Some questions about comets...

[Aspirina]

Hello guys!

In New Year I made some shells, with these shells it was the first time I used pumped comets.

The composition used was TT

with 10% of weight 3-alcohol/7-wather

The questions are:

How can I make comets more rigid? In the last shell it is seen that they break when the shell explodes ...

How can I paste the comets without using hot glue? What is the correct way to do with white glue and paper?

https://www.youtube.com/watch?v=yi8Kv6FUrg8

here the video, you can see what I have explained

thanks for all...

[Carbon796]

The proper way to paste comets, is to use paste and 30 lb virgin Kraft paper.

 

If you want to make your comets stronger. Pressing them harder may help depending on what pressure your currently using. Changing to a stronger binder, or using more of your current binder. Possibly changing your current technique could help, depending on what your already doing.

Edited January 23, 2017 by Carbon796

[lloyd]

Carbon,

Since he made us go to a 'link' to even know what he was doing, I deferred. But in his post, he made no mention of what binder (if ANY) he was using. One would think if someone were worried about the formula, they'd list what they'd used. "TT" isn't a formula, it's an effect, and not even the proper name of it.

 

It's hard to help when you don't get even the information the requester has!

 

Lloyd

[Mumbles]

From the video, it looks like you're using a syringe body and a wooden dowel. This might work if the comp was good and wet, but at 10% water you will probably need more pressure. This probably also means you'll need a stronger sleeve to take the force. It's difficult to say for certain what diameter they are, but I'd guess around 18mm? You may want to see if you can find a similar sized steel, aluminum, or thicker plastic pipe to use instead. With something stronger, you will be able to ram the comets with a mallet to properly compress them. If you have some sort of press or arbor press, that would also work. I prefer an arbor press personally, but a variety of methods will work. Generally speaking the less water you use to wet the composition, the more pressure or force you'll need to apply to properly compress them.

 

One extra trick is to use a ~4% solution of gum arabic instead of water to wet the composition. This is in addition to the dextrin or SGRS already in the composition. Doing this does not really allow alcohol to be used as it will precipitate the gum arabic. The moisture content is already pretty low with rammed/pressed comets and they dry well without it. I'm not sure if there are alternatives to gum arabic for this, but maybe others will chime in.

 

Everything else looked pretty good. Once you get the comets figured out those will be some really nice shells I bet.

[Aspirina]

I use the Tiger Tail, okey, is a efect but I thought you would understand that the ratios are the follows:

44 kno3

44 c (Pine)

6 dext

6 s

The binder that I use was only the 6% of dext, What is the maximum I can add? Without breaking the effect? I imagine that with a better press the result would improve a lot, but now with the material that I have, I can't do anything better. There is not much more information to add, I use syringe body and a wooden dowel pressed with mallet... I dont have gum arabic, but I found a chems supply in Barcelona that have in dust format.

I'm looking to get real star pump, and I also want to make a press, but as long as I do not have them I'll have to try using rudimentary tools...

With the current media, apart from adding a stronger binder and pressing stronger, could I cover my comets with paper and paste like a shield? leaving the two ends uncovered? Maybe so, and using a little less burst charge the comets will not break...

Thank you all for your answers!

[lloyd]

Above about 6.5%-7%, dextrin begins to make the composition ashy and smoky, and it detracts from other effects in the composition.

 

If you are "hand ramming" (with a mallet), keep the composition slightly to the side of 'dry'... say not more than 8% water. Otherwise, you'll get wet spots and dry spots within the grain, and lose the ability to expel air from the mix as its malleted. Keep your increments small -- about 1/2 the height of the comet diameter when compressed. (so, for a 25mm dia comet, no increment taller than about 12mm, when compressed).

 

If you are "hand PRESSING" (either by 'hand' or with a small arbor press), make the mixture more wet, up to about 12%-15% moisture, but do not get it so wet that water is expelled when pressing. With the slower pressing action and wetter composition, it is reasonable to press a whole comet in one powder load, for comets up to about 1-1/2 diameters tall.

 

Lloyd

Edited January 24, 2017 by lloyd

[MrB]

If you are "hand PRESSING" (either by 'hand' or with a small arbor press), make the mixture more wet, up to about 12%-15% moisture, but do not get it so wet that water is expelled when pressing. With the slower pressing action and wetter composition, it is reasonable to press a whole comet in one powder load, for comets up to about 1-1/2 diameters tall.

 

About that... Pressing in one go, vs multiple increments. Is there a "simple" way to figure out the pressure needed to get the same density?

I have access to a "10 ton" press in the family workshop, and as it turns out, i can press a 2" comet in a few increments, filling it "almost" to the top every time, before pressing, but it ends up lighter then if i do smaller increments, and, if i cut it open, it has "softer" areas inside, so clearly it's not enough force. I do these in 15 increments, but filling it to the top i get away with 3-4, (a small variation depending on the composition) but a product that is not as good. (and since "not as good" is a failure in my book, that's not the way i do em)

 

It's unlikely that i will replace the press with something larger, my dedicated press is smaller... So it's just curiosity, well, mostly.

B!

[lloyd]

MrB, consider somewhat smaller increments, but also consider longer 'dwell time' under pressure.

 

For the most part, one can press to reasonable 'even consistency' with increments about 1/4-1/3 of the i.d. of the mold. But it always requires enough dwell to make sure all the air is pressed out.

 

To produce 2 tons of force on a two-ton press, it takes most of 165lb of weight at the bitter end of the full-length handle to do it. In fact, most of Chinese presses work at about that formula, regardless of their rating. They make the handle longer on larger presses, so it takes about the same weight on the handle to produce the rated force.

 

FWIW... 2-tons on a 2" comet is just about right. Usually, comets press well at from 1000psi to 1500psi. To generate 1000psi on a 2" comet requires more than a full ton of force, and 1500, almost 2 tons. At full load, (If you weighed 165lb) you'd be lifting your body off the floor to get the full pressure. They don't tell you that when you buy them!

 

Lloyd

Edited January 25, 2017 by lloyd

[Limpy]

Odd, I can press a 2 1/4" comet in one shot with a 4 ton bottle jack. They work nice.

[lloyd]

Sure, with a bottle jack (slow-acting) and fairly wet composition, you can do it. I don't like 'wet comp', when I can press it more dry, even if I must press in lifts.

 

Normally, when we think "hydraulic press", we (in our business) are thinking of a quick action. With larger comets, it helps in total processing time and consistency to press them MUCH drier, and in several 'lifts', if necessary.

 

As Ned likes to say, "There are several ways to skin a cat, and some of them work darned well!". In commercial manufacture, we seek the method that uses the least total manufacturing time, not merely the fastest to press, only. Our drying rooms are only so large, and if we can cycle things through in 24 hours, that's so much better than having to build up a week's inventory there before the first item comes out. When 10-20 trays a day are going in, you can fill up a 15' x 24' drying area pretty quickly, even 10 trays high!

 

Lloyd

[OldMarine]

I press 1½" comets in one increment unless they're full of coarse charcoal. They seem to crack if I don't press those in small increments no matter the dwell time.

[lloyd]

Yes, the formula matters, as well, and I failed to mention that. I can press items that are essentially 60% or more of commercial BP in one increment almost regardless of size. But some colors and most high-charcoal comps, no, unless they are VERY wet.

 

Lloyd

[MrB]

MrB, consider somewhat smaller increments, but also consider longer 'dwell time' under pressure.

FWIW... 2-tons on a 2" comet is just about right. Usually, comets press well at from 1000psi to 1500psi. To generate 1000psi on a 2" comet requires more than a full ton of force, and 1500, almost 2 tons.

 

Yeah, the 10 ton press does fine with smaller increments, but att hat point it is both faster, and easier to work with my smaller dedicated unit.

 

The dedicated unit is a 4x6" hydraulic thing that used to be a car jack. Max "lifting" capacity was 5 tons, i inverted it, hooked it to a different, but still manual pump, put it all in a stand, and mounted a "force gauge" akin to those Skylighter has a tuturial on how to make. I hooked it to a couple of different readouts, and put different faces over the outer of the glass, so i get "correct" values for my standard sizes without having to think. From the sound of things, i "over press" my comets, but that is ok. I don't use much water, and when they come out they make a nice clinking noise, if cut apart, there are no apparent layering, so it seams they compact nicely throughout.

B!

[lloyd]

"I don't use much water, and when they come out they make a nice clinking noise..."

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

 

That's EXACTLY how they should turn out. Don't change a thing!

 

Lloyd

[OldMarine]

I have a crossette pump I haven't tried yet. The tube is too short to do a single pressing so I'll have to load it incrementally. Should I do multiple pressings or simply tamp it in until full as I've seen Mike Swisher do? I'm not sure of the measurements of his pumps but they look similar in length to the one gifted to me.

[Carbon796]

You would probably be wise to tamp it full. Like a traditionally operated hand star pump, otherwise you may risk damaging the crossette plunger.

[OldMarine]

You would probably be wise to tamp it full. Like a traditionally operated hand star pump, otherwise you may risk damaging the crossette plunger.

That's what I'm thinking because it doesn't look as if there'll be much to trim off before ejecting. I haven't had luck with under compressed comets so far, they just turn into dust sprays.

[MrB]

"I don't use much water, and when they come out they make a nice clinking noise..."

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

 

That's EXACTLY how they should turn out. Don't change a thing!

 

Yeah, but the "thing" is, i wonder how much pressure it would take to produce the same end-result with a single stroke. As i said, curiosity. I don't think i'd get around to upgrading anyway. I want to replace the hand pump with an electric, but that is probably as far as i'll take it for the dedicated one.

B!

[lloyd]

B, it's not all that complicated to build an hydraulic press from 'scratch', using things like off-the-shelf motors, log-splitter pumps, and ordinary Danley couplings..

 

I have two in my shop now, so-built, and it's hardly a day and a half's work to build a new one. You can have the parts in three days from Northern Hydraulics, or if you wish to pay extra for faster, McMaster-Carr.

 

Lloyd

[pyrohacker]

Does anybody knows how's a comet launched alone from a mortar is called?

[lloyd]

I know you want to believe it's a fancy name, but... I'm in the fireworks business, and we call them "comets".

 

Sometimes they're called "single-fire comets", but that's just to differentiate between those shot one at at time, and those shot from multi-shot plates or mines, which are called -- wait for it -- "comet mines" <grin>

 

Comets shot from shells are also called "comets", but the effect is known as a comet shell.

 

Lloyd

[Limpy]

Sure, with a bottle jack (slow-acting) and fairly wet composition, you can do it. I don't like 'wet comp', when I can press it more dry, even if I must press in lifts.

Normally, when we think "hydraulic press", we (in our business) are thinking of a quick action. With larger comets, it helps in total processing time and consistency to press them MUCH drier, and in several 'lifts', if necessary.

 

I'm pressing D1, using only 5-6% straight water. To date, I have made 1 1/2" through 2 1/2", and not one has cracked.

Edited March 22, 2017 by Limpy

[OldMarine]

That would make sense if you have a slow acting press. As Lloyd said, the slower pressing and dwell time make for better consolidation. I've found that the dwell time is more important as the charcoal content/coarseness increases. I was tempted to add more water but luckily I read here that that would make it worse.

Some things that seem to be right according to common sense are not applicable to this hobby. Cooking doesn't transfer to pyro much!

[pyrohacker]

I know you want to believe it's a fancy name, but... I'm in the fireworks business, and we call them "comets".

 

Sometimes they're called "single-fire comets", but that's just to differentiate between those shot one at at time, and those shot from multi-shot plates or mines, which are called -- wait for it -- "comet mines" <grin>

 

Comets shot from shells are also called "comets", but the effect is known as a comet shell.

 

Lloyd

Thank you for your answer Lloyd it is very helpful.