- Really - Cold weather effects on cars

For those of you who have not spend a COLD winter somewhere, you really can't imagine what it's like for your car.

When I say cold, I mean, when -20 degrees celcius is common. And -30 C occasionally. Plus wind chill that can and will give your face or fingers frostbite in MINUTES if they are not covered up. There are many reports of homeless people freezing to death up here.

-40 Celcius = -40 farenhite, so you should get the idea how cold I'm talking about if you think in farenhite.

One big thing is that rubber actually expands in the cold, unlike other elements.

http://www.fas.harvard.edu/~scdiroff/lds/ThermalPhysics/ThermalExpansion/ThermalExpansion.html

"Rubber is a solid that contracts upon heating. A large rubber band, held taught by a suspended mass, will contract when heated with a heat gun"

http://www.scienceforums.net/forum/showthread.php?t5450 "Rubber is another material that tends to contract upon heating. Long molecules, stretched when cold, but bent when heated."

Find some experiments here: http://scifun.chem.wisc.edu/homeexpts/rubberband.html

When I lived in the middle of Canada before and fixed the Fords, we had a number of issues.

New alternator belt installed in the summer, worked fine til winter. It needed to be re tightened in winter. Because the rubber belt had lengthened in the deep cold.

Tire pressure goes way down in winter. From 32 to 20 PSI or less. More air needs to be added when it gets cold. And bled out in the spring.

Because in winter, the rubber tires expand, at the same time the air contracts.

But first, you have to be careful to bleed the air hose of any water vapor, because it will freeze in your valve otherwise. Then you can't fill or deflate your tires until it's warm.

Once I didn't bleed the tires soon enough in the spring. The tire pressure went over 45 PSI. On the summer road trip, even though the pressures were back in spec, one tire blew out. Fortunately, I avoided an accident.

Another effect in really cold weather, -25 celsius and lower. Rubber tires on some aluminum rims just won't hold an air seal. Because the aluminum contracts, and the rubber expands. This happened on a co worker's Miata. He returned to the shop multiple times. Some people will just give up, and get steel rims for the winter. Steel has less thermal expansion/contraction than aluminum.

Another effect, unrelated to rubber. The oil in the car will freeze like hard ice cream. This makes the engine very difficult to turn over fast enough to start. AT the same time, the strength of the battery has gone way down in the cold.

On really cold days, if it didn't start on the first few tries, forget it. The battery had no more juice to push through the hard oil, and the crankshaft doesn't even turn. The solenoid just clicks. So, we used at least 600 cold cranking amps. And rebuilt the carb in the summer, so that it worked perfectly the first time in the winter.

That's why we have block heaters, which boil the antifreeze, which melts the oil. Someone suggested that we change our license plates to say: In block heaters we trust.

Another problem: gas lines getting frozen. After I drove my car back to Canada, the southern windshield wiper antifreeze froze up, even though it was rated to -20 C. I had to park the car in a heated garage for a day to get it to work again.

If you like, you're welcome to come try a winter up north. You can do what I did once. I'll take you to the junkyard at -30 celcius. You can lay on your back on the cold ground, and pull out a power steering rack. BTW, many of the operations require bare hands, because many things you can't do through your gloves or mitts!

So unless you have spent a cold winter as I've described, you're just a cold weather virgin, with no experience yet. :)

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On Feb 19, 12:03 am, condor snipped-for-privacy@yahoo.com wrote:

Hey buddy, air contracts when cold, wake up thats why tires loose pressure,

Block heaters can not boil antifreeze they dont have the power, design or need to, Oil doesnt melt because it doesnt actualy freeze it just gets thicker and thicker as it gets colder, if your oil is that thick when cold you should have been using a 0w 30 or 5-30 Synthetic because you get Zero lubrication if its to thick and the motor starves and bypasses the filter. And thickness increases as it get colder even at +30 f some regular oils are very thick

Aluminum contracts when cold so does steel, and crappy aluminum rims leak, its not an aluminum issue.

My belts dont get wobbly and loose at -25 to -30f nododys here do, and you the first kook to post so much nonsence.

If your gas freezes its crappy gas, as all might be, but Alcohol added cures that nicely, Denatured by the gallon for about 15$ [ im on my second gallon] works great as does that stuff every gas station carries even where it never gets below 10f in the US, its called simply Gas Line Antifreeze

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condor snipped-for-privacy@yahoo.com wrote in

~scdiroff/lds/ThermalPhysics/ThermalExpansio

Heated HOW HOT? Was the "heat gun" the sort used for paint stripping? This makes all the difference in the world. If you use a heat source that heats a substance so that it changes its molecular or polymeric structure, then of course you can get corresponding dimensional changes.

Styrofoam shrinks like crazy when thrown into a fire, but that tells you nothing about how it behaves between -40F and +70F, when it undergoes no permanent structural changes.

The poster on that forum has not specified what kind of rubber, natural or synthetic. This is of critical importance. Chances are that he's referring to natural rubber.

The two categories of "rubber" are NOT equivalent, and there are different kinds of "rubber" within each category..

Automotive V-belts are not made of natural rubber, but of synthetic rubber. Synthetic rubbers have vastly different properties from natural rubber, and in fact were developed in order to correct some serious deficiencies in natural rubber.

In addition to all this, V-belts have a fabric carcass; they do not stretch, but they do suffer from SURFACE WEAR and GLAZE, which causes them to loosen and slip over time.

This experiment involves FRICTIONAL heating imparted by stretching the rubber band by hand, a different principle from the application of an outside heat suorce.

--
Tegger


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On 02/18/2010 10:03 PM, condor snipped-for-privacy@yahoo.com wrote:

that's spelled "f-a-h-r-e-n-h-e-i-t". htf can you make sense of science experiments if you can't even spel?

http://www.fas.harvard.edu/~scdiroff/lds/ThermalPhysics/ThermalExpansion/ThermalExpansion.html

that's spelled "t-a-u-t". "taught" is something you clearly never were.

for the rest of the class, note carefully - the rubber is "held taut"

rubber that is "held taut" does indeed contract when heated - elongated rubber molecules acquire more energy to bunch up and contract. but relaxed rubber, given that its molecules are already bunched up, does not contract when heated - it's back to positive temperature coefficient.

http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

tire rubber is mostly relaxed, not elongated.

note again, "stretched when cold". as in, "held taut". relaxed rubber does not do this. fiber reinforced rubber [like tires and accessory belts] does not do this either.

yeah - "ford" was one of them.

so, of course, it hadn't worn in the intervening months. no siree!

wow dude, you're really grasping at straws there. yes, air pressure goes down with temperature, but the tire elastomers are reinforced with steel and polyester/nylon [etc] fibers. the fibers dominate the physical dimensions. they have positive temperature coefficients [at normal operation temperatures], not negative.

i think the air in /your/ tires was being heated by more than the summer sun...

dude, please, will you stop?

so use synthetics - it's what they were invented for.

my definition of "no experience" is some dude posting a bunch of crap on usenet about physical properties when they can't even spell the stuff, let alone bother to understand the actual science.

--
nomina rutrum rutrum

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