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#1 Merlin

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Posted 17 March 2017 - 02:02 PM

I have up to this point made 3" cylinder shells and 4" ball shells. I just finished a few 4" cylinders and am surprised by the weight. The are 5" in height finished and weigh around 625 grams. I figure this will require about twice the lift. The most I have ever used in a 4 inch mortar is 35 grams. 60 to 70 grams lift seems a lot to me.
I suppose the hdpe tube will take it. I have lots of 3's but only two 4"'s. I want to alternate the tubes between shots. My question is this. One of my tubes purchased a while back is longer and made of fiberglass. It seems harder and thinner than hope so are they safe as hdpe?

Edited by Merlin, 17 March 2017 - 02:05 PM.


#2 Mumbles

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Posted 17 March 2017 - 07:22 PM

The fiberglass gun should be fine assuming it's still sound.  Keep an eye out for fraying around the mouth, cracks, and significant fading of the color.  Those tend to be signs they're degrading.  Otherwise, you'll be fine even if you start building some multi-breaks (hint hint :) ).  A friend of mine says that he trusts fiberglass up to 10 lbs.  I've never pushed that, but have successfully fired shells well over 5lbs out of fiberglass as well without any modifications to the gun.  

 

It will depend what's inside, but most tend to make their breaks closer to "square", or about as tall as they are wide.  My 4" shells which are about 3.5" tall tend to come out around a pound, so your mass sounds about right for the size.  As far as lift goes, you may want to move into a different rule of thumb.  10% is appropriate for smaller shells.  As you get larger and heavier the rule of thumb is ounce per pound up to 10lbs.  This would be around 45g in your case.  Use your best judgement based on the quality of your BP.  It's probably safer to over lift than under lift.  You can always use less next time, or maybe do one of each.


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#3 Merlin

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Posted 17 March 2017 - 08:18 PM

Thanks Mumbles! Always good to hear from an expert. I may make a dummy shell to check altitude . Heads up cows! I'm really looking forward to these. For whatever reason my cylinders display much better than my ball shells.By weight I love have 3x the number of stars than my spherical shells. I plan to break with a cannula of 0.9 inches using mcrh. I felt 65 grams of lift was excessive. Glad you confirmed. I will start with 45 as you suggest on the dummy and adjust if necessary.
Thanks

#4 MadMat

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Posted 17 March 2017 - 08:27 PM

Wow, 625 grams. I've never made 4" shells but my 3" canister shells usually run around 155-170 grams (around 4" long). Does 1" in dia and length) make that big of a difference?


Edited by MadMat, 17 March 2017 - 08:29 PM.


#5 Maserface

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Posted 17 March 2017 - 08:46 PM

Ill double down on mumbles advice-  Make sure the guns are in good condition, in fact, get NEW guns and only use them for your cylinders.  Last fall I made five 5" single break cylinders (they weighed like 3.5 pounds) and I killed four out of the five guns.  These were guns that had been used for several years in commercial displays.



#6 Merlin

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Posted 17 March 2017 - 09:39 PM

Wow, 625 grams. I've never made 4" shells but my 3" canister shells usually run around 155-170 grams (around 4" long). Does 1" in dia and length) make that big of a difference?



#7 Merlin

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Posted 17 March 2017 - 09:43 PM

Volume of a cylinder 4 " diameter 5" tall is 2.2 times the volume of a cylinder 3" diameter and 4" tall.
It is acceptable to increase height 1" over diameter. Plus I completely fill the voids with polverone.

#8 Merlin

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Posted 17 March 2017 - 09:51 PM

IMaserface- I agree there is no point in shooting a mortar to the point of failure. I only used the hdpe for 20 4" ball shells last year. The fiberglass one has never been used. However you have motivated me to toss one of my threes used for three years. 3 4ths of July. Probably 120 shells.

#9 Maserface

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Posted 17 March 2017 - 10:36 PM

In my case, I don't think the standard Chinese ball shells would have killed these mortars for quite some time, but the homemade cylinders sure did the trick. It's common sense to use your best guns for your best work :)

#10 Wiley

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Posted 18 March 2017 - 07:39 PM

As Mike Swisher has often mentioned, there is no need to make a break taller than its diameter. The added components do not make the shell's display any "better," but they do add cost and weight, as you've noticed. Note that I'm referring to the height of the break, not it's filling. I make my 4" breaks using a 3.25" tall liner, which makes my breaks finish slightly squat. They display quite nicely.

 

 

At a recent shoot, I shot a 4" color to report from HDPE. That weighed nearly 3 pounds and lifted just fine. That's really not a heavy 4" shell, so as long as your mortar has a long plug (I like them one ID tall), screwed in with good screws, or better yet, through-bolted with some 3/8" bolts and washers, the mortar will be fine.

 

I've found that my single break 4" shells struggle to reach a good display height when lifted with an ounce-per-pound of 2FA. If I were to make more of them, which I would only do if testing a complete break to be later used in a multibreak, I'd use a hair more of that same 2FA, maybe 8% of the shell weight. Multibreaks have no trouble making good use of their lift :)


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#11 braddsn

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Posted 20 March 2017 - 11:43 PM

As far as HDPE goes, it is much stronger than you can imagine. I have only flowerpotted a couple shells in my pyro history, but one of them was a heavily boosted 4" color shell... im talking a very hard breaking shell. It broke in the gun, and I would have guessed it would have destroyed it. Gun was perfectly fine. I don't believe you could over-lift a 3 or 4" shell and destroy a HDPE tube. As far as fiberglass, I have no idea. I have never used one so I can't comment. But I would be willing the bet the HDPE is stronger. 


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#12 Livingston

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Posted 21 March 2017 - 12:17 AM

Steel would be ideal but is heavy and expensive. Ive heard of using HDPE with longer plungs bolted. I shoot a 9lb 6" color to report shell out of fiberglass no problem!



#13 Merlin

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Posted 21 March 2017 - 10:14 AM

Thanks for all the info. When I first started with Pyro I was buying everything from Skylighter. I bought a variety of things and the fiberglass mortar was one. Never have used it. I have worked in prior life with hdpe and it is tough and will expand under pressure. I know fiberglass will shatter and shred which is better than fragmentation. Still I likely will use the fiberglass for a few shells and toss it. I add reinforcing screws to the plugs of my hdpe and secure that to a length of 2x10 and secure that to the ground. Correct me if I am wrong but I am thinking it is not necessary to bury a 4" mortar for single breaks.
My heaviest shells are roughly 1.5 lbs.
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#14 Mumbles

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Posted 21 March 2017 - 10:37 AM

In my experience fiberglass is stronger than HDPE as far as lift is concerned.  HDPE very well could be a stronger material, but the plug is a weak point.  No matter how well secured the plug is, the point of failure is often from tearing through the walls of the gun.  Cracking the plug or blow by from expansion are also issues.  It's rare any of these will lead to total failure of the shell, but will lead to low breaks.  Granted, this is more of a safety concern for multi-breaks.  It also only really becomes a factor due to the mass of multi-break shells.  To be honest, it's only when shells get over probably 5lbs that I'd start to concern myself with the mortar material and give serious thought about it.  Below that, everything should be fine but I'd rather over-answer the question.

 

For a single break, use whatever is convenient.  Both guns will be fine.  Just don't reload the HDPE too often if you have several.  Over time it softens from repeated firings which does drastically reduce it's structural integrity.  

 

I feel more comfortable burying all of my mortars for cylinder shells if hand lighting.  Even encased in a bucket or barrel of sand, clay, or sifted earth* is better than nothing.  

 

* - It's important to remove rocks and large clumps.


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#15 Merlin

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Posted 21 March 2017 - 10:45 AM

Thanks Mumbles. Burying didn't seem necessary very small mortars but I knew at some point it would be. This year I will bury mortars- that's got to be safer. Thanks for the advice.




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