burst charge for large shells

[hondo]

in making my first 8 inch shell, I am using BP on rice chrispies, do I need to add whistle mix, granulated BP or flash for additional burst, I do when I make 4 inch and smaller shells but cant find info on 8 inch shells

[Miech]

When you use decent meal powder for your chrispies and decent pasting, meal on rice chrispies is powerfull enough. There is no need for boosters, unless you are either using plastic hemi's or multiple petals or both.

[Frozentech]

in making my first 8 inch shell, I am using BP on rice chrispies, do I need to add whistle mix, granulated BP or flash for additional burst, I do when I make 4 inch and smaller shells but cant find info on 8 inch shells

 

Larger shells take softer burst actually. Tradition would have you use BP on cottonseed, but puffed rice or rice hulls can be used as carrier also.

[noslo98]

Agreed If you are using paper then a high quality coating of the cotton seed or similar is sufficient. Now if you are using plastic I break mine with 80-120 grams of flash which most don't agree on but they break hard and big. I recently switched to paper and this combo isn't working so i'm trying KP coated hulls now but that's me and like I said most don't agree but it works. Also the other thing I do is I don't do the normal 5:1 or what ever ratio most use for coating I just do it til there black as hell we call it black to one..LOL Like I said we do things a little different but they work and make an 8" shell break like a 12" shell.

[Seymour]

Personally, when making sixes and above I use meal as a burst, and boost it with a small amount of flash. Four grams is plenty, and may indeed be overkill.

 

I use Paper for all my shells, and my flash is standard 70/30. Yes, I boost a six the same amount as an eight, but the eight obviously holds a great deal more BP!

[FREAKYDUTCHMEN]

Depends on how much you paste.

[hondo]

well I shot the first of my 8 inch shell and nothing but rice cripies and BP was added for burst, my first issue was the time fuse was too long and it burst on the way down and the second was I only primed half the stars, they were crans so I didnt think I needed to but next time I will and third was I needed more layers of gummed paper tape cause the fit in the morter was not as tight as I like it to be but I was on a dead line to have it ready for new years, but saying all that, all my friends thought it was awsome, lessons learned and number 2 will be better and number 3 better than 2, here is a link you migh have to copy and paste in your browser

 

http://www.youtube.com/watch?v=keLT14yL9lE

Edited January 28, 2009 by hondo

[Brian809]

So does anyone use Kp? Every thread or tutorial I've read recommends Kp for larger shells but the more I read the more I see most people stick to Bp for burst. I fired two 6" paper shells last weekend, 1 had willow Bp on krispies and the other Kp on krispies, Both were boosted with 10 grams of whistle. They both broke so-so but not as big as I was hoping, both shells were pasted with 12 layers of 70lb kraft.

Should I just stick with Kp and up the ratio to 6:1 or am I not going to get huge breaks with Kp alone?

 

Brian

[tentacles]

KP is expensive, BP + booster is much more cost effective. Thus, few use KP for burst - at ~$4/lb for perc, that would make for some very expensive shells.

 

6" is actually getting a bit big for KP, really. Is your BP fast? If it's not, fix that first. 10 grams of whistle really isn't enough booster for shells that size. Also, what type of whistle is it? Granulated? I'd start by trying like 50 grams of whistle in there and see where that takes you. You'll want to make sure your stars will light from a hard break, of course.

[Mumbles]

I generally use KP to break most of my shells. It is essentially because I don't have a big enough ball mill (yet) to satisfy my BP needs. I can only work on the weekends, and I'd have to run it pretty much constantly to even come close to my building requirements.

 

I break 4-6" with KP, no boosters. I don't look for huge spreads either though. It breaks plenty hard for me. It's hard to give advice without seeing the shells. Your so-so break might be ideal for me. It's possible you didn't have enough composition on your krispies though.

 

KP is pressure sensitive. A few extra layers of pasted paper may make a big difference.

[Seymour]

I'm fairly sure that the reason most people use BP (with or without a booster) instead of KP, is because BP is so much cheaper!

 

It's why I do.

Edited February 28, 2009 by Seymour

[Brian809]

Basically i'm in the same boat as mumbles, I only have the dual drum 6lb mill so making Bp is a 24+ hour run time if not longer but since I strayed away from using commercial airfloat and made willow airfloat my Bp is much improved. The whistle booster I used was just mixed up and dumped onto the kp, as far as granulating it do you do it the same way as granulating bp? and 50 grams? wow! now is that 25 grams in each half?

I've seen alot of movies here and on pyrobin of 6's breaking big with Bp but I think i'm going to work with Kp and whistle to see if I can get what i'm looking for, I am putting together 2 6's right now with 1/2" D1 stars just bobbling over the burst. Man hopping up to 6's from 4's is alot of work, trial and error I guess....the challenge is definately what I love about pyro and then of course watching these shells actually work!

 

Brian

[tentacles]

Actually the 50g may be a bit low, Linda uses 50g of "slow flash" (Ofca slow flash) to break her 5" shells, and they break huge. My experience making 5's for new years was that 7-10g wasn't even close, even though 3-4g worked great in my 3's. I figured the 5's wouldn't need as much booster but I was wrong.

[FREAKYDUTCHMEN]

I think most people use KP because shimi discribes it in his book. What he doesn't discribe is the use of hotflash, because it didn't excist.

I'm getting the same results with meal coated ricehulls and a 7:3 flashbooster, so for me there is no reason anymore to use those expencive KClO4 for breaking shells. It is just a matter of testing; amount of flash, layers and bursthight.

[Mumbles]

Tentacles, doesn't Linda also use plastic shells? They're a whole different animal than traditionally build paper shells. I've always found real hard breaks are needed in plastic to get any sort of symmetry, but that is just personal experience.

 

As I've said, it seems to be overkill to me. It seems whenever I try to boost KP, is the same time I run into priming issues. They seem to break a lot harder too. This is with maybe 5g of whistle in a 6"

[psyco_1322]

KP is a waste of materials IMHO. If you look at how much perc you use and the cost of it, you may quickly look away. Lets look at what it takes to coat 100g of rice hulls. If your using KP, suggested amounts would be around 700g of KP (1:7 ratio), with BP you only need about 400g (1:4 ratio). With those amounts your using over a pound of KClO4 for only 100g of burst, depending on your supplier that could cost 4-6 dollars, plus you have your charcoal, sulfur, and binder prices. On the other hand, bp can be made at about a dollar or two a pound, which is plenty enough to coat 100g of hulls.

 

With a little booster, you can make your money and stash go a lot farther.

[Seymour]

Actually some people get very cheap KP, and once the time and effort is added, KP is cheaper than BP, and more powerful. While this is a commercial way of looking at it, some people, particularly ones who earn big $$$ look at their spare time like this.

 

But for the rest of us you are right, Potassium perc is more attractive as an oxidiser for stars than burst.

 

As for adding 700g to 100g of hulls, you get 800g of burst, not 100g. Additionally, I would assume that you would put more BP onto a carrier than KP burst for an equivalently sized shell. Psyco_1322, I do not understand that part of your post.

[psyco_1322]

The suggested coating amounts are as follows:

Rice Hulls:Burst

KP - 1:7

BP - 1:4

 

Some people use different ratios but those are general amounts.

 

KP is a lot more dense than BP is. It is true that in that case you would end up with 800g of burst, and 500g if your looking at the bp on rice hulls. Though one does not fill shells by weigh of burst but by volume. The ratios give about equal coatings on the hulls. So looking at those numbers you can get an idea of how much more (by weight) KP burst would be needed compared to the bp burst. Thus, you end up using more KP inside the shell than and equal shell made with BP.

 

Hope that clears things up. Tell me if I'm still misunderstood.

[Mumbles]

If you're going to compare the two, at least use the same pricing basis. IE, you're using bulk pricing for BP, and small quantity prices for the perchlorate.

 

It costs me $1.55 a pound for KP, and ~$1.00 a pound for BP. Thus every 10lbs I make, it costs me an extra $5.50, which is worth it for the 180 hours I save from not having to mill it. It takes me about 3 years to use that much KP as well.

 

Your density argument doesn't work either. Since we're talking about big shells, you use the exact same ratio for KP as BP. You get a higher burst velocity, larger spread, and I feel better reproducibility due to not needing boosters. The previous data is shown in Shimizu's FAST on page 211.

 

If you're going to use BP, I'd suggest to add the booster like Ned Gorski does, coating the hulls/cotton seeds/krispies evenly. I see lopsided breaks from granular, or just piled on booster at least once or twice a club shoot.

 

I don't even know what I'm arguing about. I wouldn't use KP in anything bigger than a 6" single petal, or 8" double petal. Maybe if I was trying to be real fancy and make a 12" 5-petal shell or something. I used a toned down version of KP in an 8" double petal, and it broke quite hard. I probably should have looked harder at the data. It breaks just as hard as KP. It was with what I feel were undercoated puffed rice grains too. The video doesn't do the size of the break justice.

 

http://www.apcforum.net/Mumbles/Brocade.wmv

[psyco_1322]

Gee Mumbles, I didn't know there even was an argument.

 

Since I don't have a copy of Shimizu's FAST, I would have not known that.

 

So you get your KClO4 at a little over or around $1/pound?

 

Nice shell BTW.

[Mumbles]

$1.80 a pound. 110lb drums that I picked up probably 4 or 5 years ago. Even now the drums I've seen are a bit over $2 a pound.

[psyco_1322]

Really? Thats a nice price either way. I swear the last time I seen a drum price on Passfire, about a year ago, it was about/around $4/lb.

 

In that case, it would be a lot cheaper to produce KP burst, and would be about worth it to use, especially if you have ball mill limitations.

[Mumbles]

After last night I have no idea how your stars survived. With all the talk of boosting, I decided to give it a shot. I had a 4" blue ball shell. I broke it with KP on hulls, and decided to add 1 gram of flash to it just to see what all the hype is about. 9 layers of 35# gummed tape as normal. It completely over broke. It sounded like a salute, blew most of the stars blind. There was a low lift, but the stars were pelted into the snow, probably 150 feet up. The half dozen stars that lit were very pretty though.

 

 

So does anyone use Kp? Every thread or tutorial I've read recommends Kp for larger shells but the more I read the more I see most people stick to Bp for burst. I fired two 6" paper shells last weekend, 1 had willow Bp on krispies and the other Kp on krispies, Both were boosted with 10 grams of whistle. They both broke so-so but not as big as I was hoping, both shells were pasted with 12 layers of 70lb kraft.

Should I just stick with Kp and up the ratio to 6:1 or am I not going to get huge breaks with Kp alone?

 

Brian

[Brian809]

I figured out what the issue was with my bursts, not enough kp on the krispies. I tried a 6" D1 sat night with 1:7 kp on krispies with no booster and the burst was phenomenal, I may need to tone it down a bit. I'm making 2 more 6's that I want to use for a comparison, One will have 1:7 kp and the other 1:4 willow bp and I'll see if I can get them on video.

 

Brian