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56 great confidence in whatever that distance might be. The figures of actual results given below were sufficient to show that turbine ships were stopped from the moder- ate speeds ahead generally used in handling in practically the same, if not in less, time or distance than or- dinary twin-screw vessels of the same class, and -from higher speeds in not very much greater time or distance. It might be questioned whether the 'necessity of bringing a ship to rest from a high speed in the shortest pos- sible distance on a straight course was of common occurrence in actual sea- going experience. -In all cases where the authors. had been able to trace re- liable data the half diameter of the turning circle, or the distance run in the direction of the original course before the ship's head was turned through eight points of the compass, ' was less than the distance required to bring a ship to rest from a high speed, even with the engines con- tinuing to drive ahead; and if they were slowed or stopped, the: circle was of less diameter. In the year 1877 a committee, consisting of Lord Kelvin, W. Froude, James Napier, and Prof. Osborne Reynolds, was ap- pointed 'to study the behaviour of screw steamers when reversing the engines, and it was demonstrated in their report that "full speed astern" might often bring about a collision, whereas by steaming ahead and using the rudder, it might be avoided. As an instance, the turbine steamer Vik- ee 300 tt 8. UP and with a: dis- placement. of some 2,500 tons, when steaming ahead at 20 knots was found to have a turning circle 1,475 ft. in di- ameter, or about 4.2 lengths of the ship. Such a ship would require about 2% lengths to stop in when reversing the engines and maintain- handling her, . THe Marine REVIEW following figures might also be com- much faster than was required for pared: practical purposes. At least two tur- . t COMPARISON (¥ TURNING CIRCLES, AND DISTANCE REQUIRED TO STOP FROM HIGH SPEED. a 3 [23] < E a 7 a2 a - = eS Be o s i 4 as 5 ne SHIP AND TYPE, Bes ue Knots. Knots. Turbine ss. Viking, Chan- nel screw steamer.... 23.5 20° _ Turbine ss. Princess Eli- sabeth, Channel « screw Steamer ans. ot scone = 24 20 Turbine ss. Queen, Chan- : nel screw steamer.... 21.75 19 Turbine ss. Lubeck,* Siiall Cruiser jini es ss 23 22 Turbine ss. Destroyer... 28 27 Reciprocating ss. Nebras- ka, «battleship... 2. 6... «- 19 Reciprocating ss. Indiana, ee battleship ' a ; a Q B i & w 9 B x o & a 2 o 0 a i a o : 3 : fj % DISTANCE RUN BEFORE E : a STOPPING FROM SPEED g a = IN COLUMN 3, fs oe Feet Feet. Lengths. . Meo S: 1,475 pate i 1 45+ 690 2.0 120 16 780 2.5 Lee 12 ee 1,530 4.5 1 45 ke 900 7D 3.6 038) 16 1,050 Ce a ee ee 1,080 $50 *The figures for the Lubeck are given on authority of the Marine Rundschau, December, 1906. +This trial was made from full speed ahead. Data as to combined use of helm and engines showed even superior re- sults. For instance, the Calais and Dover steamers turned completely round, and changed from _ steerage headway to steerage sternway in wun- der 2 minutes. Reversing turbines had been fitted from time to time of such power as the conditions of service demanded. In recent turbine installations the ~revolutions astern attained at the moment of stopping the headway had been from 65 per cent to 80 per cent of full ahead revolutions in. the case of, ordinary three-shaft turbine steamers. Instal- lations with four shafts had. had astern turbines fitted to all shafts, the arrangement consisting of two turbines in series on each side of the vessel. The number of such installa- tions was still too small to enable them to make reliable comparisons as less distance than 2.5 lengths. The ing the course. It was, therefore, ev- to results. The question of speed un- ident that the ship's head could be der stern-way might be vety lightly turned through 90 degs. by combined touched upon, because if sufficient RESULTS OF STOPPING TRIALS FROM COMPARATIVELY LOW SPEEDS. : Speed Time ahead Distance run elapsed Ship and Type. before before stopping. before reversing. stopping. Knots. Feet. Lengths. M.S: Turbine ss. Queen Alexandra, river steamer..... 10 210 0.78 0 47 es Dieppe, Channel steamer....)....... 12 300 1.1 0 41 ef Princess Elisabeth, Channel steamer. 17 516 15 des 25 ee dupeck;? small critiser. 0.6 ec. on 5 165 O48 ee: = Pe Wisbeck, small "cruiser. <6. eee 3 9 360 OS et Wibeck, staall' cruisers, 6.005. oe 11 635 VB er ye Westuover, 400° ONS... . 68.6 sce ee 7 157 0.75 0°27 o Westrover, 400 tons..6.0 0. ies once 9 144 0372 0.223 a Wearcower, 400. tOnS ss cce cera eee ns 12 340 1.7 0 29 o Westover, 400) tOnS: i iiiec.cseces oes 17 560 2.8 0:33 Reciprocatins ss. Indiana, battleship............- 14.5 1.080 RO eens ra s Hamburg,*- small; cruiser..... 5 184 OA te ae as Hamburg, Small critiser... 2. 9 360 LOD: ee ee eS Hamburg, small cruiser..... 11 ' 590 Poe. *These figures are given on the authority of the Marine Rundschau, December, 1906. use of rudder and engines in much stopping power were given to the ship, she would be sure to run astern bine vessels had exceeded 16 knots under stern-way, viz., the German de- stroyer S125 and the Ostend-Dover serivce steamer Princesse Elisabeth, in the latter case the speed astern be- ie as high ds 603 per cent of . that reached ahead. _Much depended on the suitability of the stern lines for temporary use as a "bow." Reversing turbines originated with the one row of reversing blades used in the single radial flow turbine first fitted to the - Turbinia (1894), which exhausted, as in present practice, direct to the con- denser by the same passage as the ahead working blades. In the Viper and Cobra the reversing turbines were independent, but .in the next vessels, King Edward and Velox, the form now universally used in Parsons tur- bines was adopted, a parallel flow tur- bine being used, mounted on a pro- longation of the main low-pressure ahead spindle and situated in the ex- haust chamber. In four-shaft vessels with reversing turbines in series, the high-pressure reverser was built as an independent turbine (as in Viper and Cobra), while the low-pressure re- verser was of the ordinary type as above described. It might be thought that powerful reversing turbines would be desirable to enable the ahead rota- tion of the engines to be very speed- ily checked and reversed. As a mat- ter of fact this did not appear to be necessary, because so long as the re- versing turbine was revolving against the contrary flow of steam, the effec- tive steam pressure on its blades was very considerably greater than when running normally, thus forming an ex- tremely powerful brake. The amount of torque developed on the shafts was,