Civil War Essay

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References MASICH, A. (2015). Rodman’s Big Gun. Civil War Times, 54(6), 46–53. Retrieved from

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RODMAN'S BIG GUN A MASSIVE NEW UNION WEAPON COULD SINK A SHIP WITH A SINGLE SHELL, BUT WAS NEVER FIRED IN ANGER THE MASSIVE CANNON belched smoke and flame, hurtling a 10,080-pound shell from its barrel at more than 1,700 feet per second -- nearly twice the velocity of a Minié ball fired from a rifle. Nearby windows rattled and broke as the shock wave traveled from Fort Hamilton over Brooklyn, N.Y. Then the gun crew reloaded the behemoth, lowering the barrel to an elevation of 25 degrees. This time the 20-inch ball hurtled through the air for a full 24 seconds, splashing into the water 3Vi miles away. Thomas J. Rodman's ship-killing cannon, the largest gun made during the Civil War, had spoken.

The genesis of that gun and the new generation of armament it inspired was rooted in a tragic mishap on February 28, 1844, when Commodore Robert Stockton hosted a who's who of Washington society. He had invited some 400 guests for a Potomac River cruise aboard USS Princeton, including President John Tyler, Secretary of State Abel Upshur, Navy Secretary Thomas Gilmer, Senator Thomas Hart Benton and former First Lady Dolley Madison. The VIPs were to be treated to a demonstration of the fleet's most powerful cannon, dubbed the "Peacemaker," a 12-

inch wrought-iron gun with a reinforcing band shrunk onto its breech, designed by John Ericsson. Though skilled British workers had forged a prototype to Ericsson's exacting specifications, the Peacemaker commissioned by Commodore Stockton was an American-made copy that did not measure up to those standards.

When the gun captain pulled the lanyard aboard Princeton, an explosion rocked the ship, killing six people and seriously wounding another 20. The gun had been blown to pieces, along with the closest dignitaries, including Upshur and Gilmer.

Ordnance Department Lieutenant Thomas Jackson Rodman, then only three years out of West Point, set out to get to the root of the accident. He would focus his considerable talents on finding a solution to the problem of catastrophic failure in large-caliber guns. Rodman recognized that wrought-iron and bronze weapons could not withstand the high stresses demanded of Columbiads -- America's largest class of guns, introduced by Colonel George Bomford in 1811 for seacoast defense -- and warship cannons. Though iron had been used to manufacture cannons for hundreds of years, large-caliber guns made of that metal had earned a reputation for blowing up.

Rodman theorized, however, that the fault lay not with the iron itself but the casting process. As a newly cast cannon cooled in its mold, it hardened from the outside, until the molten core finally set up. The gun was then laboriously bored to the desired caliber and finished on the outside. Raised rings known as reinforces, positioned where the gun telescoped from the thickest part of the breech down to the narrowest part at the muzzle, were believed to strengthen the weapon. Speculating that air-cooling made the guns harder and denser on the outside and left them relatively soft and weak in the center, Rodman found he could drive a cold chisel its entire length into the cast-iron core as easily as if it were wood.

He opted instead to cool the casting from the inside out. He would cast the guns hollow, pouring molten metal into a mold around a hollow iron core, an iron pipe through which air and cold water could be pumped, to cool the casting from the inside.

But when Rodman explained his proposed manufacturing method at Pittsburgh's Allegheny Arsenal, where he was stationed, and also to then Chief of Ordnance Colonel Bomford and General George Talcott, there was little interest. The lieutenant was told that the Army was not interested in his idea -- though he was free to pursue it on his own.

ON AUGUST 14, 1847, Rodman was awarded Patent No. 5,236 for his cannon. By 1849, he had worked out a partnership with Pittsburgh's Charles Knapp and William Totten, owners of the Fort Pitt Foundry, assigning his patent to them. In exchange for their funded research and development of his weapon, they agreed to pay him a half cent per pound for every finished cannon cast using his system. The foundry soon cast a prototype 8-inch Columbiad on Rodman's principle, followed by 10-inch Columbiads. Finding that cracks usually occurred at any spots where a gun's exterior contour abruptly changed, Rodman eliminated any reinforces. His cannons took on the smooth "soda bottle" shape that became their most distinguishing characteristic. Testing with double

charges and double shots, followed by repeated firing with service loads, demonstrated the designs efficacy. A solid-core gun cast from the same batch of iron burst after only 74 test rounds, while Rodman's "water-core" gun showed no discernable wear to the bore, chamber or vent after 1,300 rounds.

By 1860, the Ordnance Department had ordered 8- and 10-inch Columbiads, as well as a 15-inch version with a 16-foot-long barrel weighing nearly 50,000 pounds. The largest gun cast in America to that time, it was dubbed the "Union Gun" and sent to Fort Monroe, Va., for further testing in March 1860.

As Southern states began seceding from the Union in 1861, the War Department ordered Rodman guns in 8-, 10- and 15-inch calibers. On April 15, soon after Confederate guns blasted Fort Sumter into submission, Rodman signaled that he could cast an even bigger weapon -- weighing more than 100,000 pounds and capable of hurling a 20-inch, half-ton iron ball up to five miles and destroying a ship with a single shot. But initially the need for 8-, 10- and 15-inch weapons to protect cities -- including Washington -- and seacoast defenses took precedence over the 20-inch project.

~~~~~~~~ BY LATE 1863, Rodman's hollow-casting technique was standard for Model 1860 Columbiads of his own design as well as other cannons, including Admiral John A. Dahlgren's 9-, 11- and 13-inch naval shell guns. Though Fort Pitt Foundry was still producing most of the big guns, the West Point Foundry in New York, Boston's Cyrus Alger works and Seyfert, McManus & Co. in Reading, Pa., also began manufacturing siege guns, mortars, naval guns and Columbiads using Rodman's process.

When Rodman was finally authorized to create a 20-inch weapon, Charles Knapp and new partner H.F. Rudd supervised 280 workers at the Fort Pitt Foundry who excavated a casting pit so deep that it had to be shored up and lined, to prevent the water table from filling it. The pit was engineered to accommodate a multi-piece iron flask containing a sand mold formed on an oversized wooden model measuring 6 feet, at it widest point, by 25 feet. Five furnaces burned for five hours to melt the 105 tons of "Juniata" pig iron needed for the continuous pour. Two smaller furnaces stood by as backups, while the three primary furnaces were connected by troughs, to pool their molten streams in a clay-lined collector before the molten metal was funneled into the mold.

On February 11,1864, Rodman joined ordnance officers and observers from England and Italy to watch as the red-hot metal began flowing into the mold at 10 a.m. The foundry men pumped water down through the core at a rate of 60 gallons per minute, then captured the heated water as it returned to the top through flutes scored into the fire clay coating that surrounded the core barrel. Two days later the water was shut off and cold air was forced through the core. Four days after that, cranes hoisted the cooled casting from the pit and moved it to the boring machine, which enlarged the bore from 17 to 20 inches. A mammoth lathe then turned and smoothed the 80-ton

casting into a finished gun more than 20 feet long and weighing 116,497 pounds. Twenty-four horses and an army of foundry workers maneuvered the barrel to a railroad spur, where two flatcars with double trucks (iron wheels) waited. The journey to Brooklyn's Fort Hamilton took nearly a month, moving at a crawl, to avoid excessive friction on the rails.

Rodman had an 18-ton, front pintle, iron barbette carriage fabricated at the Watertown Arsenal that was placed at Fort Hamilton's lower battery, alongside the 15-inch Rodmans overlooking the mouth of the Hudson River. The upper portion of the riveted iron carriage that would cradle the gun was designed to slide on rails pitched at a 15-degree angle, but the huge barrel was expected to absorb most of the recoil. Rodman was so confident the powder charges would not budge the barrel from its balance point that the oversized pivoting trunnions were not even capped.

THE BIG GUN would be fired only six times during the war, using charges of slower-burning gunpowder (each grain measured nearly an inch across) -- also designed by Rodman -- varying from 50 to 150 pounds (regular cannon powder was too fine-grained and would burn too rapidly, creating dangerously high pressures even for Rodmans guns). To make the powder burn more thoroughly and predictably, the inventor formed cylindrical and hexagonal cakes of compressed powder, pierced with wires: perforated cake powder that would burn progressively, to ensure internal pressures remained within the safe range while imparting maximum propellant force to the projectile.

Secretary of War Edwin Stanton attended the test firing, as a nine-man crew loaded the gun with a 100-pound blank charge. The first shot was a misfire, since the standard friction primer was not strong enough to send a flame the full 24-inch length of the vent hole drilled through the cannon's thick iron breech, known as the "preponderance." Once the charge was pulled and the vent cleared by a volunteer, who crawled 20 feet down the bore and confirmed the primer flash had been inadequate, the gun was reloaded and its vent filled with fine-grained powder. The roar was deafening when the lanyard was yanked this time, reportedly breaking windows in Brooklyn. The barrel remained in the iron cheeks, but the entire upper carriage recoiled 6 feet 10 inches, sliding back along the iron rails as envisioned.

Once they saw Rodman's big gun worked, however, officials apparently lost interest. Further testing was not carried out until 1867, when -- loaded with 200-pounds of Rodman's improved cake powder -- the half-ton ball flew nearly five miles, obliterating a target ship. Rodman went on to design devices to more accurately measure projectile velocities (1,735 feet per second), and the internal and external forces exerted by his weapons. Though his 20-inch gun was never deployed against an enemy -- and only two of the giant cannons were cast -- Rodman's guns were regarded as a potent symbol of the North's industrial might.

IN 1876, when America celebrated its centennial with an exposition in Philadelphia, one of every Rodman weapon was exhibited, including one of the 20-inch guns, which had formerly guarded Norfolk, Va., and Hampton Roads. Getting the biggest gun to the exposition was no easy task. The 100-ton ship on which it was loaded nearly capsized when the crane operator failed to center the

big gun on the deck. The big gun was the hit of the exposition. Displayed with it were the 20-foot long rammers and hook-shaped winch used to hoist the ball and load the gun, as well as a variety of 20-inch rounds: explosive shells (each capable of holding a 25-pound bursting charge), solid shot (weighing 1,080 pounds each) and "cored shot" (with a small hollow cavity to reduce weight and extend the gun's range).

The Ordnance Board eventually tried to upgrade the big smoothbores by reducing the bore diameter with inserted rifled sleeves, creating elongated projectiles and designing more easily traversed gun carriages, but by the 1880s most ordnance experts realized that built-up guns fabricated from steel were the future.

Though Rodman's mammoth guns never fired a shot in anger, they were spared the scrap drives occasioned by subsequent wars. The largest iron cannons ever cast, they can still be seen today at Fort Hamilton and across the Narrows at Sandy Hook, N.J.

Thomas Jackson Rodman was born in 1816 near Salem, Ind., the son of James Rodman and his Virginian wife, Elizabeth Burton. Entering the U.S. Military Academy in West Point in 1837, Thomas would graduate seventh of 52 cadets, and in 1841 was appointed a brevet second lieutenant in the U.S. Army Ordnance Department.

At Pittsburgh's Allegheny Arsenal, Rodman built the first machine capable of making Minié balls and other bullets by compression rather than casting molten lead. He received patents for hollow casting large cannons as well improvements in cartridges for breech-loading small arms. His progressive-burning perforated cake gun powder for seacoast and naval artillery is still used today.

Rodman spent most of the war years commanding the Watertown Arsenal in Massachusetts, and his inspector's initials can be seen stamped on the muzzles of U.S. ordnance ranging in size from the diminutive 12-pounder mountain howitzer to the largest Rodman Columbiads. By the war's end, he was still an "unconfirmed major," according to his own testimony before Senator Ben Wade's Joint Congressional Committee on the Conduct of the War, which was investigating charges of war profiteering and disloyalty.

Suspicions about Rodman likely resulted from jealousy within the Army over royalties (a half cent per pound) he supposedly received for the guns cast using his hollow-casting method. But enemies and competitors questioned his loyalty when he failed to fire salutes at the war's end -- and the fact his mother was a Virginian could also have raised concerns (she may have been a relative of Confederate chief of armories James H. Burton). Though admired for his work in the Ordnance Department, Rodman spent many years defending his conduct. He ended his career as commander of the Rock Island Arsenal in Illinois, where he died in 1871.

RODMAN'S HUGE CANNON RETURNS TO PITTSBURGH Well, to be fair, it's actually a copy of the original, but still majestic. In 2013, the LF Creative Group created a styrofoam model, reinforced with steel and coated with black fiberglass, of Thomas

Rodman's enormous 20-inch cannon that was placed on display at the Senator John Heinz Regional History Center (heinzhistorycenter.org) in downtown Pittsburgh. The massive barbette carriage that supported the gun was also re-created. Together the reproduction items weigh an impressive 18,000 pounds.

The images above show the re-created barrel being installed and displayed. The Heinz History Center is located very close to the original location of the Fort Pitt Foundry, a source of local pride for Pittsburghers during the Civil War. Some residents were even concerned that General Robert E. Lee's 1863 Pennsylvania campaign might turn toward Pittsburgh in an effort to destroy its military industry. Their fears, of course, were unfounded.

Current residents and visitors to the museum can share in that sense of pride when they take in the stunning size of the cannon exhibit. As author Andy Masich, who is also the president and CEO of the Heinz History Center, said in an interview when the facsimilie went on display, "Pittsburgh was the arsenal for the Union, and factories here could do things that could not be done anywhere else in the world. Nothing epitomizes that better than a 20-inch Rodman cannon."

PHOTO (COLOR): SLOW SPIN Thomas Rodmans huge 20-inch cannon rests atop an equally huge lathe in the Fort Pitt Foundry. Foundry superintendent Joseph Kaye sits at right.

PHOTO (COLOR): VIP MISADVENTURE A 12-inch wrought-iron cannon explodes (above) during a February 1844 demonstration aboard USS Princeton. That horrific accident spurred Lieutenant Thomas Rodman to experiment with a "water-core" casting method (illustrated in the patent drawing, opposite).

PHOTO (COLOR): THOMAS JACKSON RODMAN

PHOTO (COLOR): CELEBRITY ORDNANCE The big Rodman commanded attention for years after the Civil War. This image shows it at the 1876 Centennial International Exposition in Philadelphia. The loading crane holds a 1,080-pound solid shot, which the cannon could fire as far as 4½ miles.

PHOTO (COLOR): 'FORGE OF THE UNION' Vignettes published in Harper's Weekly in 1862 show Fort Pitt Foundry's skilled workers at a number of their tasks. From right: Ironworkers finish the trunnions that attach the barrel to a carriage; molten iron pours into a vertical cannon mold and a huge lathe slowly rotates a Rodman tube as it is bored out. The last illustration shows the molds used in casting one of USS Monitori Dahlgren cannons.

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~~~~~~~~ By ANDREW MASICH

Andrew Masich is president and CEO of the Senator John Heinz History Center, the largest history museum in Pennsylvania, and chairman of the Pennsylvania Historical and Museum Commission.

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