106 replies to this topic

[KNO3]

Andrew, on Dec 3 2005, 08:03 PM, said:

The problem with stainless is that it is very hard. No matter how hard you try to make it non-sparking it will still spark under the right conditions. Also, as it is hard, the chance of friction ignition is a lot higher. The most likely cause is probably contamination as Karl said.

You have to be carfull when commenting on the properties of stainless, there are many, many different ones, and the is such a huge range in properties, so we cant be sure that it will infact spark due to hardness. I would also say that a manufacturer of sparkless stainless would probably take into account the hardness of the stainless, and pick a softer one, to make it less sparky. So i wouldn't count on that, but it is definetly a logical possibility.

[seymour]

Today I had one of those long dreaded accidental ignitions. I was in my shed measuring a length of carrdboard tube to cut it into suitable lengths for rockets when I heard the distinctive "whhhsssssssssssh" of loose composition burning. I turned to see a stainless steel bowl previousely containing aprox 100g of 60% KN, 30% C, 10% S coreburner rocket fuel giving off a good deal of flame and smoke. Within seconds the fuel was burned and I was pumping the surrounding area with a fire extinguisher, before I threw the bowl clear of the shed out the door to prevent any embers it my contain starting a new ( more serious) ignition. Apart from contact burns to my fingers from grabbing the bowl ( which are making typing this rather painful) noone was hurt and nothing was damaged. The only potential source of ignition was an old coffee grinder I had opened up after it had overheated grinding charcoal minutes earlier. The bowl was in the sun, but compared to the coffee grinder I think that the chances of that causing the ignition are negligable. If only I had taken the coffee grinder outside before opening the motor case this accident would probably never have hapened! My practice of using my coffee grinder on the other side of my room to where I store the bulk of my comps ( the rocket fuel was out because I was in the process of making motors) could well have saved me from loosing my shed, and quite possably quite a bit of skin.


Seymour.

[Frozentech]

seymour, on Feb 21 2007, 03:02 PM, said:

Today I had one of those long dreaded accidental ignitions. I was in my shed measuring a length of carrdboard tube to cut it into suitable lengths for rockets when I heard the distinctive "whhhsssssssssssh" of loose composition burning. I turned to see a stainless steel bowl previousely containing aprox 100g of 60% KN, 30% C, 10% S coreburner rocket fuel giving off a good deal of flame and smoke. Within seconds the fuel was burned and I was pumping the surrounding area with a fire extinguisher, before I threw the bowl clear of the shed out the door to prevent any embers it my contain starting a new ( more serious) ignition. Apart from contact burns to my fingers from grabbing the bowl ( which are making typing this rather painful) noone was hurt and nothing was damaged. The only potential source of ignition was an old coffee grinder I had opened up after it had overheated grinding charcoal minutes earlier. The bowl was in the sun, but compared to the coffee grinder I think that the chances of that causing the ignition are negligable. If only I had taken the coffee grinder outside before opening the motor case this accident would probably never have hapened! My practice of using my coffee grinder on the other side of my room to where I store the bulk of my comps ( the rocket fuel was out because I was in the process of making motors) could well have saved me from loosing my shed, and quite possably quite a bit of skin.
Seymour.

The stainless bowl phenomenon is pretty well known. Never have in in the sun, if there is any comp at the focal point it will ignite. Not sure of the spot temp in that spot, but I think I have heard several hundred degrees C ? Anyone know for sure ? Anyway, this is the third case I have heard of where pyro comps in stainless bowls in sunlight lit off.

[seymour]

It had been there for less than two minutes, would that be enough?

[Frozentech]

seymour, on Feb 21 2007, 03:40 PM, said:

It had been there for less than two minutes, would that be enough?

Don't know. All I know is that it's a standard measure in several books to never use a stainless steel bowl in sunlight. At that focal point, imagine focusing a magnifying glass on your skin, etc. How long does it take ? 3 seconds maybe to reach blistering temperature ? 5 seconds to char wood ? One case I had heard of, it took no longer for a bowl of damp star comp to light than to set the bowl down, turn, and start to walk away. The other I recall was more like 15 minutes.

[dr thrust]

ive not had an accident yet being a newcomer to the art of pyro, whats the best way to safely ram a rocket with a core,should i use wood,brass,ali, a mixure of two of these to form the tooling, i am not bad at knocking things up! i don't want any mishaps just thought i would pick your brains, so i can do it safely and not end up in this forum again!!!

[maxman]

Wood , brass or nice stainless steel is fine. Just dont ram whistle mix or bits of your body will fly away! Ram only blackpowder and use extra care if it has any metal in it. Best of all use a press.

Be carefull

[Pretty green flames]

I've been using brass spindles and aluminium rammers, no mishaps yet. I'd say that these two material would be the best to make tooling from, Stainless is also good but only certain alloys are considered non spark (i think its 304 and 306 but don't take my word for it).

Just so you know, accidents can still happen if your rammer and spindle come into contact and you hit it with a hammer, the sudden jolt can cause enough friction to cause you serious troubles. So remember to stay well clear of the spindle.

Cheers

[dr thrust]

wow fast replys.may i ask how to avoid hitting the spindle with the rammer?are you talking about the top of the spindle hitting the top of the hole in the rammer,or is this a side clearance issue is the spindle quite loose in the rammer bore,just like to know before i construct many thanks for your time.

[BrightStar]

chris m, on May 30 2007, 09:01 PM, said:

wow fast replys.may i ask how to avoid hitting the spindle with the rammer?

Start off with placing your various rammers on the spindle with an empty rocket tube and see how far they go. You can then mark the rammers at the top of the tube with a permanent pen or a wrap of electrical tape. This gives you a 'do not cross' line when ramming.

Stick to BP mixes only to start off with, as with good tooling you can ram them quite safely. Beware that rocket comp can get stuck inside the rammers, reducing your safe depth. It is very important to make sure that there is no comp left inside the rammers each time you use them.

I ram 1lb rockets in the open air, with eye protection, thick gloves and a rustic cotton shirt. The most likely accident will propel the rammer away from the spindle with a bang, so make sure not to place yourself in its possible path...

Edited by BrightStar, 30 May 2007 - 08:25 PM.

[Frozentech]

BrightStar, on May 30 2007, 12:22 PM, said:

Start off with placing your various rammers on the spindle with an empty rocket tube and see how far they go. You can then mark the rammers at the top of the tube with a permanent pen or a wrap of electrical tape. This gives you a 'do not cross' line when ramming.

Stick to BP mixes only to start off with, as with good tooling you can ram them quite safely. Beware that rocket comp can get stuck inside the rammers, reducing your safe depth. It is very important to make sure that there is no comp left inside the rammers each time you use them.

Excellent point. Comp stuck inside the drift hole of a rammer caused a minor incident for an experienced pyro recently, not during the press, but while trying to remove the rammer which had gotten stuck on the spindle (due to whistle mix stuck in the drift ). Only having a very clean work area, and staying out of the line of fire saved it from being a much more serious event.

[dr thrust]

thanks for the advice! i have now made the tooling out of brass. tomarrow i'll be ramming(outside with ear defenders welding gloves, face shield), i have all these from restoring my car!. i think i'll make some small test motor's to try different rocket comps that i have seen on this forum, and in weingarts book which i received last week

[MFX]

chris m, on May 30 2007, 07:21 PM, said:

ive not had an accident yet being a newcomer to the art of pyro, whats the best way to safely ram a rocket with a core,should i use wood,brass,ali, a mixture of two of these to form the tooling, i am not bad at knocking things up! i don't want any mishaps just thought i would pick your brains, so i can do it safely and not end up in this forum again!!!

Just an idea, EOD tools are often made of beryllium copper or aluminium bronze, very strong and wear resistant and also non-sparking see http://www.technasal...uk/specials.htm for examples. A local engineering firm may be able to make up what you need and if the job isn't complex (and they're not busy or you tell them you're not in a rush for it!) you may be surprised at the cost. I was recently charged just £7 to drill and thread 7 holes in a large block of brass, (one hole was about 1" dia and 4" deep)

[BurlHorse]

Hey there Paul, Hope all is well now.

Bear

paul, on Dec 3 2005, 03:27 PM, said:

Hello everyone!

i will write this text in small letters only as i can not use my left hand very good.

today i had my first accident after about five years with my hobby. i put a 15mm id tube on my rocket spindle. it has an 20mm 6mm rod on it to make the nozzle and 1cm of the core.
the spindle and rammer is completely made of SPARKLESS stainless steel. further on i used a plastic hammer to ram them.

the composition was milled black powder. the charcoal was willow charcoal. it had 10% extra charcoal added.

so i rammed in the clay nozzle [bentonite] and went on with the blackpowder. i rammed it not very hard. suddenly a big flame as i hammered in the second increment. at this time only about 3g bp were in it. the rammer came out the case, not very fast as it went in very losely.

anyway, the rockets flame shot out of the open tube for about 1sec. my left hand, i hold the spindle for stability purposes with it, was burnt on the inside. i have a very huge white vesicle inside my hand and two fingers were burnt near the fingernail.

i had safety glassrs on and a cotton overal. what i had NOT on was GLOVES. this was my first and biggest mistake ever and should warn you to use proper safety gear when making ANYTHING relating rockets.



i wanted to inform you about that because i think the community should know about all accidents that happened to members.

i know that it was definately my fault as i did not wear gloves. i know everyone says in forums like this one, that he ever wears gloves. but i also know from many people that they do not use them all the time!!!

so PLEASE be safe and use them. they are not very comfortable to work with on this small devices. but you "see" what can happen.

i will upload an picture of that. i can still move it and so on. only the burnings burn as hell. went to a friend who is a doctor, too and he cleaned and bndaged it propperly.

with best regards,

paul

[bushman]

HI all I am new to the forum but I read with in terest the part about the composition in the metal bowl. From my experience in bushcraft and all things fire related I can say that the bowl would have been whats called a parabolic mirror sometimes used for cooking in hot parts of the world. Ignition takes literally seconds especially with something like the composition you were using.

Going back to the main thread I really hope that your hands have healed and I wondered if you had invested in an aloe plant as this has magical properties when put onto a painful burn area. I also wondered with the little debate on gloves whether anyone had tried thin leather gloves like those used for flying? These are fantastic as they are supple enough to allow someone to fly a plane without pressing all the buttons at once and yet they are amazingly good when it comes to heat and flash. Again going back to my bushcrafting I have used my flying gloves to move hot embers when they have landed somewhere inappropriate. Leather being leathjer doesn't stick to the skin either when it eventually burns through. Hope this post might be some help.