Great Plains CTA4000 Operator Manual - Manual (Page 21)

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Section 3 Adjustments
2/1/06 CTA4000 Air Drill Implement 160-269M
Great Plains Mfg., Inc.
Section 3
Adjustments
Seeding Depth
The CTA4000 has double-disk openers with depth-con-
trolling press wheels mounted on floating opener frames.
This system provides accurate depth control and seed
placement over uneven terrain. The following is an intro-
duction to the basic seeding components and how they
work.
Openers
Each opener is mounted on a floating opener frame.
Opener bodies are staggered for easy soil flow. All open-
ers pivot on a common axis to maintain consistent depth
as the opener frames follow contours. A spring provides
the down pressure necessary for opener double disks to
open a seed furrow. The spring allows openers to float
down into depressions and up over obstructions. Individu-
al openers can be adjusted to account for tire tracks.
Press Wheels
A press wheel is attached to the rear of each opener.
Press wheels provide two important functions.
First, press wheels close the furrow and gently press soil
over the seed. To provide consistent seed firming, press
wheels are free to move down from the normal operating
position. This maintains pressing action even if opener
disks encounter obstructions or hard soil.
Second, press wheels control seeding depth. To maintain
a consistent depth, the relationship between the bottom of
the opener disks and press wheel is upwardly fixed. The
upward stop is adjustable on each opener. The position of
the adjustable stop determines how deep seed will be
placed.
Opener Down Pressure
Opener down pressure controls opener penetration and
press-wheel soil firming. Use only enough down pressure
to cut the furrow and maintain proper soil-firming over
seed. Excessive opener down force will lead to premature
wear on opener components.
Hydraulic Down Pressure
There is one pressure-control valve for wing sections (1)
and one for center section (2). See Figure 3-1.
Figure 3-1
Pressure Control Valves
Set opener down pressure to 800 psi as a general starting
point. For most field conditions, adjust the hydraulic down
pressure between 200 and 1200 psi. Do not set opener
down pressure above 1600 psi. Refer to the following
chart for approximate force at the openers for a given con-
trol-valve setting.
IMPORTANT: Some tractors with load-sensing or con-
stant-flow hydraulics need a bypass valve, Great Plains
part number 810-400C, to operate the CTA4000. Fail-
ure to install the valve can cause major tractor damage.
Contact your Great Plains dealer to order the bypass
valve. Contact your tractor dealer to verify if a bypass is
needed. Before adjusting opener down pressure, set
bypass valve as explained under Load Sensing Hy-
draulics, Preparation and Setup, page 11.
Gauge
Setting
Pounds Force at Opener Disks
6-Inch Rows 7.5-Inch Rows 10-Inch Rows
200 PSI 87 92 99
300 PSI 96 103 113
400 PSI 105 113 128
500 PSI 113 124 142
600 PSI 122 135 157
700 PSI 131 146 171
800 PSI 140 157 186
900 PSI 148 168 200
1000 PSI 157 178 214
1100 PSI 165 189 229
1200 PSI 174 200 243
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