Ground Drive - Calibration
Page
39
02/07
c.
Drive the seeder forward over the
cultivated ground in a straight line so
that the marked tyre rotates at least 5
times. You will need help to
determine the number of rotations ie.
One person drives the tractor the
other being the observer. The marked
tyre should be brought around so that
the mark is at the base of the tyre as
before.
d.
Using a long tape, measure the
distance travelled after the 5 rotations
of the seeder wheel. Distance will be
approximately 19 to 25 metres
depending on the seeder model.
e.
Divide this figure by the number of
rotations (5) to determine the actual
circumference of the wheel.
f.
Use the wheel circumference along
with the known sprocket ratio and
sowing
width
to
determine
the
appropriate number of calibration
handle turns as shown below.
500 x sprocket ratio
sowing width x wheel circ. = handle turns
Sprocket ratio:
1830 seeder = 3.198
(drive wheel to
1850 seeder = 3.457
calibration handle)
1860 seeder = 3.716
1880 seeder = 4.148
2120 seeder = 4.321
2150 seeder = 4.581
Example 1
Determine the correct number of
calibration handle turns to calibrate the
seeder. After 5 rotations of the drive wheel
in extremely soft conditions on an 1850
Series Seeder the measured distance
travelled is 21.50 metres. Implement
sowing width in this case is 13.75 metres.
Therefore the wheel circumference is:
21.5 metres
5 rotations = 4.3 metres (wheel circ.)
500 x sprocket ratio
sowing width x wheel circ. = handle turns
500 x 3.457 ratio
13.75 metres x 4.3 metres = 29.2 turns
EXAMPLE 2
Sowing width of 8 metres with an 1830
Air Seeder. After 7 turns of the rear wheel
of the seeder, a distance of 27.048 metres
was covered. Therefore the wheel
circumference equals:
27.048
7 = 3.864 metres
The number of calibration handle turns
to simulate 1/20
th
of a hectare equals:
500 x 3.198 ratio
8 metres x 3.864 metres = 51.7 turns
NOTE:
After this figure has been calculated
it is best to compare it with the figure shown
in the manual on page 56. The variation
should never be more than a couple of
handle turns different (approximately 7%).
If a large variation occurs re-check
your calculations. If you still find a large
difference between your figure and the
published figure please contact your
authorised dealer for further information.
Once the correct number of handle
turns has been determined it is simply a
matter of using ‘Method B’ to calibrate your
seeder.
Use your figure for the required
number of handle turns instead of step 2
(the published figure).
NOTE:
If you intend to use your own
calibration handle rotation figure and it
differs significantly from the published figure
(by more than 5%), you should also review
the wheel factor figure in the 2200
Surveillance Monitor.
