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Electric Collier Jupiter PAPER which attracted great A ing of the Society of Naval Architects and Marine Engineers was W. R. L. Emmet's paper on "Electric Propulsion on United States Collier Jupiter", which is abstracted as fol- lows fe Mr. Emmet's paper: on "Electric Propulsion on the U. S. S. Jupiter" was as follows: i The contract for propelling machin- ery of the U. S. collier Jupiter was awarded by the government to the General Electric Co. in June, 1911. The designs had been made during ~ the previous year when it was ex- pected that the ship would be built in a private yard. The ship was built at the Mare Island navy yard, and was put in commission Sept. 15, 1913. Since that time she has made a num- Ger of trial funs in San "Francisco bay and at sea, but she has not yet had her official trials. | The Jupiter is a very large vessel of about 20,000 tons displacement, and is designed to carry about 12,000 tons of coal and oil. The length of her deck over her cargo space is occupied by a line of derricks, which must add considerably to the weight and wind resistance of the ship. She is a sister ship of the -col- liers Cyclops and Neptune. clops was equipped with reciprocating engines and has been in operation for some years. The Neptune was equipped with turbines connected to the propellers by helical gearing. The Jupiter is equipped with one turbine generating unit and two induc- tion motors, one driving each of the propeller shafts. There is also a board carrying switches and instru- ments. A comparison of the equipment of these three vessels is given by the following table: The character of the apparatus in- stalled in the Jupiter is all of a type commonly used in the electrical in- dustry and need not be described in detail here. There is only one feat- interest at the December meet- The Gy- | Mr. Emmet's Paper on This Sub- ject Provokes a Spirited Discussion ure about the generating unit which is different from the type of units ordinarily used for electrical purposes, that is, that the governor is so de- signed that it can be set to hold any desired speed through a wide range, the adjustment of the governor being normal method: of speed variation used in 'this vessel. The ship can also, if desired, be controlled by the throttle, so that the governor is sim- ply a convenience and in no sense a limitation. Windings of Generator The windings of the generator, which carry the alternating current, are on the stationary part and are insulated with non-combustible mate- rial. The generator drives its own ventilating air by powerful impellers attached to the ends of the rotor. This air is delivered from the top of the generator through a duct which connects to the space from which the fire room blowers take their air sup- ply. The heated air from the motors also passes out of the engine room through similar ducts. The revolving parts of motors are connected to water-cooled resistances through col- lector rings, and means are provided by which these collector rings can be short circuited so that the rotor circuits are closed upon themselves. Such a condition, with the resistances cut Out, ts-the normal state 'of ef- ficient operation, the resistances being used only for the purpose of giving a large torque in reversing. The ves- sel can be operated with the resist- ances continually in circuit. With this connection, the immediate movement of either motor in either direction is very convenient, and this method of operation is normally used in ma- neuvering in narrow waters or about wharves. The ship can, however, be maneuvered and reversed without the use of the resistance, and while this method has not yet been fully experi- mented with, it is thought that her reversal, even without the resistance, will be about as effective as that of : Cyclops. Jupiter Nept pie ete, One: 6 ge: 0.00 : ce Be 5600. oe Ae ngine or turbine speed at 14 knots......... 88 ©. p. m 2000. 1,250. Soperet ti. a. ot 14 knots,...........5 0. 88 : 110 -- 138 ee Weight driving machinery. tons, . 2.3.0.2. 280 156 Character driving machinery Cee sneer sree sen eee Steam consumption in lb. per s. p. h. hr... Speed maintained on 48 hr, trial . 14 (estimated) 14,6 knots 2 triple expansion 1 turbo-generator 2 turbines each and 2 motors 11.2 (tested) engines with gearing 13.9 knots vessels having existing types of equip- ment. Since the Jupiter apparatus was de- signed, a method of designing induc- tion motors has been developed which will give all the desired characteristics for reversal without the use of exter- nal resistance. Such motors will have squirrel-cage rotors, which are of a simpler character than the definite wound rotors now used. While the method of control and operation of the Jupiter is extremely quick and simple, the operations necessary with this new type of motor will be sim- pler still, With this new: method it will be extremely easy to accom- plish all the operations of speed con- trol or reversal of either propeller from the bridge if desired. a When the first tests of the Jupiter operation were made she had been lying at the navy yard dock for four months, so that her bottom was in a very foul condition. Her speed in that condition was something like 25 per cent below normal. This produced abnormal electrical conditions. since the low frequency made necessary the. use of higher magnetic densities than are desirable. Many of the conditions of these runs were very unfavorable. A large proportion of the crew were green men; in one fireroom watch a large proportion of the fireroom force were seasick. A great deal of boiler compound was used in the _ boilers, and the priming was excessive. The condensed water was much discolored by boiler compound, and water was at frequent intervals forced from the valve packings. Operation of Apparatus The operation of the apparatus dur- ing these runs was exactly in accord- ance with expectations. The turbine ran with a very perfect balance, and ran just as steadily in rough water as in smooth. The governor held its speed perfectly. The lifting of propellers to the surface at no time caused any perceptible speed variation. The only effect of such lifting of pro- pellers was a fall of current on the instruments showing a diminution of power delivered to the _ propellers. Examination of the turbine after sev- eral such runs had been made showed it to be in perfect condition, and free from rust, scale or dirt. After this period of preliminary