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22 : MARINE REVIEW. [December 6, ELECTRIC STEERING GEAR. THE APPLICATION OF ELECTRICITY TO AUXILIARY MACHINERY ON SHIP BOARD-- DESCRIPTION OF A STEERING GEAR. The waste of steam in the auxiliaries of the modern steamship has recently been the subject of much serious thought and careful investiga- tion on the part of ship builders and ship owners. The fact, as shown by Mr. W. W. White, Past Assistant Engineer, in the Journal of the American Society of Naval Engineers, that a modern vessel like the United States cruiser Minneapolis was found to require 23 per cent. of the daily coal consumption to run the auxiliary machinery, demonstrates the necessity of improved practice in the construction and operation of these auxiliaries. One of the solutions of the problem has been found in the substitution of electric motors for the small engines, the current for these motors being generated with relatively large and economical steam en- gines located close to the boilers, The Electro-Dynamic Co.,*Philadelphia, appreciating the fact that electric transmission is especially adaptable to this class of work, has, for a number of years, been making a careful study of the subject. Its officers are the consulting electrical engineers for several of the large transatlantic lines, and the company has furnished the generating sets, ventilating mo- tors, forced draft motors, etc., for many of the ships recently built. In addition to these simpler applications, some of the more difficult prob- lems of ship practice have been»solved. The company's steering gear is one of the most successful electric steering gears now on the market. That this steering gear is a success is demonstrated by the fact that, after being carefully investigated by numerous experts, it has been speci- fied for the following vessels: Gromoboy, built in St. Petersburg for the Russian government. Osliabia, built in St. Petersburg for the Russian government. Pallada, built in St. Petersburg for the Russian government. Alexander III., built in St. Petersburg for the Russian government. Pobieda, built in St. Petersburg for the Russian government. Peresviet, built in St. Petersburg for the Russian government. Variag, built in Philadelphia for the Russian government. Retvizan, built in Philadelphia for the Russian government. Hull No. 312, built in Philadelphia for the International Navigation Co. Moreover, this steering gear has steered the famous Russian cruiser -Variag, speediest of her class, on her trial trip of July 26, 1900, with the 'remarkable results already noted in the Review. In addition to the feature of fuel economy, the apparatus has many other features of desirability. The device is thoroughly protected by patents, the patentee being Mr. M. Pfatischer, who has been chief engi- neer of the Electro-Dynamic Co. for many years. In the development of this steering gear, the company have been associated with the well-known -firm of Williamson Bros. of Philadelphia, makers of steering machinery of all kinds. For ships built in the United States 'Messrs. Williamson Bros. manufacture the mechanical details of the equipments. PRINCIPLE OF OPERATION. If we prepare two equal resistances and ¢onnect them in parallel to a source of electrical current, the current will flow equally in both + (m) AM _ Fig. 2. Elementary diagram. (Fig. 2). Suppose now we provide two swinging contact arms, one to make contact at different points on each resistance. If we connect these two arms by a wire with an ammeter M in the circuit, we shall find that as long as the two arms make contact at corresponding points on the resistances, no current will flow in the connecting or "balancing" wire. : 'If, however, we move the contact arm of B to a new position a cur- - rent will immediately commence to flow in the balancing wire, and will continue to flow until the arm S is moved to a new position correspond- ing exactly with the new position of B. The direction of the current in the balancing wire will depend upon which way the contact arm B is moved, and the volume of current will depend upon how far the arm is moved around the circuit. In the above description all electricians will recognize the principle of the Wheatstone bridge, very generally used in electrical measuring instru- ments of today. The peculiar adaptability of this principle to a steering gear will be quickly appreciated. If, instead ot an ammeter, we place in the circuit of the balancing wire an electric mo- tor capable of running either way, and connect the motor by mechani- ., cal means to rotate the contact arm S, current flowing through the bal- ancing wire will operate the motor until the position of the arm S cor- responds to the position of the arm B, when no current will flow, and the motor will stop. Any change in B will be followed by a similar change in S. 5 % sasinaee Fig. 3. Steering column. If this principle could be applied to the steering gear without the in- troduction of other elements, the problem would be a very simple one. For a number of reasons, however, this is not practicable, the principal reason being that the currents continually flowing in the resist- ances would be excessive. This, and many other difficulties, had to be overcome before a practical steering gear was devised. In the apparatus described below, it will be seen that the principle is applied, but modifi- cations have been made which overcome all difficulties in a simple and thoroughly practical manner. ' In the wheel house is a neat and substantial pedestal of brass sup- porting the wheel (Fig. 3). Within the pedestal is one of the resistances indicated in the diagram (Fig. 2), also a convenient form of contact plate and the sweep making contact thereon. Suitable gearing is provided so that the sweep is rotated by the wheel. This gearing is so proportioned that the wheel makes ten turns in throwing the rudder from hard- over to hardover. This pedestal is known as the steering column. Close to the helm is located a frame supporting another resistance with its con- tact plate (Fig. 4). The resistances in this column are placed in the frame with more space between them than in the steering column. This gives more thorough ven- tilation and facilitates inspection. A water tight case surrounds the upper part of the column and protects the contact plate. The illustration (Fig. 4) shows the column re with this case removed. The sweep of this tn rudder column is connected to the helm so Fig. 4. Rudder column. as to move as the rudder moves. The re- sistances of both the rudder and steering columns are supplied with current from the dynamos of the ship, or from an independent source. The sweep of the steering column is connected electrically to the sweep of the rudder column by a small wire. In the dynamo room is placed a motor-driven generator (Fig. 5) with an exciter attached to the same shaft. Fig. 6 shows the exciter driven by a separate motor. The fields of the exciter are in the circuit with the balancing wire, connecting the steering resistance and the rudder resis- tance. The motor, driving the generator and exciter, receives current from the dynamos of the ship. By the suitable arrangement and proportions of generator and exciter the effect of the small current flowing in the balancing wire is multiplied and sufficient power to drive the rudder motor is obtained. A motor, sufficiently powerful to turn the rudder under all conditions of service, is located in the stern of the ship and geared to the helm so as to move it in either direction, as required (Fig. 7). The apparatus indicated in Figs. 3 to 7, inclusive, together with the wires connecting the different devices, constitute the entire electrical equipment for steering a ship. The motor can, of course, be adapted to whatever method is preferred for securing and moving the rudder. The Wig. 5. Motor-driven generator. two cables which carry the current from the generator to the rudder motor are large enough to transmit the necessary power for moving the rudder; the remaining. wires are very small and few in number. The apparatus is subject to certain modifications to suit the requirements ex- isting on different ships. The best equipment can be determined after the conditions have been submitted to the company. For the Gromoboy, Peresviet, Pallada and Pobieda, the equipment indicated in the illustra- tions, already mentioned, is used, the exciter being mounted on the ex- tended shaft of the generator. For the Variag a steam engine: was sub- stituted for the motor to drive the generator. This arrangement is indi- cated in Figure 8 In some cases it is desirable to have the steering gear entirely inde- pendent of the other electrical apparatus of the ship. For such a case the exciter apparatus illustrated in Fig. 6 is coupled to the engine-driven generator (Fig, 8), and all the power necessary for steering the ship is taken from one engine. When such an equipment is used suitable pro- vision is made for uncoupling the exciter, and steering the ship with power from one of the lighting generators, in case of an emergency. Let us now consider how the apparatus operates. If the man at the wheel desires to change his course, he manipulates his wheel exactly as he would if it were connected directly with the rudder. The movement of the wheel varies the position of the sweep of the resistance in the steering column. This starts a small current flowing through the bal