My first shell failures

[ryanlg95]

Hi,

I have constructed two 2" ball shells, but both have had issues.

 

My first one, the lift charge ignited, and made a big puff of smoke out of the tube, but that was all, no lift, and several seconds later the shell itself did ignite, shooting stars out of the top like a star mine.

 

 

For my second one, I thought I rectified the problem by granulating my lift charge, and wrapping cardboard around the shell to fill the gaps around it inside the launch tube.

Alas, the shell did launch from the tube, but only about five meters. And the shell did not ignite this time. I used a spolette for the time fuse, and inspection later showed that there was no powder left inside the spolette. I was not sure whether the small amount of singeing on the spolette was from the lift charge, or the spolette burning through and not igniting the burst charge.

 

So could I have some advice on how to rectify my issues.

[Mumbles]

It sounds like your big problem is low quality BP. I'd work on that first. BP should be granulated for lift. A small amount of powder fresh out of the mill should burn almost instantly. I guess that brings us to another point, it's very difficult to get good quality BP without a mill.

 

As far as spolettes go, how are you preparing them? There is a proper way to prepare them to all but guarantee that they take and give fire. This involves priming in a way of both ends.

[ryanlg95]

I was suspecting low quality BP. I don't have a proper ball mill. All I have is a homemade one using Lego motors, and fishing sinkers as media. It does turn very slow, so I think I may have to fork out for a proper one, but It will cost me twice more than what it should , because I live in Australia.

 

For the spolettes I use .25" ID tubes, and put a small amount of meal powder in and ram it in with the flat end of a drill bit that fits in perfectly. And I just keep ramming in small increments until I have desired lengths. I don't crossmatch or prime them because I didn't have an issue with the spolette for my first shell.

 

 

[Arthur]

First attempt to improve your BP. It's the most important part of pyro, it's important that it is good otherwise shells burst too close to you (200ft up is a fair safety distance!)

 

Look for rock tumblers on ebay or something like that, get enough decent media and mill a little at a time. There are LOTs of posts here about making BP - follow them.

 

Charcoal makes a LOT of difference willow is one of the best, vine and balsa is usually too violent. Other woods may be good and locally available to you.

[ryanlg95]

Would this rock tumbler be sufficient?

This is the cheapest tone I could find to Australia.

http://www.ebay.com.au/itm/Thumlers-Tumbler-Model-T-Kit-Rock-Tumbler-THU100-/160539854234?pt=LH_DefaultDomain_0&hash=item2560ebc59a

[Peret]

This is a much better deal

 

If they won't ship it direct to you, perhaps one of the APC members might be willing to receive it and ship it on for a share of the $50 savings. It will be 110V of course so you'll need a transformer.

[Mumbles]

With a little mechanical inclination a ball mill can be easily built for likely much cheaper that you could purchase one for. There are plenty of people willing to help if you'd like to go that route. Otherwise I agree with Peret. The link he posted is the economical mill that many get when they first start off. They're not fast, but you'll get good powder out of it. They'll take between 8 and 12hr for a batch where as a very efficient mill can do it in 1-3hr.

[Potassiumchlorate]

2" are a bit troublesome anyway. The only flowerpots and "almost-flowerpots" I ever had was with 2"; two exploded in the mortar and one just above the muzzle. It's easier to close a bigger shell due to much more pasting etc.

 

One professional pyro in my country told me that he had never seen a 6" or bigger making a flowerpot.

[Mumbles]

I've seen a fairly famous 10" shell flower pot at the 2006 PGI. It happens. They're actually much more likely to flower pot due to the forces on the shell. It's more of a fact that the people who make big 6, 8, 10" etc shells take pride in their shells, and do them the right way. The people who make smaller shells tend to be more willing to take shortcuts or may not be familiar with proper practices and thus it leads to more flower pots. I've only flower potted one shell in my life. I made it with a friend with his methods, and I can only imagine there was miscommunication or dicrepancy in our respective methods that combined to this. I've never flower potted one, and I've never seen him flower pot one either, so I can only imagine some shitty hybrid of our methods was to blame.

 

 

It would have made a heck of a nice mine if I intended it.

[Potassiumchlorate]

I think it was nice although being a flowerpot.

 

How much flash did you have in the salutes?

[Mumbles]

Heh, a lot. I think it was close to 30g per insert salute, and about 2lbs for the bottom shot.

[dan999ification]

are you refering to the battle in the crowds or the multi break with polystyrene compression buffer?

 

ive seen 10, 12 and 16 inch shells flowerpot [imports], smaller ones like 2 inch should have very good strength compared to larger ones and not collapse, the problem is most likely the spollette blew through or the fire in the mortar was too slow and cooked the shell, if you recovered one with an empty spollette, all i can think is that the fire spit was very small and did not reach the contents of the shell, scratch and prime with bm the lift end and pipe bm to the burs on the inside.

 

as for the drill bit, please find a more suitable tool for making spollettes with, 1/4" rods and dowells are not too hard to find, bamboo chopsticks are a cheap safe option if you cant get proper tools.

 

dan.