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KyraDune
08-19-2011, 01:28 AM
I'm not sure this is the right place to put this, but I'm trying to figure out what would happen to a car (and the person inside the car) if you ran the car into an electric fence. Basically, there is a ten foot electric fence between my hero and his goal, so I was thinking he might just hop into his car and mow the sucker down. My problem is, is that the least bit believable?

thothguard51
08-19-2011, 01:33 AM
Totally believable as he will be protected in the car from any electrical charge. More than likely, the circuit breaker will trip.

Damage to the vehicle though will be something else depending on the gauge of wire the fence is made with and any other obstructions he might hit on the way in...

lbender
08-19-2011, 02:23 AM
Totally believable as he will be protected in the car from any electrical charge. More than likely, the circuit breaker will trip.

Damage to the vehicle though will be something else depending on the gauge of wire the fence is made with and any other obstructions he might hit on the way in...

Agreed. If you're in a thunderstorm with lightning, the safest place to be is in your car. Even if it gets struck, you should be fine.

jclarkdawe
08-19-2011, 06:24 AM
Depends upon the fence. But backing up here, I don't understand exactly what we're talking about here. A ten foot high fence? A ten foot long fence?

What sort of voltage? Human killing voltage or animal stopping power? This determines the wire that is used.

Electric fences are not built for strength. What most likely will happen is the wire will pop off the insulators holding it to the poles. As the wire gets farther and farther away, it will have a harder time popping off the insulators, causing increased resistance. It can reach the point where there's enough resistance that you can't pull against it. It could snap the wire. I've seen livestock do both.

I've also seen a truck grab a low telephone wire. It pulled for about a half a mile, until all of that pulling brought the truck to a stop. It was sort of interesting seeing this truck draped with wires trailing behind it. The people who had their phone wires ripped from the house were probably less than amused. It took several days for the phone company to fix the damages.

The wire will probably have a delightful tendency to wrap around something, like the axles or drive shaft. Sometimes you get lucky and it doesn't.

And if there's enough voltage, one zap could fry the computer before it shorts out.

Best of luck,

Jim Clark-Dawe

Al Stevens
08-19-2011, 06:39 AM
The car has rubber tires. To shock anything, the current has to pass through to ground. The tires insulate the car and anyone in it from ground. When the car breaks the wire, the wire might fall to ground, which then makes sparks depending on the voltage and current.

Electric fences for keeping animals inside an enclosure will usually not harm a person unless the person is standing in a puddle. Even then, it will just knock you on your butt.

The electric part is typically one strand that stretches across the top of a fence. The rest of the fence is not usually electrified.

My dad raised goats when I was a child. I've taken many a jolt from the electric fence.

If the fence is there to keep people in or out, that is another matter. They (prisons, etc.) usually just use rolled strands of non-electrifed barbed wire. You should do some research in that case.

thothguard51
08-19-2011, 06:54 AM
I think the OP is talking about a chain link type of fence that has been electrified and not a fence with a single strand of wire running along the top of it. Thus - why the fence is 10 feet high...

blacbird
08-19-2011, 07:01 AM
One of the safest places to be in an electrical storm, with lots of lightning strikes all around, is in a car. You almost certainly won't be harmed inside the car when you plow it through one.

If you get stopped by the fence, however, the last thing you'd want to do is get out of the car, abandoning that protection. It would be very easy, I'd think, to touch a live wire and get yourself fried.

caw

benbradley
08-19-2011, 07:33 AM
I'm also scratching my head about the OP's fence too. Is it electrified as in an electric fence to keep animals in? the electricity MIGHT hurt a person who touched it (while standing on the ground, not while in a car), but wouldn't have any effect on a car touching it.

If a high-voltage electrical power wire has fallen on the fence, that's a dangerous situation. Someone in a car would be safe from getting shocked, but I can see a lots of really big sparks between the fence/car and ground, and a reasonable chance to catch the car on fire. Then, unless the person can drive the car away from the fence and wire and then get out, the person is stuck in a burning car, or will be electrocuted (in the original sense of the word: KILLED by electricity) trying to get out.

Another thing would be driving through a chain link fence. I'm thinking it would have considerable slowing power - you'd have to drive a car pretty fast to get through it, and it would cause considerable damage to the front end, and if the car does get through it, probably break the windshield. If you're going to drive through a fence like that, use a semi truck like Arnold used to drive into the building in Terminator.

benbradley
08-19-2011, 07:54 AM
The car has rubber tires. To shock anything, the current has to pass through to ground. The tires insulate the car and anyone in it from ground.
The electrical safety of a car is because the occupants are fully enclosed in a metal cage, and not because it's on rubber tires.

When lightning strikes a car it goes from the roof through the steel to the bottom metal parts with very little voltage drop because the steel in the roof and supports holding the roof makes a very good electrical conductor, even of the thousands of amperes of current in a lightning strike. It becomes "lightning" again and arcs between the car body/frame and the ground.

Don't expect to be safe from lightning in a convertible or on a motorcycle, even though they have rubber tires.

KyraDune
08-19-2011, 05:25 PM
I think the OP is talking about a chain link type of fence that has been electrified and not a fence with a single strand of wire running along the top of it. Thus - why the fence is 10 feet high...


Yes, that's exactly what I'm talking about. It's designed to keep people out of a sensitive military area, where nonmilitary people are not supposed to go. I had my hero in a convertible type car, like a jeep, though I'm not sure he could drive through a fence in that and not get fried. Also, I was thinking he might go through the gate, since that would be weaker than the rest of the fence. I think.

Al Stevens
08-19-2011, 06:17 PM
I think the OP is talking about a chain link type of fence that has been electrified and not a fence with a single strand of wire running along the top of it. Thus - why the fence is 10 feet high...

In that case, it wouldn't work. You have to insulate the electrified part from ground. A chain link fence is grounded--zero resistance, infinite current, aka short circuit--and would blow a fuse as soon as you turned it on.

Ohm's law.

Al Stevens
08-19-2011, 06:27 PM
Yes, that's exactly what I'm talking about. It's designed to keep people out of a sensitive military area, where nonmilitary people are not supposed to go. I had my hero in a convertible type car, like a jeep, though I'm not sure he could drive through a fence in that and not get fried. Also, I was thinking he might go through the gate, since that would be weaker than the rest of the fence. I think.

I suggest you do some research and bone up not only on electric fences but electricity, too. Rubber (tires) is not a conductor. The driver wouldn't be in the circuit even if he came into direct contact with the wire. You have to get his feet (or other body part) on the ground.

thothguard51
08-19-2011, 06:40 PM
The gate is only easier if the writer makes it easier...

WriteKnight
08-19-2011, 07:56 PM
Electrified chain link fences are used around prisons. The are separated from the uprights by insulators.

They are very VERY tough to 'break' through. In my opinion - not possible in your average vehicle. Not even addressing the electrocution angle.

allz28
08-19-2011, 08:15 PM
There was an old episode of Lassie where a broken power line fell on her owner's truck. The owner was not hurt. And Lassie saved the day.

Just thought I'd add my 2 cents.

Al Stevens
08-19-2011, 10:13 PM
You won't put a car through a commercial-grade prison or military fence. Maybe a tank or a bulldozer, both of which have metal tracks and might go zzzap!

slcboston
08-19-2011, 10:25 PM
Just for giggles, we had a car run into our electric (livestock) fence.

Didn't slow down at all, and somehow made it under the top wire - we raised Belgians so it was a tallish livestock fence - without even stretching it out.

Bottom two wire were a different story, though.

And yeah, car + military/prison fence? Bad for the car.

KyraDune
08-19-2011, 10:31 PM
Thanks for all the help.

Al Stevens
08-19-2011, 11:10 PM
When billygoats pee, they usually hit themselves in the beard,which is why they stink and nannygoats don't. I saw a billygoat peeing in his beard when something caught his attention. He turned his head, and the stream shot forward and hit the electric fence. That was one of the funniest things I've ever seen. It didn't seem to hurt him permanently, but the hollering and dancing was quite the sight.

Now, back on topic.

Mark G
08-19-2011, 11:16 PM
Electric fences of the chain-link variety are a staple in movies. Driving through fences is also a regular thing. Realistic? Probably not. Then again... if the Jeep dislodged the fence from the insulators and it touched a grounding element - it could short itself out...

How would the scene play out if the Jeep got tangled in the fence and the hero had to squeeze through a gap without zapping himself?

Sounds like fun.

KyraDune
08-21-2011, 03:22 PM
Electric fences of the chain-link variety are a staple in movies. Driving through fences is also a regular thing. Realistic? Probably not. Then again... if the Jeep dislodged the fence from the insulators and it touched a grounding element - it could short itself out...

How would the scene play out if the Jeep got tangled in the fence and the hero had to squeeze through a gap without zapping himself?

Sounds like fun.

I had thought about that, but my hero is under a bit of a time crunch, what with the heavily armied bad guys on his tail. If he takes too much time getting out of the jeep he'll end up full of bullet holes.

agent.grey
08-21-2011, 10:03 PM
For believability, a closed-top vehicle is much more likely to get you through without getting electrocuted (assuming the car can get through the physical barrier of a tough fence).

One thing you might want to address is what happens when he gets out. Every year there are cases of tractor and digger drivers who hit overhead power lines. They are almost invariably unhurt until they try to leave their cab. Even those who try to jump clear to avoid completing the circuit sometimes get a serious or fatal electric shock.

As a writer, there are plenty of ways to get round it, but as a reader it would break my immersion if the character just opened the door and stepped out.

shaldna
08-22-2011, 01:26 PM
Don;'t know if it helps at all, but we use electric fence for the horses - mostly it's tape - so you can see it, but sometimes we run it through the top strand of wire on the fence instead - mostly we have the tape about a foot inside the fence, to keep teh horses off the fences.

I once got caught between the fence and the tape with a foal who was stuck. I think I got shocked about 100 times before someone made it out to turn the fence off. Our fences are run off a small battery, similar to a car battery, which prooduces a pulse of electricity, rather than a constant stream. The shock is pretty mild, designed not to hurt but to, well, shock. That said, when you are repeadly shocked by it, it's not pleasant. I had to have a hospital visit and I was all shaky and weak for about a week afterwards, my heart kept doing weird palpatations and my limbs didn't seem to work properly.

It was not pleasant.

KyraDune
08-22-2011, 03:46 PM
I was thinking he would hit the gate, knock it off its hinges or whatever gates have and then kind of drive over it. That would elimnate the danger when he got out.

Agent Grey, I think you're right, I better put a top on that jeep no matter what I see in my head. Shaldna all I can say is, dang.

Al Stevens
08-22-2011, 06:11 PM
The convertible top doesn't matter. Even if the electrified part lands on your head, you are insulated from ground by the tires

Now, in case someone suggests that the electric part hits your head and the ground, no problem. The current takes the path of zero resistance, which is through the metal.

It is possible that they could build a fence with an isolated, self-contained circuit--the business end of the fence on one side of a transformer. I'd want to research that before I used it as a premise.

I don't think a Jeep can crash the gate of a military security fence. But you're welcome to experiment and try it out. I suggest Area 51 for maximum reality. :)