In search of the perfect symmetry (First ball shell)

[Aspirina]

Hello everyone

 

After many attempts, I am perfecting the construction of shells, I want to share this time with your the last two shells that I made.

 

The first one I did was my first spherical shell, thinking of getting a rupture much more symmetrical than the previous ones I decided to get to work ... I noticed my bad practice in this shells, the shell did not explode symmetrically and I dont know what is the fail, I use the Maltese method to apply the kraft paper layers, maybe that was a mistake, even though be careful to put the same layers per hemisphere in the shell. The shell hemispheres are made up of 12 normal layers of paper + 6 layers of kraft paper, starting with a tennis ball, the shell fit right into the mortar. The stars are not set in a uniform way and I use granulated b.p + slow flash powder for the burst, perhaps that is another mistake, I know that many people use coated rice hulls and more powerful flash powder.

 

On the other hand, I make a shell with the same stars, this time putting the stars well in 3 rings, 47 stars in total. Used granulated powder + kclo4 flash powder for burst. The result was very satisfactory, much more symmetrical than the spherical one, the only difference between the components of one and the other is that in this shell I used a more powerful flash powder, 2g in each case.

 

I do not have time to do a more detailed writing, I think you have given the most relevant data, ask any questions if you have. My question is, in the spherical shell that I did wrong?

 

 

3" Ball shell:

http://oi65.tinypic.com/hvaptt.jpg http://oi66.tinypic.com/2lx8v7.jpg

 

3" Can shell

http://oi66.tinypic.com/23kf7g7.jpg http://oi68.tinypic.com/10e36du.jpg

 

Ball shell:

https://www.youtube.com/watch?v=mfac2H0zVTc&t=12s

 

Can shell:

https://www.youtube.com/watch?v=8aTSLQouKlU

 

 

I hope you understand my explanations! thanks for everything...

Edited March 28, 2017 by Aspirina

[pyrokid]

The break size of the ball shell was smaller. If identical stars were used in both shells, this implies that the peak pressure generated during the break was less in the ball shell. The canister shell had spiking to aid in pressure development, while the ball shell had none. Furthermore, granulated BP is really not suited to ball shells. A carrier such as rice hulls will increase the power of the burst while reducing weight. Cylindrical stars can be made to work in ball shells but of course the optimal choice is round stars.

 

One comment on ball shells and symmetry. Your goal is to achieve as uniform a rupture as is possible. The starting hemispheres should be very thin, and the diameter/casing should be built up by pasting. In reality, we must strike a balance between efficiency and degree of pasting perfection.

[Mumbles]

Granular BP is fine for smaller shells. It's the most concentrated burst you can get from BP. Hulls and other carriers are mostly to reduce weight and conserve BP. You can break a 6" shell with 2FA black powder, but it's both heavy and wasteful. In smaller shells the mass isn't too big of an issue and in many cases you can use the extra power from having more BP per volume.

 

The grains you're using do look fairly large and fairly variable. You could consider reducing the particle size to increase the burn speed. If you don't already do so, you may also want to consider grading your powder and using specific mesh ranges for certain applications. Assuming it's the same product as the lift it seems the quality is fine.

 

The other thing I'd recommend is using a tissue paper liner in your ball shells to hold the burst in the center of the shell. Not using one can allow the burst to migrate between the stars and loosen the packing inside the shell. This can disrupt the pattern at the very least.

 

It's unclear if you did so, but you'll want to alternate orientations of your pasting. You don't want poles and seams in the same place for every layer. By rotating the shell in all 3 directions you help to equalize forces in all directions which is helpful for good breaks. You may also want to experiment with other pasting techniques and patterns to see what works best for you. If you want to stick with the method using paper discs, you can try increasing the number of layers. It looks like your paper is fairly thin, which may require more of it. 6 layers is about what you need for for strong paper and good pasting. Increasing the amount of booster will also have an effect, though probably wont get to the heart of your symmetry problems.

[Wiley]

It looks like the stars are fairly big for a ball of that size. But, if a palm is what you're going for, they should be fine. I would recommend loading them all the same way, so have them all lying down or all standing on their ends. I like the look of having pumped stars standing on their ends, but if they're longer than they are wide, that will reduce the amount of space you have left for burst. In a 3", I would think that a burst enhancer is almost necessary. I'd start with something like 3g of Spanish booster.

One of Ned's shells with pumped stars stacked in nicely:

 

And tissue paper to keep burst out of the stars:

 

[braddsn]

Aspirina: For a symmetrical break, there are a few things that are essential. 1 - 100% Star ignition (proper priming). 2 - Proper pasting, 3 - Sufficient break power, and 4) Precise star sizing. Here is a breakdown.... 1) 100% star ignition. Many people think they have good ignition, but cannot get a symmetrical break. Your break will never be symmetrical until every star lights. 2) Sufficient and proper pasting. Use 2 layers of tape per inch of shell diameter, and like Mumbles said, make sure and paste in both directions. 3) Sufficient break 'power'. This part is tricky. I use booster to control the speed in which the stars travel. The faster the stars travel before they burn out, the larger the diameter of the break. But with larger diameter, it becomes even MORE important to have 100% ignition (which comes with proper priming). And 4) Star sizing. You must use a sieve to size your stars, and they must all be precisely the same size in a shell. My stars are +/- .5mm in size. This way, the star burn duration is uniform throughout the shell.

 

Also let me add this note: Mumbles also mentioned tissue paper between the stars and burst. This is important! I only do this however with shells that are 5" and larger, but you can do it with all sizes. With 2,3 and 4" shells, I can pack the burst tight enough without paper that everything will stay in place when the shell lifts. But with 5" shells for example, the burst can migrate into the spaces between the stars and the stars become loose inside. Then, when the shell lifts out of the mortar, the force of the lift pushes the stars out of place, and the break will not be symmetrical.

 

Using booster will often help with symmetry, and using different amounts in different shells can give a different mood to the shell... in a 3" shell I will use 6g of spanish booster if I want a hard break with fast moving stars. And I will use 2-3g if I want a slower, more graceful break. Here is an example of each type of shell:

 

Here is a 4" N-1 to Green shell with a slower, more graceful break (only 4g of booster). I would use 12g of booster if I wanted a fast hard breaking shell

https://youtu.be/gQmW64LhbTo?t=7s

 

 

And here is a 4" Lime to Red peony where I used 10g of booster for a faster, harder breaking shell

https://youtu.be/A670_WxPCuc?t=7s

Edited March 29, 2017 by braddsn

[FlaMtnBkr]

Brad

 

Are those the Jopetes colors? The second shell had great colors if the video was a pretty accurate representation of the actual colors.

 

The red started to have that deep, 'darker' blood red or burgundy color which I have seen this color only a few times and only in person but not very much and would really like to find a formula.

 

From what I remember they were fairly bright but probably didn't contain very much metal if any. The shells were decent sized, probably a 6" or 8" if I were to guess, and didn't change color so were likely good sized stars which would help with brightness. Yet they were a very deep red almost like a drop of blood (opposed to being smeared out which can lighten the color) or like a dark red wine. I'm not a wine drinker but I think burgundy would be a good description.

 

Has anyone seen something like this? Or better yet, have made something similar and have a formula? I would love to find it because it's not something I have seen much at all and I really liked their appearance.

 

I have been taking a break from pyro since my daughter was born but I'm getting the itch to make something. I will likely start back trying to find this color so if anyone has suggestions it will give me a starting point. I also really like dragon eggs and they intrigue me how something so small can be so loud without confinement. I have experimented with them a lot in the past and now I want to try some ideas I have about a lead and bismuth free formula that I also want to experiment with. From past results experimenting with many different formulas I have high hopes.

 

Anyways, I'm rambling as I sit at the doctor's office getting my bimonthly infusion of the most expensive drug/medicine on the market that I will need for life. If I could figure out how to get the money instead of the medicine a few times a year I would be set. I have the equivalent of a loaded diesel F250 going into my arm as I type. I doubt my insurance company likes me very much...

[JOPETES]

Sorry for the members of the forum, I want to respond to an aspirin in Spanish because we are both Spanish and ours are going to understand better.

 

 

Hola Aspirina. He visto con atencion tus videos. Lo primero que te digo es que los consejos que te da Brad son totalmente correctos al igual que mumbles. Por lo que he visto no has empavonados las estrellas y aunque en su mayor parte la composicion D1 es polvora negra, debes empavonar cualquier tipo de estrella como ya te he explicado aunque en las lentejuelas es suficiente solo con polvora negra (capa de 1mm), El tamaño de las estrellas deben ser en proporcion al tamaño de los cascos, para una carcasa de 3" las estrellas no deben tener mas de 9mm de diametro con empavonado incluido si quieres una simetria mas o menos decente, esto quiere decir si no recuerdo mal que en 3" en pueden entrar de 70-80 estrellas. Debes lograr que las estrellas aunque sean cilindricas tengan la misma medida y sean simetricas, es decir, que la misma medida de ancho y alto. Utiliza un grano mas fino para la polvora de apertura pero si puedes hazte con cascaras de arroz y recubrelas con polvora negra y siempre dá mejor resultado alojar la polvora de apertura en papel de seda, de cocina o wc (el de limpiarse el culo). Asegurate que cuando cierres la carcasa no y la agites no debe sonar como un sonagero, las estrellas deben quedar bien fijadas sin moverse. Finalmente, en cuanto a la las capas de papel las puedes pegar en tiras poco a poco o como lo has hecho estilo maltés, pero antes de aplicar las capas siempre aplica unas vueltas de cinta de carrocero para uniro los dos cascos o hemiesferas. No te pases cuando añadas polvora trueno o flash para que la apertura no sea demasiado fuerte y algunas estrellas no enciendan, de todos modos te aconsejo que en lugar de flash utilices APERTURA pdf (ver pdf) que es más suave que el flash. Por lo demás es cuestion de tiempo y practica.

 

José

[OldMarine]

I love how google translate mangled that post. "Clean the ass" had me howling!

[braddsn]

FlaMtnBkr: Yes all of my colors that I use are from the Jopetes PDF, with the exception of some of the popular streamers and glitters.. like D-1/N-1, Tigertail, C-6, etc. The Jopetes colors are the best I have seen and used.

[Aspirina]

Thanks to all for your answers, I understand that the most important thing for a good symmetry in the spherical shells is:

- Use coated rice hulls

- Use kitchen paper to keep the burst charge in the center

- Use another pasting method

- Smaller stars, equal in size and well positioned

 

Mumbles:

“you can try increasing the number of layers. It looks like your paper is fairly thin, which may require more of it. 6 layers is about what you need for for strong paper and good pasting. Increasing the amount of booster will also have an effect, though probably wont get to the heart of your symmetry problems. “

 

As I did the shell with the 6 layers went very fair in the mortar, so much that if I put a layer more did not enter in the mortar, perhaps making the hemispheres less thick and using kraft paper to later apply more layers of paper?

José

Se que hemos hablado mucho y me has dado muchos consejos que quizás parece que no estoy teniendo en cuenta, sinceramente no quiero que pienses que paso de lo que dices... Lo de no empavonar las D1 a sido un error, simplemente no lo tuve en cuenta, respecto al tamaño de las estrellas, tengo que conseguir unos tubos aún mas finos para hacer otra herramienta, ya me costó encontrar los de la foto que te pasé por email pero habrá que seguir buscando, ¿alguna sugerencia?

Como dice Wiley, al buscar el efecto palmera, no va bien con este tamaño de estrella (1cm)? Tendré en cuenta hacer estrellas mas pequeñas cuando haga colores.

PD: Veo que nuestros colegas Americanos valoran mucho tu trabajo, tengo suerte de que seas Español jajaja

José

I know that we have talked a lot and you have given me many advices that maybe it seems that I am not taking into account, I sincerely do not want you to think that step of what you say ... The not primming of D1 is a mistake, simply did not have it In regard. For the size of the stars, I have to get some even thinner tubes to make another tool, and I struggled to find the ones of the photo that I passed you by email but will have to keep looking, any suggestions to buy?

As Wiley says, when looking for the palm effect, it does not go well with this star size (1cm)? I will consider making smaller stars when I make colors.

PS: I see that our American colleagues value your work a lot, I'm lucky that you are Spanish lol

OldMarine, JOPETES wanted to say exactly that, google translate not to corrupt nothing lol

[MudDuckPyro79]

Here is a 3 inch ball shell using paper hemi from cannon fuse (Chinese hemi) it had 5 to 1 on rice hulls with 1 gram of 70\30 in each half. The ball was pasted using the 3 strip method 3 times around.https://youtu.be/rB-W-x2ZDbo