Question Bank • QB_FM_067 NAT • 2 Marks

Section 2: Farm Machinery

Farm Machinery

Subtopic: Functional requirements, principles of working, construction and operation of manual, animal, tractor and renewable energy operated equipment for tillage, sowing, planting, fertilizer application, inter-cultivation, spraying, mowing, chaff cutting, harvesting and threshing

Question Statement:

A combine harvester has a threshing drum of $600\text{ mm}$ diameter. For threshing wheat crop, the recommended peripheral speed of the drum is $28\text{ m/s}$. Calculate the required drum rotational speed in $\text{rpm}$.

Answer Key:

891.27

Step-by-Step Solution & Explanation

Peripheral speed $v_p$ of the threshing drum is: $v_p = \frac{\pi D N}{60}$ Where: - $D = 600\text{ mm} = 0.60\text{ m}$ - $v_p = 28\text{ m/s}$ - $N$ is drum speed in $\text{rpm}$ Rearranging for $N$: $N = \frac{60 \times v_p}{\pi D} = \frac{60 \times 28}{\pi \times 0.60} = \frac{1680}{1.88496} \approx 891.27\text{ rpm}$
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