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Q3. To undertake balancing calculations for a four-cylinder hydrogen-fuelled in-line combustion engine running at a maximum speed of 5000 rpm, the main moving parts are idealised to a set of rotating masses, and a set of reciprocating masses. The four rotating masses, each of 2 kg, are at a crank radius of 50 mm. And the four identical reciprocating masses, each of 1 kg, have effective piston rod lengths of 150 mm. The phasing of the crank arrangement is: 1, 4, 3, 2, phased 90° apart, where the axial distance between each unit is 100 mm. The engine is fitted with a flywheel (closest to Unit 4) such that the mass centre of the rotating assembly lies in the plane through which the vertical centre axis of Cylinder No. 3 passes. i) In terms of primary and secondary forces and moments, determine the state of external balance of the engine. ii) To eliminate the primary yawing moment, balance masses are to be fitted on the crankshaft in the planes of Cylinder No. 2 and Cylinder No. 4, at the crank radius. Find the magnitude and relative angular positions of the pair of balance masses needed.

Fig: 1

Fig: 2

Fig: 3