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In the Absence of Lights and Buoys, Positions Must Be Reckoned by Propeller Revolutions—Instruments Developed for Submarine Navigation O OTHER vessel is so de- N pendent upon the revolutions of its propellers to determine dis- tance traveled as the submarine. When running submerged, no buoys or land marks, taffrail logs or light ships are visible, and even the instinctive method of “sniffing the air’ is of no service. The navigator must rely solely upon the propellers to determine position: While the submarine is being developed rapidly, each year finding its engines more powerful and reliable, the brains of its designers have been so busy with the main features that accessories have been lost sight of. The structural features have been strengthened and the radius of action increased, but navigat- ing appliances have stood still until re- cently. Ships are being navigated to- day, with few exceptions, as they were 50 years ago, in spite of the progress of marine engineering. No naval com- mander, whose guns and other equip- ment were 20 years old, could go suc- cessfully into action against an ad- versary with -modern equipment. Yet he is compelled to maneuver and de- termine his position by the methods used in the Civil War. Recently a set of navigation. in- struments, _ built by the Cummings Ship Instrument Works, __ Boston, has been placed on the market. These _ instru- ments, while rela- tively new, have been installed on more than 20 VACUUM PUMP DRIVEN BY CHAIN ON PROPELLER SHAFT, WHICH ACTU- ATES THE REVOLUTION INDI- CATOR AND ENGINE LOG «+ AND GOVERNS THE STOP-CLOCK 3 \ from each _ shaft. These produce a vacuum in the pipe line when run- ning ahead, afd pressure when running astern. One revolution counter is fitted for each shaft and one for the average of the shafts, ing operated through one-way gears. A one hand telltale and an automatic stop- clock are also located in the engine room. In the navigating station are the Asreri Alead+ Sage the former be-. Nav! gal Ing Sfarion engine log and stop-clock and a revolu- tion indicator for each shaft. The one- way gears are a combination of gears which will drive the counter shaft in one direction only, regardless of the di- rection of rotation of the main shaft. This device makes the counter show the total revolutions made both in ahead and astern directions. There is no troublesome reciprocating motion, the entire gearing being of the continuous rotary type. The averaging counter of the engine room instrument is driven by positive gearing from the starboard and port counter shafts, and is designed to show the algebraic average of the other two. The telltale hand is also driven by the starboard and port counter shafts. It remains stationary when both engines are running together, but if either en- gine runs faster than the other, it in- dicates by its direction of rotation which engine is ahead. The number on the dial indicates the gain in revolu- tions. The stop-clock is designed on the principle of a stop-watch, but is much more rugged, there being two cycles in operation instead of the three in a stop-watch. Auto- matically starting from zero, the hand runs at the rate of one revo- lution per minute during a period of 100 revolutions. On . high speed boats a period of 200 revolutions is employed. It is American naval vessels of all classes, from bat- tleships to sub- marines. Dead reckoning by means of the "inside Diamerer o| of Tubing 00/n Ly “th eck Vive i A yor tk Pressure When Engines” CS AL & Ru LUHOQ. ASTCL then tripped. The elapsed time since starting: Ig; > OE course, the time required to make 100 or 200 revolu-_ tions, which cor- Cummings Co.’s engine log system responds to a fixed number of is based on the revolutions per average revolu- minute. As the tions of the pro- dial is graduated pellers, | whether directly in revolu- one, two, three or tions per minute four shafts are it shows the aver- used The sys- age revolutions tem includes two per minute of both sma ll engines for the Z corer CROSS-SECTION OF SUBMARINE SHOWING GENERAL ARRANGEMENT OF Joie d Sas SeNDS, one of INSTRUMENTS WITH REGARD TO THE SHAFTS AND NAVIGATING The and oe which is driven STATION € hand remains - 163