GATE AG 2013 • Q53 MCQ • 2 Marks

Section 3: Farm Power

Tractors and Power Tillers

Subtopic: Mechanics of tractor chassis

Question Statement:

A two-wheel drive tractor weighing 21 kN has a wheel base of 2.1 m. The CG of the tractor is 0.7 m ahead of rear axle centre. The tractor is pulling a single-axle trailer with gross trailer weight of 50 kN on a leveled concrete road while maintaining the line of pull parallel to the ground surface. The tractor hitch point is 42 cm behind the rear axle centre and 52.5 cm above the ground surface. During operation, 20% of the gross trailer weight is transferred to the tractor hitch point. If the coefficient of rolling resistance for each of the tractor and trailer wheels is taken as 0.04, and their ground reactions are assumed to pass through their respective wheel centres, the gross traction ratio developed by the tractor is

Options:

  • (A) 0.061
  • (B) 0.082
  • (C) 0.108
  • (D) 0.123

Official Answer Key:

C

Step-by-Step Solution & Explanation

From Q.52: dynamic rear-wheel reaction = 26.4 kN. Total dynamic weight on the tractor = tractor weight + hitch load = 21+10 = 31 kN, so dynamic front reaction = 31−26.4 = 4.6 kN. Total tractor rolling resistance = 0.04×31 = 1.24 kN. Total pull the tractor must develop = trailer's rolling resistance (1.6 kN, from Q.52) + tractor's own rolling resistance (1.24 kN) = 2.84 kN. Gross traction ratio = total pull developed/dynamic weight on drive (rear) wheels = 2.84/26.4 = 0.108. Answer: (C). Section 4 — Soil and Water Conservation Engineering

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