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Thanks Allen. Those articles are interesting but don't get at the root cause. I started looking around for it and I am convinced Joseph Robertaccio, an environmental engineer from NY, has the answer. He wrote this comment on someone else's posting:

Looks a bit more complicated... A failure initiation zone is seen at the top of the barrel (note grey smudge)- the liner metal looks like their is an issue with the internal weld (looks like crystallization on inner rim). Suspect poor welding of the liner was the primary cause of failure. Usually these liners can take 200% of full military service charge alone (1/3 weigh of ball in powder) with a ball- it appears the rear of the liner was not properly welded and dislodged- This should not happen at the low service charges NPS uses in their guns for saluting- The high price of low bidder.....
 

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I have been waiting for a final report on this incident.

This picture speaks volumes:



Does this look like a properly shrunk fit and welded breech plug? Was this a core casting? Was this a bored and lined barrel.

My eye and limited knowledge sure says something not right with the breech plug, to start with, and things went bad from there.
 

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Discussion Starter · #5 ·
Thanks for the follow up information..... by the look of the photos of the breach it does not appear the plug was shrunk but a tight press fit.... the weld appears to be a single pass I would think on a gun this size it would require a deep "V" on the tube and plug with several passes of weld made in addition to being shrunk.... if there was 1/2 and inch to 3/4 of and inch of iron breach casting around the outer edge it would not be much.... the manufacturer has been in business for some years and from their sight appears until this to put out a good product..... they should thank God no one was maimed or killed in this......
 

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Agree with KABAR2 regarding the looks of a single pass weld. On metal this thick there should have been a chamfer or V groove all the way to the liner and multiple passes on up to and including the outside on the barrel. but not knowing what the barrel was cast of leads to even more questions. Welding high pressure oil lines were chamfered and used a seal ring which was inserted between the two pieces of oil line and then welded with multiple passes. Know about this as I had to observe the welding and subsequent hydro testing in front of witnesses and the NYCFD. Frank
 

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Check out the fouling on the OD of the plug. Couldn't have been deposited in that area unless there was a gap between it and the liner.


How come the plug is attached to the cascabel? Epoxy from installing the liner? ???


This incident shows why one should never rely on just a visual inspection of a lined barrel to determine if it's safe. Even if only for firing blanks.
 

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Good thing no one was seriously hurt, the attorney's would have a field day with this:

Forest Taylor, the proprietor of Cannons Online and manufacturer of the piece, visited
the fort the afternoon of the accident.
After he examined the damaged tube, he claimed the
fouling was evidence of overcharging and a "pressure wave" was created that shattered the
weld.
Steen and South Bend were contacted by the I.M.T. and their examination of the photo-
graphs yielded their independent conclusions that the weld failed to cause the accident, that the
sleeve was inserted too far back in the tube, and there was insufficient space between the plug
and the cascabel, and the steel sleeve cast inside of the iron tube confers inherent weak-
ness.
Pressure waves form when there is a cylinderical airspace between the powder charge and projectile. (See Burrard, Viehle and Dell)
 

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Victor3 said:
Check out the fouling on the OD of the plug. Couldn't have been deposited in that area unless there was a gap between it and the liner.


How come the plug is attached to the cascabel? Epoxy from installing the liner? ???


This incident shows why one should never rely on just a visual inspection of a lined barrel to determine if it's safe. Even if only for firing blanks.
I was thinking the same thing. Also the clear picture of the back of the casting... looks very thin section where the rear failed.
 

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Unusual things about this tube that I noted included the proof charge used, 6 lbs of fffg. Any wadding used or not? Tube was cast around the liner-who else does that, anyone these days? Liner was positioned very close to the outer surface of the cast iron in the breech area. If liner had been in center of mold prior to pouring the iron around it, it wasn't secured adequately and floated off-axis while iron was still molten. This issue alone may not have contributed to the accident but I take it as an example of the sloppy workmanship on the gun, not to mention the design issues.

I'm hoping they do a thorough investigation, which in my opinion would include x-rating, dissecting, whatever the unexploded mate.

Were liner and the steel plug welded onto it made of the same type steel? Was rod used compatible with both steels if they were different? Have done enough welding to know that if the rod and the steel aren't compatible you can get a weld that looks ok but doesn't "take" to one part or another and you may as well have used Elmer's glue. Some types of steel simply can't be welded but not everyone knows that.
 

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Discussion Starter · #12 ·
I may be mistaken doesn't Hern still cast liners in place? the reason the plug may still be attached to the cascabel knob is that there had been a centering rod welded to the plug it would have helped keep the liner centered in the sand mold sticking through the cascabel area and cut off after casting.... so the plug would be captured to the cascabel
 

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When they were still around, before the owner's untimely death, Cannon Limited cast liners in place on their guns.
My 10 pounder Parrott Rifle had a cast in place liner. They used a patented method to center the liner.
I have no idea as to how accurate the process was.

Zulu
 

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I hadn't thought about it but YES. They were likely made the same way. I believe the breechplug installation was faulty. A cannon is not worth somebody's life. Should be filled with cement & used as a dummy.
 

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The centering of the bore has little effect on guns strength. The liner system must be strong enough to stand on it's own . All I read about says you must at a min. anchor the breech plug by two methods ie welded , pinned , plate over welded again ,or threaded . Sweat or shrink fit is only to prevent and keep moisture out of plug joint . And install liner with a full cal'b. behind it .
 

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Why are they not loading Cannon grade powder in a 5 1/2" bore?
 

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Adding extenders are used for two reasons. If the vent hole is to far forward or load short it is added to back. Too the front for keeping round from flipping sideways going down the bore. Reduced blanks without sabot and ball easy fall over during ram as they are more like a pancake then cylinder . Large bore can be a challenge we have 4" and make rounds very tight to bore to keep aligned .
 
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