10" Dahlgren Gun Explosion....Why?

Jobe Holiday

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The Perpetually Frozen North
In a previous thread "Donna" posted:

"Lady Polk". Episcopal bishop and Confederate General Leonidas Polk was gratified that his men had named a 10-inch Dahlgren in honor of his wife, Frances. The rifled piece required a specially trained nine-man gun crew. It was first fired during the November 7, 1861, battle of Belmont, Missouri, in which the gunners noted the accuracy of the weapon. Its projectiles were enormous, and some referred to them as "iron gateposts". When the Federals withdrew, the fully loaded "Lady Polk" was left in place. A few days later, Polk arrived and asked to see the gun. He was warned that since the loaded cannon had cooled with a charge primed to fire, there was a danger the weapon would explode if it was fired again. Nevertheless, the order was given, and the huge cannon burst, killing ten of the thirteen men in the gun crew as well as observers. Polk was knocked to the ground and his horse was killed."

Does anyone have any thoughts, or information, as to why there would be any difference between firing the gun cold with the first shot, and firing it after it has set loaded and become cold again?

Jobe
 
I think I found the answer to your question. It from "Big Guns of the American Civil War at http://melpor.hubpages.com/hub/Big-Guns-of-The-American-Civil-War

On the section on the Lady Polk., it states: "The battle ended with one round still in the gun. Unfortunately four days later during a demonstration for the general (Polk) ten of the thirteen men around the gun were killed and the general was knocked unconscious after the gun exploded. THE EXPLOSION OCCURRED BECAUSE THE ROUND LEFT IN THE GUN FOUR DAYS AGO COULD NOT EXIT THE GUN BECAUSE THE BORE OF THE GUN HAD SHRUNKEN IN SIZE AFTER COOLING DOWN AFTER THE BATTLE."
 
Thanks, Donna, that's great research, but a hard thing to believe! That would indicate that they fired undersize shells to start with and then larger diameter shells after the bore expanded? I've fired enough full scale artillery, with rounds, not blanks, to know that just doesn't make sense. Original artillery shells always had plenty of windage clearance to load cold.

Thanks again for your reference point!

J.
 
The following paragraph in the link reads:

Despite the limited use of these guns during the war the idea of using big guns in warfare did not end after the American Civil War. This eventually led to the development of the big guns seen today on battleships. These battleships ultimately change the tide of the war with their big guns at the Battle of Midway during World War II for the United States against Japan.

Midway is famous as a battle of aircraft carriers, one of a series of battles which demonstrated that the carrier had displaced the battleship as the arbiter of sea power. Two Japanese battleships, escorting their carriers, fired at attacking American aircraft, but there was no surface action by battleships or any other combatants; indeed the opposing fleets never even sighted each other. Anyone with even a rudimentary knowledge of WWII knows this, so I would take this person's comments on military topics with a large grain of salt.
 
I have two ideas about exploding guns. (1) The big guns were cast iron not wrought iron like the ordnance rifles. These huge pieces of cast iron likely had air pockets and voids throughout the iron causing them to have weaknesses that finally gave way to the breach pressures on firing. (2) Previously fired then reloaded pieces may have allowed powder fouling to harden around the shell causing excessive pressure on firing. Just my 2 cents.
 
I did some quick internet searching and am now thoroughly confused. I've read that "Lady Polk" was a Dahlgren/Whitworth/Columbiad with a bore of 6.4"/8"/10"/20", firing a shell of 64pds/128pds, and the whole gun weighed either 7.5 or 8 tons (finally, some numbers that are actually close.)

I think the Lady Polk was actually an 8" rifled, muzzle-loaded Columbiad that fired a 128pd conical shell (normal shot for this bore would be 64pd) and was made at Tredegar. Does that sound right? Perhaps the previously loaded shell got jammed into the rifling due to some effects of the gun cooling, but it's more likely that a weakness in the casting, exacerbated by the previous firings and perhaps an overly large powder charge, caused the gun to burst.
 
In the link on "Big Guns of The Civil War" that I posted in a previous post in this thread, the author states: " The "Lady Polk" was a 20-inch Dahlgren gun... The gun weighted 16,000 pounds (8 tons) and could lob a projectile weighing 128 pounds."
See the entire article at http://melpor.hubpages.com/hub/Big-Guns-of-The American-Civil-War

As Carronade said, that site doesn't appear to be very accurate at all. According to other websites a 20-inch shell weighs over 1,000pds. Looking at basic physics, if you think of a solid iron ball with a diameter of 20 inches, I think you'd agree that it would probably weigh much more than 128pds. Iron weighs about 450 lbs per cubic foot and a 20 inch ball is much larger than a 12 inch cube.
 
Black powder is hydoscopic and not swabbing the bore after the last shot and leaving a loaded round over a short period of time causes moisture to gather in the bore and rust to form causing the bore to constrict. Excessive pressure results and any casting flaws causes a burst barrel. That's my final answer and I'm sticking to it!:D
 
My thought, for what it's worth, is that Dahlgren's had a habit of bursting (Don't ask me why.). It was the reason that the two Dahlgren's aboard the USS Monitor were only half-charged in its historic argument with the CSS Virginia.

It has been said that, if the guns fired with a full charge, the shells would have easily pierced the Virginia's sides. The reason? Dahlgren's had a habit of bursting.
 
Yes, those big guns had BIG problems with staying in one piece! This is something I had studied many years ago....don't ask why, an enquiring mind I guess, but what I found out was that the disparate cooling rate between the outside of the tube and the inner core had a tendancy to cause internal cracks. Those internal cracks had a bad habit of failing catastrophically at the most inopportune time!

Here is yet another suggestion on the failure of "Lady Polk"....Was she sabotaged? Perhaps the Confederates, knowing they couldn't remove her, charged the last powder bag with something like pistol powder! That would cause a pressure spike high enough to create a catastrophic failure!

Jobe
 
The website link given doesn't appear to be accurate at all with respect to the Lady Polk. XX Dahlgren's weren't cast until 1864. (There were XX Rodman's, but these were U.S. pieces.)

IIRC large smoothbore cannons cast with the Rodman hollow casting method were successful. It was the older non-hollow cast guns that burst. The other types that burst were rifled versions of the large bore types. The XI Dahglren's were reliable, but not fully tested at the time of the tussle with the Virginia. Initially the XI's were not hollow cast, which might have been the source of concern. XV Dahlgren's and greater were hollow cast.

The following link seems better researched: http://rosswar.blogspot.com/ There were two of these cast and both burst, one at Columbus, the other at Island #10. Tredegar used 10" smoothbore Columbiad moulds then bored and rifled to 6.4". (However, the shape is actually of Rodman pattern, but with Columbiad ratchets.)

The rifling pattern is not clear to me. Nathaniel Cheairs Hughes' The Battle of Belmont lists it as 128 pdr "Whithworth" although it was not--I just found confirmation that Tredegar made it and was aware of the burst in Charles Dew's Ironmaker to the Confederacy. The image in the link I gave shows another cannon (a 3rd?) that is at Mobile...I might have a picture of this myself somewhere. Anyway this one shows up in an appendix in Olstead, Stark, Tucker's The Big Guns as a surviving 6.4" Confederate rifle. Ripley's book states it came from Fort Powell below Mobile and it is a Tredegar piece. Unfortunately, the rifling type is not described. The image has some sort of 5 groove pattern.

I don't know whether the cooling barrel theory is correct or not. I would be equally concerned about some "flash rust" of the round in the freshly sponged barrel that had been recently fired if it was left for 4 days. Might have "welded" itself in place enough to overpressure the breech on firing. It would seem a major mistake by the crew/gun captain to leave the piece in that condition.
 
Thanks to all about the gun. I really know nothing about them. What I originally posted was about guns named after prominent ladies of the era. I just thought was interesting about how they were named.

I got my original information on all of them from Webb Garrison Sr. in his book, 'Webb Garrrison's Civil War Dictionary". He had the Lady Polk as a 10-inch Dahlgren. He also referred to her as a Rifled Piece.

I have also found reference to this on the Battle of Belmont sites.

Garrison has definition of Dahlgren as:

A classification of three types of naval ordnance designed by John A. Dahlgren during his tenure as director of ordnance at the Washington Navy Yard, which began in 1847. The first was a model 12- and 24-pound bronze boat Howitzers and Rifles that were developed just after the Mexican War. In the 1850s Dahlgren refined a series 9-, 10-, and 11-inch iron smoothbore shell guns capable of firing both shell and shot. He added 15- and 20-inch versions during the first years of the war. Because of their shape, they were nicknamed "Soda-Pop Guns". By 1860 Dahlgren had developed 50-, 80-, and 150-pound rifles, of which the 50-pound version was the most successful."
From: "Webb Garrison's Civil War Dictionary" by Webb Garrison Sr. page 82.

Webb Garrison was a best-selling author of more than fifty books on the Civil War which included "A Treasury of Civil War Tales". "Civil War Curiosities", "The Lincoln No One Knows", "Amazing Women of the Civil War", "Friendly Fire in the Civil War", and "The Unknown Civil War". Work on this book, "Webb Garrison's Civil War Dictionary", was completed shortly before the author's death in 2000. Cheryl Garrison, who co-authored, is a writer and editor who lives in Clyde, North Carolina
The book does have an extensive Bibliography on pages 346-350.
 
My thought, for what it's worth, is that Dahlgren's had a habit of bursting (Don't ask me why.). It was the reason that the two Dahlgren's aboard the USS Monitor were only half-charged in its historic argument with the CSS Virginia.

It has been said that, if the guns fired with a full charge, the shells would have easily pierced the Virginia's sides. The reason? Dahlgren's had a habit of bursting.

Nope... sorry. Dahlgren's smoothbores were known to be extremely reliable, and I can't recall offhand that any of them burst in action (as opposed to in testing). (His rifles were another matter.)

The guns in Monitor were not on half-charges because they were thought to be unreliable; they were on half-charges because it was not known what the effects of repeatedly firing them within the turret would do to the gun crews, and there wasn't much time to test to find out.

One thing is for darncertain, though... the "Lady Polk" was NOT a "20-inch Dahlgren." Dahlgren worked at casting and testing a couple of pieces of that size for Ericsson, who wanted to arm the large monitor Puritan with them, but they were never used in service; and that was later in the war.

I'm also not certain that there were any 10-inch Dahlgrens. There were nines and elevens; it is possible there were a limited number of tens, but I'll have to refer to Spencer C. Tucker's Arming the Fleet: US Naval Ordnance in the Muzzle-Loading Era to check. (My bet is on the Columbiad cited by ExNavyPilot.)
 
(My bet is on the Columbiad cited by ExNavyPilot.)

Don't bet too much. My "cite" was more a SWAG than a fact-based conclusion. All the citations I found agree that Lady Polk was a large gun (weighing about 7.5 to 8 tons), but the design and bore size are in wide disagreement. I think we can dispense with the idea that it was a Whitworth or that it had a 20" bore. It probably was in the 8-10" range, and of a Dahlgren/Columbiad design type probably cast at Tredegar. That said, it would have been vulnerable to the stress cracks caused by uneven cooling when casting large guns (prior to the inner core cooling method.) Add to this a shell that had been left in the chamber for a few days and possibly rusted, the overpressure created by the rust might have ruptured the stress-crack-weakened tube and burst the gun. So, answering Jobe's question, it looks like the bursting of the gun wasn't caused by the difference in tube/shell clearance based on loading the gun hot versus cold, but by a possible combination of two factors; tube weakness caused by casting imperfections/procedures, and leaving the gun loaded so the shell could rust and cause it to require higher pressure than usual to expel it.
 
There were 10-inch Dahlgrens, though not a lot of them. They appeared as pivot guns, one or two, on the upper decks of ships like the Merrimack class frigates and the razeed Cumberland whose main broadside batteries were 9-inch Dahlgrens. An inch may not seem like much, but in this size range it made the shell about 40% heavier. A shell 2" larger, 8-10 or 9-11, was about twice the weight.

A rough rule of thumb for solid iron cannonballs is bore diameter in inches, cubed, divided by 8 gives approximate weight in pounds, for example 10x10x10/8=125. Incidentally a similar rule for 20th century shells is diameter cubed divided by 2.

One more trivia item, the Merrimack class also had fourteen 8" shell guns on the upper or spar deck, but these were the older Paixhans type, not Dahlgrens.
 
To resummarize what I researched last night:
The Lady Polk was cast as a 10" Confederate Columbiad block at Tredegar (J.R. Anderson & Co.) These however had the profile of Rodman's, but had the ratchets of a Columbiad so they were mutts. The piece was bored and rifled to 6.4" for nominal 128 pounder rating. That Mobile piece of the same vintage with 5 land and groove rifling is the best guess we have about the rifling pattern used. Brooke rifling was 7 groove...I don't think there are any known 5 groove types.

More clarification:
The information backing it being a Tredegar cast piece is rock solid. Tredegar documents to Graham describe the bursting of their piece at Columbus and attribute it to the pig iron from the Graham furnace--the preferred source was Cloverdale and there was a contract for it, but the furnace operators were engaged in war profiteering selling on the open market rather than honoring their contract. The Tredegar gun founder list shows at least 28 of the 10" pieces cast at Tredegar from April to October of 1861. It doesn't state that any were rifled, but that often wasn't noted. (Indeed, the one survivor in Mobile was cast Oct. 17, 1861 and had the mutt Columbiad/Rodman profile that was Tredegar's normal production.) When finished as rifled vs. smoothbore the 10" castings were rifled to 6.4" while 8" castings were rifled to 5.8"
 
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