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through the turbine casing, glands are provided to prevent steam leaking out or air entering. These glands are of the combined steam and water sealed type. The water sealing is effective at all speeds above % speed. Sensitive Hydraulic Type Governor The steam chest is of the 4-valve au- tomatic type. The valves themselves are of the double seated poppet type mounted in parallel with the chest. These valves are connected to the gov: ernor operating pistons by means of a linkage. The secondary, tertiary and quaternary valve operating levers are provided with a tension spring which holds its adjacent valve closed until the preceding valve has been fully opened. The governor which operates the above valves is of the oil operated type ‘and depends for its operation on the variation in oil pressure produced by changes in speed of an oil impeller which is mounted on the turbine shaft. This makes a very sensitive and quick acting governing system. In the governor layout there is pro- vided an oil pressure relay which is connected through a small pipe to a control valve on the main control board. From this control valve a drain pipe is led to the oil reservoir. By changing the opening of this valve in the relay line the pressure on top of the relay may be adjusted, which means that the turbine can be set for operation at any speed from % to full speed and still be under the control of the governor at all times. At the forward or high pressure end of the turbine is mounted an auto- matic stop governor. This device is arranged so that it will function to cause the throttle valve to close and shut down the turbine in case of ex- cessive speed or in case of damage due to failure of the thrust bearing re- ‘sulting jin axial movement of the spindle. The throttle valve is of the oil operated spring closed type, ar- ranged to be held open by oil pres- sure. Thus, in case of failure of oil supply to the turbine, the throttle velve is automatically closed, shut- ‘ing off the steam. Each Generator, 10,200 Kilowatts Each of the two main generators is rated at 10,200 kilowatts, 4000 volts, 2660 revolutions per minute and is of the three phase, two pole type. The generator is similar in construction to the usual land type except of some- what different proportions. This is necessary in order to provide for the special characteristics required for ship propulsion which include such items as high inherent stability, large thermal capacity and operating below critical speed. In the generator frame construction, structural steel shapes are used throughout. These shapes are welded into form to give a very rigid frame of minimum weight. An unusual ar- rangement has been provided in that 40 an opening is arranged at the top of the frame, this being normally cov- ered but which can be opened to per- mit cooling air to discharge directly into the engine room in case the water cooler in the closed ventilating sys- tem should become inoperative. The stator core is made up of the best grade of segmentary steel lamina- tions, there being six segments per circle. Throughout the core, H-shaped spacers are used approximately every two inches to provide passages for ventilating air. Bach end of the machine is pro- vided with two end bells made from sheet steel, welded. The inner end bells enclose the stator end windings, while the outer bell provides the air space for directing the ventilating air. Labyrinth sealing glands are provided in the outer end bells to prevent ‘leakage of the ventilating air, since the machine is arranged with a com- Capt. K. A. Ahlin Commander of the S. 8S. President Coolidge plete closed ventilating system. Fans mounted on the generator rotor circu- late air through machine and through coolers mounted just below the gen- erator foundation. This arrangement of cooling eliminates the necessity for large ventilating ducts on the ship and reduces to a minimum the noise which usually results from air circulation in a high speed machine. The generator rotor is made from a one piece solid steel forging. Radial slots are machined in this forging to receive the field winding. As this rotor is of the ventilated type, addi- tional grooves are cut below the coil slots to form air passages. Also, holes are drilled through the rotor teeth so that air can flow radially from the ventilation under the wind- ings. The rotor winding consists of flat copper strap insulated from the slots MARINE REVIEW—November, 1931 with molded mica cells, and with built-up mica insulation between turns. A single entrance centrifugal type fan is mounted on each end of the rotor, this fan being bolted to the rotor end plate. The collector rings are made from high grade tool steel and are mounted on an extension of the rotor shaft, out- side the generator bearing. The prushes are carried in holders fas- tened to a supporting ring which is mounted on the outboard end of the pearing pedestal, | This entire col- lector ring and brush assembly is en- closed by a cast aluminum cover. For convenient measurement of stator temperatures, nine resistance coils are embedded in the armature winding and located so as to give the highest temperature obtained in op- eration. In order to protect against damage by fire, the generator is provided with sprinkler pipes in the end bells, op- posite the air gap. These pipes are connected up to a fresh water system with valves arranged for emergency use. Electric heaters are installed under- neath the stator end windings to pre- vent moisture from collecting during idle periods. There are two 750-watt heaters at each end of the machine. Synchronous Propulsion Motors The propelling motors are of the synchronous type, each rated 13,250 horsepower. They have 40 field poles, thus giving a speed reduction ratio of 20 to 1 between the main turbine and the propeller shaft. Thus the normal motor speed at full power is 133 revolutions per minute. The motors are of the self-contained two-bearing bracket type. The rotor is supported by two bearings, each being carried in a steel bracket which fits into a recess in the frame to which it is bolted. These motors are of the entirely fabricated type built up from steel plates and shapes by welding, the only castings used being the bear- ing housings and shells. These are the first synchronous mo- tors for ship propulsion of such large capacity to be built with fabricated rotor spiders. The design of spider worked out for this installation re- sulted in an extremely strong con- struction with uniform stress distribu- tion and with minimum weight. Each motor is separately ventilated by means of a motor driven propeller type blower which is mounted direct- ly in the air passage duct in the en- gine room trunk. This blower is ar- ranged so that it forms a part of the duct, thus requiring no foundation and insuring the minimum amount of space required as well as providing a very efficient blower. The driving mo- tor is of the vertical type and mounted just below the blower unit. The ven- tilating aid for the motors is taken out of the engine room and exhausted through the after funnel.