Which of the following statements regarding rotavators (rotary tillers) are TRUE?
Options:
(A) For down-cut rotation, the rotor blades push the tractor forward, reducing wheel slip
(B) Tilled bite length decreases when rotor rpm is increased at constant forward speed
(C) Specific energy consumption of a rotavator is significantly lower than that of a moldboard plow for identical soil pulverization
(D) Rotavator knives follow a trochoidal path relative to the forward moving frame
Answer Key:
A, B, D
Step-by-Step Solution & Explanation
- A is true: In standard down-cut rotavators, tangential soil reactions provide a forward thrust to the tractor.
- B is true: Bite length $L_b = \frac{v_f}{n Z}$, so increasing rotor speed reduces bite length.
- C is false: Rotavators consume higher specific energy per unit volume of soil cut compared to passive tools due to intense impact and multiple slicing.
- D is true: The combination of uniform linear translation and rotation generates a curtate cycloid / trochoid trajectory.