Great Plains 3P806NT Material Rate User Manual
Page 21
Great Plains Manufacturing, Inc.
Native Grass Rate
19
2011-10-21
151-143B
14. Calculate the area rate at current drill settings.
Weigh metered seed, and subtract the initial weight
of the container. Divide this number by SampleRows
(the number of cups measured, typically 3). Multiply
by the number of openers (which is less than 13 if
using alternate spacing)
15. If the measured rate is within 3% of your desired field
rate, no further adjustment is necessary. Skip to
step 21.
The rate just measured is used to locate a new setting in
the Native Grass Cup Rate tables on page 20.
16. Calculate the revolutions needed for the target field
rate. Multiply the calibration revolution rate by the
ratio of desired to measured seeding rate. Divide the
rate just measured by the cup revolution rate (from
the tables) at the current drill settings.
17. Find this number (or the closest number to this) in
the drive setting chart. This gives Drive Type and
Native Grass sprocket sizes. If the setting needed is
below 50 revs/ac, the Rate Reduction kit is required.
18. Set the new Drive Type at the gearbox lever.
19. Remove the access panel at the right end of the
Native Grass box, and exchange the current Driven
sprocket for the new one (from the storage tree at
drill front).
20. As necessary, exchange installed sprockets at
gearbox with those from the Rate Reduction kit (see
instructions in kit).
You may want to repeat the calibration procedure if your
results vary greatly from the seed rate chart.
21. Remove the crank from the jackshaft and store it on
the stob.
22. When drilling, check the amount of seed you are
using by noting the acres drilled, amount of seed
added to drill, and the level of seed in the box. If you
suspect you are drilling more or less seed than
desired, and you have accurately calibrated the drill
to you seed, you may need to change your sprocket
arrangement to compensate for your field conditions.
Note: On older model drills, if all sprocket combinations
result in rates higher than desired, a Seed Rate
Reduction kit (202-580A) is available.
For example, GrossWeight of containers & sample is:
13
pounds
The NetWeight (pounds) is:
8.5 = 13 - 4.5
The PoundsPerSeedCup per acre is:
2.83 = 8.5
÷
3
The PoundsPerAcre is:
36.8 = 2.83 x 13
PoundsPerSeedCup
NetWeight
SampleRows
----------------------------------
=
PoundsPerAcre
PoundsPerSeedCup
13
×
=
NetWeight
GrossWeight
EmptyContainer s
( )
–
=
In our example, the 36.8 lbs/ac rate is 115% of the
desired 32 lbs/ac rate, or 15% high. An adjustment is
indicated.
For example:
Drive Type 2, 20T Driven, and no Rate Reduction is a
cup shaft rate of:
139 RevolutionsPerAcre
The FinalRevs shaft rate needed for the target rate is
120.8 = 139 x 32
÷
36.8
FinalRevs
RevolutionsPerAcre
TargetRate
PoundsPerAcre
-------------------------------------------
×
=
For example:
The closest setting to 120.8 revs/ac is:
120 (found in the Standard rate table)
which is a configuration of:
Drive Type: 2
Driven Sprocket: 23T