Question

Which of the following results in increased seed damage during mechanical threshing?
(A). Decreased concave clearance
(B). Decreased seed moisture content
(C). Reduced threshing cylinder diameter
(D). Increased feed rate

Choose the correct answer from the options given below:

• A. (A) and (B) only.
• B. (B) and (C) only.
• C. (A) and (D) only.
• D. (A), (C) and (D) only.

Hint:

To minimize seed damage: increase concave clearance, thresh at recommended moisture levels (typically 12 % to 15 %), and avoid running the machine empty (under-fed).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Grain damage in a thresher occurs due to mechanical impacts, high compressive forces, and abrasive friction within the threshing clearance.

Step 3: Detailed Explanation:
Let us evaluate each parameter:
(A)

Decreased concave clearance: Reduces the path space between cylinder and concave, increasing mechanical impact and shearing action on the grain, leading to higher seed damage.
(B)

Decreased seed moisture content: Drier seeds are brittle, lose elasticity, and easily crack under mechanical impact. Thus, lower moisture increases grain breakage.
(C)

Reduced cylinder diameter: For a given rotation speed, a smaller diameter results in a lower peripheral tip speed, which generally reduces impact force and damage.
(D)

Increased feed rate: A higher rate provides a cushioning effect as more crop material envelopes the grains, protecting them from direct metal contact and actually reducing individual seed damage.
Thus, only (A) and (B) contribute directly to increased seed damage.

Step 4: Final Answer:
The correct option is 1, which corresponds to (A) and (B) only.