THE GYROSCOPE FOR MARINE PURPOSES. 



Bv Elmbr a. Sperry, Esq., Member. 



[Read at the eighteenth general meeting of the Society of Naval Architects and Marine Engineers, held in 



New York, November 17 and i8, 1910.] 



The uses of the gyroscope at sea fall properly under four general 

 divisions: — First, in affording means for resisting and preventing rolling 

 of vessels or even rolling and controlling their motions at will; second, 

 its use as a marine compass; third, for holding automobile torpedoes to their 

 course; fourth, for artificial horizons in connection with observations at 

 sea. There are two other uses which may be noted, that of recording the 

 motions of ships, and also the use of a small gyroscope in controlling the 

 oscillation of large active gyroscopes for purposes of preventing rolling 

 motions of the ship in their inception, and thus holding the ship against 

 rolling. The first three only will be treated briefly in this paper. 



Previous to the introduction of the gyroscope, there have been three 

 methods of steadying ships which afforded resistance to roll. "The oldest 

 steadying gear," as pointed out by Sir John I. Thorny croft, "was probably 

 the sail, though not originally intended for that purpose." He goes on 

 to say "that the extended use of steam is depriving passenger vessels of 

 this ancient steadying gear and causing increased rolling. For comfort 

 at sea, we require in our ships some device that will afford resistance to roll, 

 the need being an increasing one." 



Lord Kelvin has measured angles of roll in crossing the Atlantic of 

 40 degrees each side of the vertical, giving a total angle of motion in a single 

 roll of 80 degrees. 



The early work of Froude, his co-laborers and successors, in applying 

 athwartship tanks for prevention of rolling is well known. These, together 

 with rolling ballast and the great moving weight of Thornycroft himself, 

 all fall under the head of moving the center of gravity of the ship in attempt- 

 ing to balance the wave effect and prevent rolling. 



In the seventies bilge keels were introduced and their characteristics 

 are quite well understood, being effective only in heaviest rolling. Quite 

 large bilge keels were found to equal about three-fourths of the surface 

 hull and keel action for all angles of roll. The comparison between bilge 

 keels and one per cent, of water ballast in athwartship tanks is interesting. 

 Very large keels were found to be only one-eighth as effective at 3 degrees 



