pocket cannon

[Fiddy]

Ive got a problem in firing my cannon.

i made fuses from match heads, which burn really well, but once the fuse burns down to the cannon hole, it just goes out

any idea's on how to get round this?

 

[ElectroMagneticFreak]

How small is the hole into the cannon? It sounds like there is a lack of oxygen that is making the fuses go out when the fire reaches the hole in the cannon.

If you can get some Potassium Nitrate (oxidizer) and some cotton string you can make some fuses that won't go out when the burning part reaches the hole. The oxidizer will provide oxygen that seems to be lacking when the burning part approaches the hole.

If you can get some KNO3, you can try combining this in a 70 to 30 ratio or 50 50 of KNO3 and sugar in water and then a little dextrin as a binder (you can make your own dextrin with cornstarch heated in the oven until it turns more golden) in water to bind it so it becomes hard and sticks together on the string.

What would probably work even better though is KNO3, S and Charcoal in water with dextrin that you soak your cotton string in.

There really is no replacement for good fuses, and I know exactly what you mean when they go out right when the fire enters the hole of the firework, cannon etc. The problem is most likely a lack of oxygen together with the right amount of fuel...

What kind of charge are you using as your powder inside the cannon out of curiosity?

 

[Fiddy]

thanks man! ill have to get some KNO3 then

 

[ElectroMagneticFreak]

Cool, I hope it works!

You could even try just using KNO3 dissolved in water into the cotton string by itself and it might even work. It will burn a LOT slower as the only fuel will be the cotton string rather than any added charcoal + S or sugar, but it should keep burning regardless slowly but surely and shouldn't go out when it reaches the hole because of the even absorption of oxidizer into the cotton string.

The waiting will probably be very suspenseful, though.

thanks man! ill have to get some KNO3 then

 

[vk2fro]

Matches contain oxidizer already, otherwise they would not strike. Its got me perplexed as to why it goes out at the entry to the breech.

Match heads are basically potassium perchlorate, sulphur and a binder, which also seals the mix from air. When exposed, the perchlorate reacts with the material on the box, and ignites. The sulphur prevents the reaction from happening too quickly (i.e. bang instead of ffft) and the binder holds it all together.

 

[ElectroMagneticFreak]

Matches contain oxidizer already, otherwise they would not strike. Its got me perplexed as to why it goes out at the entry to the breech.

I was thinking the same thing. Were the matches ground up and attached to a string, or were match heads just attached inside a tube to make a fuse? If they were ground up and put in water, the oxidizer (probably KCLO3) might have been removed to the point of being in to low a ratio to provide enough oxygen for the rest of the composition.

When I used match heads as fuse, I put them in a thin drinking straw (plastic sucks) but this would probably be way too wide to use in the mini cannon hole... If you can add dissolved KNO3 to a thin strand of cotton string, and add Charcoal and S as fuel or sugar as a lesser option I think that would be the very best way to make a reliable fuse.

Adding the dextrin will be the water soluble binder (glue) that will make the black powder coated fuse stiff and resistant to disintegration with handling.

 

[vk2fro]

bugger it - make the cannon a bit more powerful. Feed the wires of a no.8 blasting cap down the muzzle and out the breech. Will be much more impressive (provided the cannon doesnt blow up!)

 

[Fiddy]

i ground up the heads of the matches then mixed with water then applied it to the string.

 

[ElectroMagneticFreak]

i ground up the heads of the matches then mixed with water then applied it to the string.

Another problem could be that the oxidizer in the matches is not water soluble enough and therefore not enough of it is penetrating into the string, nor is there a thick enough layer of the match composition coating on the external part of the string to continually sustain the burning and or this coating is not staying on the string and is flaking off.

Sometimes compositions like what is in the matches works really well attached to the match but not as well when removed. An example is red road flare composition which burns really well as a solid cylinder of composition inside the road flare but when removed and in smaller quantities in a pile or a line is actually really hard to ignite and does not sustain burning in small quantities .

If I remember correctly KCLO3 / KCLO4 is less soluble than KNO3.

Does Australia have any laws relating to pyrotechnics chemicals?

Unfortunately I think the shipping of an oxidizer to you from the U.S. pyro supply companies would either be prohibited or really expensive with hazmat fees.

Can you buy consumer fireworks where you live?

 

[vk2fro]

it would probably be prohibited - besides, if that was the case, just ship him a few meters of visco - it would last forever with the little cannon

Garden supply stores will have the KNO3. They'll take your details if you buy a reasonable quantity, but thats no issue if your using it for a harmless cannon. They only track you down when you start blowing stuff up with home made bombs

 

[Fiddy]

i can get KN03 fairly easily, i was thinking of using the oxidizer from sparklers? crushing it down into powder then applying to the string? thoughts?

 

[vk2fro]

Might work actually.

Also youtube "Sparkler bomb". Sparklers are heaps more fun than they appear to be on the packet

I made one with 16 sparklers and let it off at campsite. The explosion was deafening, and the unwanted arachnid in the hollow log was vapourized. We were a tad concerned about having discovered australia's deadliest spider right in our camp!

 

[Lazy Laser]

Yep, They banned fireworks here in Canberra awhile back..

It was great fun going firework shopping every year, I still remember having bumblebee fights :shhh:


You use to be able to get quarter sticks awhile back from the same place where all the 'naughty' shops were too..
I'm not entirely sure where you get them now but trust me, fireworks are definitely still around just not the legal type.

 

[ElectroMagneticFreak]

i can get KN03 fairly easily, i was thinking of using the oxidizer from sparklers? crushing it down into powder then applying to the string? thoughts?

It might work, but the oxidizer in sparklers could be KCLO3, KCLO4, or even Barium Nitrate which is really poisonous and water soluble. The other trick is getting the composition to reliably stick to the string. Some compositions require a minimum amount to burn reliably so may not work as well on a thin fuse. Sparkler compositions usually use a coarse metal powder as fuel which requires very high burning temps to keep going and you might need too thick of a coating of this to fit in the cannon hole.

IF you can get the KNO3 that is really the absolute best thing to use. :angel:

 

[vk2fro]

Yep, They banned fireworks here in Canberra awhile back..

It was great fun going firework shopping every year, I still remember having bumblebee fights :shhh:


You use to be able to get quarter sticks awhile back from the same place where all the 'naughty' shops were too..
I'm not entirely sure where you get them now but trust me, fireworks are definitely still around just not the legal type.

Yes, one of my camping mates knows a pyro and sometimes brings stuff along. Bangers the size of D cell batteries that do as much damage as a 16 stick sparkler bomb, rockets the diameter of 50 mil pipe, and morters the size of soft and basket balls. Tonnes of fun. We just pray its been raining the previous few nights so the remnants dont start a fire. The 12" shells are REALLY loud

sparklers in australia are the potassium chlorate and iron or magnesium mix. They are the red, blue and white packet that contain 8x8inch sparklers on a steel stick. ITs been a while since I've used one for its intended purpose

 

[ElectroMagneticFreak]

Yes, one of my camping mates knows a pyro and sometimes brings stuff along. Bangers the size of D cell batteries that do as much damage as a 16 stick sparkler bomb, rockets the diameter of 50 mil pipe, and morters the size of soft and basket balls. Tonnes of fun. We just pray its been raining the previous few nights so the remnants dont start a fire. The 12" shells are REALLY loud

You guys get to set off 12" shells in the outdoors when you go camping and its not even part of a fireworks display? It must be really far away from cities out in the wilderness or outback? I would think you would really feel a 12" shell from underneath! I worked for a fireworks company when I was 17 but I don't think we had 12" shells for that even though ours was on a barge in the ocean.

Sounds like a great time, I'm jealous! :yh: