Massive Fireball / Chemistry / Forums

Forums

4hv.org :: Forums :: Chemistry

« Previous topic | Next topic »

Massive Fireball

previous 1 2

Move Thread

LAN_403

quicksilver

Mon Jul 05 2010, 07:10PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

This child is staring death in the face.

GhostNull

Mon Jul 05 2010, 10:52PM

Registered Member #2648 Joined: Sun Jan 24 2010, 12:45PM
Location: Australia
Posts: 291

that doesn't look thaaaaat bad

HVgeek

Sat Jul 17 2010, 10:39AM

Registered Member #2998 Joined: Tue Jul 13 2010, 08:34PM
Location: Swedish forests.
Posts: 26

This child is staring death in the face.

Hardly. Maybe second degree burns at worst. And those are entirely his problem. If he's too stupid to learn from it, what'cha gonna do?

Well, I too recommend propane or butane. You really need to keep it controlled and safe if it's for a public display. Unless of course you're going to do it illegally, and i bid you good luck in getting away with it afterwards. A simple regular ball-valve and some sort of funnel to the ignotion source would do thought. As long as the whole thing is stable and safe with no loose connections and rubber hoses you might just get approved.

Read up on it though, that's my advice. There usually are standards for this type of thing in to be found in the town hall. Just ask around.

GalFisk

Mon Jul 19 2010, 08:32AM

Registered Member #3013 Joined: Mon Jul 19 2010, 07:53AM
Location:
Posts: 3

You should start the ignition before releasing the propane, I recommend a good electric spark/arc. You don't need much gas for a nice fireball, so the risk of gas from a failed collecting somewhere and igniting later is negligible if you're out in the open. When released under pressure the gas will mix rapidly with air and disperse.
It is also possible to fire liquid fuel using compressed air, by placing the fuel in a barrel after the valve. For a very different effect you can dissolve some boric acid in methanol, for a bright green fireball. Other colors are also possible with methanol.

Mike

Sun Jul 25 2010, 03:21AM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

Yep, a few years back I used to build massive air cannons. One of the coolest things to do was take a pole about 5ft tall and set a flaming paper towel or rag (maybe gas soaked) on top of the pole. Then I put about 5-10fluid oz (this may be excess, I didn't experiment with it too much) down the barallel and aimed the cannon at the pole and released. It makes an AWESOME fireball. I got around 10ft diameter and it leaves a huge smoke ring that floats up. Just be warned if you do this too low to the ground it may catch fire, and if you aren't far enough away you will get burnt. I usually opened the valve standing about 10ft from the pole but again, im not responsible for you killing yourself or causing a massive fire. gl

quicksilver

Mon Jul 26 2010, 05:33PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

Quite realistically, there is a difference between a display and an FAE. If I was considering that, I would refresh my knowledge all the idiosyncrasies of safe operation of gas ignition & control so as to avoid entrapment of gas in a manner that results in an explosion. Overhangs, ignition timing, foliage, jet size & many more issues could turn the thing sour & leave you with some serious repercussions.

cedric

Tue Jul 27 2010, 08:27AM

Registered Member #2941 Joined: Fri Jun 25 2010, 08:08AM
Location:
Posts: 143

I did something similar when I was a kid ,a metal can with 100 gram of black powder and wax powder on top to feel the rest,no compression(the box must stay open) ,electric ignition ,very convincing result ,beautiful .

Martin King

Tue Jul 27 2010, 11:21PM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

I do this sort of thing professionally and although I'm UK based large flame effects I've built have been used in the US. As others have said a Propane cannon otherwise known as a "woofer" (a term also used for air powered debris cannons) is the way to go. Powder is too unreliable/messy as it never burns completely, liquid causes a problem if it fails to ignite for whatever reason you end up with a major fire hazard (you still have a problem with gas if it fails to light but at least it disperses rather than just sits there and it tends to light a lot easier than liquid BTW see my avatar for a liquid system). For guaranteed ignition you want a large pilot flame such as that from a roofing burner (a small pilot runs the risk of being blown out), for amateur/outdoor use this can be left burning but we turn it on just before firing the cannon and have flame monitoring to check that the pilot is lit before firing the cannon. For dumping the gas you need a large bore fast acting valve. For "single shot" use a manually operated ball valve operated from a distance with a "piece of string" (tm) would do (although it will result in more of a large jet of flame rather than a fireball) but for repeated firing you need a large solenoid valve which aren't particularly cheap although you can sometimes find them surplus or from Ebay etc. relatively cheaply .To get a good fireball you need to open and close the valve fairly quickly, the shorter the time the valve is open, the smaller the fireball . A VERY early prototype I built used a small air receiver from a truck (scrapyard) and a valve from a surplus supplier, total cost about Â£40. For any sort of commercial use you're likely to need over pressure relief valves, braided hose, inert gas purging, gas leak detection, pilot monitoring and maybe even high flow-rate flashback arrestors even though they're pointless on a fuel gas only system that has inert gas purging, but try explaining that to a clueless H&S guy

previous 1 2

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob