Metric Problems

The process used for estimating costs is the same for both the SI and US Customary systems. When estimating the costs for the metric system substitute the appropriate costs. Appendix V provides the parameters needed to calculate draft using the ASABE equation. An example follows for the SI system.

Problem: A chisel plow equipped with 5 cm wide shovels is used for primary tillage in a wheat field. Depth of tillage is 15 cm. The chisel plow width is 13.7 m. The chisel shank spacing is 0.3 m. Plowing speed is 10 km/hr. The soil is a silt loam (medium texture). What is the drawbar power required to pull the chisel plow?

From Appendix V

Compute the number of tools (shanks)

wmach 13.7m wTool =-=-= 45.666 or 45 tools wtool spacing °.3 m

Calculate the draft in Newtons.

Df = Fi x [C1 + (C2 x V) + (C3 x V2)] x w x Td = 0.7 x [91 + (5.4 x 10) + (0 x 102)] x 45 x 15 = 68512.5 or 680,00 N

Calculate the drawbar power. Recall that draft is a force.

PDbkW =

60,000

The cultivator will require a tractor with at least 113 kW.

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