Abstract
1. Trapesoidal section furrow slices tilled with a triangular working plough have two merits, one is large exposed surface area and the other is large opening space.
2. The proper condition of furrow setting is as follows,
p=cosα/cos(δ-α)
where p is the ratio of breadth of plowing to tilth, α is tilting angle of share and δ is furrow angle.
3. The condition of maximum furrow surface is as next,
α=π/4+α/2
therefore p=cosα/cos(π/4-α/2)
4. Reference (2) indicates next conditions from point of view of furrow stability,
FE=FI and p=2sin(π/4-α/2) but this explanation is hard to understand.
5. The condition of maximum opening space is as follows,
cos(2δ-α)/cosδ=2sinα
6. Conditions of rectangular section furrow slices will be obtained by substituting 0 for α,
a) The proper condition of furrow setting is: p=1/cosδ
b) The condition of maximum exposed furrow surface is:δ=π/4
c) When these two conditions are realized simultaneously, δ=π/4 and p=√2
d) The condition of maximum opening space is:δ=π/4
