Pivot Weapons

Earliest Pivot Weapons

• The trebuchets that were used in the Middle Ages to lay siege to castle and fort walls were one of the earliest weapons to use a pivot. Trebuchets used gravity, consisting of heavy counterweights on the end of a long throwing arm rather than twisted cords. The long arm sat over a pivot point, acting as a two-sided lever. Soldiers loaded one end of the arm with a projectile, then pulled on ropes to lift a massive counterweight on the other end. Locked into position, with the counterweight raised and storing potential energy, a key was pulled to start the downward travel of the arm, which pitched the projectile high in the air.

Carriage Type Pivot Gun

• In 1871, Alexander Moncrief designed a carriage type pivot gun. The gun had a 7-inch diameter bore and could be swiveled up to an elevated position to shoot, then retracted down away from the gun port to remain hidden. The front part of the gun frame rested on a pivoted plate that enabled a swiveling movement. The rear part of the gun frame rested on transverse wheels, which allowed the rear part of the gun to swing from side to side.

Swivel Gun

• The swivel gun was one of the smaller varieties of artillery, and it turned on a small pivot. Swivel guns generally measured 33 inches in length and had bore diameters of 1 1/4 inches. They fired 3/4 lb. round balls from ship deck rails, or fore-and-aft decks. Swivel guns were mainly defense weapons; however, these military weapons were also used for ceremonial salutes and for signaling other ships.

Typical Carriage Mount Pivot Gun

• The most common pivot gun used a wooden frame carriage and a large metal ring, from 9 to 12 feet in diameter. The ring was constructed of iron and had a U-shaped opening, allowing full tilt up capability, while a pivot joint comprised the bottom end. The bottom pivot joint consisted of roller bearings that would ride and turn inside of a track, allowing the barrel to swing hard left and hard right.

Pivot Gun Pros and Cons

• One loader could quite easily and quickly load smaller pivot deck guns. Since these pivot weapons were typically mounted to decking and rail surfaces, recoil was absorbed by the mounting structure, rather than moving backward on a sled or wheels. Aim could be achieved almost immediately, allowing shallow, short range shots. The pivot gun's chief disadvantage came from its permanent mount, which disallowed transport to other firing stations. The pivot gun was also virtually confined as an antipersonnel weapon, unable to inflict significant damage on hull structural members. Its range was also confined to ship-to-ship broadside encounters, due to its small bore and minimal projectile size.