Question

Which of the parameter is affected by the peripheral speed of cylinder in thresher?

• A. Cleaning of grains
• B. Threshing efficiency
• C. Grain separation
• D. Aspirating efficiency

Hint:

Think about what actually knocks the grain loose from the ear as it passes the drum, not what happens afterward.

Answer 1

The Correct Option is B

Step 1: The cylinder (drum) peripheral speed is how fast the rasp bars or spikes on the rotating drum move, calculated as \( v = \pi D N / 60 \), where D is drum diameter and N is its rpm.

Step 2: This speed decides how hard the crop is struck as it is dragged between the rotating cylinder and the stationary concave. A higher impact rubs and beats the grain out of the ear or panicle more completely, so the peripheral speed directly controls how well grain is separated from the head, which is exactly what threshing efficiency measures.

Step 3: Cleaning of grains is the job of the fan and the oscillating sieves that blow away chaff and light trash, not the cylinder. Aspirating efficiency also belongs to the fan and air system. Grain separation from the straw mostly happens later at the concave grate and straw walkers, once threshing has already loosened the grain.

Step 4: So the parameter that the cylinder's peripheral speed governs is threshing efficiency, option 2. Too low a speed leaves grain in the ear, too high a speed starts to crack grains, both effects are about how completely the grain gets threshed out.