Question

Consider the following statements regarding a high speed in line engine with identical reciprocating parts with cranks spaced to give equal firing intervals

1.   All harmonic forces, except those which are multiples of half the number of cylinders, are balanced

2.   Couples are balanced if the engine is symmetrical about a plane normal to the axis of the crank shaft.

3.   In a four cylinder in-line engine, second and fourth harmonic forces are unbalanced whereas in a six cylinder in-line engine, second fourth and sixth harmonic forces are unbalanced.

         Of these statements

         (a) 1, 2 and 3 are correct

         (b) 1 and 2 are correct

         (c) 1 and 3 are correct

         (d) 2 and 3 are correct