Blue Mountains Fires - Page 1
Forum section: electronics / projects

author: gnif
author_rank: Unknown
timestamp: October 21, 2013, 01:00:53 am
content: Hi All,My house is currently under threat of fire and it looks like we will be ordered to evacuate. I have a electric water pump in an old septic tank that was converted to rainwater. I would like to make some kind of circuit that would reliably detect if a wire has been burned (figure eight), and de-energise a relay to activate the water pump. I plan to run the cable around the yard where the pump will be able to keep water on. The idea is to run the pump only once the fire gets here, otherwise it will just empty the tank prematurely.I know I could hope that the cable shorts on itself, but there is no guarantee of that, anyone have ideas for a better way? Remember, I have limited time and resources, I cant exactly order parts in, I am limited to what is in my junk bin and the few parts I have on hand.For those interested in the fires, see:http://www.rfs.nsw.gov.au/dsp_content.cfm?cat_id=683

author: Crazy Ape
author_rank: Regular Contributor
timestamp: October 21, 2013, 01:24:39 am
content: Can you work solder into the equation, if the cable was cut into sections and soldered together the heat from the fire should melt the solder and break continuity.

author: AlfBaz
author_rank: Super Contributor
timestamp: October 21, 2013, 01:47:56 am
content: Sorry to hear your predicament gnifI like the candle idea here's another...Anchor a spring to something solid, tie a string to the other end and run it around where you want to detect fire. If you need the string to change directions go around something smooth like a nail. Pull some tension on the string and attach to a micro switch to hold it open. If the fire burns the string it lets go of the switch, activating it

author: johnwa
author_rank: Frequent Contributor
timestamp: October 21, 2013, 01:52:04 am
content: Quote from: wilfred on October 21, 2013, 01:38:56 amYes, or possibly run a "trip wire" out of cotton/nylon or whatever under tension all around your house, for sensitivity from multiple directions. Set it so when the cord melts/burns, the tension releases, and the pump switches on. Sort of like one of those grab wire emergency stops, if you are familiar with them.I am planning to set up something similar myself, probably using IR thermometers, though I guess you won't have time to hack one of them.Have you looked at a redundant power supply?EDIT: I see I am not the only one with that idea...

author: gnif
author_rank: Unknown
timestamp: October 21, 2013, 01:56:08 am
content: Quote from: johnwa on October 21, 2013, 01:52:04 amI like this idea also, I think I have everything needed to do it also. Unfortunately I have no means of a redundant power supply. I have a UPS with a large battery attached, but at 2200W for the pump, I doubt it would last more then 20 minutes.Edit: johnwa, where abouts are you? I am in Katoomba and worried that if the winds carry the State Mine Fire into the national park, there is little they can do to stop it.

author: AlfBaz
author_rank: Super Contributor
timestamp: October 21, 2013, 01:59:55 am
content: Quote from: Crazy Ape on October 21, 2013, 01:24:39 amAlternatively if you have a substantial amount of solder roll, simply run that around the yard. Hopefully it has sufficient continuity to maintain the relay. It wouldn't take much to melt a thin line of solder wire run around the place. Just make sure in places where it overlaps it cant fall and short itself out again... perhaps relay latching might be something to consider

author: sleemanj
author_rank: Super Contributor
timestamp: October 21, 2013, 02:02:06 am
content: Quote from: wilfred on October 21, 2013, 01:38:56 amIt could also partially melt or burn the clothes peg which might be a problem in maintaining the contacts closed.But if you combined it with the string idea...

author: gnif
author_rank: Unknown
timestamp: October 21, 2013, 02:06:43 am
content: Quote from: AlfBaz on October 21, 2013, 01:59:55 amPerfect! I do have a large roll of solder I can use!

author: GeoffS
author_rank: Unknown
timestamp: October 21, 2013, 02:16:18 am
content: Here's hoping you remain safe and the fire misses you.

author: AlfBaz
author_rank: Super Contributor
timestamp: October 21, 2013, 02:23:42 am
content: Quote from: wilfred on October 21, 2013, 02:20:13 amgood advice. with regards to smoky roads, I live in the Illawarra and cant see clearly across the road!

author: johnwa
author_rank: Frequent Contributor
timestamp: October 21, 2013, 02:56:57 am
content: Quote from: gnif on October 21, 2013, 01:56:08 amHi gnif,I am down south, so no immediate threat. A few further thoughts: for your trip wire, you want something black and with a high surface area to volume ratio. Perhaps electrical or video tape? The tape will probably stretch a bit, so maybe rig a weight to fall ~0.5m down a metal pipe to trigger a switch.Hope this helps.

author: Vgkid
author_rank: Super Contributor
timestamp: October 21, 2013, 04:02:53 am
content: How close are you to other buildings/ flammables? Depending on this you will have a slim chance of saving your house. The best advice is to get out with any valuables/ important items, and let insurance cover the loss. Personal injury/ issues or death is not worth the risk./rant

author: ddavidebor
author_rank: Super Contributor
timestamp: October 21, 2013, 05:06:32 am
content: You need to activate the pump as fast as possible.IR radiation from a big fire is wat transform a house in a mountain of hot flammable material.

author: G7PSK
author_rank: Super Contributor
timestamp: October 21, 2013, 03:38:00 pm
content: Don't use wire use string the string holds a weighted lever which works a switch or valve. This is used in many boiler houses the string is run over the boiler in the case of a fire the string burns and the weight falls turning a lever which cuts of the fuel and turns on the fire extinguisher. I have also seen a wire used with fusible links which melt instead of the string. But it would be a lot quicker to run string around your property and have a weight on a switch held off by the string tension virtually all mechanical other than the switch. Best of luck and I hope the fire is controlled before its any further to you.

author: KJDS
author_rank: Super Contributor
timestamp: October 21, 2013, 04:44:16 pm
content: I've nothing to add except repeating the string idea and emphasizing getting out early and keeping yourself safe.

author: MacAttak
author_rank: Unknown
timestamp: October 21, 2013, 08:43:55 pm
content: If you try anything like a "tripwire" you could end up with a false trigger. Any wildlife in the immediate area is likely to be panicked ahead of the fire front.Realistically though, if a major fires bears down on your home then a little bit of water isn't going to do much to protect it.IMO, spend the time on getting more of your irreplaceables out of there safely.

author: gnif
author_rank: Unknown
timestamp: October 21, 2013, 08:58:03 pm
content: Thanks all for your advice so far,Just to let you know, we have already emptied our house out of everything we can, and we will not be staying around, once we get the call to leave, we will be leaving.I know a little water may not do much to help, but it is better then doing nothing. The main threat to our house is a few trees at the back of the back yard, we have a very long back yard so they are not close to the house. I think the building will survive, just preparing for the worst.

author: Vgkid
author_rank: Super Contributor
timestamp: October 21, 2013, 10:07:22 pm
content: How tall, and how close are the trees to your house?

author: staxquad
author_rank: Frequent Contributor
timestamp: October 21, 2013, 10:22:31 pm
content: Quote from: Vgkid on October 21, 2013, 10:07:22 pm"At very high temperatures, eucalypt species release a flammable gas that mixes with air to send fireballs exploding out in front of the fire. With eucalyptus, you see these ember attacks, with huge bursts of sparks shooting out of the forests"It probably doesn't matter how close he is to the treesWith spruce forests where I live, these ember attacks can travel a few kilometers in front of the fire. I have a sneaking suspicion that Eucalyptus fires are even more volatile."An ember attack is a naturally occurring event. During a bushfire, burning parts of trees such as twigs, branches or leaves become temporarily airborne and can be carried away upwind of the bushfire. An 'ember attack' occurs when many embers are carried by winds in a cluster. The Stringybark species of Eucalypt is particularly notorious for contributing large flaming sections of bark that due to their size, weight and shape, can be carried up to several kilometres away. The movements of embers from a bushfire are the primary cause of spotfires, which contribute to the continued spread of a bushfire."("Volatile terpenoids emitted in large quantities by the abundant eucalyptus trees in the Blue Mountains may cause mie scattering and thus the blue haze for which the mountains were named")

author: EEVblog
author_rank: Unknown
timestamp: October 21, 2013, 10:48:22 pm
content: Quote from: staxquad on October 21, 2013, 10:22:31 pmThat's why you see the photos of one house surviving in-between two houses totally burnt out. It's pot luck, and how flammable your house is. Hence the need to clear out your gutters and fill them with water etc. If you do that your odds improve a lot.

author: MacAttak
author_rank: Unknown
timestamp: October 22, 2013, 01:31:11 am
content: Burning embers can be carried for miles and spawn fresh fires if the wind is right. In hilly areas fire can hop from hilltop to hilltop like that. Not having trees immediately up next to your home is helpful, but it can't stop the wind-born embers.The water won't hurt, and might afford some slight protection. If you've already taken the steps to secure your belongings as best as possible then might as well do something to increase your home's odds.

author: Tinkerer
author_rank: Frequent Contributor
timestamp: October 22, 2013, 01:32:59 am
content: Another thing to keep in mind is that in many instances, its the heat and floating embers alone that will cause a house to catch fire, not just direct contact with the flames.With that said, I am suprised no one thought to mention simply rigging up temperature sensors to the house itself and when one hits the right temp, it triggers the water. Same thing for the yard though, but the house itself is a smaller area to cover.

author: vk2hmc
author_rank: Contributor
timestamp: October 22, 2013, 04:35:07 am
content: Nod, the fire wall is travelling several kilometers per hour.Possibly, a temperature sensor would be too slow.The only safe thing to do is make your house as fireproof as possible and get the hell out.--markiQuote from: wilfred on October 22, 2013, 02:24:37 am

author: Tinkerer
author_rank: Frequent Contributor
timestamp: October 22, 2013, 05:00:36 am
content: Quote from: wilfred on October 22, 2013, 02:24:37 amTis true. I guess not many people have alot of temperature sensors laying about.

author: walshms
author_rank: Regular Contributor
timestamp: October 22, 2013, 05:14:56 am
content: Quote from: EEVblog on October 21, 2013, 10:48:22 pmIf I had the time, I'd get soaker hoses and tack them to the roof on either side of the ridgeline and about half-way down the slope, tie them to a stout pump and give them as much water as I could get through them. If you can keep it wet, it stands a chance.

author: G7PSK
author_rank: Super Contributor
timestamp: October 22, 2013, 08:03:06 am
content: With flying ember spread fires you don't actually need much water as a damp surface will stop ignition, so what you need is a system that sprays a mist over your house. I suspect that you do not have the time available to set up such a system.What does occur to me though is if you want an electronic trigger for your pump is to use IR but not just plain static IR but varying IR, this is used in automatic welding masks a static IR source such as an electric heater or even the sun wont shut the mask but if you wave your fingers in front while looking at such a heat source the screen goes dark. If I were you I would GTFO. and stay safe.

author: AlfBaz
author_rank: Super Contributor
timestamp: October 22, 2013, 08:21:35 am
content: I was watching the news this afternoon and they were talking to a fellow who's property is in the line of fire (pardon the pun). He has large water reserves, diesel pumps and hoses every where. So that he can be there up to the last minute he has built an underground concrete bunker in his back yard with a 1200l compressed air tank which he can jump into should it get out of hand

author: amyk
author_rank: Super Contributor
timestamp: October 22, 2013, 10:02:59 am
content: Quote from: walshms on October 22, 2013, 05:14:56 amI agree with this suggestion. Water has a very high heat capacity so it is effective in absorbing heat. In rocket engine tests it's used to prevent the exhaust (which is going to be much hotter than any wood fire) from melting concrete.

author: EEVblog
author_rank: Unknown
timestamp: October 22, 2013, 11:04:44 am
content: I heard some news that everyone has been asked to leave the Blue Mountains by 10am tomorrow.

author: EEVblog
author_rank: Unknown
timestamp: October 22, 2013, 11:11:33 am
content: I've just heard a story that someone in the mountains in the last major fire had their house "saved" by the fire department, only to have the insurance company refuse to pay out for the huge water damage because their house wasn't lost in a fire, and hence the fire insurance clause did not cover itIn which case it would have been better to have a big sign out the front of the house that said "please don't save my house!" and let it burn to the ground instead.

author: GK
author_rank: Super Contributor
timestamp: October 22, 2013, 11:20:11 am
content: Apparently elephants and goats are the future for fireproofing the Blue Mountains:http://www.abc.net.au/lateline/content/2013/s3873911.htmQuoteA " low emissions fuel management technology" ?What about all the farting of those ruminants? I remember the big stink either the Tasmanian or NZ government caused when they proposed an anti-global warming "fart tax" for farmers with livestock and subsequently large methane emissions.

author: AlfBaz
author_rank: Super Contributor
timestamp: October 22, 2013, 11:26:51 am
content: Driving from the Blue Mountains, out to Oberon and down to Goulburn at dusk/night was a nightmare trying to avoid roo's, I guess elephants would be easier to spot

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: October 22, 2013, 11:41:22 am
content: Quote from: GK on October 22, 2013, 11:20:11 amWell, if the PC alternative is an army of people, all equipped with SUVs and chainsaws...I guess letting nature take its toll with smaller, naturally occurring forest fires, thus balancing dead wood and undergrowth, won't be a good alternative to mention right now?

author: SeanB
author_rank: Super Contributor
timestamp: October 22, 2013, 07:31:48 pm
content: I remember watching CNN once when the LA hills were burning, and there was a crew out in the desolation in acres of chimney stacks and burned out acreages, and were at the only house left standing interviewing the owner. He was a Korean immigrant engineer, and when the Bimbo asked why his house was the only one to survive undamaged aside from soot marks on the walls he replied in a Korean accident "I thought everyone knows wood burns". His 2 story house with a tile roof was built out of brick and plaster, and he had been scrupulous about keeping the trees and bushes trimmed around it so there was no danger of fire hitting the beams. He had run a hose on the roof until the water died though to keep the tiles damp and the underlying beams wet.

author: nctnico
author_rank: Super Contributor
timestamp: October 22, 2013, 11:29:58 pm
content: I guess a stone wall around a house wood help against bush fire. This is popular over here for decorative purposes and preventing land slides:Anyway I hope the people can return to their (hopefully intact) homes soon. A fire front which spans 300km doesn't even fit in 'my' country so a big kudos to the people working on putting it out.

author: MacAttak
author_rank: Unknown
timestamp: October 23, 2013, 07:04:04 pm
content: Quote from: AlfBaz on October 22, 2013, 08:21:35 amThat sounds like a human kettle to me.

author: nctnico
author_rank: Super Contributor
timestamp: October 23, 2013, 09:19:13 pm
content: Rock/stones have a very low heat conductivity. A thick wall will keep the heat out for a long time. This is why old churches are usually so cool on the inside even if they are baking in the sun. If you create an underground bunker then it won't get much warmer than 15 degrees Celsius or so.

author: MacAttak
author_rank: Unknown
timestamp: October 24, 2013, 01:00:36 am
content: This is what came to mind immediately:http://www.foxnews.com/story/2006/06/16/two-men-found-dead-in-mount-merapi-bunker/But granted there is a large difference between volcanic ash and an intense wildfire - in temperature as well as duration. And it seems like there are companies that sell bunkers specifically for this purpose:http://www.wildfiresafetybunkers.com.au/So probably much more safe than I assumed.

author: walshms
author_rank: Regular Contributor
timestamp: October 24, 2013, 05:02:38 pm
content: Quote from: EEVblog on October 22, 2013, 11:11:33 amI think it's criminal, but insurance companies are very good at getting out of paying claims. You have to read the policies with a magnifying lens, get legal advice, etc. before you can really understand what it is that you're paying for in the first place. They've already paid their high-powered attorneys to design it so that there's as many escape clauses as they can cram into the policies; getting them to honor their commitments sometimes requires equally high-powered attorneys.It's a very strange system we've designed for our world...I hope that person whose house was saved found some relief somewhere...

author: walshms
author_rank: Regular Contributor
timestamp: October 24, 2013, 05:07:52 pm
content: Quote from: MacAttak on October 23, 2013, 07:04:04 pmActually, that might work. If the bunker is at least a few feet underground, the soil alone might provide enough insulation to keep the heat down to a manageable level. Concrete conducts a bit better, but it would probably take a while for it to heat up, and by then the fire above ground might have burned its way through all of the fuel.

author: nctnico
author_rank: Super Contributor
timestamp: October 24, 2013, 05:52:00 pm
content: Still I wouldn't want to be in the bunkers fromhttp://www.wildfiresafetybunkers.com.au/for more than half an hour. What is missing is an air supply. Imagine the top of the bunker is in a fire with temperatures way over 500 degrees C. The air will be very hot and likely deprived of oxygen. So you'll need a supply of oxygen and maybe even CO2 scrubbers. If you get locked into a closed space you won't die from a lack of oxygen but from an excess of CO2.

author: Zero999
author_rank: Super Contributor
timestamp: October 25, 2013, 01:41:40 pm
content: Quote from: nctnico on October 24, 2013, 05:52:00 pmQuote from: FAQhttp://www.wildfiresafetybunkers.com.au/faq.htm

author: SeanB
author_rank: Super Contributor
timestamp: October 26, 2013, 06:17:32 am
content: Fire front moves, it is not like Dresden. If you are really worried keep a full SCUBA tank in the room with a regulator, it will provide around 5 hours of air at ambient pressure, or keep a few CO2 scrubber packs in a hermetically sealed box and break them out when you are in there to keep the CO2 from rising too high.