In fig. 19 the sequence of events in the two cylinders, whose pistons are connected to cranks set at an angle of 180 degrees, is shown. In the diagram the circle represents the path of a crank-pin, and the piston is shown in its relative position. When at the top it is about to begin a downward movement, and an opposite movement when shown, at the bottom. It will be noticed that when the piston of the
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Fig. 19
first cylinder is on its first downward stroke (1) the piston of the second cylinder is on its upward stroke. Taking the sequence of the first cylinder from a to b (1) a charge is drawn in; from b to c (2) it is compressed in the combustion chamber; from c to d (3) the charge is ignited and a working stroke obtained; while from d to e (4) the burnt gases are expelled. In the second cylinder it will be noticed that the sequence is directly opposite to that in the first, and in order to make this clear
