188 SOME GRAPHIC STUDIES OF THE ACTIVE GYRO STABILIZER. 



Mr. H. C. Higgins, Member: — I would ask how much space the stabilizer occupies. 



Mr. E. L. M. SivarDj Member: — I would like to know about what Mr. Sperry men- 

 tioned earlier in the day, about some observations he had made on the influence of the 

 gyroscope stabilizer on the stresses of the ship — if there are any data on that subject, I 

 would like to have them. 



The Chairman : — Apparently there is no further discussion, Mr. Sperry, except these 

 questions which have been asked. 



Mr. Sperry : — Mr. Higgins asked a question as to how big the stabilizer is, how 

 much space it occupies, and that is important. It is brought out in this paper and the 

 one last year that it occupies only a small percentage of the space occupied by the tanks 

 and weighs only a fraction of their weight. You can understand that the stabilizer plant 

 for any ship will depend on how large a single wave increment you require the plant to 

 stabilize against. The constructors in our navy have made a study of this factor; conceive 

 of a single wave increment large enough to throw a great warship over 3)4 to 4 degrees, a 

 very large contract, because the rolling of a ship is usually a matter of an accumulation of a 

 great many increments ; it is very seldom that any one increment rolls a ship greatly ; it is 

 usually an accumulation of smaller increments. Referring, however, to the individual incre- 

 ment, suppose we were to stabilize a ship against 4 degrees single increment, or 8 degrees 

 per period, a large quantity as you will observe, more than twice the stabilizing power here- 

 tofore proposed for battleships. Such a roll would require a wave of more than 2 degrees 

 apparent wave slope against which the ship must be held, and we must remember that the 

 wave moment would have to maintain itself for, say, 8 seconds, while the great mass of the 

 ship is getting under motion. Very few waves persist for any such period of time. Now, 

 then, figuring 4 degrees stabilizing power, or 8 degrees per period of the ship, the whole 

 stabilizing plant, everything included, would be a little under 1 per cent of the total dis- 

 placement. As a matter of fact, you could hardly find it in a battleship, it is so small. This 

 is quite well illustrated by the model. This model is much more than full size for the model 

 of a 32,000-ton battleship, large enough to carry about 20 persons, and yet this stabilizer 

 plant could almost be put in an overcoat pocket ; besides, I think those who have had experi- 

 ence will agree with me that a model equipment can never be built as small in proportion as 

 the full-sized plant. For instance, these wheels are so small that their stresses are away 

 down, only a few hundred pounds per square inch, even at the high speeds which they at- 

 tain. Of course we would never think of putting a wheel in a battleship that did not have 

 as much maximum stress, certainly, as occurs in the hull, yet a spinning wheel at moderate 

 stress is one of the safest things in the world, because you cannot imagine anything happening 

 which will do but just one thing, that is, stop it; nothing can happen to accelerate its speed 

 because its air frictional power consumption increases as the cube of its speed. A certain 

 amount of power put into it will bring it up to a certain speed and bump its head against 

 this law. Unless you get a great deal more power into it you cannot drive the wheel very 

 much faster; and where is this power to come from? The motor is small and purposely 

 limited in size. Then, again, we run away below the elastic limit, and when the elastic limit 

 is reached the wheel, which is still perfectly safe, will then flow and swell. There is a rigid 

 casing close to the wheel and long before any danger point was even in sight a slight swelling 



