Smoke Grenade Troubleshooting

[Scttgrffths21]

Hello gents,

 

I've been building various smoke grenades for the last few weeks; testing concepts out, different ingrediants, ratios, etc. I feel like I went from knowning nothing to knowing just enough to hurt somebody in that time, and now I'm trying to make that last leap into having them work safely and consistently. However, there's a couple areas I'm struggling with, and I'm hoping for some assistance.

#1 Carmelizing Sugar and Potassium Nitrate
I mixed well, and kept on a low heat for a long time.... a LONG time. Damn near two hours later nothing has happened. So I move the heat up to the next notch, and it finaly starts to carmelize. However, the carmelizing process lasted about 2 minutes total, and when done I was left with super chunky looking peanut butter. Never did I see it form into any liquad substance for more than a few seconds. In order to get it to liquidize, I again have to turn up the heat. At this point, I have to stir constantly or else it will start smoking, however, it does allow me to get the mix into a malleable state. Unfortunately that state lasts maybe a minute, so it is VERY difficult to fill any type of mold or two as the substance hardens and sticks to everything.

 

Question: Wtf? Everywhere I read says low heat and it will melt. I see videos of people doing it, and then pouring it like gravy into a mold... I don't understand. I match the ingrediants exactly and ratios to within .01 grams, yet unless this process is supposed to take 3 hours per 100g batch, Im missing something. This has happened consistently for me through 10+ batches.

 

 

#2 Addiing Baking Soda to KNO3/Sugar mix.

When I make 100g mix, and carmelize it together, the substance fills about half a toilet paper roll. When I add in a tablespoon of baking soda and stir, the substance expands significantly and now I can fill 3-4 rolls all the way to the top.

Question: Does Baking Soda degrade the efficiency of the KNO3/Sugar mix? Since the substance is less concentrated it would make sense to me that it is not as potent... but what do I know?

 

 

#3 Proper Ventalation and Burn Rate

So far in my testing I've noticed that my burn durations are shorter than 30 seconds. When I research the problem, I find a conflict: 1) The flame is being exposed to too much oxygen, so I need to make a smaller hole for the smoke to vent. I've read that if you do this right, the substance will burn without a visible flame (anyone know if that's true?). However, I've also read that if you don't have proper venting you may inadvertently make a bomb.

 

Question: Is there some formula of what size diameter you should use for what size container or weight of substance or anything like that?

Question: If the hole is so small as to not allow any flame, does it really run a risk of exploding? It would seem to me (again, I'm an idiot at this stuff) that if it doesn't have the oxygen to burn, it would likely put itself out long before it built up enough pressure to explode. Even if pressure was mounting because the hole gets clogged or something... wouldn't the pressure blowout the hole before blowing up the rest of the container?


#4 Cardboard tube containers

I've used a couple different materials to shell the smoke grenade. My end goal is to have something I feel comfortable enough using at paintball fields, and I have a pretty high regard for safety. So far all of my TP-roll-shells have simply gone ablaze when the grenade gets primed. I've wrapped them in duct tape, aluminum foil, and a combination of the two... and the result is still a fiery mess. Over the last week I've moved to 1.5" ABS tubing with caps on the end. The tubes get a little hot and soft after you use them, but then they can be re-used which has been handy. I'm not sure what unintended effects that may be causing me though.

Question: Are these really a top option?
Question: Any known issues with ABS tubing for smoke grenades? Obviously its not the greatest substance to breathe, but that can be said about most types of smokes.



Thank you guys. I'm so happy I found this forum!!! Already learned a lot and going to go do some more studying, Thanks!

-Scott

[schroedinger]

For those easy smoke bombs, a god point to start is using plain 1:1 sugar to pottasium nitrate mix. It melts butter than the 35:65 and is better to be poured.

 

Take a paper roll from toilet paper, seal one side with a disk or masking tape and pour your propellant in. There you got one of the easiest done smoke bombs.

 

For preparing the propellant, specially as a beginner use an oil bath, it takes out a couple of the risks you are experiencing now. Start by heatin to 120ºC and heqt up slowly until you mix got the right liquidity to be poured (the oil should not start to smoke). Use a pot which can't fall into the bath or brake.

 

Don't use ABS if it ruptures, it can send shrapnell all over.

 

If you still got problems with an open flame, increase the sugar ammount or use a thick walled paper tube, ram a clay plug inside and dril a hole (about 1/3 of the tube diameter) inside this. Now pour your grain in and let cool. After this ramm a claiy plug to close it up or use 2-3 paper end disks glued in.

[bob]

Just plain old sugar and potassium nitrate smoke bombs have their limits, for instance in my experience getting a good, slow, flame free burn, consistently is, well, for me impossible.

Check out the PyroGuide Youtube channels smoke bomb tutorial.

Make sure you subscribe eh.

Oh and yeah the sugar and potassium nitrate ones your making can explode, they have on me.

bob

http://youtu.be/tUI3OwWX5gE

Edited June 17, 2014 by bob

[BurritoBandito]

1) It is always very thick for me as well. Just try to keep it hot and work fast.

2) Adding baking soda will help to retard the flame, but it increases the amount of smoke, so it actually improves the performance.

3) As far as I know there is no simple formula to determine the minimum sized vent hole that will not explode. There are too many variables... Surface area, moisture content, degree of compression, exact composition, etc. I would try packing your mixture in to assure that only the surface burns. Air pockets will cause pressure spikes as they increase the surface area exposed to burn. Decreasing the size of the vent hole will not extinguish the mixture, the KNO3 provides it oxygen.

4) I'd stick with cardboard tubes wrapped in foil. If you are experiencing burn throughs, add more foil.

 

Can I recommend the "Legendary Smoke" mix? It produces much better smoke and is less prone to flare up. It is a little more difficult to light, but if your fuse won't do the trick by itself, you can always prime it with a bit of hot BP. The ratio I like to use is 43:27:30 - KNO3:Sugar:Paraffin.

[Scttgrffths21]

Thanks for the feedback everyone. Lots of valuable information.

 

I have graduated to the parrafin wax method, but haven't done any tests yet. I'm making a few different model containers to see what one works best for me. I used 60g/40g/40g and figured I'd experiment from there.

 

The problem I have with cardboard and aluminum, besides its tendency to becoming a molten fireball, is it just looks like garbage. I'd like to have the finished product look clean and of somewhat decent quality. I dont feel like TP rolls and foil are going to lead me to the consistency I'm aiming for. Anyone know a good way to fix the presentation of the TP roll method?

 

This week I've been hung up on getting my ignition system working right. I'm using a some KNO3/Sugar mix in a Christmas light, then a fuse inserted. First time I set it up it worked perfectly... since then like 4 duds in a row. They don't seem to want to light easily. The overall plan was that id connect the wires to plates on the inside of the cap, so to activate the fuse id just tap a 9v battery against the plates.

 

I'm open to using other compounds... I just have no idea where to begin. Again, my ideal solution is one that provides me with a product that I can safely use around children and in the woods.

[BurritoBandito]

You could roll a cardboard tube with sodium silicate, to make it flame retardant, and pleat the ends like you would for a canister shell. The larger commercial smoke grenades that I've seen are just a cardboard tube, with clay plugs and visco fuse, that are wrapped in a piece of paper with camo or some other design. Personally, I like the kraft paper look.

[schroedinger]

For igniters there are several ways to go.

The christmas tree bulps work better with blackpowerder, but still is is easy to destroy the filiament.

 

If you use a 12 V battery the easiest way is to use visco and commercial talon igniters. If you wan't to make the igniters yourself, get some NiCr wire of abou 0.15 to 0.2 mm diameter and wrap it around the fuse like a sprihg (about 5 times) and attach the leads to your power source either by soldering to a copper shooting wire or using crocodil clamps (you need to make sure that these can't touch after firing, the soldering step should be preferred)

 

Or you can make a reusable clip on igniter by fixing a thicker NiCr (1-2mm) wire onto a wooden clip, like they get used for drying cloths, and clip these onto a visco. But these need quite a god power source

[Scttgrffths21]

Thanks again for the info again gents. Follow up question...

 

When I mix 60/40 KNO3/Sugar and carmelize, I have enough to fill half a TP roll... if that. When I add a little baking soda to the mix I then get enough to fill 2 and a half tubes. If the baking soda doesn't degrade the integrity of the mixture, could you add the mixture to some melted parrafin to add the benefits of the slow burn/extra smoke that the wax provides?

 

The question arises because I keep using recommended measurements and ending with a much smaller quantity than the recommended container (TP roll) can hold. Perhaps they are only supposed to fill 1/3 of the tube, but if so I'm intrigued by the idea of using baking soda to double-triple the amount of grenades per batch i can make. My biggest concern is that the fluffed up composition may cause it to burn differently.

[BurritoBandito]

I think that if you add the parafin prior to the NaHCO3 it will inhibit the CO2 production that you are experiencing. If you add the NaHCO3 first, I think you'll end up losing the volume while incorporating the paraffin. Give it a shot and see what happens.

[bob]

You can checkout pyroguides igniters tutorial here, http://m.youtube.com/watch?v=z_x2qDnXPBY#

Hope it helps, and if it does make sure you subscribe eh!

bob