3
SECTION 2: SPREADER CALIBRATION
Two Items must be considered when calibrating a spreader. The first is the distribution pattern of the spreader. That is, the
pattern the product makes as It strikes the ground after being thrown out by the spreader's impeller. There are many factors which
affect the distribution pattern of a rotary spreader and some of them relate directly to the product. For this reason, we recommend
that the spreader be calibrated separately for every product to be applied. Spreader calibration should be checked at least once
a month, or more often when the spreader is used frequently.
The second item is the product application rate, that is the amount of product applied per thousand square feet. This is impor-
tant because over-application can be costly and may cause plant injury, while under-application will reduce the effectiveness of
the product.
A.
CHECKING THE SPREADER DISCHARGE HOLES:
Check the spreader discharge holes with the
operating lever in the closed position. If the discharge
holes are not fully closed, thread the upper nut on the
operating lever rod further up the rod. Tighten the
lower locknut and recheck. Repeat this procedure until
the holes are fully closed.
B.
TO ACHIEVE A UNIFORM DISTRIBUTION PATTERN:
The accurate method for checking pattern uniformity
is to lay out shallow boxes or pans in a row on a line
perpendicular to the direction of spreader travel.
Eleven boxes or pans, two inches high placed on one-
foot centers will provide accurate calibration. To
conduct the test, begin with the remote and third hole
slide plates completely open and set the calibrating
slide at the suggested approximate setting. Make
three passes over the boxes, pushing the spreader in
the same direction each time. The product caught in
each box is then evaluated to determine the
distribution pattern. Weighing the product in each box
Is the most accurate, but a simpler method Is to pour
the contents of each box into a separate small vial or
bottle. Then set he eleven vials or bottles side-by-side
in order. This makes the pattern variation quite visible.
• To reduce the amount of discharge to the right side
(operator's right) partially close the remote slide plate
using the remote cable lever and repeat the test until
the distribution pattern is uniform.
• To reduce the amount of discharge to the left side
(operator's left) loosen the knob and partially close
the third hole slide plate and repeat the test until the
distribution pattern is uniform.
C.
TO ACHIEVE THE CORRECT APPLICATION RATE:
The approximate spreader settings printed on the
product label should only be used as the initial setting
for calibration. Set the calibrating slide at this
approximate setting. Using the collection boxes or
pans, make a single pass over them to determine the
effective pattern width. The effective pattern width is
twice (2x) the distance to the point where the rate
drops by one-half the average rate at the center.
Example: If the product In the vials from the center
boxes averages two inches in depth, count out to the
vial which has one inch of product. If this is the fifth
vial from the center and the boxes were on one-foot
centers, the effective pattern width is ten feet (2 x 5
ft.).
Knowing the effective pattern width (ten feet),
measure out a lineal distance to equal 1,000 sq. ft. (10
ft. x 100 ft. = 1,000 sq. ft.). Weigh 20 Ibs. of product
and place it in the spreader hopper and spread it over
the distance necessary to equal 1,000 sq. ft. (100 ft.).
Then weigh the product left in the hopper and subtract
this amount from the amount with which you started.
The result is the application rate for this product in
pounds per 1,000 sq. ft. that your spreader is currently
adjusted to disperse. Adjust the calibrating slide as
needed and repeat this procedure until the correct
application rate is achieved.
D.
TO USE THE CALIBRATION GAUGES:
The calibration gauges provide a series of “steps”,
numbered in 1/32-inch increments, that will allow you
to “fine-tune” the spreader. Once you have calibrated
your spreader for the product chosen, open the
operating lever and insert the calibration gauges until
you determine which step fits tightly into one of the
open holes in the hopper bottom. Record that step
number for future reference when using that product.
You may choose to set other spreaders for application
of the same product by adjusting the main slide plate
to that calibration gauge step. This will provide
consistent settings for all of your spreaders. To
recalibrate your spreader after a period of use, adjust
the calibrating slide to the “S” position. Open the
operating lever and insert the even-numbered
calibration gauge into one of the open holes in the
hopper bottom. Close the operating lever and let the
main slide plate on the underside of the hopper make
contact with the number ten step on the calibration
gauge. Move the calibrating slide back toward the “A”
position until the bottom of the slide makes contact
with the calibrating rod. If your spreader is properly
adjusted, the calibrating window should be pointing at
setting “D” on the top of the calibrating slide. To
correct a variance, adjust the calibrating window by
loosening the machine screws which hold it.
E.
SPREADER OPERATION:
1.
Always push the spreader; do not pull.
2.
Push the spreader at a consistent speed (approximately
3 m.p.h. is recommended).
3.
Always close the operating lever before filling the
hopper.
4.
Be sure the screen is in place to prevent lumps or paper
scraps from plugging the holes in the hopper bottom.
5.
Always start moving forward before opening the
operating lever; close the operating lever before forward
motion is stopped.
6.
Hold the handle at a height that will keep the impeller
level.
7.
Empty the spreader after each use. Wash the spreader
thoroughly and allow it to dry. Keep the impeller clean.
8.
Lubricate all linkages with spray lubricant. Grease the
gears with general purpose gun grease.
