Stephen TranovichOkay, it is time! Let's get started!
A HUGE welcome to @brice.farrell for joining us today and talking about FIRE!
Thanks Stephen. Hello Everyone! I'm Brice Farrell - I built Shorter Pounder and helped (re)build Battle Royale with Cheese on this season of BattleBots, I've done a lot of propane boofers for ice carvers (and because they're fun), and I shoot professional fireworks on the weekends :)
I've got my matches ready
hah, Ziggy!
Okay, let's not dilly dally and dive right into things!
Matches are great for little matchstick rockets. Which are harder to do well than the youtube videos make them look. Still a lot of fun if you get some friends together and start experimenting
The first question that is on everyone's mind: How do WE not catch on fire when building flame systems?
Humans are decently flame-resistant, so the main concern is making sure that nothing ON you catches on fire, and then transfers that fire to you. I personally avoid liquid fuels, since they can get on you and then you catch on fire...
The other thing to watch out for is your clothing. Most of the synthetic clothing out there will melt, become a liquid fuel, and then stick to you while it burns. For shooting pyro we are required to use natural-fiber clothes. I personally go with a leather jacket and jeans. Cotton or flannel are also good choices - while they can catch on fire you can pull them off and they won't stick to you.
what about wool?
Wool burns
nomex is the best.
Apart from that, it's mostly a matter of being cautious - have a few safety switches, keep muzzles pointing away from you, ask yourself "what is about to go wrong" and have some extinguishers / hoses around you.
Wool is ok, but it's typically already 90* F when we're shooting pyro so wool would be quite warm.
Do you have a safety checklist you use or give newer people to your projects? Something people in this chat who want to try their hand at fire hacking should keep with them to be safe(r)?
Nomex is the best, but it's expensive and we don't need that level of protection, since any exposure to fire should be momentary in most of our applications
Checklists are cool
OK then, fire at will!
:o)
*anything* can burn given enough motivation
chlorine trifluoride. motivates well.
I don't have a general fire checklist... I have a couple for pyrotechnics? But generally: Natural fibers, eye protection, fire extinguisher, and work your way up during testing
work yor way up?
cutoff valves?
are there special cutoff valves that detect fire?
So for example, with propane stuff, I'll test it with 10, 20, 30, 50 psi of pressurized air first to check for leaks, then I'll switch to propane and start down at 5psi. If that goes well I'll go to 10, then 20 psi of propane
like, a GFCI, but for fire
acetylene fire arrestors
@Arsenijs a normally-closed electromagnetic valve with electronic control (gas sensors for leaks, fire/smoke sensors...) and fusible link as backup?
You can use solenoid valves as cutoffs, and there are parts that you can get for furnaces that detect fire - they use them to cut the fuel if the pilot light goes out. Everything I build is always under direct human supervision, so I don't install automatic safety valves like that. I do use extension hoses so that the tanks and their valves are 15+ feet away from the fire, so that they can be accessed safely if something goes wrong.
With safety covered, let's hop into more of the community questions! @Arsenijs askes: Which spark generators do you use for lighting the gas up, say, when you're making a flamethrower kind of thing? We did have to jerryrig a 555+IRF840+ignition_coil contraption recently for our flamethrower bicycle, wondering if there's something better.
Personally, I really like glow plugs out of furnaces. They take ~24vdc at around 1A and glow orange-hot, hot enough to light gases on fire. I used one in Shorter Pounder, and I know several other teams at battlebots were using them too. In fact, if you watch Mohawk's most recent match you can see a little 1cm glowing orange rod in the tip of his beak - that's a glow plug! They are a little fragile for battlebots, so bring spares.
For potato canons and larger fireballs where you need that instance spark, I tend to use "taser" style ignition. You don't need anything fancy, I typically use a cheap automotive sparkplug and a $5 high-voltage spark transformer from ebay.
@Joshua Young that answers your potato cannon question!
Thanks!
there are those high voltage ignition modules on ebay, low few $ a pop. the 15kV ones with naked transformer aren't really too powerful but the potted ones generally give thick fat loud spars. can also be found on stun guns. what do you think about those?
wait, sparkplug+spark generator? why use the sparkplug, can't you just use wires... or is the problem that they burn out?
I know we used nails and had to clean them from time to time, I'm guessing this is the same problem
Spark plug is cool, because that would be easy to thread in and hold a seal. Also it is super easy to adjust spark gap.
There is a new chip from TI for dimming 8 RGB leds with a I2C interface and internal gamma correction. (LP5024).
I even bought an eval board for it but broke it.
The chip is not available yet from distributors what are the chances of TI sending me samples?
The wires tend to catch on fire, or droop into each other and short out, or droop too far apart from each other. A spark plug maintains that gap with basically zero effort on your part
Me as in only me and no company email behind it requesting the samples.
@NikiSchlifke get an .edu email (or a friend with an .edu email), or an email associated with a company
isn't the gap too small, for cases where we don't have enough control over gas distribution in the fuel-air stream (which then can be too rich or too lean at the moment)? how to address this problem?
The cheap ebay spark generators are fine, it's more about spark size and placement. You want it to be a few mm long and at the edge of the fuel stream so there's a lot of fuel-air mix
I personally need to finally get a landing page for zerophone.org, then I'll be all about that "free samples" shit
Sort of too late I already contacted them with my gmail...
@NikiSchlifke hang in here, we can discuss it after this HackChat easier
I'll bend the spark plug contacts to stretch the gap a bit, but I've had good luck. The mixture doesn't have to be perfectly stoich, it can be rich or lean as long as it will catch a little bit, and then that will propagate and catch on fire a lot of bit.
You can also add a pilot light somewhere where the tip of the pilot is in the gas stream, and the base of the flame is out of the gas stream - otherwise you'll blow out the pilot light with the puff of gas.
Here's another question from @Arsenijs: I've seen simple flamethrower devices built in neighbour countries' hackerspaces - pressurised gas container + solenoid + igniter. Anything else that's as low-effort (or similar) but stands out? We've built a Rubens tube last year, for example, it's not exactly low-effort but it's simple enough.
Hey, I would like to see a pic or two playing with fire, do you have any, please?
are there any guidelines how to debug flame torches/burners? what signs show that the mix is too lean, too rich, too fast flow, wrong orifice size...?
I've seen that flamethrower done with solonoids and servos (solenoids are safer because they let go when they lose power, servos are easier).
Are there any laws regarding flamethrowers?
Another great intro project is a miniature fireballer using a glow plug from a model plane and a little ball of flash cotton. This can easily be turned into a miniature cannon - I built a little single-shot muzzle-loader airsoft pistol this way
could we get both? a spring-loaded servo, force-balanced so the spring can push the servo back when not powered and the servo is stronger than the spring+controlled thing? then for the cost of small additional work we get the advantages of both the solenoid and the servo - the servo can also be used with a spray can.
@Thomas - That should work
then we can also gut the servo electronics and just power the motor.
@RoGeorge: How 'bout a video?
https://www.youtube.com/watch?v=10E9aIEtDHY
Yeah, a video!
Wow, that's awesome!
sweeeeet!
That is super cool! And public! Let's talk about some of the community's legal questions!
@t.w.otto asks: for profireworks what certs or licenses do you need to stay legal?
random thought. in-situ on-demand gas production from solid state? e.g. the acetylene-water way, where if the acetylene is contaminated with enough phosphides it can even self-ignite?
and @Cameron asks: How do you become a PGI certified pyrotechnician? It it just a test, does it have prerequisites, etc.? What does it allow you to do that someone that isn't certified wouldn't be allowed to do?
Regarding laws: Generally flamethrowers are esoteric and poorly defined enough that fireballers don't fit. For public displays you generally need to get things checked by the fire martial - the event above we had a marshal check over everything - but remember, they probably haven't seen one before either. So as long as you show you have some safety mechanisms (like a keyed safety-switch, etc) they'll usually give you permission
Sounds surprisingly easy to get a pass!
What is certification used for, and how do you get it?
PGI Certification is mostly a PR thing... it's a test you take, and then you get bragging rights, clients are more likely to choose you, and fire marshalls are more likely to bless your projects. PGI has a "textbook" you can study that will cover all the questions. For me, my pyro company sponsored me and we did a full day of training - including some of those things you're never supposed to do (like loading the wrong shells in mortars, upside down, etc) - and then we had the test
the "error recovery" is important to have procedures for. any hints here?
"not supposed" does not equal "won't/can't happen". :(
Most states don't have licenses, so as long as you are working on a permitted shoot you don't need to worry about training. Almost everything comes back to the ATF certification - which the company will take care of for you. They'll even look into you and send you an "employee possessor" form letting you handle all the product as long as you're on one of their jobs.
That makes sense! It's a good segway into a few more safety questions that popped up: @Arsenijs also asked: What are the maybe-obscure safety precautions when working with pressurized containers of gas? I know there's little chance of them exploding because of gas pressure being more likely to create a fire jet than an explosion (correct me if I'm wrong, PLEASE), and you need the right air+gas mixture for things to explode and not just burn, yadda yadda. However, is there some obscure (or even non-obscure) scenario where a pressurized container of [propane (non-damaged) poses an explosion risk when doing, say, a flamethrower device? some kind of gas leaks, like leaking solenoids, over a long period of time in a confined space? Something else?
(the equivalent of unexploded ordnance procedures...)
I am licensed in Delaware, which was also pretty easy. You just need to review the documents they say the test is based on, and then schedule a test with the fire marshal. As far as getting ATF certification for a company... that's apparently quite difficult and expensive- I recommend working under a company that has already done all that work for you
Is it true that if I mix equal parts gasoline and orange juice concentrate I get napalm? /s
no, that's agent orange. /s
soap works well
candle gel polymer is the best.
Are you aware of the "roman candle drone" thing?
There are bunch of youtube videos on it.
All compressed gas containers are a safety risk due to the sheer amount of energy high-pressure gas has. But you're right, they won't fail via explosion because they have safety valves. So you basically need to mechanically compromise them while they are on fire to get an explosion. That said, if I have a tank on fire (which has never accidentally happened to me) I'll just leave it alone to burn out.
styrofoam works the best in my experience. Half gas half used motor oil then dissolve styrofoam to saturation
unless the tank itself is surrounded with fire. because BLEVE, aka blast leveling everything very effectively...
Thomas asks: are there any guidelines how to debug flame torches/burners? what signs show that the mix is too lean, too rich, too fast flow, wrong orifice size...?
For leaking valves: I always disconnect my tanks when I'm not using my devices. You can smell it long before it gets to explosive levels of leaks, but why take that risk?
also, i'd suggest vents in the room where the bombs are stored. ceiling-level for hydrogen/methane, floor level for heavier hydrocarbons.
bombs -> cylinders. bloody different languages...
For actually UXO - like fireworks: LEAVE IT ALONE. I've watched shells go off 20 minutes after we lit their fuse. We'll soak them in water after leaving them alone for a half hour, but still nobody is really comfortable about it. I know a lot of guys with scars from temperamental firework shells.
nah we call hydrocarbon sample cylinders, bombs, in the states
can a thermal camera be helpful to assess the "health" of such a shell?
interesting question. Maybe you can notice a "glow" of some kind.
I'm very curious, can one make a living from fire installations/shows or this is a side activity, somehow sustained only by passion and some other regular day-job
?
I should get myself a FLIR module or something =)
For debugging: First look at the flame. Especially if you've ever played with an oxy torch you should have an idea of how flames respond to ratio. In general, if it's sooty orange flame it's too rich, and if it's abnormally short or small it's too lean. In a contained solution you can read the sparkplug and based on it's color figure out if you're too lean or too rich. Mostly, just play around with it. Try things, see what happens.
Thermal camera might help, but it's most likely a false sense of confidence, the shells that scare you are the once with just the smallest ember, and its usually down at the bottom of a mortar.. So it's dangerous even to reach a camera over the mortar to "look" at it.
too blue, too lean, too purple spark, too rich. the problem i have is the gas flow being apparently way too fast and blowing out the flame.
(selfie stick?)
I have one more community question for
Discussions