Rodman gun

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The Rodman Gun was an 80-ton cannon produced during the American Civil War. It was the largest gun in the world at the time.

The cannon was made at the C. Knapp Foundry in Allegheny, Pennsylvania, later the Fort Pitt Foundry and now Mackintosh-Hemphill. Named for Lt. Thomas J. Rodman, commander of the Allegheny Arsenal, it was designed to project an iron ball up to seven miles. Rodman designed several other heavy guns of lesser size and they were also known as Rodman guns.

[edit] Metallurgy

Thomas Jefferson Rodman (1815–1871) was born at Salem, Indiana and graduated from West Point in 1841. Ordnance became his field of endeavor.

He realized that a stronger barrel could be constructed by first cooling the inside of a gun casting while the outside remained hot. Cooling the outside last produced compression on the already cooled interior, which strengthened the casting. A gun casting using the Rodman method was tested in 1849.

[edit] Characteristics

Rodman guns share a "bottle" shape with the earlier Dahlgren gun. Most muzzle loading cannons have at the butt end some means of attaching a sling or hook to aid in the lifting and placement of the barrel into a mount. In the Dahlgren and earlier cannons this would be a knobbed protrusion cast into the butt, which would sometimes break due to the stress. One innovation of the Rodman is that this handling knob is replaced with a groove around the butt, which is essentially unbreakable and forms the primary external distinguishing feature for identification. The area at the butt may then contain a track of depressions for insertion of a lever with which the elevation is controlled