The final drive system of a tractor comprised a planetary gear drive. The ring gear has 70 teeth and is held stationary. Power comes into the sun gear which has 34 teeth and rotates clockwise at 100 rpm. Power comes out of the gear set on the planet carrier which drives the rear axle shaft. The speed of the rear axle in rpm is
Options:
(A) 32.7
(B) 47.0
(C) 54.4
(D) 71.4
Official Answer Key:
A
Step-by-Step Solution & Explanation
For an epicyclic (planetary) gear train with the ring gear fixed, sun as input, and carrier as output: N_carrier = N_sun × Z_sun/(Z_sun+Z_ring). N_carrier = 100 × 34/(34+70) = 100 × 34/104 = 32.69 rpm ≈ 32.7 rpm, matching option (A).
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