15 replies to this topic

[inonickname]

As part of a challenge between me and a few (mainly forumer) friends we're building small bore (1-3mm) blackpowder cannons. I'm machining the chamber from solid 20mm high carbon bar and using sleeved brakeline (which will be blued) for a barrel. The cannon will be set up in a polycarbonate case (we won't be anywhere near them, just to protect the camera and chronograph mainly) with electronic ignition (at this stage, probably a medium sized cap bank discharging through a small metal filament).

I'm looking for a primer mixture to use in the aim of attaining the highest muzzle velocity I can. The primer mixture must not be too substantial in volume (as in, there must be a much larger amount of black powder than primer mixture).

The primer mix will be made just before it is used (so storage issues are not an issue) or at a time which is suitable for the mixture (like, if the synthesis of X will take 2 hours to complete, it will be made beforehand).

I was thinking of using a small amount of armstrong's mixture as a priming mix (yes, I mix it wet and don't store it). Any suggestions? It only needs to be safe enough so that it can be loaded into the cannon and the breech closed safely (keeping in mind noone will be anyone near it).

Noise and similar issues are not a problem. I have a fair range of oxidizers, acids and fuels to use so any mixture that isn't too exotic should definitely be doable.

By the way; I'm not a kewl.

[dagabu]

With electronic ignition you don't need an unstable prime like Armstrongs. The risks of making, transporting no mention that you cant legally make it aside, you would be blowing the BP (I assume you will be using BP) out without ignition. Use an accepted pyrogen.

D

[inonickname]

So, something like a mix of zirconium powder and oxidizer would be good for this purpose?

[dagabu]

I wouldn't reinvent the wheel here, what you are looking for is a hot fire that will allow all of the BP to ignite so as to build all of the pressure it can before expelling the shot. Anything that goes high order is more of a 'shock' then a push and causes a pulse wave that can actually diminish the muzzle velocity.

Use smaller grain BP to gain the advantage in speed and just find a reliable pyrogen to light it. I suggest 70% Potassium Perchlorate and 30% dark Al mixed in a slurry with Nitrocellulose Lacquer. Dries hard, lots of flame and will not explode.

Dave

[inonickname]

Thanks, I'll read up on the mixing with NC and think about it. Alternatively, with more ignition energy (a few hundred joules) I could step the gun up to operating as an ETC- where the energy discharged into the filament basically becomes the primer.

[elliotmotocross]

I made a reasonably sensitive primer today for exploding targets.
I tested a few different compositions.
Quite similar results. The first two were easy to set off but they all were sensitive enough to be used as a primer.
I wouldn't recommend using the ones with ____ so much. The titanium was pretty much just to add a bit of effect and increase chances of ignition.

Sorry comps removed, deemed too dangerous.

Edited by elliotmotocross, 11 April 2010 - 07:27 AM.

[Arthur]

Davis take on primers in his COPAE is:

"In a typical case the primer cap contains a mixture of mercury fulminate with antimony sulfide and potassium chlorate."

A good ematch primer compound is 5% nitrocellulose powder with 47.5% of each of potassium chlorate and Antimony trisulphide. The method is important so READ this FIRST

Weigh out some nitrocellulose powder (shooters powder works) weigh out some pot chlorate at finer than 200 mesh weigh out some antimony trisulphide at finer than 200 mesh so that the ratios by weight are NC 5% chlorate 47.5% and antimony trisulphide 47.5% and preferably make MUCH less than a gram

Put the NC powder into a jar and dissolve it til it's thin and runny with acetone or amyl alcohol stir in the chlorate and let it disperse, then stir in the antimony trisulphide and let that disperse. Then let the solvent evaporate til the product has the viscosity of double cream. If you mix the dry powders they may well ignite.

A drop of this on a 50 gauge wire will ignite immediately with serious flame but there is so little that it does not make a pressure wave. It is certainly enough to fire BP.

Any spare paste is either kept in a bottle of acetone or disposed by remote fire before it dries. This stuff is sensitive!

To use with BP the chlorate igniters are best coated in plain NC lacquer after the pyrogen lacquer. (I got a really funny look from the sales assistant when I bought a pot of bright yellow nail varnish ( I'm 5'11 balding and 18 stone!) I couldn't really explain that I wanted to make igniters or I'd probably get locked up!

[Mumbles]

I'll only say this once. If you post outrageously dangerous formulas like that again, you're banned. We don't screw around here with safety.

[dagabu]

Mumbles,

Would you be so kind as to explain to those that don't know what the dangers are and why?

D

[Ralph]

The formulas contain (2 of them) permanganate which can cause spontaneous ignition especial in the presence of sulfur and moisture here is some more info
the second two would be sensitive but similar compositions (but wit chlorate) are used for specialised applications such as breaking crossest


eiliot after you were told not to post them on another forum (which many have told you is more tolerant) did you seriously think it was a good idea to post them here ?

Edited by Ralph, 10 April 2010 - 09:56 PM.

[elliotmotocross]

The formulas contain (2 of them) permanganate which can cause spontaneous ignition especial in the presence of sulfur and moisture here is some more info
the second two would be sensitive but similar compositions (but wit chlorate) are used for specialised applications such as breaking crossest


eiliot after you were told not to post them on another forum (which many have told you is more tolerant) did you seriously think it was a good idea to post them here ?

I was legitimately trying to help here.
Probably too late for it but I'll remove them straight away.
Sorry about that.

[dagabu]

Ralph,

I just wanted the mods to explain what the issue was. I just got done reading BAFN III again and there are a few articles in a row about "death mixes". I am just not sure why people want to publish them at all unless it is in warning only.

D

[TheSidewinder]

Well, basically, the issue is that Potassium Permanganate has no legitimate use in Pyrotechnics any more. There are chemicals which are much better substitutes, and *far* less dangerous.

Its use in any formula is more than just asking for trouble. It's kicking down the door to trouble, and spitting in its face.

[Dr Boom]

Its use in any formula is more than just asking for trouble. It's kicking down the door to trouble, and spitting in its face.

That's a really good analogy and quote-worthy SW- KMnO4 is very unstable for use in the recreational pyrotechnics field, and that's a gross understatement. I've spoken with a few members here and in other forums concerning "old" formulas, exotic chemicals and discontinued practices and while some have merit in an academic sense, they are no longer practical because of MUCH safer alternatives that have been developed.
Inonickname, what are you actually trying to accomplish here? Seeing who can build the best small scale cannon? And shoot the largest charge?
You understand that your first post with not very wise to start the way you did-

I'm looking for a primer mixture to use in the aim of attaining the highest muzzle velocity I can.

If you are really starting out a cannon from scratch, you want to start with the least amount possible and work up from there. You want to chrono the shot and see what the velocity is? Are you confining the shot with a wad or cardboard disk of some kind?
Nominal fps and pressure build up of black powder is around 900fps and 17,000 psi from a .44 caliber barrel that is 7 ½ inches long using a 200 grain round ball. I reload my own .44 black powder and smokeless btw- and there are MANY very important variables that would hinder your work with the chrono and getting a high velocity with conventional black powder compositions. For starters, nature of the metal you are using, heat treatment, length of barrel, projectile mass, powder charge, powder composition, igniter position, igniter composition. The last of these being what you asking about… Have you considered buying a black powder nipple and No.11 caps (which I use) and make a simple spring-loaded trip hammer to fire it?

IF you are looking to make the primer from scratch, you will be hard pressed to find and discuss something safe and sane outside of the HE side of the house which doesn’t belong here anyway.
There are other black powder variations that give higher muzzle velocities but these *must* be used in today’s good steel muzzleloaders and replica pistols. I would be reluctant to use anything other than low velocity BP in something I made in my garage unless I over-engineered it like crazy.

Do you have any pictures of the work so far or is this just research at this point?

[Jeffdyjeff]

Use a party popper. It is Armstrong's mixture, its easy to use and it will light powder.

[Jeffdyjeff]

In a tiny cannon, the little paper roll in a party popper works similar to the pull-strimg primer in large civil war cannons. Ive used them on small cannons and pull-string fuses.