Duncan EcoSeeder, Original Instructions Manual, Page: 24 / 81

22
Basic Calibration Procedure (Continued)
Calibration Deviations
Deviations Between the Calibration Test and the Actual Seed Rate
The most frequent cause for changes between the calibration test and the seed rate lies in the
flowing properties of seed during sowing. These changes in properties generally result from
reactions of the dressing agents to temperature, humidity or abrasion. These changes will
become even more obvious when the bottom flaps are incorrectly set. If the setting of these
flaps leaves too large a gap an uncontrollable additional flow of seed can occur during seeding;
especially when assisted by the drill bouncing, a condition not simulated while conducting the
calibration tests. For this reason the basic setting of the bottom flaps should be checked at
regular intervals.
Residues from the seed dressing on the bottom flaps and metering wheels can also influence
the flowing properties of the seed and thus the seed rate. In such cases a balance will occur
only after a period of time and it is recommended to repeat the calibration test to confirm the
seed rate after 2-3 seedbox fillings, nominally when the seed box is half empty. Only then will a
balance occur and the seed rate will stabilise.
Wheel Slip Deviations
It is always possible with rubber tyred drills in extreme ground conditions to get wheel slip. Not
normally a problem with cleated type tyres in good condition, but more so in the arable situation
with the less agressive tread patterns. The result: large differences between the calibration test
and the actual sowing rate, obviously less seed deposited than required. The number of crank
turns indicated on page 20 is correct in most circumstances other than those mentioned above.
To check number of crank turns for calibration
Should you require to check this in a practical way proceed as follows:
For an area of 250m
2
(1/40 Hectare), the travel distance for your machine is shown below. Place
the crank handle over the hexagonal drive dog on the gearbox. Move the machine forward over
the measured distance, counting the number of turns of the crank handle as you go. Using this
number of crank turns repeat the calibration.
Machine
Size
Travel
Distance (m)
Turns for 1/40
Hectare
Sowing Width
(m)
14 Run 120.3 29 2.079
16 Run 105.2 25 2.376
18 Run 93.5 22 2.673