NOZZLE AND FIN ASSEMBLIES

Figure 2-7.—Nozzle and fin assembly (2.75-inch). NOZZLE AND FIN ASSEMBLIES.— The nozzle and fin assembly (fig. 2-7) used with the Mk 4 and Mk 40 motors consists of a nozzle plate, four nozzle inserts, a fin-actuating mechanism, four fins, and a fin retainer contact disc. The nozzle assembly for the Mk 66 consists of the nozzle body, carbon insert, fins, contact band assembly, and weather seal. The fins are attached by pivot pins to lugs machined on the aft part of the nozzle plate. When folded, the fins lie within the 2.75-inch diameter of the rocket. The fins are notched at the tips to allow attachment of a fin retainer. The fin-actuating mechanism is a steel cylinder and a piston with a crosshead attached to its aft end. When the rocket is fired, gas pressure from the motor operates the piston, cylinder, and crosshead. The crosshead is pushed against the heels of the fins, causing the fins to rotate on the fin pivot pins to the open position after the rocket leaves the launcher. After the fins have opened to the final flight position, the crosshead prevents the fins from closing. There are four nozzle inserts and the detent groove in the aft end of the nozzle plate. They hold the rocket in position after it is loaded in the launcher (fig. 2-8). The major difference between the nozzle and fin assemblies used on the Mk 4 and Mk 40 motors is the type of nozzle inserts used. Figure 2-8.—Nozzle and fin assemblies. (A) Mk 4 Mods motor (B) Mk 40 Mods motor. 2-6