Duncan Uni-Seeder, Owner'S Manual

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18
Recalculating the Constant
It is especially important in these situations to check the rolling circumference of the groundwheel
when in the cultivated area to be sown, and if necessary, recalculate the constant and hence the
number of crank turns.
If there is a significant difference between the figure used for calculations in this manual, the constant
should be recalculated and hence the crank turns for those particular conditions.
Note - If a significant difference is found in the rolling circumference the H1 setting should also be
adjusted on the hectaremeter.
1 To recalculate the constant due to altered conditions or specific requirements use the formulae
detailed below.
2 To obtain the rolling circumference of the groundwheel 1/2 fill the seed/fertiliser boxes or simulate this
loading.
Mark the groundwheel of the drill at 90
0 to the ground and the point of contact on the ground. Move the drill
forward 3 revolutions until the mark on the tyre is again at 90 0 to the ground. Measure the distance along the
ground and divide by 3 to give the rolling circumference of the groundwheel.
Example of Calculation for Cranks Turns
Formula:
Crank Turns / Hectare = Area in Sq Metres x Constant
Working Width
The constant is dependent on the drive ratio and the effective rolling circumference of the groundwheel
High Ratio Constant
- For gearbox input sprocket on 15t and layshaft sprocket on 19t (High
Speed)
= 0,4114
Low Ratio Constant
- For gearbox input sprocket on 19t and layshaft sprocket on 15t (Low Speed)
= 0,2564
Example:
For 3,0 metre machine set on high speed
Crank Turns / Hectare = 10000 Sq Metres x 0,4114 = 1480 Turns
2,78m
For 1/40 Hectare = 1480 = 37 Turns
40
For 1/10 Hectare = 1480 = 148 Turns
10
Because the constant is affected by the effective rolling circumference of the groundwheel; if the
effective rolling circumference of the groundwheel changes due to it penetrating the ground to a different
depth than that used for all original calculations the formulae for calculating the constant are shown on
P14. Use new circumference of groundwheel as obtained by method 2 above.