GATE 2017 ME (ME2) – Question 42
A gear train has gears P, Q, R and S on parallel shafts. Q and R share a shaft. Their tooth counts are 24, 45, 30 and 80 respectively. P rotates at 400 rpm. S rotates at ______ rpm.
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Correct answer: 119 to 121
Explanation
Trace the actual gear contacts in the drawing: P drives Q, and Q drives S. Gear R is attached to the Q shaft but is not a separate intermediate contact on the P-to-S path. Therefore N(Q)=400·24/45 and N(S)=N(Q)·45/80=**120rpm**. Multiplying by an additional30-tooth ratio would describe a different train.