DIESEL ENGINES.

Southland Times, Issue 20675, 22 December 1928, Page 16 (Supplement)

DIESEL ENGINES.

MR. RICARDO’S VIEWS. ' At a conference of the Institute of Civil Engineers recently held in England, one of the papers delivered was by Mr H. R. Ricardo, who dealt with the internal combustion engine. Some of the points from his paper, which are most comprehensive and interesting, are as follow:—Referring to the light high-speed Diesel engine which uses crude or heavy fuel oils and fires the mixture by means of its high compression, eliminating sparking plugs and electrical apparatus, Mr Ricardo said that it was (surprising how few technical defects have been encountered. But how far the saving in cost of fuel will compensate for the dirt and smell inseparable from the use of heavy oil yet remains to be seen. It is evident that if the Diesel engine were developed to an extent comparable to that of the petrol engine, its advantages in the way of lower fuel cost would soon disappear. To-day there is practically nothing to choose between the production cost of petrol and fuel oil, and the relative price is governed by demand, not supply. This seems a very important point considering that the chief claim made for this type of engine is the extremely low cost of the total fuel it uses. Some interesting figures are given on the weight of the various types of engine. The lightest Diesel engine yet constructed weighs approximately seven pounds per horsepower, while the average weight of such commercial high-speed Diesel engines as have yet been built is between fifteen pounds and thirty-five pounds per horsepower for powers from thirty horse-power to three hundred horse-power. The lightest engine yet made, namely the nine hundred horse-power Bristol “Mercury” aero engine, weighs exactly eleven ounces per horsepower, complete with all its auxiliary gear, while the average weight of the high-speed engine of to-day, as installed in motortrucks, is approximately ten pounds per horse-power, just half the weight of similar engines built ten years ago. It seems remarkable, considering the strides that, have been made, that there is so little difference between the engine of to-day and that of twenty years ago. It is really by purely detail design that the efficiency has been increased by more than 50 per cent and the engine speed by more than 120 per cent in that time. Twenty years ago the normal maximum output of an engine was approximately six horse-power per litre of cylinder capacity; ten years ago it has risen to twelve horse-power; and to-day it is well over twenty horse-power.