Vent reconditioning

[Cat Whisperer]

...
back in the day, when [the vent] eroded to .400", the right vent was filled with molten zinc, tin or lead and the left vent was then drilled through,
...
Tracy and Mike

Interesting - I'd not heard of TIN being used.  BUT from experience, tin when cast into a stone-cold mould, makes a perfectly filled out wrinkle free bullet.

It's cheap too.  ($11 a pound or so, unless you get it like I do - from work at LTL scrap prices.)  Let me know if you need a bit for this purpose.

Now the question.  SInce tin casts into a HARD (Rockwell B of 42-42 - the same as a copper jacketd bullet), does it erode faster or slower than zinc or a copper insert?

[dominick]

I think noticable erosion takes place where there is a movement of high velocity gasses as there is through the vent.

[Cannoneer]

Tim,

If 9 & 11-inch Dahlgren shell guns are the intended topic here then it isn't inserts (the French term is bouche) that were used on them, but the fact that some were actually manufactured with two vents. Some Dahlgren models had two vents bored off to each side (not in the center of the line of metal), one vent was bored all the way through to the powder chamber while the other was only bored most of the way, and then filled with molten zinc, because this would be easier to bore out at sea. When the first vent became too enlarged ("burnt out") that vent would be plugged at the bottom then filled with molten zinc, and the second vent would be bored out for use. Other large iron artillery pieces also incorporated this feature, the 13-inch Seacoast mortar had two vents.
The bouche or insert was mostly used on bronze artillery; when the bouche opened up to the point of losing too much pressure it would be unscrewed and replaced.

Civil War Naval Ordnance by Eugene B. Canfield
http://www.alternatewars.com/ACW/Civil_War_Naval_Ordnance.htm

[dan610324]

in some old bronze pieces Ive seen vents large enoug for me to put my thumb inside .
here you can see 2 pic of a repaired vent on a 1665 cannon
but here they have used brass

[Cat Whisperer]

I still wonder about the longetivity comparisons of diferent metals.

Guess I'll just have to run the experiments myself.

Think I can get a federal grant to fund 10,000 rounds in each of two or three 24 lb cannons?

But wait, there's more!

A serious thought - if one drills the vent too large, casting it full and redrilling IS AN OPTION!

[Double D]

Or just make a larger vent liner....

[Cat Whisperer]

But casting with tin is so simple and doesn't involve threading (there are some strength advantages).

Smooth surfaces don't bond well.  But merely having a rough surface will suffice.  Threading is ok (it obviously has worked well for years), but reduces the strength of the outside material by introducing the sharp vee - a stress riser.

[Double D]

But casting with tin is so simple and doesn't involve threading (there are some strength advantages).

Smooth surfaces don't bond well.  But merely having a rough surface will suffice.  Threading is ok (it obviously has worked well for years), but reduces the strength of the outside material by introducing the sharp vee - a stress riser.

Thats why proper thread forms have rounded roots.

[Cat Whisperer]

But casting with tin is so simple and doesn't involve threading (there are some strength advantages).

Smooth surfaces don't bond well.  But merely having a rough surface will suffice.  Threading is ok (it obviously has worked well for years), but reduces the strength of the outside material by introducing the sharp vee - a stress riser.

Thats why proper thread forms have rounded roots.

Agree.  But even then, one looses about 50% of the strength when one cuts the threads.

Let me repeat, threaded liners work.  They have worked for a LONG time.

[Artilleryman]

Tim,

If 9 & 11-inch Dahlgren shell guns are the intended topic here then it isn't inserts (the French term is bouche) that were used on them, but the fact that some were actually manufactured with two vents. Some Dahlgren models had two vents bored off to each side (not in the center of the line of metal), one vent was bored all the way through to the powder chamber while the other was only bored most of the way, and then filled with molten zinc, because this would be easier to bore out at sea. When the first vent became too enlarged ("burnt out") that vent would be plugged at the bottom then filled with molten zinc, and the second vent would be bored out for use. Other large iron artillery pieces also incorporated this feature, the 13-inch Seacoast mortar had two vents.
The bouche or insert was mostly used on bronze artillery; when the bouche opened up to the point of losing too much pressure it would be unscrewed and replaced.

Civil War Naval Ordnance by Eugene B. Canfield
http://www.alternatewars.com/ACW/Civil_War_Naval_Ordnance.htm

The original 8 inch siege mortar that we have has two vents, one drilled to within an inch of the bore.

[seacoastartillery]

      Just how much trouble are you fellows willing to put up with as you search for the perfect vent liner?  I bet not quite as much as CSN Commander John M. Brooke had to when he was confronted with repeated failure of the various vent liners he tried during testing of the high pressure 7" Treble-Banded Brooke Rifle in 1862 and 1863.  They were traditional copper vents at first which didn't blow out, but rather closed, preventing the fire from the following friction primer from reaching the next powder charge.  The bolts were 100 to 120 pounds and the Monitor punching powder charges were very heavy at 20 pounds, twice that of the 100 Pdr. Parrott.  He calculated the pressure to be in excess of 35,000 psi.

     He tried all types of experiments, including sending a spy north to Connecticut to obtain some platinum with which to plate the copper vent.  This and all the other types failed repeatedly until he tried something completely counterintuitive.  He ran the tip of the bouche, (what Brooke called it) into the chamber by varying distances, and found that a protrusion of between 3/8 and 1/2 inch worked the best.  He called for opinions of his best ordnance testers and they all agreed that tearing the powder bag was a possibility, but a minor one, because the vent was so far back in the truncated cone chamber, very close to it's small, hemispherical end.   The vent closure problem was mostly solved.

Just a little history,

Tracy

[Cannoneer]

I still wonder about the longetivity comparisons of diferent metals.

CW,
The only material used for historic artillery vent pieces that I've read about is copper, and at a later date copper with some form of platinum plating applied (which was thought to prolong the life of the bouche). This practice originated in Europe, but I've never read of the reasoning behind choosing copper as the go to metal for making vent pieces.
This excerpt is from "Artillery for the United States Land Service" by Brevet Major Alfred Mordecai, published in 1849. "The vents of brass guns are bored in vent pieces which are screwed into the gun; they are made of pure copper, hammered and annealed."


If any of the contemporary steels such as 1018, 4140-45, or 416 stainless were the materials being used to make an artillery barrel today, and if timely and proper maintenance were always carried out after firing black powder in them; even if the piece saw heavy duty use, would the vent have the possibility of burning out in a person's lifetime?

[Cat Whisperer]

Good bit of history, thanks, John.

The question of whether or not it would ever bun out in a lifetime was, however, raised by T&M.   

I am exploring the HOW of the process and looking at alternatives.

We know from hand loading cast bullets that gas-cutting of the lead can be severe along the side of the bullet.  We know from internal combustion engines that gas cutting past an exhaust valve can cut into steel.

Copper may have been the material of choice because of it's qualities to be formed into the necesary shape.  Sealing around the outside of the bouche may have been a critical issue.

One of my questions is focusing on how different materials last under these conditions.  If "a" lasts longer than "b", then it would be in the running for first choice - all other things being equal.

Is the gas cutting a function of thermal conductivity?  I'm assuming that copper conducts heat away from the surface much faster than tin but less well than silver.  Would the 3% silver and 1/2% copper in my tin alloy be of significant difference.

I have a handfull of micro-morters in which I drilled a 1/8" fuse hole - OOPS.  Way too big.  They will get sleaved, but I don't think it will make squat worth of difference in MY lifetime.

(I've seen platinum plated spark plugs too - but my feeling is that's an advertizing gimick.)

[GGaskill]

(I've seen platinum plated spark plugs too - but my feeling is that's an advertizing gimick.)

I have to say that the platinum sparks last at least 5 times as long as the old style plugs.  I have 125,000 miles on the set in my truck and they are still working well.

[Cat Whisperer]

(I've seen platinum plated spark plugs too - but my feeling is that's an advertizing gimick.)

I have to say that the platinum sparks last at least 5 times as long as the old style plugs.  I have 125,000 miles on the set in my truck and they are still working well.

I've run just two sets - two different cars and both sets developed high speed misses within 4,000 miles.  Not for me - the regular 79 cent plugs (now $1.98) work just fine.

[Cannoneer]

Tim,

If 9 & 11-inch Dahlgren shell guns are the intended topic here then it isn't inserts (the French term is bouche) that were used on them, but the fact that some were actually manufactured with two vents. Some Dahlgren models had two vents bored off to each side (not in the center of the line of metal), one vent was bored all the way through to the powder chamber while the other was only bored most of the way, and then filled with molten zinc, because this would be easier to bore out at sea. When the first vent became too enlarged ("burnt out") that vent would be plugged at the bottom then filled with molten zinc, and the second vent would be bored out for use. Other large iron artillery pieces also incorporated this feature, the 13-inch Seacoast mortar had two vents.
The bouche or insert was mostly used on bronze artillery; when the bouche opened up to the point of losing too much pressure it would be unscrewed and replaced.

Civil War Naval Ordnance by Eugene B. Canfield
http://www.alternatewars.com/ACW/Civil_War_Naval_Ordnance.htm

The original 8 inch siege mortar that we have has two vents, one drilled to within an inch of the bore.

You refreshed my memory, Artilleryman; the three M1861 large mortars (13, 10, and 8-inch) were equipped with two vents.


Does your original Parrott have a copper vent liner/bouche?