Top fusing a ball shell

[cogbarry]

I'm curious if anyone has done this and/or everyone's thoughts on it.

 

1) Does anyone do this?

2) Any reason(s) not to?

 

I had a muzzle break that I couldn't really explain and I'd like to do everything I can to avoid more of them. It was a WASPed shell with a passfire tube, chinese time fuse and I used hot glue and a good size fuse washer so the layer of hot melt was quite thick. The only theory I have is that the shell may not have been completely dry when I fused it and the shrinking of the drying shell could have caused the hot melt to crack/separate where it fused to the paper shell. I've heard a few opinions including one suggesting I don't use hot glue.

 

I had been using tissue paper as a barrier packed around time fuse where it penetrated the passfire tube, then attaching fuse washer and filling with hot glue. I know that some use wood glue and string for this. After the muzzle break I have been using a similar method but I first fill the recess created from cutting the magnet out with cork borer with wood glue, then I attach fuse washer and fill with hot glue. I should probably post an image but those of you familiar with fusing a WASPed shell should be able to picture this.

 

One other thought is that the bond between hot glue and paper on shell is not that strong. Even if the glue adheres well, it only needs to tear the outer layer of paper to fail. However, I believe the method I use is a common method among WASP users.

 

Hope that's clear enough, just thought I'd throw this out there to see if any of you had any knowledge of this issue. Thanks for any info or ideas!

[Peret]

What was inside the shell? Any chlorates, whistle or flash? There are other reasons for muzzle breaks than fire penetration. As a rule, fire penetration causes a flower pot inside the mortar, where the pressure is highest. If the shell leaves the mortar and then explodes above the mouth, it's more likely possible that it ignited internally from setback friction.

[cogbarry]

What was inside the shell? Any chlorates, whistle or flash? There are other reasons for muzzle breaks than fire penetration. As a rule, fire penetration causes a flower pot inside the mortar, where the pressure is highest. If the shell leaves the mortar and then explodes above the mouth, it's more likely possible that it ignited internally from setback friction.

 

Now that you mentioned it, there was one other thought along those lines although I didn't think it was likely. The shell was a 4" salute, filled with 280 g's of 70/30 flash, rice hulls to keep fluffed (if you will) and had some remaining space for mixing as I didn't premix - used binary method. Also, I have had a habit of over lifting. I am slowly backing off on this but I'm anal about changing too much/too many things at once and I guess I've seen a lot of low breaks from other pyros, I like to put untested shells up to a safe height. I was also using GOEX 2fg. So these shells were lifted with a pretty good thump but I wouldn't have thought it enough to cause a failure. Your comment has me thinking again though. Thank you for that. I will add that I've built quite a few shells (salutes and color shells) with this construction method and this was the first failure. Is there something about the methods I used that would make such a shell prone to setback friction? Unlike my color shells, this salute would not have been packed tight but I believe the method I used is commonly accepted/used. It was flash but again, it was 70/30, it didn't even contain titanium.

 

Oh and Peret, thanks for your explanation of the flower pot/muzzle break likelyhoods. It does seem logical that a fire penetration would be more likely to occur while the shell is still in the gun.

Edited October 25, 2012 by cogbarry

[cogbarry]

Now that I've started this thread, I'll ask another question related to safety. This shell was fired from a steel gun that was buried. However, I'm thinking this may not be the safest way to fire a large salute shell, especially after the stories from this years PGI event. In my state, it is illegal to reload HDPE and I don't think fiberglass is acceptable either. Any thoughts on this would be appreciated as well but it seems to me that a buried HDPE mortar would be much safer.

[Potassiumchlorate]

If the mortar is buried entirely, I don't think it matters, but the more experienced guys might beg to differ.

[dagabu]

Like this?

 

 

-dag

Edited October 25, 2012 by dagabu

[marks265]

That dude looks like an all right guy. At least he can do stuff like that safely and not get kicked out of a club over a few puny inserts that he can't get to work properly let alone pick up after himself. Gee I wonder who that was! DAG By the pic at least I got mine to light!

[dagabu]

Yea, Mark is a good guy, we all get a little protective once in awhile. BTW- my pic was not an insult, just an example of a blown steel mortar, I will change the pic to one without you, sorry.

 

-dag

Edited October 26, 2012 by dagabu

[Algenco]

?????

[cogbarry]

Potassiumchlorate,

I think Dag is right. I've seen a few shells burst in the gun, all were either salutes or multibreak cylinder shell with bottom shot, one was in a steel gun (above ground though). The gun DID NOT contain anything and became a dangerous, jagged piece of steel whipping through the air and barely missing a couple of us. One person suffered a nasty gash in the face, one a really red welt in the ass from (I think) a piece of wood from the rack. Most of us got hit but not hurt by rocks and such. Then there is this years PGI with the Dr X shell(s) that burst in the gun (steel and buried) and sent shrapnel flying. I am convinced that using steel guns for salute shells takes us from fireworks to weapons. The laws prohibiting the use of HDPE mortars for reloading or for single use in ground are wrong IMO. So what if reloading at a heavy rate (and I think it would be hard to do) could cause the mortar to heat,weaken,distort or even fail? I'll take that over steel flying through the air any time and we all know that burying doesn't stop this from occurring.

 

Please correct me if I'm wrong. What I'd really like is some more ideas on what may have caused my shell failure. With Peret's comment, I'm thinking this may not be a fire penetration issue. So what did I do wrong?

[cogbarry]

Also,

From Dag's picture (I mean the current one, not sure about the history here, hope I didn't start anything), this gun looks like it has a pretty thin wall. Honestly, I just don't get it. I know that there is a history of different types of guns failing, plugs being blown out,etc. However, I don't see why the steel option is so appealing, especially if it is thin walled. What am I missing?

[dagabu]

Also,

From Dag's picture (I mean the current one, not sure about the history here, hope I didn't start anything), this gun looks like it has a pretty thin wall. Honestly, I just don't get it. I know that there is a history of different types of guns failing, plugs being blown out,etc. However, I don't see why the steel option is so appealing, especially if it is thin walled. What am I missing?

 

The history:

 

A fantastic shell builder made a shell that didn't go as planned and it went off in the mortar. I now own that mortar and intend to place it in a public sculpture garden after I make a brass ball that will go in behind it. I changed the picture due to the addition of a person in the picture. I just posted the mortar by itself. I think we are working on a truce but only time will tell, there is a lot of history here.

 

In an effort to keep the peace and come clean, I do in fact post a lot of information that is not mine but are lists, tables, musings from others much more experienced than I. I strive to share the truth, of my own experiences when I can and the experiences of others when I cannot. If anybody here has a qualm with me, please pull up your big boy pants and email me coldfire11@msn.com or PM me.

 

I am not so full of myself that I cannot admitt when I am wrong but I am glad to do so if I am.

 

Back to the topic everyone....

 

-dag

[marks265]

The pic is from PGI this year. There was a lot of carnage this year. That is me with my oops. The gun is an 8" steel gun that is 6 feet tall. I laid it out flat with a 35 pound 3 break 8 that never made it upward. The wall thickness of that size gun is about .330 (about 3/8"). The bottom shot caved on that shell. At PGI this is what we call "crater night" because things can happen and will. The PGI safe guards as much as possible with very capable people. Steel guns are needed for multi-break shells because of extreme pressures that other guns can't handle. There are projects out there to improve on this, but very much in an infancy. To think the steel guns will go away for these big shells is a ridiculous thought for most astute pyros.

Also Crater night at the PGI is a competition for the largest of shells. The pic above is from the "Best exhibition Cylinder shell" competition. I took last in that category as well as first place with a 50 pound 8 inch three break to bottom shot. These shells are electrically fired and for good reason. They are placed well spaced in competition to keep from taking out the other guy. These guns are buried in the ground almost to the muzzle and steel containers block each side. This has been effective until this year and I am sure changes will be made at least in distances if nothing else (my guess).

When shooting pyro you should always plan to fail and not fail to plan. I don't care what size shell or device is being shot. It is a golden rule that bites so many people it seems. For instance lighting a salute in your hand to throw would be planning to fail. Distance is your friend!

 

The pics are in my gallery and you can ask me any question anytime and I will give you a good answer or tell you I don't know. None of this "I think" BS.

[marks265]

The history:

 

A fantastic shell builder made a shell that didn't go as planned and it went off in the mortar. I now own that mortar and intend to place it in a public sculpture garden after I make a brass ball that will go in behind it. I changed the picture due to the addition of a person in the picture. I just posted the mortar by itself. I think we are working on a truce but only time will tell, there is a lot of history here.

 

In an effort to keep the peace and come clean, I do in fact post a lot of information that is not mine but are lists, tables, musings from others much more experienced than I. I strive to share the truth, of my own experiences when I can and the experiences of others when I cannot. If anybody here has a qualm with me, please pull up your big boy pants and email me coldfire11@msn.com or PM me.

 

I am not so full of myself that I cannot admitt when I am wrong but I am glad to do so if I am.

 

Back to the topic everyone....

 

-dag

 

That was a fun night. I was about 75 feet away when the gun was auctioned off. There were so many people for the afterglow and it was so load in there I never knew it was being auctioned off. Dag got it in the end. He wanted me to sign it and I was going to. He made a mistake and mentioned that it was pyro art and it looked like an arse. After that thought I changed my mind. You can enjoy it Dag You did me a favor because after having a few I would have paid more that night because I was so happy I won the competition that night.

 

All is good Dag just keep the PM's handy for reminders LOL

 

Mark

[dagabu]

I will Mark, I certainly will. Thanks for your counseling.

 

-dag

[cogbarry]

Thanks for the explanation and the tips. The purpose of my post of course was to get some ideas of 1) avoiding this type of failure and 2) planning in case there is a failure. I understand that these multi-break shells need a stronger gun, in my case, it's a ball shell so I thought HDPE in the ground is my safest option. Please correct me if you think this is wrong.

 

Peret really has me wondering if this was something other then fire penetration.

[marks265]

HDPE buried 3/4 deep would be the safest. This is something that is taught in a display operator training course. However many shows and shells are shot with the guns in racks above ground and either hand fired or fired electrically. Keep in mind that the shells shot in this manner have been approved for use. Any test shooting and inexperienced shooting is best done with the gun buried and the same goes for your case in regard to your safest option.

For single break shells when shooting at our club all guns are buried and are fiberglass and HDPE. Unless we are shooting a show, then racks of guns are brought in. Even then all guns 8 inches and larger still get buried.

[cogbarry]

Thanks marks265. The display company I work for uses all HDPE in racks unless the shell is over 6" in which case it is buried 3/4 with no more that 8" above ground (this is the law in my state). There is a gun for every shell - no reloading. Most shells that are in large strings such as opener,mid,finale are electrically fired and this is where most salutes are, therefore, there isn't much hand lighting of salutes.

 

Our club uses both racked HDPE and buried steel guns for reloading because that's the law. I plan to use buried HDPE for large salutes or ANY shell that is untested or that we don't trust for any reason. However, it is illegal to reload HDPE in my state. I don't really agree with this law as I think the benefits out weigh the risks,at least for single break shells and I really don't think we would be using the gun at a fast enough rate to cause an issue from heating. In any case, I will insist on using HDPE in the ground in some cases even if I can only use it for a single shell.

 

Regarding the large multi-break shells at the PGI, I'll be interested in seeing how they address this. I know they attempt to barricade and there was a thread on passfire with all kinds of ideas being passed around. These forums are great as many of us can learn from mistakes/mishaps from others and from events we did not attend. I'm quite sure these forums have already saved many from injuries or worse.

[nater]

The problem with reloading HDPE is the material gets soft with repeated firings and is more likely lead to a failure. This would be a hazard for those that still reload during a 20 minute show, but I don't think it applies that much in a club setting. At HPA shoots, anything member made gets a buried mortar. I don't think we reload a single mortar quickly enough for heat to build up to the point they would get soft.

 

[Potassiumchlorate]

I was obviously wrong. I didn't realise that a mortar buried in the ground could "jump" like that when shattered.

[WonderBoy]

Here's another aftermath shot from Crater night, I am not sure which shell it was from:

 

https://docs.google....N2h5SzFLMVJrMGM

 

Cog, I agree with Nater that, in general, HDPE will be suitable for a club shoot scenario. The only time when we are quickly reloading is when our curfew is coming up soon, and the ready box is still half full of product... In a scenario like this, I would recommend fiberglass. If my memory serves me correctly, fiberglass can be reloaded as often as you would like.

 

I am not experienced with ball shells, so I can't really comment on what what led to a fireleak or shell collapse. I would have a hard time believing that 7:3 ignited on it's own, just from lift setback though. Were you using strawboard hemi's? Were there any bubbles in the hotglue around your fuse? How long did the shell dry before applying the glue, and then how long did it sit before firing?

 

 

WB

[spitfire]

...one thing i never understood: why on earth reload mortars during a show anyway....?? It is incredibly dangerous and not necessarily. Mortars don't cost that much, certainly not if your life depends on it! Shells in some kind of case are tossed around while fireworks are going of, or did a few seconds ago. That is the most stupid thing one can do. It's like smoking in a gunpowder factory. Asking for accidents. As a club, order a few hundreds of mortars and you're set. As a hobbyist buy it for your own sake. Reloading isn't worth risking your life. Buy them directly in China, fiberglass mortars are relatively cheap. It saves you so much. Edited October 26, 2012 by spitfire

[cogbarry]

Here's another aftermath shot from Crater night, I am not sure which shell it was from:

 

https://docs.google....N2h5SzFLMVJrMGM

 

Cog, I agree with Nater that, in general, HDPE will be suitable for a club shoot scenario. The only time when we are quickly reloading is when our curfew is coming up soon, and the ready box is still half full of product... In a scenario like this, I would recommend fiberglass. If my memory serves me correctly, fiberglass can be reloaded as often as you would like.

 

I am not experienced with ball shells, so I can't really comment on what what led to a fireleak or shell collapse. I would have a hard time believing that 7:3 ignited on it's own, just from lift setback though. Were you using strawboard hemi's? Were there any bubbles in the hotglue around your fuse? How long did the shell dry before applying the glue, and then how long did it sit before firing?

 

 

WB

 

Yes. strawboard hemis, then WASPed. The WASPed shell requires fusing after pasting, which means sealing only the outside. A pass fire tube is glued to the inside of hemi (over a hole of course) a magnet is placed in passfire, the shell is pasted, magnet location is found with another magnet, cork borer is used to cut through pasted layers, hole is found and shell is fused. Care must be taken not to cut through strawboard hemi, I don't think I ever have, I'm pretty careful about that. I use a fuse washer as well so the hot melt penetrates into the passfire (I use tissue paper to stop it from running down into passfire) to some degree, fills the void between hemi and pasted layers, then fills the fuse washer providing a "beefy" layer of hot melt. I'll even stop and let the melt cool if I'm afraid a bubble may be trying to pop through. Seriously, it's hard for me to imagine a leak that goes through all this hot glue. Even so, I have been starting my seals with wood glue, then applying hot melt in the last few shells I've built. This can cost me a couple days as it takes a while for the wood glue to really cure at times.

 

My first theory on this failure is that it was due to fusing a shell that may not have been completely dry. I think it was Ned that pointed this issue out on a thread somewhere. The shell shrinks and breaks the bond from hot melt. Honestly, I don't have notes on the failed shell and I don't know how long I waited between pasting and fusing or the temperature/humidity. I can only say that I think I was aware of this issue to some degree at least (maybe I hadn't read Ned's article yet but my common sense knew it might be a bad idea to make an important seal with glue to a wet shell) when I built the shell. I usually judge the dryness of a shell by it's hardness, I could have misjudged, especially if the climate was not conducive to a fast drying shell.

 

I don't mean to waste everyone's time on this when I obviously may not be able to provide enough info to expect any realistic diagnoses. But as the title of this thread indicates, I was really just wondering if top fusing a ball shell is something I should consider and if anyone else had experience with this. Getting some general ideas on possible causes or safe ways to prepare for this type of issue were secondary objectives for this thread.

 

Oh, and the shell sat for a long time before firing, months I would say.

Edited October 27, 2012 by cogbarry

[AirCowPeacock]

I feel simarily on the reloading thing, plus youll be too busy reloading to watch the show!

[cogbarry]

Wait....... yes I know, some of you are jumping in on this thread late and haven't read all the posts. As I said, we don't reload guns in most of the shows we do with the professional display company I work for.

 

The club setting is much different. Imagine a club in which folks are building shells, folks are donating product at the last minute and we do open shooting from 1:00 PM until 9:00 PM one night, maybe open shooting and then a public show on the 2nd night. This would be similar to say, the PGI but on a smaller scale. You would not have a "shell count", you may have all kinds of shells including some that can not be fired out of HDPE and cannot be fired from guns in above ground racks. You may have 16" shells. If you're familiar with this scenario, you know that 1 gun for every shell is not realistic and you must set your location up for reloading. I'm not talking about an "old home day" show at your small town with a 15 minute display dropping 400 chinese ball shells into 400 racked guns.