The following text may have been generated by Optical Character Recognition, with varying degrees of accuracy. Reader beware!

52 quantity of lubricating oil used is also reduced. In the early diesel engines the cost of lubricating oil sometimes almost equalled the cost of the fuel oil consumed. Automatic lubrication, with consequent reduction in waste, has meant that it is possible to guarantee 1500 brake horsepower hours per gal- lon of lubricating oil, which is about one-fourth of that required by some of the early engines. While increased dependability of the diesel oil engine may be partly attrib- uted to improved design, better manu- facturing methods have also had an important share in bringing about this result. One of the troubles experi- enced in the early engines was in con- nection with crankshaft failures. Many engineers thought that this was due to the inherent characteristics of diesel engine operation, but later experience has shown that it was due almost en- tirely to lax manufacturing methods. Improve Crankshaft Manufacture Crankshaft manufacture is a met- allurgical problem and by the adop- tion of metallurgical methods it has been possible to produce crankshafts CONTROL SIDE OF SIX CYLINDER UNIT MARINE REVIEW This operation refines the metal through its entire cross section, which is not the case where steam hammer methods are used. Heat treatment is under the control of the laboratory and the treatment for each shaft is determined by the actual analysis of a bar taken from the shaft. Micro photographs show the grain structure both before and after heat treating and the physical and chemical characteristics are checked for every shaft. It would be possible to elaborate but the point to keep in mind is that LOOKING AFT—THE SMALL HANDWHEEL CHANGES THE SETTING OF THE GOVERNOR SPRINGS GIVING A WIDE VARIATION FOR STARTING which will stand up in service. In the marine diesel engine, which has been described here, the specifications for crankshaft steel call for pouring the ingot in a special mold, so that the metal runs in at the bottom and rises to the top. This top metal com- prises 80 per cent of the ingot and is cropped off and discarded. The in- gots are then heated in furnaces and the shaft is worked out into rough shape under a huge hydraulic press. OF SPEED CONTROL—THE LARGE HANDWHEEL IS AND REVERSING the modern diesel engine is dependable, not only from the standpoint of de- sign, but also because of the care which is taken in building it. As a result, cracking of cylinder heads and breakage of crankshafts and oth- er troubles have been eliminated. On account of this mechanical de- pendability, repair expense is very low. With the possibility of crankshaft breakage and cracked cylinder heads eliminated, there is not much else in February, 1926 the case of the two cycle airless in- jection engine which can go wrong. In fact, records of installation show in a great many cases that the repair expense has been under $100 a year over a period of several years. Will Not Become Obsolete One of the points which always comes up for consideration is the probable life of a diesel engine. This life has a direct relation to the de- pendability of the unit and it also rests upon a consideration of obsolescence. Mechanical equipment, such as steam EXHAUST SIDE OF THE SIX CYLINDER UNIT LOOKING AFT—THIS ENGINE IS BUILT IN TWO SIZES—360 HORSEPOWER AND 180 HORSEPOWER engines and motors do not wear out, but rather become obsolete because new types of equipment are brought out which are so much more efficient that it is no longer profitable to keep on using the original installations. The whole history of steam power devel- opment is full of instances where steam turbines and engines have only been operated three or four years and then have been replaced by more efficient machines. The diesel engine, however, is so nearly a perfect machine from a ther- mal efficiency standpoint that the room for improvement is not .very large. For that reason most of the improve- ments have been along mechanical lines to insure greater dependability in operation. A diesel engine therefore does not become obsolete and there is no need to replace it from that standpoint. Under reasonable conditions the en- gine should operate almost indefinitely and certainly an assumption of a life of 25 years is quite reasonable.