Military Factory
flag of United States

Rodman 20-Inch Cannon (1864)

Authored By JR Potts, AUS 173d AB | Last Updated: 8/22/2014

The Rodman 20-Inch of 1864 was the largest muzzle-loading cannon ever forged on US soil.

Tweet
The 20-inch Rodman was the largest muzzle loading cannon ever forged in the United States. The ability to forge cannon of that size required new technology that was developed by Thomas Jackson Rodman. This new casting process came about because of Rodman's interest in cannon advancement as acquired during his training at the U.S. Army's Military Academy at West Point New York, and a particular tragic event that occurred on the USS Princeton in 1844.

Second Lieutenant Thomas Jackson Rodman was assigned to the Army Ordnance Department at the Allegheny Arsenal in Pittsburgh, Pennsylvania after graduating seventh in his class from West Point in 1841. In 1844, the USS Princeton was one of the most advanced ships of her time - becoming the first screw steam warship fielded by the United States Navy. She was fast-equipped with a 14 foot, 6-blade screw powered by a coal burning boiler. She needed guns that projected power so the Princeton sailed for New York in January of 1844 to receive her two big cannon - named "Peacemaker" and "Oregon".

The Oregon was a 12-inch (300mm) smooth-bore, muzzle-loaded cannon made of wrought iron and could fire a 225-pound (100kg) shot some 5 miles (8 km) using a 50-pound charge of gun powder. Made in England by the Mersey Iron Works, the weapon was sold to the US Navy in 1841. A new built-up construction process was used, this accomplished by arranging iron hoops delivered hot from the forge, around the back of a casted cannon. The process was to allow higher amounts of gun powder to be used to prevent an explosion when firing. The second cannon - the Peacemaker - was made in the United States by Hogg and Delamater of New York and was also a 12-inch muzzle-loader able to match the shot and range of the English-made Oregon. The construction process was different, however, as the Peacemaker did not make use of additional bands for support. The breech end was increased in metal thickness during the casting process itself. The weight of the gun was greatly increased without reducing the flaws experienced in wrought iron cannon construction prior.


Text ©2003-2014 www.MilitaryFactory.com. All Rights Reserved. No Reproduction Permitted. Email corrections/comments to MilitaryFactory at Gmail dot com. Material presented throughout this website is for historical and entertainment value and should not to be construed as usable for hardware restoration, maintenance or general operation. Consult manufacturers directly for such information.

Specifications for the
Rodman 20-Inch
Cannon


Country of Origin: United States
Manufacturer: US Army / Fort Pitt Foundry - USA
Initial Year of Service: 1864
Production: 6


Focus Model: Rodman 20-Inch
Crew: 16


Overall Length: 22.93ft (6.99m)
Width: 3.35ft (1.02m)
Height: 6.56ft (2.00m)
Weight: 0.1 US Short Tons (58kg; 128lbs)


Powerplant: None.


Maximum Speed: 0mph (0 km/h)
Maximum Range: 5 miles (8 km)


NBC Protection: None
Nightvision: None


Armament:
1 x 20-Bore Muzzle-Loading Gun Tube


Ammunition:
1 x 1,080lb Shot; 750lb Shell; 200lb Charge


Variants:
Rodman 20-Inch - Base Series Designation; six examples produced.


Operators:
United States