ACTIVE TYPE OF STABILIZING GYRO. 211 



cable drums of each gyro is secured a pair of cables connected direct to the 

 cable drum upon the engine, so that by operating the engine the gyros can 

 be turned slowly back and forth upon their vertical pivots by means of 

 cables lying in grooves, plainly seen in Plate 86. 



This oscillation constitutes the precession movements of the gyro, under 

 constant and instant control in either direction. 



CONTROL. 



The arrangements for control are such that the precessional movements 

 on the vertical axis could be either controlled by hand or automatically. 

 The automatic control was through an auxiliary, magnetically operated pilot 

 valve, similar for all purposes to the little gyroscopically controlled steering 

 engine of the Whitehead torpedo. 



AUTOMATIC CONTROL. 



Several methods of automatic control have been investigated. Froude 

 in 1873 developed an apparatus for simultaneously recording the rolling of 

 vessels and the slope of the waves producing or contributing to such roll. 

 In this apparatus lies a clue to one simple form of automatic control of the 

 precessional movements of the gyros so as to measurably forecast or antici- 

 pate the rolling of the vessel. 



A method, however, has been discovered of combining Froude's short 

 and long pendulum in one comparatively simple apparatus and also greatly 

 increasing the length of the long pendulum, as well as very materially aug- 

 menting its mass moment. This control is based upon the peculiar arrange- 

 ment of two small gyroscopes weighing about ten pounds, and the pendulum 

 so obtained represents a mass approaching half a ton with a pendulous length 

 of ten miles. The control thus constituted has been finally brought to the 

 point where it responds to only one component of universal angular motion. 

 That is, it is not in the least affected by any amount of pitching of the ship 

 or angles of yawing or azimuth or other movements. A close view of the 

 apparatus is shown in Fig. 1 1 , Plate 83. As indicated by results, this simple 

 control apparatus causes the gyros to instantly neutralize the direct effect 

 of all sea impulses, as elsewhere more fully described. An eminent essential 

 of such control apparatus is that it shall be independent of period and that 

 it shall be free from any liability to harmonize with any periodic motion of 

 the ship. The operation of the device indicated that it successfully fulfils 

 all these conditions. 



One important feature of the active type of gyro is its power to arti- 

 ficially roll the ship on which it is mounted. 



