The Norden Bomb Sight manual

ment, the stabilizer gyro brush moves off the neutral sector of the torque motor contact sector (isolated sector). That movement closes the tor- que motor circuits and causes one of the two mag- nets to be energized. The energized magnet at- tracts its clutch disc to engage the corresponding clutch gear. The clutch gear is corkfaced, and it is the cork which provides the friction for the clutching action. The torque transmitted from the clutch gear to the clutch is transmitted through idler gears to the ring gear mounted on the stabilizer gyro cardan. It is this torque which precesses the gyro until its brush is cen- tered on the neutral sector of the isolatedsector. It must be emphasized that the torque motor clutches slip even when engaged. If one should "grab", the torque motor would then exert such a powerful force upon the ring gear that the gyro would move past the neutral. At the neutral point, the magnet would be de-energized, and the clutch would release. However, the momentum of the gyro would carry the brush across the neutral. The result would be a rapid hunting across the neu- tral sector and a chattering of the clutches. For this reason, the torque motor clutches are care- fully adjusted at the factory to transmit only enough torque to slip and not to grab. The bayonet springs are to adjust and main- tain the clearance between the clutch plate and the corkfaced gear.

G. Preces- sion Motor

The precession motor assembly consists of a reversible electric motor, an adjustable solenoid, a vertical actuating shaft, and necessary gears and wiring. Located on the base of the stabilizer gyro is a bail with an offset ridge. In close tolerance to this bail is a roller which is the top of the actuating shaft. The other end of the actuating shaft fits into an adjustable solenoid plunger. When the solenoid is energized, the shaft is moved upward and the roller comes in contact with the ridge of the gyro bail. Through the precession motor and its intermediate gearing, movement is transmitted to the actuating shaft which causes the shaft to rotate. The shaft may rotate either in a clockwise or counter-clockwise direction,