Author Topic: Proof Load New Tube (Read 1904 times)

ironball · « **on:** February 25, 2012, 01:17:28 PM »

I recently recieved my 3" Coehorn from Hern, but before I go through the trouble of building the base I want to test fire it with a much heavier load than what I will use for general use.

That way I will have no qualms about firing normal charges with spectators around. With foil wrapped charges, I plan on a blank containing of a full pound of FFg, and for live fire, an 8 oz charge under a can of beans. While I don't believe it's needed, I plan on setting the mortar down inside a few old tires, just in case.

Is this a valid test? What do you guys think?

Cat Whisperer · « **Reply #1 on:** February 25, 2012, 02:04:24 PM »

To intentionally overload a cannon or mortar is to push the stress (pressure) up the curve (stress-strain) towards the point of permanently deforming the metal. You have a proven design/product, trust the manufacurer; stay within the manufacturer's recommended loads.

Artilleryman · « **Reply #2 on:** February 25, 2012, 02:06:39 PM »

I personally don't believe in proof loads. I think that doing so may stress (weaken) the barrel to the point where it may fail later with a "regular" load.

ironball · « **Reply #3 on:** February 25, 2012, 02:12:28 PM »

In Europe, they don't trust the manufacturer's recommendations. They test each and every gun. It seems to have worked well for the last several hundred years, and I don't really see how our "let them sell anything, and sue the pant's off 'em later " system works any better.

P.S. I don't believe I am overloading anything, I'm just above the "fraidy cat" loads reccomended here on this site.

Cat Whisperer · « **Reply #4 on:** February 25, 2012, 02:18:49 PM »

I don't know who 'they' are in Europe. I do know of Hern's reputation.
I'll stick with not violating the strength of the material.

ironball · « **Reply #5 on:** February 25, 2012, 02:21:02 PM »

Quote from: Cat Whisperer on February 25, 2012, 02:18:49 PM

I don't know who 'they' are in Europe. I do know of Hern's reputation.
I'll stick with not violating the strength of the material.

So are you stating that I'm violating the strength of the material? What do you base this on?

Cat Whisperer · « **Reply #6 on:** February 25, 2012, 02:35:28 PM »

Quote from: ironball on February 25, 2012, 02:21:02 PM

Quote from: Cat Whisperer on February 25, 2012, 02:18:49 PM
I don't know who 'they' are in Europe. I do know of Hern's reputation.
I'll stick with not violating the strength of the material.
So are you stating that I'm violating the strength of the material? What do you base this on?

No I am not saying that you ARE. I am saying that you don't know how much you're stressing it.

I am saying that by overcharging you drastically increase the pressure (strain) on the metal.
I am saying that you have no way of knowing how far up the stress-strain curve you're going.

All you have to do is to stress one area too much. It becomes brittle. A crack starts. Your first indication of that is when it fails SOMETIME in the future. It may take years.

ironball · « **Reply #7 on:** February 25, 2012, 02:41:12 PM »

But I mantain that I am NOT overstressing it. You are the one saying that.

seacoastartillery · « **Reply #8 on:** February 25, 2012, 02:41:43 PM »

Ironball, We agree with CW and Artilleryman on this topic, but if you decide that you absolutely have to do it, please do not trust a couple old tires to save your hide if she lets go. Do it SAFELY!! Dig a proper pit a minimum of two feet deep and lay your tube horizontally on the dirt at the bottom. Use at least two feet of standard green cannon fuse. Have yourself on the other side of a hill with twenty yards of dirt between you and your test. Remember that without taking before and after tube dia. dimensions, you will have learned NOTHING.

T&M

GGaskill · « **Reply #9 on:** February 25, 2012, 02:47:12 PM »

Does the Hern have a chamber? If it does, a full chamber is the manufacturer's definition of a full charge. If you put in more powder than the chamber holds, you will be relying on the thinner tube walls to carry the load.

But to each his own.

Cat Whisperer · « **Reply #10 on:** February 25, 2012, 02:48:24 PM »

Not overstessing it? Based on what? Is that charge within the manufacturer's recommendation?

I've seen too many things (in failure analysis) broken from repetitive stressing (supposedly within design specs) to risk overstressing (which would only accelerate the strain).

Show me the numbers. Dig out your references in materials. Do the calculations. Figure BOTH strength and toughness. Show us that the forces that you're applying are well within reasonable stress-strain loading.

If you can't, you're guessing.

ironball · « **Reply #11 on:** February 25, 2012, 02:50:05 PM »

Past experience tells me that I can load a tube of this size flush with the muzzle, and nothing bad will happen. But you folks who have never tried it all seem to know better.

Cat Whisperer · « **Reply #12 on:** February 25, 2012, 02:54:15 PM »

Quote from: ironball on February 25, 2012, 02:50:05 PM

Past experience tells me that I can load a tube of this size flush with the muzzle, and nothing bad will happen. But you folks who have never tried it all seem to know better.

What we are saying is that one or two overloads successfully survived MAY have damaged the tube that will result in failure perhaps years down the road. That is a risk not worth taking. It's OK right up to and including the shot before it fails.

Cat Whisperer · « **Reply #13 on:** February 25, 2012, 03:00:05 PM »

Here's an example of a stress-strain curve.

http://www.tppinfo.com/defect_analysis/yield_strength.html

Keep the pressures in the linear part of the curve and the material stretches and returns to normal.
Exceed the stress (yield stress point) and you have permanent deformation and hardening.

That is why T&M recommeded you take MEASUREMENTS before and after proofing.

ironball · « **Reply #14 on:** February 25, 2012, 03:00:55 PM »

Whatever. I'll leave it for another day, as it's time for me to watch Kill Bill Vol. 2 again. Samuri swords and Tamagashi steel is another one of my interests.

copdoc · « **Reply #15 on:** February 25, 2012, 04:02:01 PM »

Please, caution with shooting the Hern tubes. They are cast iron with pipe liner, no powder chamber and 90 degree anlge at base. Their web site say they are "decorative". I have a Hern Coehorn and have shot it using high/low pressure loads. I fired a bamboo Hou Qiang (hand cannon) in a similar way for the History Channel. It is a dangerous thing to do. That is why I would not let Gunny hold it and shoot. We fired it about 10 times and no failure but is was made of paper and bamboo and was shooting a 1.25 inch rock at nearly 250 fps.

All modern cartridge guns that I know of are proof fired in the US. I have fired some at S&W and Ruger with proof loads. Since there is no standard for the cannon we build I do not know how you would actualy calculate the charge. Too much of an overcharge could damage the barrel. I did "proof" test the first one I built in 1976 but did have even the small amount of knowledge I have now on how to do it. (It was 10-12 inches below ground and in a ditch with 6 foot wall, thankfully I knew that) I would think that unless it were tested and standardized proof loads might damage your barrel.

I hope this helps. $0.02 worth

PS lining the bolt holes up in the sled is more difficult than it looks with hand tools.

copdoc

Double D · « **Reply #16 on:** February 25, 2012, 05:28:43 PM »

Quote from: ironball on February 25, 2012, 01:17:28 PM

I recently recieved my 3" Coehorn from Hern, but before I go through the trouble of building the base I want to test fire it with a much heavier load than what I will use for general use.

That way I will have no qualms about firing normal charges with spectators around. With foil wrapped charges, I plan on a blank containing of a full pound of FFg, and for live fire, an 8 oz charge under a can of beans. While I don't believe it's needed, I plan on setting the mortar down inside a few old tires, just in case.

Is this a valid test? What do you guys think?

No your test is meaning less.

Proofing is done to very specific set of parameters looking for specific results.

The European system is an antiquated system that only marginally test the strength of the gun, and absolves the manufacture of most liability from failure of the arm. European arms are only proofed to 120% of peak working pressure. It is a system that is promoted by the Arms Makers to get them out of responisiblity.

The US system is for the manufacture to build and proof test the design. That proofed arm is retained by the manufacure for future reference. US proof standard is 140% of peak pressure. Once the design passes proof there is no need to proof arms made to that design. If a component is changed the the design is reproofed. Most companies do periodic and or random proofing of arms coming off the line.

Every U.S. arms manufacturer does function testing of their guns but only Savage proofs every gun and they only proof to European standards 120%.

Proof testing failure isn't when the gun destructs, that is way beyond failing proof. A gun that doesn't destruct does not necessarily pass proof. After proof testing the gun has to be measured to determine if dimensional changes occurred.

Bottom line you have no idea what pressures are developed by the load you are purposing.. They may be high they may be low. Unless you know your load pressure you test is meaningless.

You asked us what we thought, we told you.

Quote from: ironball on February 25, 2012, 02:50:05 PM

Past experience tells me that I can load a tube of this size flush with the muzzle, and nothing bad will happen. But you folks who have never tried it all seem to know better.

Once again you come to this board make statements that by their content show your total lack of knowledge on the subject. You have no idea what you are talking about. You do not know who the people are here or what their knowledge or expertise, yet you poor mouth them.

You are troll. It seems the only reasons you ever come here is to start a flame war.

Perhaps you could do us all a favor and find some other board to share your vast lack of credible knowledge!

ironball · « **Reply #17 on:** February 25, 2012, 06:04:19 PM »

Quote from: Double D on February 25, 2012, 05:28:43 PM

Quote from: ironball on February 25, 2012, 01:17:28 PM
I recently recieved my 3" Coehorn from Hern, but before I go through the trouble of building the base I want to test fire it with a much heavier load than what I will use for general use.

That way I will have no qualms about firing normal charges with spectators around. With foil wrapped charges, I plan on a blank containing of a full pound of FFg, and for live fire, an 8 oz charge under a can of beans. While I don't believe it's needed, I plan on setting the mortar down inside a few old tires, just in case.

Is this a valid test? What do you guys think?

No your test is meaning less.

Proofing is done to very specific set of parameters looking for specific results.

The European system is an antiquated system that only marginally test the strength of the gun, and absolves the manufacture of most liability from failure of the arm. European arms are only proofed to 120% of peak working pressure. It is a system that is promoted by the Arms Makers to get them out of responisiblity.

The US system is for the manufacture to build and proof test the design. That proofed arm is retained by the manufacure for future reference. US proof standard is 140% of peak pressure. Once the design passes proof there is no need to proof arms made to that design. If a component is changed the the design is reproofed. Most companies do periodic and or random proofing of arms coming off the line.

Every U.S. arms manufacturer does function testing of their guns but only Savage proofs every gun and they only proof to European standards 120%.

Proof testing failure isn't when the gun destructs, that is way beyond failing proof. A gun that doesn't destruct does not necessarily pass proof. After proof testing the gun has to be measured to determine if dimensional changes occurred.

Bottom line you have no idea what pressures are developed by the load you are purposing.. They may be high they may be low. Unless you know your load pressure you test is meaningless.

You asked us what we thought, we told you.

Quote from: ironball on February 25, 2012, 02:50:05 PM
Past experience tells me that I can load a tube of this size flush with the muzzle, and nothing bad will happen. But you folks who have never tried it all seem to know better.

Once again you come to this board make statements that by their content and show your total lack of intelligence and true knowledge on the subject. You have no idea what you are talking about. You do not know who the people are here or what their knowledge or expertise, yet you poor mouth them.

You are troll. It seems the only reasons you ever come here is to start a flame war.

Perhaps you could do us all a favor and find some other board to share your vast lack of credible knowledge!

You, sir, are glaringly in violation of the board rules with this sort of name calling. I would have expected better of you as a past moderator, but I can see now why you had to resign.

Double D · « **Reply #18 on:** February 25, 2012, 06:17:43 PM »

Ah you quoted posted while I edited out my imprudent comments. You quote my original words, my post is edited.

You are indeed a troll. It defines a type of internet conduct. It is a statement of fact.

http://en.wikipedia.org/wiki/Troll_%28Internet%29

Quote

In Internet slang, a troll is someone who posts inflammatory,[2] extraneous, or off-topic messages in an online community, such as an online discussion forum, chat room, or blog, with the primary intent of provoking readers into an emotional response[3] or of otherwise disrupting normal on-topic discussion.

Your latest post reinforces that statement of fact.

Quote from: ironball on February 25, 2012, 06:04:19 PM

You, sir, are glaringly in violation of the board rules with this sort of name calling. I would have expected better of you as a past moderator, but I can see now why you had to resign.

ironball · « **Reply #19 on:** February 25, 2012, 06:22:44 PM »

LOL, call me anything you want, but editing posts after you have been reported sound somewhat dis-honest to me.
Oh, and please tell me how I am disrupting on-topic discussion when I am the originator of this topic.

GGaskill · « **Reply #20 on:** February 25, 2012, 06:49:47 PM »

Is this a valid test? What do you guys think?

The above is from your lead post. You have gotten lots of replies, most if not all disagreeing with your position and giving reasons for the disagreement. If you truly were asking for the opinions of the forum members, you got them.

You are free to do what you want here but it seems absurd to believe you really came here without having already made up your mind. If that is the case, why ask in the first place?

ironball · « **Reply #21 on:** February 25, 2012, 07:01:34 PM »

Well, yes, I have made up my mind to try those loads. I did not expect to be called a troll, or be accused of a "lack of intelligence". I thought being polite was a rule here. So sorry.
But I won't be leaving, I have thicker skin than that.

BoomLover · « **Reply #22 on:** February 25, 2012, 08:53:57 PM »

Austin, please don't let the remarks of one bad egg spoil your experiences here. This ironball character seems to delight in posting questions, with his mind already made up, just to revel in negating the responses he gets. He truly does not understand what he is saying, and doesn't understand that by filling his cannon up to the mouth and lighting the fuse, he is creating such a hazardous condition that he really can't comprehend his own words or actions. His challenging senior members of this forum who have built and studied the ends and outs of cannons, mortars and howitzers for many years is only exposing his immaturity and lack of knowledge of this subject. Usually, with folks like this, the old saying goes, "Give them enough rope, and they will hang themselves". It's times like this when John Wayne's quote comes to mind,..."Life's tough, it's even tougher if your stupid.". I beg the indulgence of the members of this forum for my remarks, but I really felt compelled to have a word on this subject. Thanks, BoomLover

Cat Whisperer · « **Reply #23 on:** February 26, 2012, 12:52:03 AM »

Quote from: ironball on February 25, 2012, 07:01:34 PM

Well, yes, I have made up my mind to try those loads. I did not expect to be called a troll, or be accused of a "lack of intelligence". I thought being polite was a rule here. So sorry.
But I won't be leaving, I have thicker skin than that.

Show us the evidence of intelligent planning and calculations of your experiment.

Cast Iron starts out being brittle.

Cast Iron has was shunned because of catestrophic failures - contrast that with bronze (which has about the same STRENGTH but is much more DUCTILE).

Inside corner of the bore being square is a STESS RISER - great way to start the cracking.

Using a product that is sold as a DECORATOR with maximum load?

You may well get away with it. You may well loose it on the first shot or then maybe the 1000th shot from having started the crack on the first.

It is a casting, yes? Have you a good place to measure the bore diameter before and after (surface roughness may be an issue)?

An intelligent discussion would investigate ALL the alternatves.

Shall I hold your beer for you when you do this?

oltom · « **Reply #24 on:** February 26, 2012, 01:47:32 AM »

ironball....just buy my cannon and have fun...she has been shot hundreds of times...but now sits all forelorn in mom's garage waiting on a buyer...and with her comes a box of balls, and fuze! I don't shoot anymore...I moved over to flintlock/powder horn making!

Warlock1 · « **Reply #25 on:** February 26, 2012, 04:45:25 AM »

This is a great forum for anyone looking for information on how to do things safely, with a reasonable amount of safety for spectators (which is the original intent of this thread. Unfortunately this thread has turned into complete BS. Ironball I believe your specters would be safer if you listened to the other member offering their input, the name calling is very wrong, please look past that. If its not a cannon its a bomb......have fun and be safe.

ironball · « **Reply #26 on:** February 26, 2012, 06:04:01 AM »

1: It is cast, but has a 1/2 inch steel liner with a concave breech plug.
2: I don't have a G-mail account.
What was that about ME not knowing what I was talking about? LOL!
I will hold my own beer, thank you.

Graybeard · « **Reply #27 on:** February 26, 2012, 06:51:31 AM »

A lot of rules violations going on here and so far I see no evidence of the Moderators handling it in spite of multiple reports to moderators. I trust on my next return that will have changed.

KABAR2 · « **Reply #28 on:** February 26, 2012, 08:45:44 AM »

Ironball,

We had a fellow on here for a short time called Phalanx for a short time.... he was thin skinned and short fused argumentative.... you remind me very much of him..... or are you him? You have just enough knowledge to be dangerous when people do not agree with you on safety concerns you become argumentative because it strikes some macho thing in you..... Well since you appear to be an "Expert" (my definition is in another post) HAVE AT IT!
.
Just remember a fool and his mortar are soon parted.....

Oh and as far as DD calling you a troll you prove it by your own words......

Quote from: ironball on January 14, 2012, 07:25:03 PM

If you really want to view Face Book images, you can always create a fake persona to view the posts. Create a fake e-mail (yahoo, Gmail, etc.) to log on incognito.

For who but a troll would think to fake their identity? This board... No this forum would be far better off without those who being bored need to create drama and b.s.

Allen <><

IvarForkbeard · « **Reply #29 on:** February 26, 2012, 09:15:20 AM »

Quote from: ironball on February 25, 2012, 01:17:28 PM

I recently recieved my 3" Coehorn from Hern, but before I go through the trouble of building the base I want to test fire it with a much heavier load than what I will use for general use.

That way I will have no qualms about firing normal charges with spectators around. With foil wrapped charges, I plan on a blank containing of a full pound of FFg, and for live fire, an 8 oz charge under a can of beans. While I don't believe it's needed, I plan on setting the mortar down inside a few old tires, just in case.

Is this a valid test? What do you guys think?

When you ask a question like this and are told this is not a valid test, then ARGUE that you think it is shows the height of arrogance. it was pointed out that following the advice of the maker will keep you safe, yet you insist that unsafe practices are just fine. If you refuse to accept the advice of those you ask it of, please, go elsewhere to argue.