18 replies to this topic

[Sparky]

Hi all,

I'm not yet in a position to mill good quality BP for reliable lift powder and as I'm only experimenting with small star shells (circa 1 inch od tubes) and 2 inch mines, I've been trying Benzolift as an alternative. I appreciate it contains whistle so am wet mixing both the oxidisers before the fuels so I never have dry whistle mix making it this way.

So I've done some very small scale testing today and have tested in a 1 inch cardboard tube firing a 30g dummy star shell. Also tested with a 3/4 inch tube firing a 10g dummy.

I started on the 1 inch tube and used 2.5g of Benzolift which was a fairly fine powder (I powdered it as it was a bit granular from when I made it) and was what I thought I'd have used if I was using a really good BP. This did a pretty good job on the tube and blew it to bits

I later tried 1g of exactly the same Benzolift comp with the same 1 inch tube but this batch was granulated via a 20 mesh. This worked much better indeed and I lost my dummy shell in some bushes.

I did a few more tests on smaller tubes etc and I noticed that Benzolift seems VERY sensitive to pressure and if you dare to contain it in the slightest it just destroys the tubes even nice thick walled ones. Can anyone suggest whether granulating will have a beneficial affect with regard to controlling its tendency to do this? Or do I simply need to make sure I don't contain it too much with tight fitting shells and make sure I get my quantities spot on?

Also...

I want to make small shells using cardboard tubes and I know commercial manufacturers do this a lot for small to large cakes. I've been making some very small cut stars and rolled them in prime. I'll plug one end with clay and glue the other and use some good visco for timing them. To break them I was going to use a simple flash e.g Potassium Perchlorate and Aluminium (Dark) as I've read this is how they do it in commercial shells of this size. My question is: Is this going to be too powerful and just blow them blind or even just destroy the stars? Is there a way to make the composition hotter and slower by simply increasing the amount of fuel? Or maybe using a larger mesh Alu? Was intending on testing with 1g of flash to start.

[Deano 1]

Hey Sparky, I think you've got yourself in a rutt of power, power, power. You really don't need all these flash powders and benzolifts, you can get just as good if not better and a lot safer lifts and breaks with just different grades and grains of black powder. I've made consistant lifts and breaks on 3" shells with just bp, and I've never had a tube explode. I did a lot of experimenting with different charcoals and you can get some potent bp's with such as balsa and straw. It's only my opinion through experience, but I think you should look at the safer options, I think you'll find them more rewarding.

Stay safe Dean

[Sparky]

Just need to clarify a few things I think may have been misread.

1. I am certainly not using flash for lift!
2. I do not have a ball mill or anywhere I am happy to let it run with the associated risk.
3. I have performed an autopsy on the very small 1 inch shells you see in cakes and they do use flash as the break. I presume it is not optimised for power, possibly excess metal (alu) for additional heat and slower burn?

Where do you get your balsa or straw charcoal for BP from and how much can you reliably make by hand in a mortar and pestle? I've had little sucess making BP by hand even using a wet method to dissolve the KNO3 and get it into the charcoal.

[www.oliverbrown.co.uk]

Where do you get your balsa or straw charcoal for BP from and how much can you reliably make by hand in a mortar and pestle? I've had little sucess making BP by hand even using a wet method to dissolve the KNO3 and get it into the charcoal.

Quality of charcoal AND the milling process are key to fast BP, you can have the best charcoal in the world and stick it in a Nation Geographic rock tumbler, doubt you would ever get very quick BP. The milling process is just as important, my mill can knock out what I call quick BP in 4 hours flat (1/4" tube from cooperman, rammed like a rocket with 30mm of BP, burns out in 1.4 seconds).
I'm not convinced there is as much difference between tree types as we are lead to believe, obviously some perform better than others but I think there are plenty that if cooked properly and milled well can produce quick BP.

A mate of mine makes charcoal from Japanese knot weed, now I'd say that is quicker than I can get from wood, I use that for burst!!

Ah, Sparky, my phone just sounded! I see you bought some charcoal from my ebay account, I'll add some paulownia for free, that is supposed to be the best you can buy, let us know your thoughts!

[www.oliverbrown.co.uk]

Hey PyroPDC I completely agree, there are some suspect charcoals sold on eBay, not sure about BBQ grade but certainly substandard, the first ever time I tried to make BP was using charcoal bought from eBay, it was slow as hell and was a good job my mate knew the importance of quality charcoal or I might have given up right there!!
As you said the best charcoal available is made in your own back yard!

[Sparky]

Nice one, is it Alex @ Oliver Brown?

[www.oliverbrown.co.uk]

Nice one, is it Alex @ Oliver Brown?

Thats me!

[starseeker]

I did not have a mill for two years,but found that as long as you bought ready milled quality charcoal and then used the cia method,i had no problem lifting 3 and 4inch shells.

[Sparky]

Thanks for all your replies. I think by the end of this I will be an expert on what does NOT work for lift :-)

I'm not really very comfortable with running a ball mill in my back garden as I'm in a terrace. I mainly test my larger fireworks at my partners parents place which has an enormous garden and at home I tend to stick to gerbs, wheels and occasional small rockets. What is typically the smallest run you can do in a ball mill and if the worst did happen how big a mess is it? I've got a solid brick wall and I could box it in, add sand bags etc but it still makes me edgy.

I've also seen the double milling process discussed where you mill KNO3 and C in a non-explosive mix ratio then the S and C in another run. Finally you mix by hand together. Anyone tried this?

I'm going to try the CIA method now and let you know how that goes though. Seems like workable solution for now.

[Sparky]

Wow the CIA method is messy

I presume the chemistry behind it is that you are putting the oxidiser into solution which then allows it to penetrate the charcoal pores. I'm not sure what the cold alcohol does except cool it rapidly. Pouring the hot mixture into the alcohol sure did cool it fast.

It's still wet though so I presume the alcohol also plays a part in driving the water out and preventing the KNO3 crystallising out of the C?

[cooperman435]

adding the alcohol does a few things, it masively reduces the waters ability to hold the desolved nitrate and cools it again reducing solubilty. Both of these result in very tiny crystals of nitrate being formed rather than big ones.

but yes its messy n still wouldnt be as good result as milling.

Edited by cooperman435, 14 June 2012 - 01:31 PM.

[pyromaniac303]

What is typically the smallest run you can do in a ball mill and if the worst did happen how big a mess is it?

There is a previous Spark article, though I forget which issue it was, where several mill jar explosions were simulated with various loads, and the damage recorded. This would be a good starting point to assess whether a mill is a safe option for you.

The only limitation on load is the size of the mill jar and milling media, along with the torque and speed of the motor. For example if you run a mill optimised for a 50g load with a much larger load, you greatly increase your milling time. Conversely if you run it with a smaller load then you speed up the milling time.

I would assume (possibly wrongly) that there is no real lower limit to the batch size you can mill, though if you run batches of only a couple of grams with unhardened lead media for long periods of time, the level of contamination from the media may become a significant problem. For example I once left my thoroughly cleaned mill on over night with 20g of potassium nitrate to see how fine I could get it, and found that it had a slight grey tinge to it the following morning which I can only assume came from the lead media.

I swapped the hopelessly underpowered AC motor on my rock tumbler for a more substantial DC motor, ensuring that the mill housing was well sealed of course to prevent any powder coming into contact with it in the event of the mill jar splitting. This will now quite happily turn 2kg of 12mm lead media for days on end without any problems.

I'm not sure how effective the double milling process would be, as I have always thought that the KNO3 was required to penetrate the pores of a large proportion of the charcoal in order to make reasonably quick BP. It will surely make it more consistently than the CIA method though, which is more important than power as you need to know it will perform the same way each and every time (so you don't end up with a mixture of CATOs and upside down gerbes on a stick).