THE SPERRY GYRO-COMPASS IN SERVICE. 287 



wholly suppressed, will tend to process, or turn, about the vertical axis in an 

 effort to place its plane of rotation coincident with that of the earth. The 

 question of utilizing this phenomena in an instrument which would seek and 

 maintain the true north and south meridian, regardless of position, speed or 

 course or oscillating movements of the body on which it was mounted, 

 involved a great many problems. 



Early in his work, Mr. Sperry became convinced that the major problem 

 was one of pure engineering in devising a suspension which would be friction- 

 less about the vertical axis, allowing the gyroscope to turn with perfect 

 freedom in its effort to seek the meridian. 



In the most powerful gyroscopic compass which has ever been devised, 

 the maximum directive force (axis at 90 degrees from the meridian) exerts a 

 power which is equivalent to only .015 watt-seconds. In this connection 

 it is interesting to note that even though the directive force is minute, it is 

 approximately three hundred times that of the Navy standard magnetic, 

 ten times that of any other gyroscopic compass, and fifteen hundred times 

 that of the magnetic compass when placed in the same location in the ship. 

 The directive force decreases in proportion to the cosine of the angle which 

 the axis makes with the meridian until, when the axis is exactly on the 

 meridian, the directive force is zero. The suspension must be such that 

 the gyro is free to return to the meridian under the very minute directive 

 force exerted when the axis has left the meridian by only a small fraction 

 of a degree. 



The solution of this problem alone involved years of experimental work, 

 inasmuch as no ordinary suspension could be used because of the weights 

 involved. The problem was finally solved by suspending the gyroscopic, or 

 sensitive, element from a stranded wire, the top of which is carried in a frame 

 surrounding the gyroscopic element, this frame being oriented by an elec- 

 trical follow-up system in such manner as to cause the frame to follow any 

 tendencies of the gyroscopic element to move about the vertical axis. This 

 constitutes a highly frictionless suspension with the result that, while great 

 power is available for driving the compass card and repeater transmitting 

 system, the gyro itself has extremely little work to do and consequently can 

 be made very sensitive while ruiming at quite moderate speed. This sus- 

 pension has made possible a strong, durable, and very accurate instrument. 



Numerous other problems, quite as difficult of solution, were encoun- 

 tered. Perhaps the most difficult of all was that involved in so suspending the 

 sensitive element that it would be unaffected by acceleration pressures 

 arising from movements of the vessel on which it was mounted. In develop- 

 ing this point it was necessary to collect a large amount of data relating to 



