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346 is kept constantly running through the filters in order to freshen the water, make up for leakage, waste, etc, S The basin can be pumped out in by 4 four hours 12-in. centrifugal THE MARINE REVIEW inertia to give an appreciable flywheel action resisting sudden variations of speed. Four motors drive the car- riage, one on each corner. The speed is controlled by electrically operated "brakes". Current from an "exciter" A COMPLETED MODEL OF A WARSHIP pump, electrically-driven. Two other pumps are also installed, and both electrically-driven. One is a 4-in. pump, connected with troughs on each side Of the basin just at the surface, by which the water can be "scummed"'. The other is a three-throw plunger pump, having a capacity of about 75 gallons per minute. This is used for drainage and piped to take the water from inside or outside the basin as desired. The troughs on each side already referred to, which are of steel, about 12 in. square in sections, and just be- low the usual working level of the water, act very efficiently as absorbers of wave disturbances. In addition, there is at the-northern end of the basin, a "wave-breaker", consisting of a large number of square strips. of wood, set vertically at varying dis- tances apart. These in combination with the side troughs give entire sat- isfaction; any wave motion set up by a run of a model subsiding into minute ripples. Without wave-breaking appli- ances it would be a very lengthy op- eration to make trials at high speeds, as very long waits between runs would be necessary in order to allow subsidence of waves. The apparatus for determining the resistance of models is all placed upon the traveling carriage spanning the basin. This carriage weighs about 70,000 Ibs., and hence has sufficient READY TO BE TESTED IN THE. TANI generator at 110 volts is used to keep constant excitation in the field coils Of ine "motors. Curtent. from ihe same exciter is passed through the controlling rheostats on the carriage October, 1913 load. The generator armature is in series with the motor armature, so that all the. current developed at the generator passes through the motors, the voltage at the generators varying according to the amount of excitation of the generator fields, which is con- trolled from the carriage. The result in practice is to give the carriage accurate speed control and regulation. The maximum speed of which the carriage is capable is about 20 knots, developed in a run of about 200 feet. With such a heavy mass moving at this speed in a confined space it was necessary to devise the arrangements for stopping with the utmost care. A very powerful electrical braking ef- fect is obtained from the driving mo- tors, through the back current which they generate when the exciter current from the generator is shut off or re- versed. This enables the carriage to be stopped more rapidly than it is started, and in practice works very well. But this method of stopping could not be relied upon alone, since it would fail if the circuit is broken accidentally or by the automatic cir- cuit breakers in case of an overload. This method also necessitates proper manipulation on the part of the per- Sou Operate. the carriage, It<1s necessary for this reason to have at least one method of braking which shall stop the carriage in the mini- mum possible distance, be independent of the electric current, and require no manipulation, on the part of. the person operating the carriage. Fric- FRAMEWORK OF THE MODEL OF A PROPOSED CRUISER and also around the field coils of the main generator. The main generator is kept running at constant speed by a _ governor, which limits variation of speed within, 1% per cent from no load to full tion brakes closed by hydraulic pres- sure were finally chosen. At the north end of the basin is a Pair of iron strips on each side, securely anchored at one end to the main concrete supporting walls of the