A right hand offset disk harrow is operating with front and rear gang angles of 15° and 21° respectively. The centers of the two gangs are 2.45 m and 4.25 m behind a transverse line through the hitch point on the tractor drawbar. The horizontal soil force components are: Lf = 3.1 kN, Sf = 2.65 kN, Lr = 3.35 kN, and Sr = 2.65 kN. The amount of offset of the center of cut with respect to the hitch point is
Options:
(A) 0.740 m
(B) 0.795 m
(C) 0.968 m
(D) 1.006 m
Official Answer Key:
A
Step-by-Step Solution & Explanation
Taking moments about the hitch point: the opposing side-force components (S_f, S_r act in opposite lateral senses on front/rear gangs of an offset harrow) create a net turning moment that is balanced by the couple of the draft (L) forces acting at the lateral offset, e, of the line of pull: e = (S_f·d_f − S_r·d_r)/(L_f+L_r) = (2.65×2.45 − 2.65×4.25)/(3.1+3.35) = −4.77/6.45 = −0.740 m (magnitude 0.740 m).
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