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# How to Tell When It's Safe to Drive a Car on a Frozen Lake

07/30/2009 11:10 AM

how do you calculate ice thickness (on a lake) = to the weight you want to put on it. in other word want calculations do you need to know, ie: how thick does the ice have to be before drive a car on it?

can you do a calculation for it?

thx.

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#1

### Re: ice thickness (on a lake) = to the weight you want to put on it

07/30/2009 11:23 AM

this is complicated, if you base it on floating the car on ice, then you can get a volume and choose your area to give you the thickness, but ice from edge to edge will form a structure that will support more weight for less thickness, then you have the quality of the ice - is it porous or clear? and finally you have the weight you are applying to the area (i.e. the pressure) and the rate at which the load is applied, think of polar bears walking gently or sliding to spread the load on thin ice.

having considered the above, no I can't

(there is an interesting section in On Walden Pond by Thoreau where he investigates the ice on a nearby lake)

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#2

### Re: ice thickness (on a lake) = to the weight you want to put on it

07/30/2009 11:54 AM

thx. for the respond

it would be form edge to edge

(is it porous or clear) i think it would be porous because for the freezing of winter and snow?

is there a standard calculation for this?

where can i find this section on Walden Pond by Thoreau plz post a link. thx

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#4

### Re: ice thickness (on a lake) = to the weight you want to put on it

07/30/2009 12:38 PM

HUX is right. A lot of it depends on the surrounding conditions.

The density of clean fresh water is 1.0 and the density of that kind of water is about 0.93 give or take a bit depending on how it froze. A very slow freeze will create clear ice where a rapid freeze will trap a lot of air bubbles making it frothy but not really porous. The more air you trap, the less the density.

Anyway, if it is simply floating ice then the ability to continue to float depends on the weight of the extra load plus the weight of the ice together divided by the weight of the water it displaces.

Since density is mass/volume and because you are comparing two volumes (the mass doesn't change for water in any state but the volume will) then the capacity to float is pound for pound dependent on the ratio of 1.0/0.93. So 1 pound of ice will remain floating as long as you don't put more than 1.2 ounces of additional weight on it.

Note that not all ice is equal. Clear ice has less air and therefore less capacity to support additional weight. But clear ice is rare because it takes a long time to form.

Switching to metric, water weighs 1000 Kg per cubic meter. A cubic meter of ice can therefore float about 75 Kg. Unless the ice you venture out on is full of cracks, your weight will be transmitted to some infinitesimal radius. An island of ice that is 2 Cm thick must be 500,000 Cm2 in order to equal one cubic meter of ice. But step over a crack and all bets are off.

In short, if you can't crack it by jumping up and down on it, then it is likely to support your weight. But make sure you know how to save yourself or someone else if you do fall through. It is the extreme cold that will kill you.

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#14

### Re: ice thickness (on a lake) = to the weight you want to put on it

07/31/2009 5:12 AM

http://www.gutenberg.org/files/205/205.txt

Then to my morning work. First I take an axe and pail and go in search
of water, if that be not a dream. After a cold and snowy night it needed
a divining-rod to find it. Every winter the liquid and trembling surface
of the pond, which was so sensitive to every breath, and reflected every
light and shadow, becomes solid to the depth of a foot or a foot and a
half, so that it will support the heaviest teams, and perchance the snow
covers it to an equal depth, and it is not to be distinguished from any
level field. Like the marmots in the surrounding hills, it closes its
eyelids and becomes dormant for three months or more. Standing on the
snow-covered plain, as if in a pasture amid the hills, I cut my way
first through a foot of snow, and then a foot of ice, and open a window
under my feet, where, kneeling to drink, I look down into the quiet
parlor of the fishes, pervaded by a softened light as through a window
of ground glass, with its bright sanded floor the same as in summer;
there a perennial waveless serenity reigns as in the amber twilight
sky, corresponding to the cool and even temperament of the inhabitants.
Heaven is under our feet is well as over our heads.

Early in the morning, while all things are crisp with frost, men come
with fishing-reels and slender lunch, and let down their fine lines
through the snowy field to take pickerel and perch; wild men, who
instinctively follow other fashions and trust other authorities than
their townsmen, and by their goings and comings stitch towns together in
parts where else they would be ripped. They sit and eat their luncheon
in stout fear-naughts on the dry oak leaves on the shore, as wise in
natural lore as the citizen is in artificial. They never consulted with
books, and know and can tell much less than they have done. The things
which they practice are said not yet to be known. Here is one fishing
for pickerel with grown perch for bait. You look into his pail with
wonder as into a summer pond, as if he kept summer locked up at home, or
knew where she had retreated. How, pray, did he get these in midwinter?
Oh, he got worms out of rotten logs since the ground froze, and so he
caught them. His life itself passes deeper in nature than the studies
of the naturalist penetrate; himself a subject for the naturalist.
The latter raises the moss and bark gently with his knife in search of
insects; the former lays open logs to their core with his axe, and moss
and bark fly far and wide. He gets his living by barking trees. Such a
man has some right to fish, and I love to see nature carried out in him.
The perch swallows the grub-worm, the pickerel swallows the perch, and
the fisher-man swallows the pickerel; and so all the chinks in the scale
of being are filled.

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#16

### Re: ice thickness (on a lake) = to the weight you want to put on it

07/31/2009 6:51 AM

GA from me, but you also forgot temperature as something that affects the strength of the ice, as does salt content in lakes/rivers where tidal changes push seawater up and down in the area concerned, even if diluted, in an otherwise for me, almost perfect answer....

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#3

### Re: ice thickness (on a lake) = to the weight you want to put on it

07/30/2009 12:28 PM

1" keep off

2" one may

3" small groups

4" OK

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#7

### Re: ice thickness (on a lake) = to the weight you want to put on it

07/30/2009 4:33 PM

I suggest you go to the link that #5 set up. You're giving really bad advice according to the DNR for the state of Minnesota.

That advice is put in most newspapers in Minnesota every year. Still people fall through.

Note that ice is not a uniform thickness throughout the surface.

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#5

### Re: ice thickness (on a lake) = to the weight you want to put on it

07/30/2009 1:09 PM

Good website, covers it all - adds more factors to consider, such as age of ice, currents, fish, more

http://files.dnr.state.mn.us/education_safety/safety/ice/dangerthinice.pdf

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#6

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

07/30/2009 2:23 PM

Ask the Old Guys who always get out on the ice first?

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#8

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

07/30/2009 6:10 PM

It depends on the tensile strength of the bottom half of the ice (the top half is in compression).

Anonymous Poster
#9

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

07/30/2009 7:12 PM

Hello,

See: http://www.crrel.usace.army.mil/

It is the website of the US Army Corps of Engineers -- Cold Regions Research and Engineering Laboratory (CRREL) They have reference literature available that gives the formula and tables for vehicular static and dynamic ice loading -- and recommended safety factors...

Cheers,

DoctorWhy.com

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#10

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

07/30/2009 7:32 PM

ddk Is obviously the most qualified to advise Ice-Man.

He lives "north enough" to know.

I live in have a place in Minn. and the local authorities let you know when it's safe, and when to get your house off the ice.

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#11

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

07/31/2009 12:10 AM

Winterpeg... does the ice every really go away?

(born in Brandon.)

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#21

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

07/31/2009 10:06 AM

lol...ya

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#12

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

07/31/2009 12:13 AM

Joltinjoe in number 5 gave a good answer. GA from me. Anyhow, there is a lot of good info there. Look for the yellow box on the 1st page, it will give you thicknesses.

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#13

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

07/31/2009 1:24 AM

awesome discussion.... i as a reader got an idea about driving a car onto frozen lake...

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#25

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

08/02/2009 6:26 AM

don't try it. your frozen like is nowhere near the conditions at OP's.

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#15

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

07/31/2009 5:58 AM

Don't drive on iced lakes.

Lots of variables:

1. Air pockets in the lake (how long did it take to freeze)

3. Size of lake - how far between supporting edges (ice is a bridge between the solid edges)

4. Cracks and deformities in the lake will either hinder or help, depending on their direction, to spread or concentrate the load - see articles on pre-stressed concrete.

If you have to drive on ice, you do it very slowly, with someone walking in front, testing the ice and listening for cracking. Only after driving over it do you know it might be safe; you have no way of knowing what lies beneath.

regards

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#26

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

08/02/2009 6:30 AM

GA. don't understand why people should risk it. too many unknowns.

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#17

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

07/31/2009 7:31 AM

Most insurance policies end when you drive onto the ice, on purpose. If your vehicle goes through, you can be fined for every day it is in the water. So check the local laws and check the thickness of the ice. Ask the ice fishermen how thick the ice is, most times they will be happy to tell you.

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#19

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

07/31/2009 8:46 AM

Then they really are Nice fisherman.....

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#18

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

07/31/2009 8:27 AM

You could always tell a neighbor that you have already done the calculations and it's safe to drive over, then see how far he gets. If he has a heavier car and doesn't break through the ice then it's a safe bet that you'll be ok.If he does go through...well maybe you should wait a few more days.

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#20

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

07/31/2009 9:02 AM

I live near Lake Erie. It seems a regular event is a section of ice breaking loose with a few cars/SUVs/snowmobiles on it. The ice was thick enough, it just decided to go somewhere else.

In the '30's, drivers used to remove doors adn tie long poles across their cars, then drive to the islands in Lake Erie's westen basin (i.e. Kelly's), but cars didn't weigh as much back then.

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#22

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

08/01/2009 12:45 AM

Hello IM,

=

=

The search list above and below may include sea and fresh water:

These are two different searches and both look to have some useful sites which answer your question.

Good luck, and I mean that sincerely!

Take care.

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#23

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

08/01/2009 12:55 AM

Hello IM,

I found this site on how the Army goes about crossing ICE, and I think they have probably got more experience than almost anyone? The site is .pdf and I can't copy it at the moment. But here is the address:

http://www.crrel.usace.army.mil/ierd/tectran/ieieb13.pdf

=

Good luck as before..........

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#24

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

08/01/2009 8:16 AM

Not sure about calculations but I saw this a little while back

It may or may not be relevant to your discussion, but it sure impressed me.

We don't get it so bad in Australia.

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#27

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

08/03/2009 8:58 AM

Here we have a law that does not allow driving on frozen lakes unless the ice is a minimum of 4 inches thick per 2000 lbs of vehicle weight.

One suggestion would be to have a pizza delivered to the questionable location. If the ice is good you have pizza. If not you get to be a hero, and rescue the poor delivery person.

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#28

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

08/04/2009 3:58 AM

I wonder who goes out and measures the ice?

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#29

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

08/04/2009 9:35 AM

We have an office located in downtown Ft. Lauderdale that does the measuring for Broward County. I am not sure where the people that measure Miami-Dade, or Palm Beach are located.

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#30

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

08/04/2009 10:20 AM

I always thought it was Brevard county.....but thats a few years ago mind you.....

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#31

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

08/04/2009 3:34 PM

There is both a Broward, and a Brevard. Broward is just above Miami-Dade. Brevard is about 150 miles further north, on the east coast.

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#33

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

08/17/2009 5:20 PM

Many thanks for tidying that up.

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#32

### Re: How to Tell When It's Safe to Drive a Car on a Frozen Lake

08/06/2009 3:11 PM

The best calculation method for determining safety (as opposed to mere thickness) is always let someone else's (preferably comparable or larger/heaver) vehicle be first on the ice. The "calculations" are fairly straightforward from there.

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