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370 sailing in ballast; and whether her bottom is clean or foul. The com- puting cams of the instrument can be changed as readily and as easily as the disks of a phonograph. Speed of Ship also Given The dial hands and distance coun- ters always turn forward, whether the propellers are turning forward or are reversed and the instrument indicates in which direction the propellers are turning. It can be located anywhere desired on the ship, or any number of instruments can be used, located in different parts of the ship. The use of a single switch will start and stop all the instruments in unison. The instrument is so designed that all parts are readily accessible. Con- struction of the instrument is strong and simple. There are remarkably few parts, no complicated or delicate parts and few wearing parts. All electric contact points are immediately accessible, and can be quickly and easily replaced. The instrument is quiet in its operation and has a specially designed water-tight case. The case cover swings on hinges and can be quickly and easily opened or closed, and is provided with a lock ot prevent tampering with the instru- ment. Two designs are furnished. The navigator’s log which is the complete instrument showing the revolutions of each propeller and the average revolu- tions of all the propellers, minute by minute; the direction of revolution of each propeller; and the miles trav- eled. The engine room log, which is a smaller instrument, shows the pro- peller’s revolutions, minute by minute, and the direction of revolution of the propellers. This instrument does not show the average propeller revolu- . tions, nor the mileage, as this infor- mation is not required in the engine room. Starting, stopping and resetting of the dial hands, of all instruments on a ship, is controlled by a: single mas- ter clock provided with electrical con- tacts. A water tight contact box is located near each propeller shaft. Each pro- peller shaft is directly connected to a shaft in its contact box which rotates with the propeller shaft. Electrical contacts on the shaft in the contact box operate magnetic motors in the log instruments which synchronize with the propeller shaft revolutions. The contact boxes also contain a set of one way gears so designed that they drive the contact shaft in one direction only, regardless of the di- rection in which the propeller shafts rotate. These one way gears also MARINE REVIEW control an electrical switch which op- erates propeller direction signals in the instrument. A direction signal for each propeller is provided. A main connection box is located in any convenient place on the ship. Cables containing the required num- ber of wires, are brought into this box from the clock and from each propeller contact box. From this connection box a main cable, contain- ing all the wires, is taken anywhere desired on the ship. Secondary con- nection boxes are located along the line of the main cable wherever it is desired to take off a branch cable to an instrument; the main cable end- ing at the last instrument. There are two sets of dials for re- cording the propeller revolutions; an upper set and a lower set. Each set has a dial for each propeller, and a dial to record the average revolu- tions of all the propellers. Each dial has six hundred graduations, each graduation indicates a propeller revo- lution. The hands of the two sets of dials operate alternately. During the first minute the hands of one set of dials (for example the upper set) will rotate; at the end of the minute the hands of the upper set. will stop, indicating the number of revolutions of each propeller and the average rev- olutions of all the propellers for the first minute. When the dial hands of the upper set stop, the hands of the lower set start to’ record the revolu- tions for the second minute. About four seconds before the end of the second minute, the hands of the up- per dials reset to zero. At the end of the second minute the hands of the lower dials stop, and the hands of the upper dials start to record the revo- lution for the next minute. Continuous Record of Revolutions The dial hands of the two sets al- ternately start, stop, and reset, con- tinuously, as long as the instrument is in operation. Thus the instrument records continuously, minute by min- ute first on one set of dials, then on ° the other set the exact number of revolutions of each propeller and the average number of revolutions of all propellers. There is no interval of time between the stopping of one set of dial hands and the starting of the other set of dial hands. The same electrical contact in the clock stops one set and starts the other set. The time during which each set of hands runs is the exact minute. The time is the exact cycle of a minute because the contact which starts and stops the dial hands, is operated by a shaft in the clock which rotates once a minute, thus insuring the recorc: October, 1925 ing by each set of dial hands during each exact minute without any fine adjustment. Other electrical contacts in the clock control the resetting of the dial hands to the zero mark, ready to start recording the succeeding min- ute. The alternation in operation of the two sets of dial hands, and the resetting of the hands, is accom- plished by the clock contacts acting through two unique relay switches in the instrument. The dial hands are reset by means of.coiled clock springs. A small synchronizing magnetic mo- tor has been developed which is used in the instrument to rotate the dial hands. The instrument is provided with one of these motors for each propeller shaft. Each motor is oper- ated by its propeller shaft, by means of the electrical contacts in the con- tact boxes. previously mentioned. These motors synchronize absolutely with the propeller shaft revolutions at any and all speeds, or with any sud- dent or violent changes of speed. Driven by Magnetic Motors These motors by means of a train of reduction gears and magnetic clutches, rotate the dial hands in syn- chronism with the propeller shafts; so that each dial hand advances one count for each revolution of its pro- peller. The gears, driven by the. mo- tors, rotate continuously and each dial hand is controlled by a magnetic clutch. At the beginning of each minute the magnetic clutches of one set of dial hands cause the hands to rotate with the gears. At the end of the min- ute these clutches release their dial hands, and the other set of hands are started by their clutches. When the dial hands are released by the mag- netic clutches they are held against any retrograde movement by means of ball clutches. To release the dial hands for reset- ting by the springs, the balls of the ball clutches are raised from operat- ing position by means of electro mag- nets controlled by the clock. The average revolution dial hands are likewise rotated and _ controlled, through differential gearing, driven by all the motors. In the four shaft in- struments the average dial hands may be operated to show the average revo- lutions of all four propellers, or of only two propellers. Directly over each pair of propeller revolution dials is located the direc- tion signal for that propeller. When the propeller is turning ahead, the word ahead shows in plain black let- ters. The instant a propeller re- verses its direction the word ahead