Seperate Lift Charge (Japanese Show)

[Tony]

Two weeks ago we have seen the set up of a Japanese show by Tamaya Kitahara in Tarragona. The set up is almost the same as the set up's we know. There is only one thing that i dont understand. The Japanese shells dindt have any lift charge. The lift charge is dropped in the mortar and after that they put the shells in the mortar. Why are they using this system? What is the difference between shells with and without lift charge?

 

[reflections]

im guessing that they put the lift charge seperately so that they will not have to put a not electrical fuse in the shell if they are using electrical firing so that by the time they press the button it will just go off without any delays!!! well that was just a guess so sorry if its wrong im just a 13 year old guy hehe!!!

 

[meggsy]

My guess is that they can determine the break height more acurately....say if you design a sequence where you want to layer similar caliber shells, you can reduce the amount of powder in the lift charge of some of the shells. Its a guess will ask around.......

Steve

 

[xavier]

In my opinion there are 2 reasons :

1) Transport

I think the danger will be less when you transport the blakpowder (with speedfuse) and the shell seperated.

2) production

Production will be easyer and more accurate for the liftingsharge.

 

[Luqa - Malta]

Most interesting!

It must be what Xavier said as they are the only good reasons I could think of.

Well there is really not much of a difference. Our ball shells also have a seperate lift charge but they are then taped to the bottom of the shell. The Japs probably transport them without the charge and then just conect it on the site.

On another note, the Japanese manage to impress me in almost everything they do! and not just fireworks. Education, technology, cars, Martial Arts, weapons especialy traditional, you name it and they are up there.

 

[Alexy]

Maybe because they want some shells to reach a higher point of explosion, so they can place a liftcharge that has some more SAS in some mortar-tubes. Maybe it sounds pretty stupid, but I don't have a clue why it could be. (sorry for my bad English)

 

[appiehappie]

Perhaps the best explanation can be found in Takeo Shimizu's elaborate technical explanations of the manufacturing of Warimono and Poka Shells in his book Fireworks, the Art, Science and Technique, Pyrotechnica Publications, Austin TX, 1996 .

In it Shimizu displays this process in a series of very clear pictures (pages 238-260); in general, he states, the Warimono and Poka shells are made without the lifting charge fitted onto it.
He indeed mentions it to be a safety precaution, just like Xavier said, but moreover: it enables the Pyrotechnician to adjust the bursting delay. Either through adjusting the main fuse or by applying a different lifting charge.

The nature of the Warimono shells (and even more so with the Poka Shells) demands that the structural strength of the shell must be maintained; made up of two hemispheres fitted together, its effect could be influenced by the prefixed mounting on top of a lifting charge: the main fuse chamber could easily become its weak spot and henceforth hindering the full display of the intended effect, thus he argues.

The clean break of the weld between the hemispheres is critical, in essence.

Another explanation could be the preperation of star-mines: a process in which the lifting charge (Shimizu describes a Cartridge that looks similar to what the two technicians are holding on the aforementioned picture) is put at the bottom of the tube. Then one (or multiple) mines or shells are lowered down the tube, in a previously devised pattern, and seperate small stars are deployed too, thus creating the scattering, wide wall of stars from which the shells emerge (pages 267-269)

It's a process, Shimizu says, that is common practise with shells up to 5-6 inch: about the diameter of the tubes on the picture.

 

[Vavoom]

<snip>
The nature of the Warimono shells (and even more so with the Poka Shells) demands that the structural strength of the shell must be maintained; made up of two hemispheres fitted together, its effect could be influenced by the prefixed mounting on top of a lifting charge: the main fuse chamber could easily become its weak spot and henceforth hindering the full display of the intended effect, thus he argues.
The clean break of the weld between the hemispheres is critical, in essence.
<snip>

I haven't had any reply from Japan sofar, but I think the message posted above says it all and leaves no possibilities for speculation.

On the other hand, though, I don't really understand how a prefixed lifting charge could influence the delay fuse. I can imagine that the delay fuse is more susceptible to shear and friction when a lifting charge is fitted closely to the fuse. But now I am speculating. Does Shimizu go into more detail on that?

 

[appiehappie]

On the other hand, though, I don't really understand how a prefixed lifting charge could influence the delay fuse. I can imagine that the delay fuse is more susceptible to shear and friction when a lifting charge is fitted closely to the fuse. But now I am speculating. Does Shimizu go into more detail on that?

According to Shimizu, it is not uncommon for Pyrotechnicians to adjust the delay on the spot. In paragraph 26.4 on Preparation of Shells (page 306) he puts down the procedure that is used in many Japanese shows. The fuses of the shells are cut at the end with a knife, basically making it a V-shape. Thus the fuse can be more easily ignited. And more importantly: by adjusting the size of the cut, the burning time can be speeded.
But perhaps the best reason is that the main fuse can be inspected prior to firing. The chamber can be checked for cracks etc.

Also, because of the nature of which the Fuse Chamber is constructed in Warimono and Poka shells close inspection prior to firing is essential. Some factories still use a process known as 'Nuki-shin', its exact translation is lost to me (my Japanese isn't up to par(laugh) ) but the technique is as follows:

The internal sphere (i.e. the bursting charge) is fixed in the middle of a length of tube, in which a small hole i bored to introduce the fire from the fuse in the tube. It looks like the Greek letter Phi which is this one:

The hemispere around the central column being the chamber that hold the bursting charge. Its a delicate form of applying a bursting charge, but still very commonly used. Because of the clean break it ensures of the (outer)shell and thus creating the magnificent perfect circle-effect of many Japanese shells.

A too powerful lifting charge could easily blow out the central fuse, i.e. igniting instantly because the chambers' walls ruptures. Or it could clogg the firing hole in the center, thus causing a misfire or a 'Black Shell': where the shell falls back, unexploded and could explode through the shock of the impact on the ground: perhaps unnecessary to mention that many color compositions (and moreover the bursting charges) are very shock-sensitive

If I could, I would've put some scanned images in this post, but that didn't work, alas.

Quotation are from this book, it is the book around used by many pyrotechnicians, with feedback on basically every aspect of Fireworks: the science, the formulas of blackpowder, color compositions, bursting charges, reports. The Chemical components of it, fuses, timing etc. etc.
Was long out of print but there's a new 1998 copy available.....

 

[HocusPocus.Pyro]

Dear Appiehappie, Dear FPM'ers,

Thanks for sharing your views. I am glad to see you refer to the great book by Dr Shimizu. There's not much like that book which tell you things about traditional Japanese shells. I know, since I have been a fanatic collector of fireworks books.

First, I want to make a few comments on your post.

A Poka shell is a shell that typically bursts with a soft break. For soft breaking shells, most often the shell may easily break along it's equator, without "punishment" (i.e. that will not be detrimental to the effect one wishes to achieve). Poka shells do not need as a strong "confinement", by having a thick shell casing. The bursting charge to break a poka shell is typically little, but just enough to break the casing. Poka shells also were used to display relatively fragile materials, parachutes, lanterns, figures of paper, flags.

A Warimono shell is quite different from a Poka, in that is must have a hard break. This is in general achieved with a strong "confinement", by having a think shell casing in combination with a larger more powerful bursting charge. A Warimono type shell must break into small equally great fragments.

Time-fuses can be "blown inwards" by the pressure that exists inside the launch tube during lift-phase, if the pressure is too high, or if the construction that holds the time-fuse in place is too weak. Normally additional pasted paper, and string with glue do the job properly. A malfunctioning time-fuse indeed results in a blind shell, but these fuses can not get clogged during the lifting phase.

I think that Xavier in reply number 4 in this thread answered the question properly. To support that, I would like to add: Traditional Japanese shells are used a bit differently than we are used to, here in Europe. It is not uncommon that Japanese shells are treated as individual pieces of art. Huge shells are fired at festivals. Some Japanese shells indeed seem to be made and shipped from the factory with time-fuses not yet cut. That requires at some point in time that someone with the proper knowledge determines at which length time fuse must be cut. In theory it is an option that the time-fuse is cut at a somewhat longer length, so that an extra length of time is available for the shell to reach it's apogee in flight. However, please understand that this thread started about a show by Tamaya Kitahara who were taking part in the Tarragona fireworks festival. Most likely this will have been a show were a few hundred of shells were used. This would make last-minute altering time fuses a significant effort, with issues to be dealt with like logistics, laws/regulations/permits, quality control. I am not saying it can't be done. Maybe they needed to, since I think it is likely that Tamaya Kitahara only shipped their shells and not their normal launch tubes. And it may have been done with help from a local factory.

Just my 2 cents worth.

Sincerely, your magician HocusPocus.Pyro

PS: I'm sorry, I have to keep it short, since I am still unpacking from boxes after our move.

 

[Vavoom]

According to Shimizu, it is not uncommon for Pyrotechnicians to adjust the delay on the spot. <snip>
But perhaps the best reason is that the main fuse can be inspected prior to firing. The chamber can be checked for cracks etc.

Also, because of the nature of which the Fuse Chamber is constructed in Warimono and Poka shells close inspection prior to firing is essential. <snip>

Thanks for your elaborate answer, but I still don't see how a prefixed liftcharge could influence (i.e. damage) the delay fuse.
Maybe it's just me being tired from racing my bike this afternoon.

 

[Vavoom]

And just to add an easy way to remember the difference between Warimono and Pokamono shells. You should remember that "Po" or "Pok" resembles the sound that the shell makes when it breaks.

And too be complete. Next to Warimono (Shimizu suggests H3 break) and Pokamono (black powder break) there is a third type of Japanese shells of which the strength of the break is in between Warimono and Pokamono. It still breaks symmetrically, but uses much less break than a Warimono. This type of shells is called Kowarimono. An example of Kowarimono is a shell of shells. Kowari translates best as subdivide.

There might even be a fourth type of Japanese shells. Some think of the Hanwarimono as an individual type. This being a semi-warimono. This break is often used for Kamuro shells that need a break less powerfull than Warimono, but more powerfull than Kowarimono.

There are also Katamono shells. These are figure shells, but are a subdivision of the Warimono type.

-------------------------------------------------------------------------------

Remark (without going into too much detail about the exact composition): H3 is a Chlorate based break. At 1 atmosphere it is three times faster than black powder, and twice as powerful. It is "quite unexpectedly insensitive to shock and friction" when pure. It can be quite dangerous in contact with other fuels, especially sulphur or sulphides, so it is dangerous for loading shells with many stars containing these substances in their primes. The "burning rate of H3 does not particularly depend on pressure".

In comparison (again without going into too much detail about the exact composition):
A Potassium Perchlorate (KP) break is also twice as powerful as Black Powder (BP), has a flame temperature of 3600 C, vs. 1800 C for black powder, is more sensitive to mechanical action than black powder, and has a burning rate highly dependent on pressure. At 1 ATM, it's burning rate is 1/2 that of black powder. It requires an especially strong shell wall, compared to H3, to get the benefit of its great force, because at low pressures it burns so slowly that a weak shell will burst spilling out unburned KP. Since it contains sulphur, like BP, care must be excercised when loading chlorate stars since this is a very dangerous operation. (Because KP differs so greatly from BP in flame temperature, pressure dependency of burning rate, and force of explosion, it would seem that attempts to substitute it for black powder would be difficult).

I might have gone slightly off-topic here. (eek)

 

[HocusPocus.Pyro]

... I still don't see how a prefixed liftcharge could influence (i.e. damage) the delay fuse.

In my opinion, there is no logical connection to having the lifting charge connected with a cup, paper bag OR that it is placed as a loose bag (see image in post 1), and the chances of the time-fuse failing (blown inwards), or the time-fuse having a negative impact on the burst-symmetry. The time-fuse creating a gas-leak, or the time-fuse being blown inwards, would typically be the a result from abnormally high pressures in the launching tube, or errors in the construction of the display shell, assuming we are discussing shells that are made professional way. The pressures that result in the launch tube are generally not dependent to any significant extent on the bag/cup material. The pressure rise in a launch tube is typically quite gentle, since there is a significant by-pass of hot gasses between the shell and the tube, during launch phase. The pressure-rise that one observes is largely dependent on the lifting charge powder (pressure exponent), the clearence between the shell and the tube, the mass of the projectile, friction of shell in tube, length of the tube, etc.

Remember also that alot of shells have two time-fuses in parallel, for redundancy reasons, so that if one fails, the other will do the job properly.

Although the side-track discussion is very interesting, the original question was the original interesting bit that caught our attention.

The bursting charge discussion is interesting, but it is not logically connected with the way the shells are launched from their tubes. In other words, one would typically use the same method for launching a softer-break shell as one would a hard-breaking shell. Or am I missing something here?

I still think that the reasons why these shells were lifted with loose pastic bags of lifting powder, are much the same reason as were discussed already.
1.) Transportation and safety, born historically in Japan
2.) Production, born historically in Japan
3.) Flexibility to adjust to parameters like type of launchtube, height, etc

Kind regards, your "pyro-magician" HocusPocus.Pyro

 

[Tomas]

Hi!

I heard also, it&#180;s more cost efficent to buy and ship the shells without lift charge, it&#180;s alot of weight when you talk thousands of shells.....
Black powder for lift charge is quite cheap to buy here in Sweden...
Tomas

 

[meggsy]

I'm guessing Tamaya used a seperate lift charge on this :blink1: .....picture sent by Tamaya to one of the companies I work with.....

 

[Flash Salute]

hmmmm thats sweet :nuts: I imagine the lift charge quick of this shell :blink:

 

[Ernie]

Maybe because they want some shells to reach a higher point of explosion, so they can place a liftcharge that has some more SAS in some mortar-tubes. Maybe it sounds pretty stupid, but I don't have a clue why it could be. (sorry for my bad English)

i think thats the correct answer ! An higher point of explosion can be reached by this.

 

[Flash Salute]

its a good point to use a shell and a lift charge separatly but he take 2x of your time to load a mortar, i dont know why japanese use that type of shell..the disney compagny use air pressure lift charge ! thats seriously nice because the lift charge produce no smoke and the spolette in the shell are specialy used to be fired with a air pressure mortar ! BIG DEAL