2o8 ACTIVE TYPE OF STABILIZING GYRO. 



present; that is, it is a constant drag in all weathers. The power for 

 operating the precession is trifling, only sufficient to absolutely control and 

 limit the precession movements at all times. This arises from the fact that 

 in stabilizing the constant tendency of the ship is to do precession-wise work 

 upon the gyro. This is fully borne out in practice as it is found that the 

 power required for the precession engine is almost nil, it being only sufficient 

 to control the implacement of the positive and negative energizations 

 delivered to the ship. 



It must be remembered that the weight of Thomycroft was specifically 

 seven times that of the water in the tanks. The gyroscope is ideal in another 

 sense, for with it we have the weight of Thornycroft greatly augmented as to 

 mass moment by the simple fact that it is in rotation, which constitutes a 

 multiplier of tremendous magnitude, even though the actual rotative speed 

 is comparatively low. 



That Thornycroft was correct in his line of attack on this problem has 

 now received emphatic confirmation. The effectiveness and mass moment 

 of his weight have been mightily augmented on the one hand while on the 

 other decreasing its gravity load upon the ship and at the same time never 

 shifting its position with regard to the ship or changing the center of gravity 

 of the latter in the slightest degree. If all these things had originally been 

 in the hands of our distinguished contemporary it is impossible to predict the 

 very great advance that the art of stabilizing ships would have by this time 

 achieved, as only last year he stated: — "I came to the conclusion twenty 

 years ago that it was possible to make ships perfectly steady." 



In connection with dealing with each individual increment, let us for a 

 moment again refer to Plate 79. As we trace the envelope of these curves in 

 their rise and fall, as they are near the center line where the phase is usually 

 shifted, there is always the first impulse of a new cycle, the one which sets 

 the cycle. Now if no cycle of rolling ensued we would have simply a suc- 

 cession of these beginnings, which will naturally be of various signs and mag- 

 nitudes. These are more numerous in a vigorous, choppy sea where, as 

 stated, the cycles themselves are shorter and the individuals which shift the 

 periods appear oftener. Now if each of these beginnings could be efficiently 

 suppressed neither the cycles nor the individual rolling constituting these 

 cycles would ever come into evidence, and it is just this suppression that we 

 are enabled to effect by the active gyro. 



Calculations dealing with a known tank equipment well illustrate the 

 powers of the active gyro stabilizer. Let us take the case of Figs. 4 to 7, 

 Plate 80, where acomparatively small fraction only of the roll was dampened, 

 owing to the sea being out of synchronism even by but a slight percentage. 



