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so the two control stations are close together in the middle of the boat. The engine room telegraphs are mounted conveniently on these ma- neuvering stands, and in general this control is arranged so that one man can conveniently maneuver both engines. Control is also possible by an operator at each engine. The design of the engines departs from the usual construction in that the joint between the base and the frame is carried up from the center line of the crank shaft to approxi- mately the lower end of the cylin- der liners. The base is of cast iron, and because of the height makes a very strong rigid member which as- sists materially in making a rigid engine and a rigid seating for the erank shaft. The main bearing sup- ports are all bored out at a single setting to insure a uniform height of all of the supports for the main bearing shells. The single thick- ness in all shells is of material bene- fit when replacing any shells if this should become necessary. Details of Engine Design The location of the joint between the base and the frame at the prox- imity of the lower end of the cylin- der liners makes it much easier to maintain an oil tight joint than it would be if this joint were located at the center of the crank shaft. The frame is a box-like structure into which. are inserted the removable cylinder liners. The main function of this frame is to form a rigid sup- port for the cylinder liners and to form a water jacket around these. The frame is bolted to the base by means of long studs which extend from the bottom of the frame down to the lower part of the main bear- ing supports in the base. This fea- ture puts the metal in the base into a state of pre-compression, and in this way, reduces the deformation due to the combustion pressure to a minimum. The crank shaft is a solid forging with the crank pins and main bearings bored out to form an oil passage. These holes are Engine room of the Tom Saw- yer, showing one of the two 8-cylinder die- sel engines, di- rect connected to propeller. Both engines controlled from one station Another visw of the engine room of the Tom Sawyer, Sl Oo Ae tath 0, switchbourd with power control system and automatic control devices. All auxil aries are electric driven bored relatively large which greatly reduces the weight of this shaft by removing metal which contributes only slightly to the strength of the part. The Kingsbury thrust collar is part of this shaft forging, and the Kingsbury thrust, itself, is part of the engine base. The cylinder heads are equipped with dual air and exhaust valves which permit a very high volumetric efficiency, and to a large measure accounts for the excellent fuel econ- omy and low exhaust temperature obtained with these engines. The heads are so designed as to get good water circulation around the _ ex- haust valve seats, and, therefore, frequent grinding of the exhaust valves is not necessary. The pistons are made of cast iron and are air cooled. They are prc- vided with a sufficient number of rings to seal the gasses in the com- pression space, and in addition these pistons have provisions for two oil wiper rings. These rings prevent the lubricating oil from creeping up from the crank chamber into the combustion space and fouling the piston rings and valves. The cam shaft is mounted in bush- ings which are pressed into the main frame. The cams are ground out from the solid forging. Two sets of MARINE REVIEwW—July, 1933 cams are provided for each cylin- der, one is for ahead, and the other set for astern. These two sets of cams are joined together by sloping surfaces, which permit the cam shaft to be moved endwise during maneu- vering without removing the cam- rollers from the cams. The actual endwise shifting of this cam shaft for maneuvering is done by means of air rams which are mounted on each end of the cam shaft. The air for these rams is controlled by the reversing handwheel. The fuel in- jection system consists of ‘‘Bosch’’ pumps and nozzles. The fuel pumps are mounted on a separate pump body which is bolted to the side of the frame at the middle of the en- gine. The fuel pump cams are so made that a single cam suffices for both ahead and astern operation. Lubrication of Main Engines The engines are entirely enclosed and are completely lubricated py the pressure system. This includes lubrication of the push rods and rocker arms which operate the air and exhaust valves. Oil is supplied under pressure by means of an oil pump which is mounted in the en- gine base and is driven by a gear from the main crank shaft. This pump forees the oil through a cool- er and then through an oil filter be- fore it enters the engine. The oil is led to the main bearings and through suitable drilled holes to the crank pin bearings and through the connecting rods to the piston pin bearings. The oil is also introduced into the push rods and _ lubricates the rollers and valve lever mechan- ism. The cam shaft is also lubricat- ed by this pressure system. Performance of the engines both during the shop trials and the dock and river trials indicate that they should have a long life with a high degree of reliability and a minimum of maintenance. Due to the rug- gedness and simplicity of design both the main engines and the aux- iliary engines are well suited for towboat service where dependability £7