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is of utmost importance. The engine crank case is kept dry by a Viking rotary pump driven from the propeller shaft by a roll- er chain and arranged for revers- ing operation through check valves. A vee belt driving wheel is mounted on the forward end of the crank shaft. Direct Connected To Propellers Each main engine is direct con- nected to a propeller shaft on which is fitted an inboard turning pro- peller 5 feet 9 inches in diameter with four Dyson fan type blades hay- ing a total projected area ratio of 0.68 and designed to absorb 500 prake horsepower at 300 revolutions per minute and to give the vessel a speed of eight statute miles per hour. The large area ratio is ne- cessitated by the large power to be absorbed, and the limited diameter due to shallow draft. Hach engine is provided with an extra large ex- haust silencer. An unusual feature of the elec- trical generating system is that variable speed generators are driven through vee belts from the main en- gines and are automatically con- trolled to maintain constant voltage between 700 and 1200 revolutions per minute in either direction of ro- tation and to automatically switch on or off with the proper voltage differ- Outboard pro- file, Tom Saw- yer. Develop- ment of tunnels to obtain shal- low draft based On previous ex- perience al UY 18 qe er fi att ential between the bus and the gen- erators. Hither one of the above gen- erators will operate on the main bus together with a 30 kilowatt auxiliary generator set while a 56 cell stor- age battery is ‘‘floating’”’ on the bus. The batteries supply current when the speed of the belted generators is too low for supplying it, and the standby diesel driven generator will be used only to keep the battery in a charged condition when excessive loads are applied in the harbor. Bach vessel is also equipped with one 45 brake horsepower, 30 kilo- watts, McIntosh & Seymour diesel engine driven generator set, with General Electric generator. The en- gine is of three cylinder, four cycle, trunk piston, mechanical injection, air starting type, of 5% inch bore and 9 inch stroke, turning at 760 revolutions per minute, and direct connected to a single bearing gen- erator. The generators referred to above, driven by belt connections from the main engines, are of 30- kilowatt capacity and 120 volts. These generators were also supplied by the General Electric Co. The switchboard with all power control switches and automatic con- trol devices was also supplied by the General Electric Co. and is equipped with Safety Car Heating & Lighting voltage regulators. The 56. cell storage battery is of Exide ironclad Quarters of the chief engineer on the towboat Tom Sawyer. All living quar- ters are com- fortable and convenient MARINE REVIEW— July, 19338 type with 286 ampere hour capacity at 8-hour discharge rate, supplied by Electric Storage Battery Co. The generators are all direct current. Automatie alarm signals are pro- vided for low jacket water pressure, low lubricating oil pressure and low condition of battery charge. Auxiliary Machinery, Equipment The Tom Sawyer and = sister boat Huck Finn are each equipped with latest design auxiliary machin- ery. Three heat exchanger units for cooling both jacket water and lubri- cating oil were supplied by the Alco Products Co. The 5 horsepower, electric motor driven raw water pumps, one for each heat exchang- er, were furnished by Allis Chalmers Co. One 7% horsepower electric driven stand-by jacket water pump of Goulds make is driven by a Gen- eral Electric motor. General Electric motors are also used to drive two 15 horsepower 2 stage, air compressors with inter and after cooling and automatic unload- ing valves. Each unit has the ca- pacity to supply air at 250 pounds per square inch pressure for 36 starts of one engine per hour. The air compressors were supplied by the Sullivan Machinery Co. There are six air storage tanks, each of 31 cubic feet capacity; also, one small auxiliary air storage tank. The American Engineering Co. supplied two 15 horsepower electric motor driven double barrel capstans and two 71% horsepower electric mo- tor driven gypsies. Both capstans and gypsies are driven by Diehl Mfg. Co. electric motors. Two 5. horsepower. electro-hy- draulic steerers were furnished by the Hyde Windlass Co., and are driven by Diehl motors. For the two-ton stern derrick there is one 3% horsepower electric driven double drum hoist of Lidger- wood Mfg. Co. with General Electric motor. Pumping equipment consists of one 8 horsepower electric driven bilge pump of self-priming type of Nash Engineering Co. make; one 10 horsepower centrifugal fire pump: made by Worthington Pump & Ma-