ACTIVE TYPE OF STABII^IZING GYRO. 225 



pendulum may then actually be found to be increasing the motion instead of 

 decreasing it as expected. This very phenomenon has been observed at sea with 

 tanks and, when repeated in period, renders them positively dangerous, as stated 

 in my paper. 



Work with a compound pendulum, especially when truthfully representing, as 

 far as possible, sea conditions as to original energizing impacts, shows in the most 

 emphatic manner the necessity for breaking away from devices limited to resonance 

 or periodic phenomena. On the contrary, the device to be effective must not be 

 tangled up with some past happening that has excited it, but should be free to 

 grapple and fully deal with each present disturbance and so neutralize it that no 

 motion of the pendulum or ship can result; and then deal with the next, and the 

 next, independent of their direction, time or intensity. If no individual impact 

 is permitted to move the ship, the ship never begins to move and therefore remains 

 motion-free. 



Referring again toFigs. 4to 7, Plate 80, weare informed that these tests extended 

 over several hours. What is more important, we know, as stated above, that they 

 are absolutely representative of the several conditions. We also know that with 

 heavier sea conditions the percentage of departure from synchronism when the 

 tanks fail is smaller than on light seas. Compare this percentage in Fig. 7, Plate 80, 

 with that of the other figures on Plate 80. Mr. Blohm mentions that the above facts 

 with regard to heavier seas "are not justified." He also stated that "he (Sperry) 

 has not published any data or curves to prove his words." I ask: What further 

 proof is required? If Mr. Blohm considers the performance in, say Fig. 7, Plate 80, 

 where all the tanks were in full operation as useful stabilization, I for one certainly 

 take issue with him, and will add that it has been definitely ascertained that there 

 are sea conditions where the ship is actually obsessed with more total motion 

 with the tanks in operation than when they are out of operation. 



It is of course understood that the air line is used to render the tanks inactive 

 at will, or when they become dangerous. The difficulty is that the remedy comes 

 too late, and a complete closure of the air line locks the water on a listed boat so 

 as to maintain the list. Considerable adjustment and attention would be required 

 to keep the period of the tanks in harmony with that of the vessel, which Mr. 

 Blohm states has been found to vary nearly 30 per cent from different loading, and 

 also from changes in period due to different steaming velocities, especially in case 

 of a tender ship, as stated in my paper. 



It is also important that our stabilizer shall deal with the most aggravated 

 and mixed seas, because they are almost universal and also because they are most 

 vigorous and most disturbing; probably because such seas are entirely outside 

 the practical scope of tank operation, Mr. Blohm tells us that they are unimportant 

 and with characteristic Teutonic directness and finaUty we are informed "that 

 any anti-rolling device has to be designed ONLY for the case of resonance." The 

 emphasis upon the ONLY is Mr. Blohm's. 



Improved and more perfect methods will always prevail. Improved methods 



