Adding touch hole (Vent) liner to HERN 5/8 scale carronade

[nad]

Greetings!

I am part of a group that fires a pair of HERN 5/8 scale carronades for demonstrations. We have done so with out incident for the last 4 or 5 years. One of our members saw the NSSA rules for artilery and noted that they required brass vent liners, and he feels that we should retrofit the cannons with Brass touchhole (vent) liners.  We do not participate in NSAA re-enactments, and we only fire blanks (no ball) in our demonstrations.

These leads to a couple of questions.

1) Are the vent liners nessary?  What are the pros and cons of adding them?
2) Is there any good source for instructions, or diagrams on HOW to do the vent liners?
3) Any recomendation on places to get the materials needs to make/install vent liners?

Dan

[GGaskill]

Do your guns have bore liners?  If not, there is no rush to install vent liners as there is no joint where sparks might collect.  If they do have bore liners, then a vent liner is a good idea but it has to fit properly so it doesn't create its own joint for sparks to hide.

[KABAR2]

Dan,

Welcome to the forum!

The concern is that a lined barrel when cleaned with water allows moisture to get into the vent,
this can cause rust to form between the iron casting and the liner which overtime can eat away at
the iron as the gun is fired rust and derbies are moved out the vent and after years of use could cause
a void between the liner and barrel.

There may be a sticky on the subject at the top of the page,
it is easy enough to install a liner all you have to do is bore a hole and thread it for your chosen liner material
it is a good idea to use a never seize compound on it so if needed it can be removed and replaced at a future date.
hope this helps.


Allen <><

[Double D]

Everything has been pretty much covered by others response The only thing I can add is that Antique Ordnance Publisher includes information about vent liners, including drawings.  You might contact them and get a copy.  Here is a link to their catalog of plans Antique Ordnance Publisher Give them a call and see what they can do for you.

[RocklockI]

Demonstrations Live fire or Blanks . in either case I would tell you venting them is a waste of time and money .

How many shots are you ever really going to fire ?

In Montana I was rockin and rolling with 15 shots in a day . And thats not much , as far as corrosion getting between the liner and the iron ........

Forget about venting them . Unless you are firing heavy loads of live ammo .......but even then I wouldnt .

Gary

[KABAR2]

Gary,

I have to disagree, when doing demonstrations in public the crew manning the gun has to keep safety in mind,

the group should have insurance in case there was an accident..... but in this day and age everyone on the crew

could be considered libel if one of the public is injured in an accident,  there was a case where a restaurant had

a cannon it fired daily it had a customer light it off,  the customer was injured .... there was an investigation by

a person knowledgeable in artillery  he found from years of firing the touch hole was eroded and rather large

when it is a personal cannon for your own use one can choose not to line the touch hole but it is a whole

different arena when the public is involved and our hobby does not need negative write ups like the one last

year at Fort Niagara or the fellow in Pa.  when precautions can be taken.

Allen <><   

[Cat Whisperer]

nad - dan -

Great handle!

Welcome to the board.  When you can, we'd love to see pictures of smoke and flame!

[RocklockI]

But Kbar2 ....you said they shot it every day . That is entirly differant from my meaning .

Besides I dont believe they are nessecary unless you are shooting a high pressured iron clad killer .

Then you better you better you bet !

Gary

[gulfcoastblackpowder]

Has a vent liner ever blown out of a cannon?  As many times as I've seen them discussed on here, I've never heard of such a thing, but I was discussing this with a friend of mine, and he thought the liner could become a projectile, which would be far worse than not having one at all.

[RocklockI]

Yes they have evaporated in the big Parrotts and Brooks . I think they finally used platnium IIRC

Tracy will be along soon to correct me . But they had a heck of a time getting the heavy rifles to take a vent liner .
Gary

[GGaskill]

I suppose it could happen if the threads weren't well done, but a typical liner is maybe 1/2" in diameter (.2 sq in) so it would see about 4000 lbs force at 20,000 psi chamber pressure, which is a high figure.  And the force would be of very short duration so I don't think there is much likelyhood of one coming out unless there wasn't much thread engagement.

[Double D]

If you are going fire even one shot a year in a barrel that is lined you need a vent liner.

The original monometal barrels used a liner to deal the problem of vent erosion or to repair an eroded vent.

Modern lined barrels need the liner to prevent the effects of galvanic corrosion between the two different metals of liner and barrel, which is accelerated by black powder fouling.    This type of corrosion takes place over a period of years. It has been documented in the past in the Artilleryman.  It is a safety issue and should not be compromised.

[gulfcoastblackpowder]

I suppose it could happen if the threads weren't well done, but a typical liner is maybe 1/2" in diameter (.2 sq in) so it would see about 4000 lbs force at 20,000 psi chamber pressure, which is a high figure.  And the force would be of very short duration so I don't think there is much likelyhood of one coming out unless there wasn't much thread engagement.

That's my concern with them.  Cast iron doesn't hold threads very well, so the primary engagement is in the sleeve-vent interface.  Any recommendations on thread to ensure a good fit?

[dominick]

Cast iron should have coarse threads.