The Proper Number of Cylinders.

Progress, Volume I, Issue 5, 1 March 1906, Page 105

The Proper Number of Cylinders.

Without peering too far ahead into the realm of the turbine, some authorities state that the ideal engine is a two-cylinder one which shall run as smoothly as the four. It is not an impossible ideal, they say, but it cannot be regarded as a practical one at present, because no such engine has been made, and it is questionable whether it would be worth while to make one, because the only objection to fourcylinders worth mentioning is the extra complication. A two-cylinder engme which gave the same results as the four could scarcely be a simple, singleacting type. The question arises whether the three cylinder engine can be taken as a reasonable compromise between the two and the four. In regard to the three-cylinder engines a great deal of misunderstanding undoubtedly exists. Those who ardently believe in them say that they are better in every way than four-cylinder engines. Those who object to them imply that they are no good at all. 4s is generally the case, the truth lies midway between the two. For balance of reciprocating and revolving parts the three-cylinder engine has not been proved equal to a four, and when the distributing element of the explosion behind the piston is introduced, the four-cylinder is unquestionably the better engine, so far as absence of vibration and higher frequency of impulse are concerned. So far as smoothness of running is concerned, it may be said the more cylinders the better, as their turning effort of the engine becomes more and more nearly constant. On the other hand, it is found that the four-

cylinder engine is a wonderfully satisfactory compromise, because it gives much freedom from vibration at all speeds, and it is not unduly complicated. Undoubtedly six or more cylinders have certain advantages of their own, but these engines are far above the average requirements.

The question, therefore, is which is the better compromise, three cylinders or four The three-cylinder engine is the simpler. It is not quite so smooth in running and, of course, at any speed, it must propel its car with three blows or explosions, where in a four-cylinder car there would be four of the same effort, but of less individual intensity ; consequently, in this respect the three-cylmder engine must always be inferior to the four. This, however, in itself is not a great matter. Wonderfully smooth running has been obtained with one or two makes of three-cylinder engines, and while it might have been even better with four, the results were so good that the makers were justified m their contention that, so far as their particular engine was concerned, all average requirements were met by its excellence of running. There seems little doubt, however, that four or more cylinders will be used by those who, ignoring all other considerations, require the utmost possible smoothness of running, and this must remain the case till it is demonstrated that the three-cylinder engine is practically as good as the four.