Question

In an epicyclic gear train, an arm carries two wheels ‘A’ and ‘B’ having 24 teeth and 30 teeth respectively. If the arm rotates at 100 rpm in the clockwise direction about the centre of the wheel. ‘A’ which is fixed, then the speed of wheel on its own axis is _____

(a) 20 rpm anticlockwise

(b) 25 rpm anticlockwise

(c) 180 rpm clockwise

(d) 225 rpm clockwise

The question was posed to me in a job interview.

Question is from Numericals on Estimation of Tractor Power in division Tillage, Disc Plough & Numericals of Farm Machinery

Answer 1

Correct choice is (c) 180 rpm clockwise

Easiest explanation: y=-100

X + y = 0

X = -y = -100

Speed of wheel B = Y – X \(\frac{Ta}{Tb} \)

= -100 * 100 * \(\frac{24}{30} \)

= -100-80 = -180

180 rpm clockwise.