Can "slow flash" go off from the kick of the lift-charge?

[Ubehage]

The title holds the question

 

I am planning what I should make for new years eve, and among many things I am considering to make a "mean motherfucker" of a 5" shell with bottomshot for midnight.

If this is the worst idea you ever heard, just tell me and I will skip this idea.

 

But, it leads me to the question if slow flash might get ignited from the kick when launching a shell of this size?

[Maxim]

Why should it? It will only press itself a bit,

[Ubehage]

Why should it? It will only press itself a bit,

When I started pyro, I was almost scared away from all uses of Flash in general, until I read in here that it's not quite as dangerous as it's hyped up to be.

But I have learned that slow Flash is generally more sensitive that normal Flash - and so I just wanted to confirm

[Carbon796]

No, it won't be a problem.

[schroedinger]

Normally it shouldn't be, but make sure to use propper constructiin technics.

[OblivionFall]

KNO3:Al:S takes about two or three hard hits with a hammer to explode. You will be fine, don't worry. Only flash I can think of that might ignite from lift is potassium permanganate flash powders or KClO3:Mg:S or KClO3:Al:S

 

I recommend 6:3:1 (KNO3:Al:S) as apposed to 5:3:2, especially in bigger shells. gives a much deeper boom and brighter flash.

 

Have you considered just using a mix of BP + 10% (fine flake) Al? I'm going to test it in a week or two but it is supposedly close in power to slow flash but not nearly as sensitive. Ned Gorski has had success making a 10g BP+Al cube firecracker that sounded like flash powder. Much safer to work with and I figure you have lots of BP ready to go. Just mix meal D BP and Al together and follow Wiley's method of making report shells (look at the gallery.) Generally the bigger the shell the slower the report comp. you can use. You wouldn't use BP+Al in a 10g shell but in a 5" shell where you could use up to 1 lb of report comp I think BP+Al would work.

 

I hope you realize the magnitude of a 5" salute shell. I don't think I've seen a video on any 5" salute shell ever. Biggest ones I've seen were 3" and those take 100g of flash mixed with sawdust/rice hulls.

 

This isn't a terrible idea. It's an educated risk. As long as you don't cut corners everywhere and be super cautious and level-headed with this it will go fine. Don't be afraid to spend some extra $$$ if it means you will be safer.

 

If you do actually make this please please please take a video of it because it will be ridiculous

Edited December 19, 2015 by OblivionFall

[Arthur]

The traditional makers of salami shells sometimes use a lift piston between the lift and the bottom shot. It comprises a pair of discs with the gap stuffed with rolled newspaper. As the paper compresses it absorbs the shock of the lift and also squeezes out sideways to form a "piston ring" against the mortar side, meaning that less lift may be needed.

 

The two discs of card or thin sheet wood also mean that the fire of the lift is a little further away from the flash powder of the bottom shot.

[mabuse00]

One thing to consider is that your shot is most likely not 100% filled.

Typically salutes aren't filled to the brim, but 50% or so to facilitate deflagration.

 

That means they become much more compressible, compared to shots filled with stars and BP on a carrier material, as they will bolster the hull.

 

 

The typical failure-scenario (imho) is that your shot is squeezed and flash dust is blown out, igniting.

[nater]

When using a hand rolled bottom shot, it must be filled entirely full to maintain its structure. As you mention, they can compress leading to a failure.

 

Some do under fill salutes, especially when using thick, spiral wound tubes and filled using the binary method. Personally, I don't buy the theory that salutes need to be underfilled. If my report comp is already mixed, I fill them up.

[mabuse00]

 

Some do under fill salutes, especially when using thick, spiral wound tubes and filled using the binary method.

The binary method is indeed nice if your raw materials are airfloat.

 

 

Personally, I don't buy the theory that salutes need to be underfilled. If my report comp is already mixed, I fill them up.

I'm unsure about that.

If your salute is big enough and the flash is hot, maybe it's not necessary.

 

But Ubehage mentions nitrate flash. This stuff will hardly go DDT.

[Seymour]

It really depends on what flash you use. In my experience under filling has never been necessary with any type I've used, but I am sure there're varieties of flash where it helps, but these should not be used for bottom shots if used this way in my opinion.

 

I only leave an air gap if I want less flash than a casing requires for some reason, but always in salute inserts I completely fill. With well mixed KP/Dark Al, I have even pressed it in as hard as my arms and hands can manage and crammed literally every last gram, and it works perfectly.

 

But as far as flash goes, 70/30 with Dark flake is not the most brissant, but it's definitely at the hot end.

[gregh]

Oblivion, I have witnessed 5" salute lampare shells that Caleb made. And yes, they are ridiculous. They hurt your guts when they went off. However, I believe he used whistle in those.

[Arthur]

The important things to check are 1/ the bottom of the rising shell is strong enough, 2/ the bottom of the rising shell is fireproof enough.

[lloyd]

The real 'bottom line' on this issue is that lift (alone) is not enough to ignite any flash powder we use, including high-antimony chlorate flash powders.

 

IF an ignition occurs during lift, it's either due to passing fire through bad joints somewhere, or due to relative motion of the contents, causing local friction. The relatively low 'impact' (setback, really) caused by lift just isn't a concern.

 

To bolster that concept, consider small (say 3/4") crossettes lifted from a cake. They're filled with really hot antimony-containing flash burst, and they lift with about six times the G-forces of any 2" shell... and they don't auto-ignite from the lift.

 

Lloyd

Edited December 19, 2015 by lloyd

[OblivionFall]

One thing to consider is that your shot is most likely not 100% filled.

Typically salutes aren't filled to the brim, but 50% or so to facilitate deflagration.

 

That means they become much more compressible, compared to shots filled with stars and BP on a carrier material, as they will bolster the hull.

 

 

The typical failure-scenario (imho) is that your shot is squeezed and flash dust is blown out, igniting.

If made with an actual spiral tube with a thick 1/2" wall and 1/4" thick chipboard discs this shouldn't be an issue. I could see this happening if you rolled a bottom shot casing on a case former with 30lb kraft paper. Can he not just build it sturdy enough so that it does not become compressed?

[OblivionFall]

Oblivion, I have witnessed 5" salute lampare shells that Caleb made. And yes, they are ridiculous. They hurt your guts when they went off. However, I believe he used whistle in those.

Explain "hurting your gut." If you mean to say that a 5" salute a couple hundred feet in the air is powerful enough that you can feel the thump of the explosion then I'll be damned and so will ubehage when he makes this.

[OblivionFall]

When using a hand rolled bottom shot, it must be filled entirely full to maintain its structure. As you mention, they can compress leading to a failure.

 

Some do under fill salutes, especially when using thick, spiral wound tubes and filled using the binary method. Personally, I don't buy the theory that salutes need to be underfilled. If my report comp is already mixed, I fill them up.

The main reason to under fill salutes is this:

You have a 1" I.D. salute that is 3.5" long. You fill it with 15g of flash powder so that it is 2/3-3/4 of the way full. Then you make another one that is full enough that the end plug touches the power when you put it in. You light both.

Guess what? They make about the same bang! Even though one has up to 33% more flash powder in it, the one filled 2/3rds of the way is as loud because of the room to build pressure. In the salute where there is no space to build pressure the extra flash makes up for it.

 

The only reason people fill aerial salutes the whole way up is compression and not wanting flash moving around too much in the shell.

 

But in this case I would recommend Ubehage binary mix blue aluminum flash into a very sturdy 5" salute tube or use BP + 10% Al like I suggested.

[OblivionFall]

With well mixed KP/Dark Al, I have even pressed it in as hard as my arms and hands can manage and crammed literally every last gram, and it works perfectly.

That... I... uh... what???? That seems like a terrible idea....

[braddsn]

Explain "hurting your gut." If you mean to say that a 5" salute a couple hundred feet in the air is powerful enough that you can feel the thump of the explosion then I'll be damned and so will ubehage when he makes this.

I am not sure what you meant to say here Oblivion, but Greg is on the money. The shockwave from a 5" salute travels through your body with authority! I have felt said shockwave. Also, what Seymour is saying is not actually a terrible idea. He works with flash on a regular basis and knows how to handle it. Flash is not the devil, it just needs to be respected. The lift from a shell, or pressing it by hand is not going to make it ignite. Think of all the salutes that get launched... if lift ignited them, salutes would quickly become a thing of the past.

[Mumbles]

To simplify things, there is a "multiquote" button as well. Just click whatever posts you want, and a little box should pop up. You can reply to everything, individually quoted, at once.

 

You absolutely should fill a bottomshot to the brim. Most importantly, it provides structural support to the report itself and provides a robust base to support the shell during lift. Consider where the advice is coming from. When you have builders like Lloyd, Nater, and Seymour recommending this, you can rest assured it's sound advice and done for a reason. I think you guys are being unnecessarily concerned. The amount of flash in a half full 5" bottom shot will make you just as dead as a full sized bottomshot. Since you're toast either way, you might as well take the extra precautions to make your shell safer and sturdier.

 

A 5" salute does pack quite a punch. Not surprising since they often contain well over a pound of flash. As you approach this size of salute, things really step up. They attack your vision, hearing, and literally hit you in the chest for the trifecta of sense assault.

 

It should be noted that there is a point of diminishing returns in terms of perceived volume. 1000g is not ten times louder than 100g. It's not all about just volume though. For me, that's the least thrilling part. The brightness and concussion scale much more with amount of flash than volume. The biggest salute I've ever seen was a Dr. X special containing somewhere in the ball park of 50lbs of flash I think. The one I'm thinking of was fired during the day in Fargo 7 or 8 years ago. To be honest, it wasn't much louder than a lot of other salutes I've experienced. The concussion though. I thought I was going to get knocked over, and I was at least a comfortable 1/4 mile away.

[OblivionFall]

I am not sure what you meant to say here Oblivion, but Greg is on the money. The shockwave from a 5" salute travels through your body with authority! I have felt said shockwave. Also, what Seymour is saying is not actually a terrible idea. He works with flash on a regular basis and knows how to handle it. Flash is not the devil, it just needs to be respected. The lift from a shell, or pressing it by hand is not going to make it ignite. Think of all the salutes that get launched... if lift ignited them, salutes would quickly become a thing of the past.

Ok I understand. I guess people just tell you not to press flash because someone new to it will do it wrong. I figure you could only really press flash thats pot. perch. / aluminum 7/3 or less sensitive. But I'd rather not press flash powder to be honest with you.

 

 

 

To simplify things, there is a "multiquote" button as well. Just click whatever posts you want, and a little box should pop up. You can reply to everything, individually quoted, at once.

 

Didn't see that. I'll use it from now on

 

It should be noted that there is a point of diminishing returns in terms of perceived volume. 1000g is not ten times louder than 100g. It's not all about just volume though. For me, that's the least thrilling part. The brightness and concussion scale much more with amount of flash than volume. The biggest salute I've ever seen was a Dr. X special containing somewhere in the ball park of 50lbs of flash I think. The one I'm thinking of was fired during the day in Fargo 7 or 8 years ago. To be honest, it wasn't much louder than a lot of other salutes I've experienced. The concussion though. I thought I was going to get knocked over, and I was at least a comfortable 1/4 mile away.

 

I heard about that point of diminishing returns thing before. I think you can feel the difference but at some point you can't really hear the difference. The difference between a 10g salute and a 100g salute is a matter of 5-10 decibels and a deeper boom.

 

Is there a video of the Dr. X 50lbs salute??? That sounds absolutely ridiculous.

There's a video on youtube of a guy in his basement with a 12" Shell of flash powder ( something like 10lbs I think) and he can't ignite it because he's still trying to get the permission to somewhere.

Edited December 20, 2015 by OblivionFall

[Ubehage]

If your salute is big enough and the flash is hot, maybe it's not necessary.

 

But Ubehage mentions nitrate flash. This stuff will hardly go DDT.

I have had previous success with 2" and 3" salutes made with nitrate flash.

Those were mixed with ~5% rice hulls and filled all up.

 

As far as I have learned, you only underfill them when you need the space for binary mixing.

[OblivionFall]

I have had previous success with 2" and 3" salutes made with nitrate flash.

Those were mixed with ~5% rice hulls and filled all up.

 

As far as I have learned, you only underfill them when you need the space for binary mixing.

You're right about all of that. If you have had success with 2 inchers and 3 inchers I don't see a 5 incher being much different. Just bigger and you should make it to a higher quality.

[Seymour]

 

The main reason to under fill salutes is this:

You have a 1" I.D. salute that is 3.5" long. You fill it with 15g of flash powder so that it is 2/3-3/4 of the way full. Then you make another one that is full enough that the end plug touches the power when you put it in. You light both.

Guess what? They make about the same bang! Even though one has up to 33% more flash powder in it, the one filled 2/3rds of the way is as loud because of the room to build pressure. In the salute where there is no space to build pressure the extra flash makes up for it.

 

I definitely agree with most of this. Why add more if you don't get more effect from it? Especially back in my purely hobby days, lets face it, we burn money, and tricks like this make that investment burn for a bit longer

 

I am not convinced that the extra space actually does always help produce pressure, or help in any way other than in the case of very slow flash that is reluctant to go bang spreading out and having spaces between the particles for propagation to occur. I could be wrong, but my gut feeling is that the extra hot flash you can fit in from filling a case is not easily noticed due to the diminishing returns, and people have guessed that the space is helping. Combined with people using flash that is so slow that it often simply burns inside the case instead of exploding if it is even lightly consolidated, people talk about how the air space helps them, and I feel that the importance has gained a reputation larger than the actual reality of what help it serves, and in what context.

 

I'm not sure where the advice about not pressing flash comes from. Perhaps it is in case people mistake ramming for pressing and ram flash?

 

Otherwise it could be because, especially with cored rocket tooling, accidental ignitions do occur very rarely, and if it was flash being pressed, this would be a much more serious accident than black powder. However the same applies to whistle...

 

Ultimately I do feel uneasy about pressing flash (using a mechanical press, like for rockets etc) but I would not fully rule out doing it. I've pressed whistle many times, and feel a little bit uneasy as I do it. Same goes for my BP + Flash + MgAl + wax rockets. I feel that the paranoia is a healthy thing when working with whistle, flash and so on, as it keeps you aware of the realities of what you are working with.

 

I am as relaxed about pressing flash in to a casing with my hands and fingers as I am about simply scooping the flash in there using a piece of card as a spoon. That is to say, I'm still one spark away from death, but the force of my hands pushing the flash down will not set it off.

[lloyd]

I'm concerned about this "pressing flash" issue folks keep talking about!

 

Commercial manufacturers DO 'press flash'. There's a particular formula called "white mag" (which has not a single trace of magnesium in it) that is basically flash powder with a little red gum and dex as a binder. It's pressed into comets and rolled into stars. It burns WHITE HOT, and fast, and leaves virtually no tail -- just a brilliant white corona around the star.

 

But the stuff is dangerous. More than one manufacturer has had fatal accidents working with the material.

 

One should NOT press flash, unless you have a very controlled environment and the experience to do it safely.

 

That said, it's already been mentioned in this thread that the reason for filling bottom shots full is to provide mechanical support. You should fill them full -- right to the rim.

 

Does it sound much louder than, say, a salute filled to 80%? No, probably not. But the shell is more likely to get aloft intact with it filled full than partially.

 

Lloyd