does a convertible still have a complete faraday cage?
September 4, 2011 5:10 PM Subscribe
top gear taught me cars are protecting their occupants from lightning by working pretty much like a faraday cage. they also taught me car companies don't really test this. I drive an audi TT convertible with not much more than a bit of cloth above my head in thunderstorms. should I be scared of lightning or am I still inside a faraday cage?
No you should not be scared of lightning. For one, the chances of being struck are ridiculously low and two, in the normal operation of a motor vehicle you are not in touch with anything metal which connects to the vehicle's exterior.
posted by dougrayrankin at 5:17 PM on September 4, 2011 [2 favorites]
posted by dougrayrankin at 5:17 PM on September 4, 2011 [2 favorites]
Response by poster: the chances of being struck are ridiculously low
granted. I am merely being curious.
not in touch with anything metal which connects to the vehicle's exterior
interesting. I was wondering why hammond wasn't scared of pieces of metal on his body, etc.
posted by krautland at 5:22 PM on September 4, 2011
granted. I am merely being curious.
not in touch with anything metal which connects to the vehicle's exterior
interesting. I was wondering why hammond wasn't scared of pieces of metal on his body, etc.
posted by krautland at 5:22 PM on September 4, 2011
"Nope, you aren't in a Faraday cage. A quick Googling confirms it."
Could you provide the link you used to reach that conclusion, because my quick googling doesn't agree with your quick googling.
posted by 517 at 5:48 PM on September 4, 2011
Could you provide the link you used to reach that conclusion, because my quick googling doesn't agree with your quick googling.
posted by 517 at 5:48 PM on September 4, 2011
link. This link actually specifically addresses convertibles.
posted by 517 at 5:50 PM on September 4, 2011
posted by 517 at 5:50 PM on September 4, 2011
interesting. I was wondering why hammond wasn't scared of pieces of metal on his body, etc.Cause to be electrocuted there would need to be arcing from the car to him, and given that he provides a longer route to earth why would it?
posted by dougrayrankin at 5:53 PM on September 4, 2011
The Boston Museum of Science covers this pretty well. Short answer: convertibles are not safe from lightning.
posted by Dimpy at 5:55 PM on September 4, 2011
posted by Dimpy at 5:55 PM on September 4, 2011
in the normal operation of a motor vehicle you are not in touch with anything metal which connects to the vehicle's exterior
In the normal operation of a convertible with a cloth roof, the occupants' heads are entirely outside the vehicle from lightning's point of view. They don't need to be hanging onto a metal conductor to make this so; they might as well be sitting on a park bench.
posted by flabdablet at 6:04 PM on September 4, 2011 [1 favorite]
In the normal operation of a convertible with a cloth roof, the occupants' heads are entirely outside the vehicle from lightning's point of view. They don't need to be hanging onto a metal conductor to make this so; they might as well be sitting on a park bench.
posted by flabdablet at 6:04 PM on September 4, 2011 [1 favorite]
Could you provide the link you used to reach that conclusion, because my quick googling doesn't agree with your quick googling.
This is a quote from that link:
"A metallic car or other vehicle can also be a safe place in an electrical storm for the same reason. A car with a fiberglass body or a cloth top convertible will not form a Faraday cage, however any vehicle with an enclosed metallic shell will."
posted by InsanePenguin at 6:07 PM on September 4, 2011
This is a quote from that link:
"A metallic car or other vehicle can also be a safe place in an electrical storm for the same reason. A car with a fiberglass body or a cloth top convertible will not form a Faraday cage, however any vehicle with an enclosed metallic shell will."
posted by InsanePenguin at 6:07 PM on September 4, 2011
517, I'm not sure why you think the article you linked - the one that "specifically addresses convertibles" - supports the proposition that a convertible is a Faraday cage. Here's what seems to me to be the relevant passage:
posted by flabdablet at 6:10 PM on September 4, 2011
A metallic car or other vehicle can also be a safe place in an electrical storm for the same reason. A car with a fiberglass body or a cloth top convertible will not form a Faraday cage, however any vehicle with an enclosed metallic shell will.(emphasis mine)
posted by flabdablet at 6:10 PM on September 4, 2011
"Nope, you aren't in a Faraday cage. A quick Googling confirms it."
We don't need a quick googling. We can perform an experiment.
Go sit in your car with the doors closed. Ready? Now try to make a cellphone call.
If you can make the call, you are not in a Faraday cage, which blocks radio frequency transmissions.
Q.E.D.
(This test can also be performed with a GPS, web-enabled device, or portable radio.)
posted by IAmBroom at 6:16 PM on September 4, 2011 [4 favorites]
We don't need a quick googling. We can perform an experiment.
Go sit in your car with the doors closed. Ready? Now try to make a cellphone call.
If you can make the call, you are not in a Faraday cage, which blocks radio frequency transmissions.
Q.E.D.
(This test can also be performed with a GPS, web-enabled device, or portable radio.)
posted by IAmBroom at 6:16 PM on September 4, 2011 [4 favorites]
I thought the deal with lightning and cars was that the tires pretty much guarantee that there is going to be a better target elsewhere, like a tree or guardrail or something that isn't insulated from the ground. Maybe I should look it up.
posted by rhizome at 6:21 PM on September 4, 2011
posted by rhizome at 6:21 PM on September 4, 2011
Don't the rubber tires protect you?
I'm with rhizome.
posted by jbenben at 7:01 PM on September 4, 2011
I'm with rhizome.
posted by jbenben at 7:01 PM on September 4, 2011
Sorry InsanePenguin, I misunderstood your initial comment. It's been a long day.
posted by 517 at 7:03 PM on September 4, 2011
posted by 517 at 7:03 PM on September 4, 2011
That's cool, I've been working ten hour days cleaning my business after Irene hit, I thought I had misread the article at first when you replied.
posted by InsanePenguin at 7:05 PM on September 4, 2011
posted by InsanePenguin at 7:05 PM on September 4, 2011
From the Boston Museum of Science link (which is kind of cool, because it has both a theoretical discussion and actual first-hand discussion of what it's like being in a metal cage subjected to simulated lightning):
During part of our regular lightning shows the demonstrator raises the cage so that it will be struck by the sparks. We do this to demonstrate why it is safe to be in a car during a lightning storm. Most people believe that the reason has to do with the rubber tires, rubber being an insulator. Air is also an insulator, however, and almost as good a one as rubber! If a lightning bolt has just traveled two or more miles through air, an inch or two of rubber will not make much difference. Indeed, it has been calculated that you would need solid tires about a mile thick to be safe!posted by Dimpy at 7:08 PM on September 4, 2011
Don't the rubber tires protect you?
LOL. Lightning has enough current to travel through a couple miles of air. You really think 1/2 inch of rubber is gonna stop it ? Air is a pretty good insulator, pretty much everything else isn't, in comparison. (although, large voltage differentials can cause ionization... point is, its not the tires).
You'll be less safe in a convertible than in a hard top, but even at that, you're reasonably safe since you aren't a good path to ground in comparison to the metal chassis of the car. You are a big bag of salt water, but you're covered in leather and not touching the ground.
Anyway, the windshield frame sits higher and is a far more likely target, and once it hits that, the metal chassis will carry the current around you. Like a bird on a wire.
However, lightning is reasonably unpredictable, and being near any sort of high energy phenomenon (turbine engines, kilns, arc welders, etc.) incorporates some measure of danger for humans. They're pretty fragile - although crunchy and good with ketchup.
posted by Pogo_Fuzzybutt at 9:36 PM on September 4, 2011
LOL. Lightning has enough current to travel through a couple miles of air. You really think 1/2 inch of rubber is gonna stop it ? Air is a pretty good insulator, pretty much everything else isn't, in comparison. (although, large voltage differentials can cause ionization... point is, its not the tires).
You'll be less safe in a convertible than in a hard top, but even at that, you're reasonably safe since you aren't a good path to ground in comparison to the metal chassis of the car. You are a big bag of salt water, but you're covered in leather and not touching the ground.
Anyway, the windshield frame sits higher and is a far more likely target, and once it hits that, the metal chassis will carry the current around you. Like a bird on a wire.
However, lightning is reasonably unpredictable, and being near any sort of high energy phenomenon (turbine engines, kilns, arc welders, etc.) incorporates some measure of danger for humans. They're pretty fragile - although crunchy and good with ketchup.
posted by Pogo_Fuzzybutt at 9:36 PM on September 4, 2011
Best answer: There's a saying about coming across an angry bear in the woods: you don't need to outrun the bear, you just need to outrun another hiker.
Lightning is the bear. It will travel on the easiest path it can find. Easiest is a combination of shorter distance and lower resistance. So, if you want to not be hit by lighting, you don't have to be perfectly insulated in a faraday cage. You just need to be in the "lightning shadow" of something that is a better conductor than you are.
The metal body of a coupe is a much better conductor than you are, and it surrounds you, so you are pretty darn safe should lightning choose to hit your car ... rather than the nearby tractor-trailer or wet tree or power line or billboard or cafe or street sign or house or skyscraper or mountain. A ragtop is a poor conductor except for the metal around the windshield so you are not so safe as in a coupe.
But lightning almost certainly isn't going to hit your car because there will be a nearby tractor-trailor or power pole or wet tree or billboard or cafe or street sign or house or skyscraper or mountain or something else much taller or a much better conductor instead.
In fact you are far more likely to be in danger of an object (like a tree) that has been hit by lightning falling on you or the road while you are driving nearby than of the lightning hitting you directly. Which would suck if you were in a ragtop.
Don't worry too much about being personally hit by lightning. Just drive according to conditions. And if you do decide to pull over in a lightning storm, find a bridge or something to stop under, instead of that one tree all by itself by the side of the road with no nearby power lines.
posted by seanmpuckett at 6:18 AM on September 5, 2011 [2 favorites]
Lightning is the bear. It will travel on the easiest path it can find. Easiest is a combination of shorter distance and lower resistance. So, if you want to not be hit by lighting, you don't have to be perfectly insulated in a faraday cage. You just need to be in the "lightning shadow" of something that is a better conductor than you are.
The metal body of a coupe is a much better conductor than you are, and it surrounds you, so you are pretty darn safe should lightning choose to hit your car ... rather than the nearby tractor-trailer or wet tree or power line or billboard or cafe or street sign or house or skyscraper or mountain. A ragtop is a poor conductor except for the metal around the windshield so you are not so safe as in a coupe.
But lightning almost certainly isn't going to hit your car because there will be a nearby tractor-trailor or power pole or wet tree or billboard or cafe or street sign or house or skyscraper or mountain or something else much taller or a much better conductor instead.
In fact you are far more likely to be in danger of an object (like a tree) that has been hit by lightning falling on you or the road while you are driving nearby than of the lightning hitting you directly. Which would suck if you were in a ragtop.
Don't worry too much about being personally hit by lightning. Just drive according to conditions. And if you do decide to pull over in a lightning storm, find a bridge or something to stop under, instead of that one tree all by itself by the side of the road with no nearby power lines.
posted by seanmpuckett at 6:18 AM on September 5, 2011 [2 favorites]
This thread is closed to new comments.
posted by InsanePenguin at 5:15 PM on September 4, 2011