the angle
(d) The proper radius (R) is then equal to:
transducer box. Using an Ohmmeter measure the re-
R = Boom length (step (a)) x .6428 + Boom foot
sistrance from pins "S" to "L" in the end of the recep-
offset (step (b)) + Sheave radius (step (c))
tacle on the transducer enclosure (see fig. 8-7). Be sure
Drop a plumb bob from the center of rotation of the
the ohmmeter is rezeroed every time the scale is
machine. Mark this spot with a metal post. Measure the
changed. Rotate the transducer box, on the slotted
proper radius, corresponding to the boom length for
holes, to reduce the reading to a minimum ohmic value.
50 from the metal post to the end of the boom point
Swing the pendulum and the reading should increase in
sheave. Mark this spot on the ground. With the radius
either direction when properly calibrated. Absolute
Change 1 8-15