Oxy-acetylene, meet wire fence

[David Evil Overlord]

I have a quick question about fire. Specifically, an oxy-acetylene kind of fire. If it was used on a wire mesh fence, about how long would it take to cut a man-sized hole?

I'm assuming it would go through the fence like a hot knife through butter, but I'm not a trained professional so I won't be trying this at home.

Um, this is for writing, not burglary. Just in case anyone is worried.

 

[Vertigo]

From my limited experience of oxy-acetylene I think you would need to allow a second or two for each wire. IE. not quite a hot knife through butter but still fairly quick; a few minutes for a man sized hole I would reckon.

 

[Abernovo]

I've also only got a limited experience with oxy-acetylene torches, but I'd say roughly the same. It might depend upon what grade of wire you're talking about, but for normal fences only a very short period of time, I'd think.

You'd possibly be quicker with bolt cutters or wire cutters, again depending on grade of wire. I always found wire cutters quick and reliable, due to precision and ease of use. In my experience of building livestock fences, that is.

 

[Montero]

Long ago in a lab I used an oxy-methane torch for glass blowing. Mains gas plus 5 feet tall oxygen cylinder. Suspect that oxyacetelyne rigs have to be more smaller, lighter and more mobile, possibly on a trolley. Just something to think about - the weight and access issues. Also lighting it out of doors - the joys of matches in a breeze.

Also read up on gas cylinder safety. There are some "fun" ways to kill yourself with a gas cylinder that may not occur to you. (Just to get the realism right.)
Main ones are - keep upright, don't knock the tap, don't use the metal cylinder as a roller for moving heavy items (you do not want metal fatigue or other cracks in a high pressure cylinder) and don't let it sit in a fire. (Whenever you hear about a main railway line being closed due to a fire in an industrial park next to the line, that is often about gas cylinder safety. As in the fire brigade know they are in there somewhere. Think putting an aerosol cannister in a bonfire. But bigger.)

 

[Biskit]

You'd possibly be quicker with bolt cutters or wire cutters, again depending on grade of wire.

I'd go with Abernovo's advice.

Easier, safer, and not so hard to explain - No, officer, I was just taking the gas cylinders for a walk, get them out of the house for a while... No, not trying to break in through someone's fence... honest.

OK, the bolt-cutters need some explaining, but they're probably easier to drop out of sight. Even small gas cylinders can be heavy and awkward to shift around. Most of the cylinder handling gear I've come across 'assumes' that you are working on nice, flat concrete etc.

 

[The Ace]

While it would work, the weight of the equipment involved makes it little better than wire cutters - you can also wave goodbye to concealment, as the flame will be visible quite a long way off - and that's before you set fire anything, a virtual certainty.

 

[JoanDrake]

If you try it with actual oxy-acetylene you will almost certainly blow yourself up, as a canister of acetylene cannot safely even be "walked" across a finished concrete floor. You might be able to get away with a backpack rig using MAPP gas, (actually a substitute, it's no longer made) as it's considerably less explosive. However, unless there is some reason you simply cannot use bolt cutters they will work much better for the reasons outlined.

 

[Lucky_Lola]

My Dad has an oxy-acetylene rig for welding, and I have to agree with these guys *points up*. It's not terribly mobile. Basically a steel hand-truck with two 5 foot tall high-pressure canisters, and hoses everywhere*. Dad never let us anywhere near it, with good reason - both gasses can be quite volatile.

Sorry to dampen your fire, DEO, but I have to agree. Bolt cutters would be far far more quiet, compact and can be tossed into a bush with greater ease ;P Unless your character has an excuse for having an oxy plant beside a fence, of course!




*Granted, my Dad's setup is probably about thirty years old. There may be more compact plants nowadays, but I haven't the foggiest.

 

[David Evil Overlord]

Thanks, guys. What I was hoping to achieve was this:

Character wants to throw somone off a bridge. However, after the last such incident (which probably inspired him), the authorities erected a "suicide-proof" wire mesh fence along the outside of the bridge. Nothing bolt cutters couldn't deal with, but...

...Character parks his car on the bridge, puts on his hazard lights, raises the car bonnet (hood for Americans), and generally makes it look like his car has broken down. Then he gets his oxy-acetylene gear out of the car and starts cutting through the fence.

Passers-by raise the alarm. The character is surrounded by police who can't shoot for fear of exploding the cylinders (no such fear if he's using bolt cutters). And the police are sensible enough to know:

A) Making someone explode does nothing to save them from what appears to be their suicide attempt.

B) Getting close enough to use capsicum spray means getting close enough for him to use the oxy-torch as a weapon.

Then he drags his victim out of the car, keeping the cylinders between him and the cops as much as possible. what started out looking like a suicide is now an attempted murder (possibly a successful attempt). Shooting him now may be their only option, but if those cylinders go up...

 

[Vertigo]

I see two problems there. 1. It would have to be a van; you might just about get an oxy-acetylene rig in a large estate car (station wagon) or big 4 by 4, but I wouldn't bet on it. They are pretty big. 2. Even from a van you'd almost certainly need two people to get it out of the van. they're also very heavy.

 

[ctg]

Well, I hope police hasn't been watching mythbusters as it's very difficult to explode gas cylinders with normal or incendiary bullets. And thing is that I'd believe that some of those officers would be carrying rifles in their trunks, so shooting the baddie would be easier than letting him carry out a murder at front their eyes.

 

[Vertigo]

Actually depending on what country it's set in they may not have any guns at all. Certainly wouldn't in the UK. Unless a gun had been reported and they'd call in the armed cops.

The other problem actually comes back to your original query. Whether torch or cutters, I think he'd be long gone before the police actually arrived.

 

[David Evil Overlord]

Here in Australia, the cops have semi-automatic pistols. There is a Special Operations Group with greater training and firepower, but by the time they got there...

Hmmm. Perhaps the cops can pin him down between the car/van and the fence. Since he's planning on killing her anyway, he wouldn't be opposed to using her as a human shield.

The important thing, of course, is (spoiler alert!)...to get her thrown off the bridge just as a flying super hero arrives. Okay?

 

[juelz4sure]

I know I'm a bit late but the time it takes for an Oxy-acetylene torch to cut through a wire mesh (I will admit I haven't cut through wire but I have cut through 1 inch steel ) would depend on the amount of oxy and acetylene. With that said it still at the most would only take a few seconds, and could get down to as quickly as instantly. Hope that helps.

 

[TheTomG]

So my thought is the police wouldn't see it as a suicide attempt. Cutting through the fence with anything is just pretty much too involved for a suicide attempt, let alone the torch in question. Why not just drive to another bridge that isn't so inconveniently protected, or choose some other less troublesome and likely to be interrupted method?

You give "the point is..." and to be honest, it all feels a bit contrived just to get to that point, at least as it reads here. Heck, even if you are going to throw someone off a bridge, you'd still just go to a more convenient one, or choose another method that is less likely to be spotted and interrupted.

Anything less contrived that can be thought of? Is the attempted murderer a main character, or just there for this part of the plot?

 

[The Judge]

I couldn't help with the oxy-thingy question, but now we're getting onto plot issues...

I agree with Tom, it reads as far too convoluted for the pay-off. I can't believe any cop would think it a suicide attempt -- why would a suicide put the hazards on and make it look like the car has broken down? If someone is driven to suicide by the car breaking down, why would they be burning through wire instead of running in front of the other cars which are presumably around or just finding someone else to jump from.

Plus, if he's gone to the trouble of making it look like he's broken down, that must mean he thinks he might be seen -- in which case he's setting himself up to be caught. A friendly passer-by offering to help, someone calling the cops or whatever, or even someone just remembering the car and its description after the body is eventually discovered. Unless he actually wants to be caught, the would-be murderer would surely dump the not-yet dead body somewhere more accessible and with far less risk of being seen.

And if the cops are there, why on earth would the murderer in fact throw the body off the bridge? Up until then he might be guilty of some crimes but there's no evidence of actual intent to murder so he'd get a relatively light sentence. As soon as the body goes over he'll be arrested (if not killed first) and he's got no defence to a murder charge.

Can't the FSHdo the necessary somewhere else instead?

 

[chrispenycate]

Thermite powder on double-sided adhesive tape.

Nice and spectacular, gives your hero a nice aiming beacon, relatively easy to transport.

I don't see how to convince the gunmen that it's likely to explode, though.

 

[David Evil Overlord]

Always possible to change location, Your Honour.

To reveal a little more, the murderer is meant to be one of those who thinks the whole world is against him since his divorce, so he's decided the answer is to kill his child and let the ex-wife live with that for the rest of her life. He actually wants the police* and a media circus. He wants it repeated on prime time news and front page, so he rubs his ex-wife's face in what (he believes) she "forced" him to do.

This is a minor character whose entire purpose in the novel is to point out to the hero that maybe the problems she's having with her own father ain't quite the end of the world. However, it's proving difficult for me to climb into the head of a character who can think like that (something I'm grateful for).

*Whereever and however he does it, he'll need some way to keep the cops helpless to intervene. So I'll keep Chrispy's explosives in mind.

EDIT: Easiest change of venue would be a tall building. But it's unusual for tall buildings to have unrestricted access to the roof. There are totally-enclosed viewing platforms on some skyscrapers, though. And that toughened glass wouldn't stand up to explosives...

 

[The Judge]

Ah-ha! Makes more sense now if he wants the media to see him and isn't afraid of the murder charge -- but in that case, I'd expect him to be rather more pro-active about getting the media there.

Can you have him work in a skyscraper, and he knows how to get access to the roof, or a window ledge? Then he goes up on a day his co-workers aren't around, gets out there on the ledge or whatever, phones the media and gives them the spiel about his wife. Next thing it's prime time and cops everywhere. If he's holding the (unconscious) child, or she's tied to his wrist or something, the cops can't shoot him/try to knock him out as he'd go over taking her with him. He, on the other hand, can simply let her go. or slip the knot, and she's gone leaving him safe -- especially if he throws himself backwards onto the roof/into the room. (If up until then he's talked of committing suicide, the cops are less likely to think he'd let the girl go on her own, and therefore won't be expecting him to be able to drop her.)

Thinking about it, you can still have your bridge, for the same effect, but have him use bolt-cutters to get a hole made quickly and have him standing with the child where he can jump. However, you're likely to make a bigger splash (literally...) if it's in the middle of the city because more people will be able to see** -- think of all the other buildings and people with mobile phones taking snaps. Plus, people falling from bridges into water can survive the drop so he's unlikely to want that chance -- however slim -- arising and spoiling the whole affair.

** where does the mother work? Doing all this in the building opposite so she can see it all (and he'd phone her before the TV crews arrive telling her to look out the window) would be an extra twist of the knife as far as he's concerned.

 

[David Evil Overlord]

The bridge I was thinking of, the chances of survival are slim. I've spoken to the Water Police here, and their descriptions aren't pretty. If she did survive the fall, she'd most likely be stuck in the mud at the bottom of the river. For two or three days, until gasses in the bloating body made it rise to the surface again.

But that's two or three days. He wouldn't want her to "vanish" for that time. He'd prefer something like the graphic footage of people jumping and falling from the World Trade Centre during the September 11 terrorist attacks.

Especially if the mother can see it all unfold.