2o6 ACTIVE TYPE OF STABILIZING GYRO. 



chronism or when their period is not adjusted to that of the ship and, when so 

 adjusted, then at each time the phase changes. In this connection it will be 

 of interest to note that the period of the ship varies with its speed. A change 

 of 30 per cent has been noted in one instance between period of a ship at 

 15 knots and that at o knots, thus showing that the period undergoes changes 

 from more than one disturbing factor. 



The interesting work of Dr. Schlick in connection with the passive type 

 of gyro was another effort in this same line which dealt with the motions and 

 necessarily periodic motions of the ship after they had been developed by the 

 actions of the sea, utilizing, as in the case of water tanks, the natural motions 

 on the part of the ship in developing reactions for the purpose of damping 

 oscillations of greater amplitude ; thus in both cases some motion is primarily 

 necessary. In the case of the original paper of Dr. Schlick, the accompany- 

 ing mathematical treatise by Dr. A. Froebel was in fact entitled "Schlick's 

 Gyroscopic RoUing Brake," the action being limited to the damping of roll 

 and the suppression of excessive rolling. In descriptions of all of this work 

 a favorite expression which is employed is that the "rolling was reduced 

 six-tenths to one-half," etc. 



It is to an entirely different method of operation that I wish to call your 

 attention, where the object has been to deal with individual increments or 

 energizations of the ship regardless of synchronism or any other relation they 

 may bear to the rolling period of the ship. By thus completely neutralizing 

 each energization at its beginning or inception the ship is prevented from 

 taking on or setting up motion. 



As was pointed out by me in a paper read before the Society two years 

 ago, each individual energization of the ship, regardless of its direction, 

 amount, or its relation to period, should be dealt with as it arises; in this 

 manner dealing with and counteracting forces which are acting on the ship, 

 as contradistinguished from damping the motion of the ship. The question 

 of distinguishing between damping motion and resisting it was a year later 

 quite distinctly stated by Sir John I. Thorny croft before the Royal Institu- 

 tion of Naval Architects and Marine Engineers at their London meeting. 

 Sir John says that the perfect apparatus must not depend upon synchronism 

 but must be entirely free from any synchronism between sea and ship, or 

 between the period of the ship and that of the stabilizing apparatus. "The 

 perfect stabilizer must act against the forces which are acting on the ship in 

 such a way as to always resist the effect of the sea in producing motion." 

 It has been found under service conditions that this is easily accomplished 

 and is of full effect long before the ship has had time to get her great mass 

 into the motion which constitutes rolling. 



