Great Plains 4336 DH Operator Manual - Manual (Page 29)

Great Plains Manufacturing, Inc. Table of Contents Index Operating Instructions 25
05/22/2012 Table of Contents Index 556-100M
Adjusting and Using Tractor Hydraulics
Depth Control
Refer to Figure 21
14. When you have machine level and set to the desired
working depth, set the depth stop on the depth stop
tube . This is located at the front of the machine. This
will maintain a constant depth each time after raising
and lowering machine.One full turn of the handle
will
change the depth approximately 1/4”. Turning the crank
clockwise 1 turn is a 1/4” shallower working depth. Turn
2 turns counter clockwise is 1/2” deeper working depth.
Note: Tires must remain on the ground at all times. Wheels
off the ground will induce high loads on level linkage
and hitch, causing premature wear and possible frame
failure.
Tractor Detents
15. After the depth stop on the tractor is set, in order to pre-
serve the life of the cylinders, it is important to properly
set the detent on the tractor. The 3000 and 4000 series
disk harrow is equipped with re-phasing lift cylinders.
These cylinders have a re-phasing port at the top of the
cylinder (end stroke). If the tractor flow rates and detents
are not set properly, extreme oil flow through these ports
can destroy cylinder seals causing internal leakage.
16. Tractors with timed detents (electric over hydraulic): The
flow on the tractor should be set so the disk will raise
from field position to full lift in approximately 3 to 5 sec-
onds which is about 10 gpm. Not 10 on the tractor indi-
cator (most new tractor can pump up to 30 gpm). More
important is the detent. Once the flow has been set, set
the timed detent so that it is 1/2 to 1 second longer than
it takes to fully lift the unit. If you set it less than this it will
not properly re-phase the cylinders. If you set it more
than this, you may be causing damage to the seals.
17. Tractors with Pressure Detents: Set the flow control so
the machine raises completely in approximately 3 to 5
seconds. Detent should kick out automatically at the end
of stroke. If detent kicks out prematurely, slow the flow
on the tractor. If the flow has to be slowed to the point
that the unit does raise in an acceptable time frame, the
detent pressure on the tractor may need to be
increased. Contact your dealer for information on how to
do this. If this problem still persists, contact the factory
service representative for other possible adjustments.
Do not try to adjust the valves on the disk harrow without
first contacting the factory service rep. Tractors with
pressure detents do not allow the system to “automati-
cally” re-phase at the top of the lift cycle. This must be
done manually. It is recommended that after every cou-
ple of trips back and forth across the field that the raise
lever be pulled back and held there 1-2 seconds after
the machine is fully raised. This will purge any air that
has been ingested into the system.
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2
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Figure 21
Depth Stop
41205
4
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