Subtopic: Design and selection of machine elements – gears, pulleys, chains and sprockets and belts
Question Statement:
For smooth, continuous, and shockless power transmission between a pair of mating involute spur gears in a combine harvester transmission, the contact ratio must be:
Options:
(A) Greater than 1.0 (typically between 1.2 and 1.8)
(B) Strictly less than 0.8
(C) Exactly equal to 0.5
(D) Negative
Answer Key:
A
Step-by-Step Solution & Explanation
The contact ratio represents the average number of pairs of teeth in contact during engagement. To prevent tooth disengagement shocks and ensure uninterrupted motion transfer, the contact ratio must exceed 1.0 (standard commercial gearing is designed for 1.2 to 1.8).