Question

In case of rubber roll huller, rollers

• A. Rotate at same speed
• B. Rotate at different speed
• C. Vibrate at same frequency
• D. Vibrate at varying frequency

Hint:

Rubber roll huller achieves $> 85\%$ dehusking efficiency with lowest broken grain percentage due to differential speed shearing.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Rubber roll dehusking machines use differential peripheral surface speeds between two counter-rotating resilient rubber rolls to generate a shearing force that removes the paddy husk.
Key Formula or Approach:
\[ \text{Speed Differential (\%)} = \frac{N_{\text{fast}} - N_{\text{slow}}}{N_{\text{fast}}} \times 100 \approx 20\text{--}25\% \]

Step 2: Detailed Explanation:
A modern rubber roll paddy huller consists of two rubber-coated cylinders rotating inward in opposite directions at different rotational speeds.
Typically, the fast roll operates at \(\approx 1200\text{ rpm}\) and the slow roll at \(\approx 900\text{ rpm}\).
When a paddy grain passes through the adjustable roll gap, the differential peripheral velocity creates a strong tangential shearing friction force across the grain surfaces, cleanly peeling the husk off with minimal brown rice kernel breakage.

Step 3: Final Answer:
Hence, the rollers rotate at different speeds, corresponding to option (B).