Question regarding my ball shell (shell break)

[Pyrophoric30]

Hello pyros, i recently made a 3inches ball shell using homemade hemis. I need some of your thoughts to improve the break of my shell. I want a stronger break with faster star traveling outwards not falling. Dont mind the excessive delay. Spolettes bp from a fountain mix. I typically timed my 3inch shell at 3 seconds. 
 

i pasted my shell using 3/4 inches gummed tape with 30pcs strips wrap around. Burst charge was mcrh 7:1 with flash booster of 3grams kclo4:dark alum. 
 

does thicker hemis contributes to symmetrical and stronger break? More confinement? More booster? Does it arc and falling to the ground that results in falling star? Please enlighten me😁

[Darude90]

Looks pretty decent to me tbh. But Because of the long delay an it falling down already, it looks a bit weird.

if you want it bigger and faster traveling you should up the booster and tune it in to you likings 

Edited July 7 by Darude90

[Pyrophoric30]

3 minutes ago, Darude90 said:

Looks pretty decent to me tbh. But Because of the long delay an it falling down already, it looks a bit weird.

if you want it bigger and faster traveling you should up the booster and tune it in to you likings 

Well yeah. I know it would happen due to the bad bp used in the spolette. I timed it at 3 seconds but i dont know why it happens. Also, maybe my new technique to passfire. I crossmatch and then dipped to nc laquer bp.

Do you think it needs more flash booster? Slow flash or standard flash? I use standard 7:3 flash at 3 grams. IIRC i read that for flash booster a gram for an inch. I dont know if that was correct. I like it to be like chinese shell where it is over broken.

[Zumber]

To me burst seem good.

Yeah Spolette timing need to be adjusted you should correct next time.

Hemisphere thickness dont contribute to shell burst rather pasting contribute to burst ,remember there are two forces acting opposite to each other first is force developed due to burst charge acts from center of shell towards surrounding atmosphere and second force i.e. shell pasting opposes this both these forces contributes shell burst in sky.

Hemispheres just provides housing for stars and burst charge and other shell contents. So its thickness should be such that it matches its equator at stable position too thin hemisphere dont match well.

Booster and type of burst charge  helps to burst shell in air.

Booster increment works till certain level until force produced by booster is equal to force opposed by shell pasting, beyond that level in the sence if force produced by booster is greater than force opposed by shell pasting in such case booster do not contribute to spread shell more In such case spread is increased by pasting more layers again.

This phenomenon is continued till you get desired burst or for tuning shell bursting. In both cases too less or too much booster and too less and too much pasting both doesnt works well you may also have to focus on your star to lit and stay ignited.

-Zumber

[Pyrophoric30]

7 hours ago, Zumber said:

To me burst seem good.

Yeah Spolette timing need to be adjusted you should correct next time.

Hemisphere thickness dont contribute to shell burst rather pasting contribute to burst ,remember there are two forces acting opposite to each other first is force developed due to burst charge acts from center of shell towards surrounding atmosphere and second force i.e. shell pasting opposes this both these forces contributes shell burst in sky.

Hemispheres just provides housing for stars and burst charge and other shell contents. So its thickness should be such that it matches its equator at stable position too thin hemisphere dont match well.

Booster and type of burst charge  helps to burst shell in air.

Booster increment works till certain level until force produced by booster is equal to force opposed by shell pasting, beyond that level in the sence if force produced by booster is greater than force opposed by shell pasting in such case booster do not contribute to spread shell more In such case spread is increased by pasting more layers again.

This phenomenon is continued till you get desired burst or for tuning shell bursting. In both cases too less or too much booster and too less and too much pasting both doesnt works well you may also have to focus on your star to lit and stay ignited.

-Zumber

Thanks Zumber, so it’s all about manipulating the booster and the paste layer to get the perfect balance. Not too bad for my second 3 inch shell i think. How about flash booster, plain standard flash powder is what im using. Ive read couple of threads where they use slow flash (kno3 based) and some are whistle mix, does that matter. 

[pyrojig]

While flash boosting does help, your math changes as the shell size increases. Once you start getting up into 8 inch and bigger shells too much flash causes problems. Over pressures. there’s so much black powder to break the shelf that you don’t need as much booster. Standard 70/30 seems to be good if you don’t want any blinding flash in your breaks to take away from the stars  .
zumber is correct in his description. 
 

*pasting or spiking with fiberglass reinforced tape may aid in confinement. 
 

*The method of pasting is the next area I would take a close look at.

Until I started changing up my method of pasting I didn’t get the best breaks. I am spoiled with a wasp now, but I use a similar hand technique. It’s an almost continuous wrap, circling around the poles about an inch away. So I draw two (1”)circles on each pole fuse side and opposite( for a control line to not paste past). I then wrap my gum tape overlapping the next layer halfway as I go so I get two layers per complete wrap. I then finished the poles off with a three step  type finish so they don’t have a buildup like a lemon . Usually I will do this about three times which equals about six layers of gum tape. I will then measure the width of the shell to make sure it’s about a quarter inch under the tube DIA. ( if not keep pasting till you get desired dia shell, about 2.75”)This allows for your fuse/ quick match to have space .

Edited July 8 by pyrojig

[Zumber]

3 hours ago, Pyrophoric30 said:

Thanks Zumber, so it’s all about manipulating the booster and the paste layer to get the perfect balance. Not too bad for my second 3 inch shell i think. How about flash booster, plain standard flash powder is what im using. Ive read couple of threads where they use slow flash (kno3 based) and some are whistle mix, does that matter. 

Flash have tendency to blow stars blind. Thats the reason why fast burning slow amount of booster is utilized and if slow burning booster is used then its percentage needs to be increased a bit. Booster does aid  BP burst to burn faster and helps to increase pressure suddenly.

For small shell under 3 inch KP burst without sulphur is utilized everywhere this burst shell even hard than standard BP MCRS.

You have to pay attention regarding its safety like to avoid friction, too strong impact during its preparation and shell assembly.

Or you just stick to previous method and tune your shell burst by pasting more papers and adjusting booster or use hot burning BP (ball milled)

[Pyrophoric30]

29 minutes ago, Zumber said:

Flash have tendency to blow stars blind. Thats the reason why fast burning slow amount of booster is utilized and if slow burning booster is used then its percentage needs to be increased a bit. Booster does aid  BP burst to burn faster and helps to increase pressure suddenly.

For small shell under 3 inch KP burst without sulphur is utilized everywhere this burst shell even hard than standard BP MCRS.

You have to pay attention regarding its safety like to avoid friction, too strong impact during its preparation and shell assembly.

Or you just stick to previous method and tune your shell burst by pasting more papers and adjusting booster or use hot burning BP (ball milled)

So slow flash and standard flash are inversely proportional to volume. How do i use kp as burst charge? Integrate it with rice hull as well? I use a plain bp 75:15:10 that was ballmilled at least 4 hours until it sticks to the walls of the drum. I think i will stick to my bo because perclorate cost twice as much as my nitrates. I will just increase the booster until my stars go blind and also it will give nice thumping sound when i breaks.

[Zumber]

1 hour ago, Pyrophoric30 said:

So slow flash and standard flash are inversely proportional to volume. How do i use kp as burst charge? Integrate it with rice hull as well? I use a plain bp 75:15:10 that was ballmilled at least 4 hours until it sticks to the walls of the drum. I think i will stick to my bo because perclorate cost twice as much as my nitrates. I will just increase the booster until my stars go blind and also it will give nice thumping sound when i breaks.

Thats fine....you may work on it.

Yeah KP is also integrated with rice hulls.

[All10Fingers]

You could always try milling you BP longer. I know a lot of people always try all kinds of things to skip a few extra hours in the tumbler.  And to some extent the power increase will taper. But I promise you, a solid 12 hours in the mill make better performance than 4 hours.  Idk about sticking the side. Mine doesn't do that. You might have to stop it and scrape the sides a couple times. But if your looking for a better break, and like using BP. Then make better BP. 

[Mumbles]

BP sticking to the sides of the mill is usually a sign of moisture in your chemicals.  It's most often the nitrate or charcoal.  It doesn't always mean it's done milling.  I've gotten spurned a couple of times by this.  

I'm not sure what Zumber is talking about, but KP generally does not work the best in smaller shells.  Definitely not the version without sulfur.  I don't recall it's name, but it's in F.A.S.T.  No. 46 or something perhaps.  KP is also not something you would want to mess around with adding a booster to.  While BP and KP are both good bursts in their own right, they also can't really be treated as analogs to each other.

In some ways, the weaker the shell casing, the better the burst.  Ideally, you want all the reinforcement to come from the pasting layer which should provide reinforcement equally in all directions giving a symmetrical burst.  In practice, I've had thicker casings tend to work better.  That's not to say that thicker is better or contributes to the burst in a meaningful way.  I just believe that they were higher quality and held their roundness better in storage, loading, and finishing.

[kingkama]

There are no problems in burst, only in timing spolette Is 3 seconds longer, this cause the asimmetry. Shells must explode at the apogee in the Moment of the stop, a bigger boost made of mg/al/kp and granular BP can make a difference and boost the performance also if confinement is poor.

[Zumber]

I was reading Lancaster book and in burst charge manufacturing  section I have read.

"Value of non explosive weight is 75 kg"

What does it mean?

Steady weight over composition till it becomes unignited??

 

[Kalifireworks]

1 hour ago, Zumber said:

I was reading Lancaster book and in burst charge manufacturing  section I have read.

"Value of non explosive weight is 75 kg"

What does it mean?

Steady weight over composition till it becomes unignited??

 

Id say thats the maximum ammount of composition that will deflagrate when ignited, any ammount above 75kg will explode.

 

Usually there is a big difference tho if the composition is inside a drum or a open tub, is there anything like that mentioned in that text?

[Zumber]

3 hours ago, Kalifireworks said:

Id say thats the maximum ammount of composition that will deflagrate when ignited, any ammount above 75kg will explode.

 

Usually there is a big difference tho if the composition is inside a drum or a open tub, is there anything like that mentioned in that text

No not mentioned 

First test is 2 kg drop hammer test by" Yamada friction testing apparatus" 

And second one is just mentioned that valve of non explosive weight.

I am under confusion when I read word Weight.