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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 important because
over-application can be costly and may cause plant injury, while under-
application will reduce the effectiveness of the product.
TO CALIBRATE A SPREADER, FOLLOW THESE
STEPS:
Check the spreader discharge holes with the operating lever in the
closed position. If the discharge holes are not fully closed, thread the
upper jam 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.
TO ACHIEVE A UNIFORM DISTRIBUTION PATTERN:
The accurate method for checking pattern uniformity is to lay out shal-
low 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 pattern slide completely open and set the rate control arm 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 pat-
tern. Weighing the product in each box is the most accurate, but a sim-
pler method is to pour the contents of each box into a separate small
vial or bottle. Then set the 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)
the pattern slide should be partially closed and the test repeated until
the distribution pattern is uniform.
TO ACHIEVE THE CORRECT PRODUCT APPLICATION RATE:
The approximate spreader settings printed on any product label should
only be used as the initial setting for calibration. Set the rate control arm
at this approximate setting. Using the collection boxes or pans, make a
single pass over them to determine the effective pattern width. The ef-
fective pattern width is twice (2x) the distance to the point where the
rate drops to 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 dis-
tance to equal 1,000 sq. ft. (10 ft. x 100 ft. = 1,000 sq. ft.). Weigh 20 lbs.
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 prod-
uct 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 dis-
perse. Adjust the rate control arm up or down as needed and repeat
this procedure until the correct application rate is achieved.
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 rotary spreader for the product chosen, open
the operating lever and insert the calibration gauges until you deter-
mine which step fits tightly into one of the open holes in the hopper bot-
tom. Record that step number for future reference when using that
product. You may choose to set other rotary spreaders for application
of the same product by adjusting the shut off plate to that calibration
gauge step. This will provide consistent settings for all of your spread-
ers. To recalibrate your rotary spreader after a period of use, adjust the
rate control arm to the "24" position. Open the operating lever and in-
sert the even-numbered Calibration Gauge into one of the open holes
in the hopper bottom. Close the operating lever and let the shut off plate
on the underside of the hopper make contact with the number 10 step
on the Calibration Gauge. Move the rate control arm back toward the
"6" position until the bottom of the arm makes contact with the shut off
plate. If your spreader is properly adjusted, the top of the rate control
arm should be at setting "10". To correct variances, remove the rate
control arm, place the bottom of the arm (up to the bolt hole) in a vise,
and bend either to the right or the left.
SPREADER TIPS:
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 walking 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 moving parts. Apply grease to the five grease fittings;
two in the axle supports, two in the gear support and one in the idler
wheel (if the idler wheel has a steel hub).
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