Gas Mines--in a can

[Wiley]

So, I was able to test my soup/peach can gas mines the other day, and I got some good results. I also got some weird results and four cases of the gas not igniting.

 

Here's my setup.

 

1. Lift charges: 1.5 teaspoons of Goex 3Fg for the 3" (soup can), and 2.5 teaspoons of 3Fg for the 4" (peach can), wrapped in five layers of heavy duty aluminum foil rolled on tightly by hand. The tape wrap on the fuse is meant to provide protection for the fuse as the lift charge drops into the can, and to provide a visual aid as to where the fuse needs to be attached to the can.

 

2) Fuel: I put 1" of water in the bottom of the 3" ones, and 1.5" of water in the 4"ers. The can is then filled up to the top ring in the can with straight gas.

 

3) Firing setup. As you can probably see from the second picture, the fuse of the lift charge is affixed to the can in such a way that it burns through just above the protected part of the fuse (I used epoxy to do this before I started using the tape, and that's what I used in this picture). I have come up with several ways to do this, and this picture shows an older method which I no longer use. Still the concept is the same.The lift charge then drops into the can, settles on the bottom, and fires, simultaneously dispersing and igniting the gas. Because of the water layer in the bottom, all that's left behind is water, so there is no residual burn in the can or on the ground.

 

Most of the time this works great, however, I experienced some anomalies as I noted above. The gas not igniting was clearly because the lift burns too quickly to adequately transfer fire to the fuel. In the videos of successful fireballs, you can see the fuel cloud only ignites from the extreme bottom and the flame then travels through the cloud, while Youtube videos of the PGI fireball workshop show a forming vapor cloud which is almost always completely ignited by the next frame of video. I'm quite sure that they are using a mix of 4FA and 2FA in their lift to achieve this. The bigger particles get thrown out of the mortar still ablaze, and reliably ignite the gas every time. I do not have access to blasting powders, nor can I easily get my hands on cannon grade Goex (2FA equivalent). What I intended to do was to keep using the 3Fg since it does work most of the time by itself, but sub out half of it for 1Fg, which has a particle size of about double that of 3Fg. Do you think this is a good choice?

 

Further, making the charges by rolling on each layer of aluminum foil can be time consuming and a bit laborious. I intend to start using only one layer of foil to initially enclose the powder, and then systematically wrap it with tight layers of electrical tape. Since the charge is only in the can for a few seconds (and only in the layer of gas for a fraction of a second), it doesn't have to be sealed with bondo fiberglass resin. If I ever decide to efire these, then that step will become necessary.

 

The first video is of a 4" that worked perfectly. The next video is of a 4" blowing the fuel blind, and the last one shows two gas mines, the first with straight gas, and the second with 50:50 gas/diesel. Both of those are examples of the "weird" results I had, where the fuel burned, but it doesn't look complete, and there's hardly any smoke at all. I think these weird results were very nearly blown blind, but just barely ignited. It looks like the incomplete burn could be because the fuel cloud dispersed too much and lit too late.

Let me know what you guys think about the lift charges.

Edited December 23, 2013 by Wiley

[ddewees]

Why do you put water in the cans?

 

The only time I had issues was when the gas would leak into the 2fa. I now dip the bp charge into bondo fiberglass resin, and have left them sitting in gasoline for over an hour without any issues.

[Wiley]

The water is there to keep the can from burning and distracting the audience. All that stays in the can is water, and water doesn't burn. I also noted that I cannot obtain 2FA or anything like it, so would 1Fg (4FA equivalent) work ok with my setup?

[psyco_1322]

The water is there to keep the can from burning and distracting the audience. All that stays in the can is water, and water doesn't burn. I also noted that I cannot obtain 2FA or anything like it, so would 1Fg (4FA equivalent) work ok with my setup?

 

It's your experiment, Wiley, go try some 1Fg and see if it works. Just larger granules, a bit slower, so you might need a bit more, but maybe not, hard to say.

 

I think you might be popping the gas out a little too hard. It's over dispersing the fuel, and not all of it is "thick" enough in the air to roll a nice fireball. I never did notice much smoke from small gas mines when I used to play with them, even when adding in lots of oil.

Edited December 23, 2013 by psyco_1322

[Wiley]

I just picked up a pound of Fg and made a small charge with 50:50 3Fg and Fg. I also made a straight 3Fg charge as a control. The 3Fg burst with very little visible flame in the dark, but the mixed charge looked more like a tiny aerial shell burst. I think this might work. Will give it a go as soon as I can and post results if folks are interested.

Edited December 24, 2013 by Wiley

[Seymour]

As already discussed, adding larger grain goes a long way towards avoiding blind fireballs. Titanium is another popular option, and even silver stars can do the job as well as adding an extra sprinkle of hollywood to the explosion.

 

1fg should work very well, and I expect that there would be no ignition issues, as your photos visualize. I still like to put Ti, even if justto make it look purtey

[Wiley]

Seymour, I'd like to add Ti, but with shipping costs, it winds up more expensive than a pound of coarse BP.

[Wiley]

Made a few adjustments, and hey, looks like they worked! Both of these shots used lift charges consisting of a 50:50 mix of 3Fg and 1Fg (half a teaspoon of each for a total of one teaspoon per charge). The powder was wrapped with a layer of heavy duty aluminum foil, formed into a ball, and wrapped with electrical tape. They were then coated with epoxy to help keep them from "unraveling."

 

The first video was a 3" soup can with 1" of water and straight gas up to the top ring in the can, and the second was a 2" pipe about a foot long with a welded cap on the base. The 2" gas mine used 500 mL of gas and no water. Looks like it could have used some. I was surprised at how quiet the 2" was, since it has always made a healthy bang with the older lift charges. I guess softer lift will do that . I was also able to capture some pictures of the ignition sequence on the 2" gas mine, which shows the spray of sparks shooting through the gas cloud and igniting it evenly, just like you'd think it should. Judging by how high those sparks are going, I have high hopes that my 4" steel mortar will be able to actually light its gallon of gas for the first time. I might find that out tomorrow.

[Wiley]

Did some more testing today. Pictures are of a 3", 4", and 6" respectively. The last one is a picture of the smoke ring from a 4" hovering about 100 feet above the ground. The 6" used half a gallon of gas and about 2 ounces of lift powder. The coffee can mortar is essentially single use. All of these shots finished with heavy black smoke (even the little ones) that 9 times out of 10 formed into a wonderful smoke ring. I've never been able to consistently get black smoke before, so I assume that it must be as a result of a more complete fuel burn caused by the coarser black powder lift I'm now using. I may write a tutorial on these once I get all the kinks worked out.

Edited December 28, 2013 by Wiley

[ddewees]

You don't need to use that much lift for 1/2 gallon of fuel.

 

My 6" mortars hold over 4 gallons, and 70 grams of 2fa works great.

 

I love gas mines too... nothing beats that heat they give off.

[Wiley]

ddewees, does that hold true even on really short mortars? A coffee can is only 7.5" tall. And I had a minor brain fart there: the 6" uses two tablespoons of powder, which totals about 30 grams, pretty close to one ounce. Two ounces would almost certainly result in a blind fireball.

Edited December 27, 2013 by Wiley

[ddewees]

You edited your original post. You had said two ounces, not thirty grams. Thirty sounds about right, and from the looks of it... worked out well for you.

I buy 36" length, 6" dia, schedule 10 steel pipe from a business down the road for $21 ($7 per foot). You just need someone to weld a plate on the bottom.

I'll see if I can find a video of the last one we shot. I had people saying they thought their leg hairs had been singed.

Nobody was really that close, but the drastic rise in temperature really is a powerful effect.

 

 

The fireball is at the 2:00 mark:

 

http://www.youtube.com/watch?v=PQZLcHtoMpI

Edited December 27, 2013 by ddewees

[pyrokid]

ddewees what is the green to purple crossette zipper that goes after the fireball? That's fantastic!

[ddewees]

It was a 300 shot crossette cake from flying Phoenix. Can't remember who makes it, but it's pretty easy to find on his price sheet. Green to purple, I think it's called.

[Wiley]

Yes I did edit it, and probably should have made note of that in my next post. Just wanted to keep everything in order.

 

That is a spectacular fireball ddewes! Are you using Ti in your 2FA lift to ignite the gas? You said that your 6" holds 4 gallons right? Must be pretty near full!

 

I tested the 6" gas mine again today (twice), along with a 2" steel mortar about a foot long (once). The 6" performed perfectly both times, so I've deemed it ready for New Years. I've attached pics and video for your viewing enjoyment.

 

The 2" mortar was a little different. It has wasted more gas in blind fireballs than any other design I've used, and apparently its just because of its higher length to diameter ratio. Take a look at the video. You can see the vapor cloud form and begin to disperse, and then it just barely lights from the bottommost extremity of the cloud. The lift charge was 1 teaspoon Fg. This is the second time this has happened. Otherwise, it blows the gas blind or (rarely) makes a perfect, quiet fireball. I can't understand why. You can even hear how gentle the lift is. My 3" can style gas mines look and sound better than this with the same lift charge and maybe even a little less gas, so I've no reason to try to perfect this design. I just found it interesting somehow.

 

The pics attached out of order. Weird.

Edited December 27, 2013 by Wiley

[ddewees]

I only use 2fa, no Ti. We also have 85 octane fuel here (high elevation) so that may help with ignition too.

[Wiley]

Hmm, that's interesting about the lift. I always assumed that for longer guns people used a mix of 4FA and 2FA or threw some Ti in with 2FA. And 85 octane fuel? The stuff that's burning in those photos is 87 octane.

[Wiley]

Hey ddewees, how long does that schedule 10 6" pipe last? Seems kind of thin, but if you're getting it to work, I'd like to know a little more about it. Thanks!

[ddewees]

Bill Zuber recommened schedule 10... works great, and is much easier to carry.

 

I assume it can last indefinately, if taken care of. They rust, but if you want colored alcohol flame effects, you can just line it with a trash bag (so I've been told).

 

I kind of used this as a guide (written by Bill), but realized you can actually fit 4+ gallons in there with room at the top. 70-80 grams of bp works great too.

 

http://www.oregon.gov/OSP/SFM/docs/Codes/TA11_12.pdf

 

 

I've also found that using multiple mortars in a cluster seems to work better than going larger than 6" diameter. So... I'd rather have (3) 6 inch mortars clustered together, than use a 12 inch single gun.

Edited January 3, 2014 by ddewees

[Wiley]

Thanks, that's what I needed

[Wiley]

Though it deviates from the original topic about using cans as mortars, I built a 6" steel mortar 13" long that holds a whole gallon of fuel and 2" of water. Those same electrical tape wrapped, epoxy dipped 1 ounce black powder charges (1 tbs Fg+1tbs 3Fg) that I was using to fire half a gallon worked great for the whole gallon mortar.

[ddewees]

 

Looks like fun. Don't light the forest on fire...

Edited January 8, 2014 by ddewees

[Wiley]

Yeah, your mention of the 70 grams to loft 4 gallons of gas got me thinking that using nearly 30 grams for half gallon of fuel was a bit of a waste. I might even be able to use a bit less than 1 ounce for my 1 gallon mortar, but I think the fireballs look and sound great just the way it is. What's great about e-firing these is that I could conceivably bunch a number of these 6" mortars together to create a larger effect without having to make a larger mortar with different sized lift charges.

Edited January 8, 2014 by Wiley

[ddewees]

Exactly!

 

Nice welds by the way... I wish you lived closer to me.

 

 

I shot three at the 5 minute mark trying to get a "wall" effect. didn't exactly look like a wall, but was pretty decent.

 

 

 

THIS is a wall effect

 

I believe he said they used 1 gallon milk jugs filled with gas on the ground with a salute underneath each one.

 

[Wiley]

Oh, yes, Al's wall of fire! That would be something to see (and feel) in person!

 

Nice show and fireballs btw! I like how the larger ones last long enough to really enjoy. Though I think you may find that putting some water in the gun will cut down the "instant campfires" which may or may not distract the audience. You don't need much; I only put 2" in the bottom of my 1 gallon gun, which is enough to cover the charge. I bet if you put, oh, 3-5 inches of water in those guns, you'd get fire in the air and nowhere else. For what its worth .

 

Thanks for all the good info!