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The train system uses two electric motors (fig. 5-55) to drive the reduction gear assembly and move the gun in train. The electric motors are lightweight (25 kg) low-inertia, dc motors with permanent magnet fields and printed disk rotors. The rated output of each motor is 3 kW at 3,000 rpm.

The left electric motor (No. 1) has an electromechanical brake assembly installed on the top of its output shaft. The brake assembly consists of an electromagnet, a braking disk, and a rotating disk splined to the motor output shaft. With no power applied to the brake, steel springs around the top of the electromagnet push the braking disk up. When power is applied to the brake, the electromagnet pulls the braking disk down (compressing the springs) and releases the rotating disk. The electromagnet remains energized, and the brake remains released as long as power is applied to the brake.

The brake has a manual release handle for power-off operation. It also has a push button for use with a manual hand crank, The pushbutton releases the brake only when the servo system power is on and the hand crank is installed.

The hand crank fits into an opening in a bracket on top of the brake. The hand crank is used to train the gun mount manually during maintenance and power-off operations. A proximity switch, mounted under the bracket, turns on the TRAINING HAND CRANK IN

Figure 5-55.-Train power drive (cutaway).

lamp at the GCP (refer to fig. 5-29 and table 5-3). The proximity switch also disables the train amplifier ready circuit and this, in turn, disables the motor start-run circuit. With the hand crank installed, a microswitch, mounted under the bracket, is actuated. This action enables the brake to be energized by the brake push button.

The right electric motor (No. 2) has a tachometer control assembly installed on the top of its output shaft beneath a protective guard. The tachometer produces voltage in direct relation to the motor speed. This voltage provides feedback to the motor control system.


The train reduction gear assembly (refer to fig. 5-55) reduces the high rpm rate developed by the electric motors by a 308.7-to-1 ratio. This reduction ratio and the motor control circuitry produce a maximum train rate of 65 degrees per second. The reduction gear assembly consists of the gear housing, two pairs of reduction gears, and the pinion gear.

The reduction gear assembly is mounted on the rear platform of the carriage. The train pinion gear extends through the carriage and meshes with the stationary ring of the roller path assembly. The two electric train motors are mounted on top of the reduction gear assembly. The pinion gears of the electric motors drive the gear train.

The reduction gears operate in a lubricating oil bath. A fill plug is located on the side of the assembly, and a drain plug is located on the bottom. Removing the fill plug permits the oil level to be checked and, if necessary, permits oil to be added. Removing the drain plug permits the oil to be drained.


The train synchro control box assembly houses the train synchros. The train synchro control box assembly and the train synchro transmission gear assembly (fig. 5-56) are mounted on the rear of the carriage platform forward of the elevation power drive. Graduations and a marker on the outside of the train synchro control box assembly provide an installation benchmark.

The train synchro control box (fig. 5-57) houses the train synchros, the tilt-angle potentiometer, the motor and firing cutout camstack assembly, and the dials and dial-illuminating lamp components of the train servo system.

Figure 5-56.-Train synchro control box assembly and transmission gear assembly.

Train Synchros

As the gun moves in train, the train response shaft rotates the synchros through the synchro gearing in the bottom of the train synchro control box. The antibacklash gears and the couplings ensure that the rotation of the synchros exactly matches the train movements of the gun mount.

Three of the train synchros are control transformers (CTs). Two CTs receive position signals from the FCS and generate error signals-the third is a spare. The error signals, when amplified and processed by the motor control circuity, regulate the current applied to the train motors. One of the Cts (1X) is for coarse control (error signal greater than 1.5 degrees); the other CT (36X) is for fine control (error signal less than 1.5 degrees).

In addition to the 1X and 36X CTs, the train synchros include two torque transmitters (Txs) and five control transmitters (CXs). The 1X TX continuously transmits the train position to FCS and to a torque receiver synchro at the GCP. The torque receiver synchro operates the train position indicator dial. The 180X TX continuously transmits a superfine indication of train position to FCS.

Figure 5-57.-Train synchro control box components.

One of the five CXs is for tilt-angle correction. This CX adds error through the tilt-angle potentiometer to the output of the elevation 36X CT. The error is based on the tilt-angle difference between the roller path of the gun mount and the master level of the ship.

Of the remaining four Cxs, one is for the high nonpointing zone, one is for the low nonpointing zone, and the other two are spares. The outputs of the nonpointing zone Cxs are used to temporarily override training orders. This output prevents the barrel from training into a nonpointing zone until it elevates over the zone.

Tilt-angle Potentiometer

The tilt-angle potentiometer adjusts the intensity of the correction signal from the tilt angle correction CX. This adjustment is made during installation. It compensates for any angular difference between the plane of the gun mount and the plane of the master level of the ship. The tilt-angle potentiometer can correct an angular difference up to 10 minutes. On ships outfitted with the FCS Mk 92, the potentiometer is set at 0 and is locked down since the computer makes this correction directly.


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