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:
The flywheel of a hand operated chaff cutter with two cutting knives is rotated at 30 rpm and is connected to a worm gear assembly for driving the feed rollers. The number of teeth of the worm gear is 24 and number of starts (threads) of the worm is 2. If diameter of each of the feed rollers is 15 cm, the chaff length in mm will be
Options:
(A) 9.8
(B) 12.8
(C) 19.6
(D) 39.2
Official Answer Key:
C
Step-by-Step Solution & Explanation
The worm (2 starts) driving the 24-tooth worm gear advances the gear by 2/24 = 1/12 revolution per worm (flywheel) revolution — so feed-roller speed = 30/12 = 2.5 rpm.
Linear feed speed = π×D_roller×roller rpm = π×0.15×2.5 = 1.178 m/min.
Cutting frequency = knives × flywheel rpm = 2×30 = 60 cuts/min.
Chaff length = feed per cut = feed speed/cutting frequency = 1.178/60 = 0.01963 m = 19.6 mm. Answer: (C).
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