air chamber?

[eod20]

i was reading this an have no idea what it means   -   please enlighten me   
 
12.75-inch Blakely seacoast rifle. Total length and weight are unknown. Rifling is four-groove Scott with right-hand twist. Two of these rifles and their carriages were delivered at Wilmington NC in August 1863 for installation at Fort Fisher. Before they could be mounted, General Beauregard requisitioned them for the defense of Charleston SC. Unfamiliar with the characteristics and purpose of an air chamber, the Confederates burst one tube at the first fire. When John Mercer Brooke deduced the air chamber's purpose, the second tube was properly loaded and served at Frazier's Wharf while the first tube was repaired. Both were later blown up to prevent capture.

[Cannoneer]

eod20,

This site (Captain Alexander Blakely RA) was created by fellow member Starr 2011: Open "Cannon for the South" in the menu, and scroll down to "The Greatest Guns 1863" for information on the construction of these huge Blakely rifles.

http://captainblakely.org/default.aspx

[seacoastartillery]

     Eod20,  So nice of you to ask that question!  That gun has always fascinated me and I made a special trip to an obscure government office in Charleston with Mike to get a rare publication about it, which, if I could find it, I would tell you the title of it.  However the most information you can gather comes from CSN Commander Brooke's diary and ordinance notebook which is great grandson reproduced in a book called Ironclads and Big Guns of the Confederacy.  After the dolts in Charleston blew the breech off the first 60,000 pound Blakely, they sent a telegram to Brooke in Richmond asking, "What happened?"

     Brooke knew exactly what questions to ask as to the loading procedure and gun's construction to deduce precisely what happened and how to prevent it from re-occurring in the future.  From the ordinance engineer assigned to do the measurements in Charleston, he found that this unusual gun had a bronze something at the end of the chamber area that resembled a vase.  It had a void three times as long as it was in dia.  He figured it would be stupid to design a chamber for extra powder that had only a 5 inch thickness of bronze surrounding it.  The material that it was designed to hold had to be either marmalade or air.  He chose air, which was again, a correct deduction.  He theorized it's purpose was that of an air cushion to lessen the powder gas pressure's peak.  Again, correct.

     Blakely later wrote Commander Brooke that he designed it with this in mind and also that a thin tendrill of a powder bag was to go back for a distance into the air chamber, but he agreed with Brooke's instruction to the Charleston Artillerists, which was to load 40 to 60 pounds of naval gun powder, depending on the range desired, to the base of the powder chamber only, with none in the narrow air chamber.

That's the long and short of it.  Only anecdotal stories of the gun's effectiveness exist.  They all indicate that accuracy was nothing special, with one observer noting that, " After the huge explosion, a voluminous cloud of smoke issued forth and the 600 pound projectile shaped just like a nail keg was seen to go end over end, across the river and onto the trees.  Such a commotion was seen on the opposite shore in the wood that we surmised that 5 or 6 full sized trees might have been cut down."

Tracy and Mike

[eod20]

when i read that i was thinking  "pipe bomb"   really big pipe bomb

[Starr 2011]

 Thanks, Cannoneer, for pointing eod20 in the right direction!
 
Just to add to what Tracy and Mike have said – there is an excellent piece in the “South Carolina Historical Magazine”, April 1996 edition, called “Charleston’s Civil War Monster Guns, the Blakely Rifles” by C R Horres. This gives a good description of what happened before and after the damage to the first 13 inch Blakely gun.
 
I quake in my boots correcting Tracy and Mike, but the Men in Grey didn’t “blow the breech off” the big gun – there were either three or eleven cracks (depending whether you read the Navy or Army version of the incident) in the breech casting. Eason Brothers in Charleston were able to add reinforcing rings and bolts in a couple of months and the damaged gun was then fine.
 
It is very true to say that no one in Charleston (like you and I, eod20!), not even the army chief of artillery or the navy ordnance officer there, understood the purpose of the air chamber.
 
The gun was a CS Army purchase and responsibility for investigating the accident was in the charge of General Josiah Gorgas, chief of the army bureau of ordnance. He was livid over its misuse and deputed General Rains, at the Atlanta arsenal, to carry out an enquiry.
 
Commander Brooke of the CS Navy was consulted as he knew more about Blakely big guns than anyone else in the South. Brooke had confidence in the 13 inch guns and was interested in finding a way to adapt them for use on board ships.
 
Starr 2011
PS My avatar is Blakely’s own sketch of the 13 inch gun.

[Cannoneer]

The gun was a CS Army purchase and responsibility for investigating the accident was in the charge of General Josiah Gorgas, chief of the army bureau of ordnance. He was livid over its misuse and deputed General Rains, at the Atlanta arsenal, to carry out an enquiry.

I’m far from being a Civil War scholar, but I’ve read enough to realize that Jefferson Davis was the type of person that we today would refer to as a micromanager. He felt a need to have his hand in almost every aspect of any matter involving the CSA, whether it was important or mundane; so I’d just love for a document to come to light that would expose the extent of 'his displeasure' concerning the damage that was unwittingly caused to one of his nations new, and rather expensive guns.