Figure 4-37.--Ball erector diagram.

uses a small stabilizer or start gyro mounted in its own

gimbal, which, when started, comes very quickly to a

vertical position, providing a fairly accurate level

reference for the roll-pitch phantom.

The stabilizer gyro rotor is the squirrel cage portion

of a 3-phase, 115-volt, 400-Hz induction motor, and

spins within the stator at 22,500 rpm in ball bearings that

are in the top and bottom of the gyro case. A ball erector

mechanism (fig. 4-37) is employed for maintaining the

gyro spin axis vertical. This mechanism consists of a flat

cylindrical enclosure suspended from the gyro case by

means of a ring that also serves as a bearing surface. It

is geared to the rotor shaft and rotates at 22 rpm about

an axis parallel to the gyro spin axis. When the gyro is

vertical, eight small balls are massed in the center of the

concave surface of a disk in the bottom cover. Eighteen

Figure 4-37.--Ball erector diagram.

holder pins are equally spaced near the edge of the

concave disk. When the gyro tilts, the balls roll to the

The starting system functions to level the gyros and

lower side of the disk, where they are held loosely by

bring the meridian gyro to the meridian in as short a time

the holder pins and carried ahead, in the direction of

as possible. The starting sequence is accomplished with

rotation, toward the higher side. As each ball reaches a

a minimum number of manual operations by the

point where it can drop past the holder pin, it falls across

compass operator. The system includes a fast erect

the disk and resumes its cycle. The center of gravity of

system, a system control assembly, and part of the

the balls, so displaced, is at a point 90 from the low

control panel.

point, in the direction of rotation. Thus, a torque is

created that precesses the gyro in a clockwise direction

When the compass is to be started, the roll-pitch

viewed from above. The ball holder rotates in the same

phantom will be off its level position. A fast-erect system

direction and is easily observed because of its slow

is employed, which greatly reduces the time required to

speed.

bring the roll-pitch phantom (and therefore the gyros, as

they are caged to their vertical rings and the azimuth

Flat roll and pitch synchro transmitters are mounted

phantom during starting) to a level position. This system

on the stabilizer gyro (fig. 4-38). The output from the

Figure 4-38.--Fast-erect system.

4-34