The Rodmans of Fort McHenry
Three types of Rodman Gun are depicted in this photo from Fort McHenry: Nearest the camera is a 15-Inch Smoothbore. The next two are 8-Inch Smoothbores. The next three are 8-Inch Rifles converted from 10-Inch Smoothbores. Finally, in the distance another 8-Inch and a 15-Inch can be seen.
The 8-Inch Rodman is not a small cannon. It only appears so when placed next to a 15-Inch Rodman. Left and right are 8-Inch Rodmans. At center is a 15-Inch Rodman. At Fort McHenry near Baltimore, Maryland
Again, the 8-Inch Rodman is not a small cannon. It is heavier - perhaps by about 1,000 pounds - than this French 36-Pounder. This type of cannon was the largest available to the American defenders of Fort McHenry in 1814.
Taken in isolation, the US Army’s 8-Inch Rodman would be an impressively large and heavy piece of artillery. Weighing 8,500 pounds, it was a bit more massive than the largest cannon used to defend Fort McHenry in 1814: the French 36-Pounder. However, Thomas J. Rodman’s innovations in the casting and manufacture of heavy cannon allowed a similar weight gun to be far more effective. The 8-Inch Rodman could fire a shot weighing about 65 pounds - nearly double the 36-Pound shot of the old French guns - with a greater propellant charge. The 8-Inch Rodman was also very capable of firing exploding shells.
The 10-Inch Rodman was much larger still - weighing about 15,000 pounds it could fire a 128 pound shot or roughly 90 pound shell. And both guns were dwarfed by the 15-Inch Rodman which weighed about 50,000 pounds and fired a 440 pound shot or 360 pound shell.
All three types are on display at Fort McHenry. Next to the massive 15-Inch Rodmans, the 8-Inch Rodman appears diminutive. It is not. It only looks so by comparison.
The 10-Inch Rodmans present are actually all guns which were converted in the 1870s into 8-Inch Rifles. I’ve described this conversion process in a previous post. Three are muzzle insertion conversions. One is a breech insertion conversion.
The carriages of the three 8-Inch Rifles (converted 10-Inch Smoothbores) are interesting as they had a hydraulic cylinder, rubber bumpers, and gears added - again showing the attempt to modernize these ancient muzzleloaders in a world of steel breechloaders.
Weighing nearly 50,000 pounds and capable of firing a 440 pound projectile, the 15-Inch Rodman is a massive gun.
The three cannon at right are 10-Inch Rodmans that were converted in the 1870s to 8-Inch Rifles by boring out their barrels to 13.5 inches before inserting an 8-Inch rifled sleeve.
The 8-Inch rifled sleeve of this converted cannon may be seen here.
One of the four 8-Inch Rifle conversions is of the “Breech Insertion” type. This was an attempt to create a stronger cannon using a sleeve that was a greater diameter at near the breech. They can be distinguished from the muzzle insertion type by the square shaped cascabel which is where the sleeve was threaded into the existing gun.
The rifling of the breech-insertion conversion may be seen. At left are two of the 8-Inch rifle conversions. In the left background are two 8-Inch smoothbore Rodmans and a 15-Inch Rodman.
Two 8-Inch and one 15-Inch Rodman guns at Fort McHenry showing the lever-post-socket elevation arrangement (missing the lever) of later Rodman guns.
Note the gearing and rubber bumpers on the carriages of the three rifle conversions. Not shown is a hydraulic cylinder beneath the cannon.
A muzzle-insertion 8-Inch Rifle conversion with the breech-insertion conversion in the background.
Two 15-Inch Rodmans
From left to right: Three 10-Inch Rodmans converted to 8-Inch Rifles, two 8-Inch Smoothbore Rodmans. One 15-Inch Smoothbore Rodman. In the background are the remaining portions of the destroyed Francis Scott Key Bridge.
This interpretive sign shows an image of the Rodman guns being fired near the very end of their service with the US Army in 1903. It also notes the 1888 additions of the hydraulic cylinders and rubber bumpers on the carriages for the 8-Inch converted rifles.
The Star Spangled Banner yet waves on the parade ground at Fort McHenry
