Rodman 15 inch Gun - Ship Island MS - Static Artillery Displays on Waymarking.com

One Rodman 15 inch gun from Fort Massachusetts was saved from being sold for scrap iron and is being preserved. These cannons did not have rifled barrels and could fire shells or shot. It took 12 men to operate these guns.





Rodman gun refers to a series of American Civil War–era columbiads designed by Union artilleryman Thomas Jackson Rodman[1] (1815–1871). The guns were designed to fire both shot and shell. These heavy guns were intended to be mounted in seacoast fortifications. They were built in 8-inch, 10-inch, 13-inch, 15-inch, and 20-inch bore. Other than size, the guns were all nearly identical in design, with a curving bottle shape, large flat cascabels with ratchets or sockets for the elevating mechanism. Rodman guns were true guns that did not have a howitzer-like powder chamber, as did many earlier columbiads. Rodman guns differed from all previous artillery because they were hollow cast, a new technology that Rodman developed that resulted in cast iron guns that were much stronger than their predecessors.
Hollow casting

Engraving showing a gun being cast using Rodman’s hollow casting technique. The engraving shows the gun mold in the casting pit. The outer iron flask, the fire built outside the flask, and the cooling core are also shown.

Guns had been traditionally cast solid and the bore was bored out of the solid metal. With this traditional method, the gun cooled from the outside inward. Castings shrink as they cool. As each succeeding layer cooled it contracted, pulling away from the still molten metal in the center, creating voids and tension cracks. Drilling out the bore removed the voids, but the tensions in the metal were still toward the outside. Rodman devised a method of casting where the gun cooled from the inside out, so that as cooling occurred, it created compression rather than tension. This resulted in a much stronger gun.

With Rodman’s method of casting, a cooling core was placed in the mold before casting. This core consisted of a watertight cast iron tube, closed at the lower end. A second, smaller tube, open at the bottom was inserted into the first. As the molten iron was poured into the mold, water was pumped through the smaller tube to the bottom of the larger tube. The water rose through the space between the two tubes and flowed out at the top. The water continued flowing as the metal cooled. To further ensure that the gun cooled from the inside out, a fire was built around the iron flask containing the gun mold, keeping the gun mold nearly red-hot. For an 8-inch Rodman columbiad, the core was removed 25 hours after casting and the flow of water continued through the space left by the core for another 40 hours. Over 50,000 gallons of water was used in the process. For larger guns, the cooling periods were longer and more water was used.

After cooling the gun the machining process began. The bore was bored out to proper size, the exterior was turned smooth, the trunnions were turned on a trunnion lathe, and a vent was drilled.

Columbiads were not the only guns cast using Rodman’s method. Dalgren XV-inch shell guns for the U.S. Navy were also hollow cast. A 20-inch hollow cast gun, which may not have been identical to the two guns supplied to the U.S. Army, was sold to Peru.

Rodman guns were cast at the Fort Pitt Foundry, Pittsburgh, Pennsylvania;[2][3] the Scott Foundry, Reading, Pennsylvania; Cyrus Alger & Co., Boston, Massachusetts; and the West Point Foundry, Cold Spring, New York.
Rodman guns

Rodman guns were all nearly identical in design, with a curving soda bottle shape, the only differences being the size of the gun. They were all smoothbore guns designed to fire spherical shot and shell, primarily against ships. The guns were elevated and depressed by means of a lever called the elevating bar. The point of this lever fits into ratchets on the earliest guns cast, or sockets on the later guns. The fulcrum, called the ratchet post, fit on the rear transom of the upper carriage. The ratchet post was cast iron and had several notches for adjusting the position of the elevating bar.

Only one 13-inch Rodman gun appears to have been made, but it was placed in service. (Ripley 1984, p. 79). Two 20-inch Rodman guns were emplaced at Fort Hamilton, New York. A third shorter 20 inch gun was cast for the USS Puritan using the Rodman technology. One 20-inch Rodman gun remains in a park just north of Fort Hamilton, another is at Fort Hancock, Sandy Hook, New Jersey.[4]

The other, smaller Rodman guns were placed in seacoast fortifications around the United States. It took 8 men to load and fire a 10-inch Rodman gun, and 12 men for a 15-inch Rodman gun.

Over 140 Rodman guns survive today and they may be seen at coastal fortifications around the country.

Where is this artillery located?: Military Grounds Artillery is no longer operational: yes Still may work: no What type of artillery is this?: Not listed What military of the world used this device?: Not listed Date artillery was in use: Not listed Date artillery was placed on display: Not listed Parking location to view this Waymark: Not Listed Cost?: Not Listed Are there any geocaches at this location?: Not listed

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