THE SPERRY GYRO-COMPASS IN SERVICE. 291 



tact for energizing the azimuth motor. These contacts and segments are 

 provided in dupUcate so that while the compass is running they may be 

 removed and cleaned one at a time. The master compass is placed in a pro- 

 tected position well below the water-line and auxiliary compasses, known as 

 repeaters, are provided at the wheel, in the steering engine-room, in the 

 conning- tower, or at any point desired in the ship. The cards of these 

 repeater compasses are driven by small six-pole motors, the poles of which are 

 energized in succession from a transmitter on the master compass. The 

 frame of the master compass is so geared to the transmitter that each one- 

 sixth degree movement of the master compass is reproduced in the repeater. 



Because of the simple mechanism involved, these repeaters can be made 

 durable and substantial, requiring less care than is given a well-made clock. 

 A dynamotor dynamo is provided for furnishing current for driving the com- 

 pass wheel by means of an induction motor and for supplying the repeater 

 system with low voltage current. The repeaters are also provided with 

 cutout switches controlled from below, and with means for synchronizing 

 them with the master compass. 



Figure 3, Plate 102, is a photograph of the master compass with covers 

 removed. The dials for setting the automatic correction device will be seen 

 in the center at the top. 



Figure 4, Plate 1 02 , is a photograph of the master compass with top cover 

 removed. 



Figure 5, Plate 103, is a view of the master compass from above. 



Figure 6, Plate 103, is a view of a portion of the master compass showing 

 a correction applied to the lubber's line. The position of the small black 

 pointer on the scale just above the correction dials shows the amount of the 

 automatic correction which is being applied. 



Figure 7, Plate, 104, is a photograph of the wheel casing and vertical sup- 

 porting ring. The two posts which carry the silver trolley wheels may be 

 seen at the top. This photograph also shows the suspension wire and the 

 levels referred to before. The space between the lower part of the casing 

 and the vertical ring is allowed for the pendulum or yielding connection. 



Figure 8, Plate 105, shows the gyro wheel and bearings, also the stator of 

 the three-phase induction motor for spinning the wheel. The internal per- 

 iphery of the wheel itself constitutes the rotor. 



Figure 9, Plate 104, is a photograph showing the phantom ring which is 

 made to surround the sensitive element and which is driven by the azimuth 

 motor to follow all tendencies of the gyro. On this ring is mounted the 

 compass card as shown, and in the center is the suspension head for sup- 

 porting the sensitive element. 



