Which of the following statements regarding the geometric angles and operational characteristics of standard agricultural disc ploughs is/are CORRECT?
Options:
(A) The disc angle is the angle that the plane of the cutting edge makes with the line of travel, typically ranging between $42^\circ$ and $45^\circ$
(B) The tilt angle is the angle that the plane of the cutting edge makes with the vertical line, typically ranging between $15^\circ$ and $25^\circ$
(C) Increasing the disc angle increases the penetration capability of the disc in extremely hard soils
(D) Increasing the tilt angle up to about $25^\circ$ improves disc penetration by creating suction into the soil
Answer Key:
A, B, D
Step-by-Step Solution & Explanation
Analysis of disc plough geometric angles:
- **Statement A is correct:** Disc angle is measured between the disc cutting face plane and the direction of forward motion in the horizontal plane; standard range is $42^\circ\text{--}45^\circ$.
- **Statement B is correct:** Tilt angle is measured between the disc cutting face plane and the vertical plane; standard range is $15^\circ\text{--}25^\circ$.
- **Statement C is incorrect:** Decreasing the disc angle (making the disc plane more parallel to forward travel) increases penetration, whereas increasing disc angle increases the furrow width of cut and soil throwing action.
- **Statement D is correct:** Tilt angle provides vertical downward component of soil reaction (suction); increasing tilt angle from $0^\circ$ to about $20^\circ\text{--}25^\circ$ improves penetration.