Odd Theory, Paint Color and Vehicle Heat

[BJoeHandley]

Has anybody else here ever noticed or even played around with this theory? I noticed it some on my electrics a couple of years ago that darker paint will affect how hot an ESC/battery/motor will get while running. You guys think there might be a decent magazine tech article in this too?

[Cotharyus]

I somehow doubt it. I know on a 1:1 that you leave sitting in the sun it will affect your interior temps, but with air moving through an R/C constantly (well, ok, it moves through my R/C's constantly) while they're in the sun, it really shouldn't make enough difference to be worth talking about.

[Fluke]

it might affect you if you're running a closed body like a buggy.

[BJoeHandley]

That's where I've run into the issue, usually with a black paint job and on a hot day. I've actually had the polar Drive kick in on the Novak Fusion I was using on my elcectric 4-Tec while running a 12t speedgem (the Fusion's limit is 12t/6 cell or 13t/7 cell), and have gotten a Traxxas XL-1 extremely hot

[rocknbil]

I worked in the printing industry for 12 years or so as a scanner operator, have a BFA in Art in which I studied color theory very deeply, and know more than I EVER want to know about the theories of how color works and does not. :D Here's my input.

First off - the color of the coatings on various parts is **not** going to significantly change the speed at which it cools. There have been claims that black engine heads disperse heat faster - this is likely to be false for the reasons that follow, and even if there **were** some change in how the heat disperses, it would not be enough to be significant.

Color, or our interpretation of it, is a reaction of light reflecting (or not reflecting) off a surface. Since the amount of light reflecting off a surface hasn't a single thing to do with how fast a material disperses heat, it's rediculous to think a black anodized head will disperse heat faster than a white or silver one.

Even if it were, black would INCREASE the temperature, and here is why.

No one, and this means NO ONE, knows how we interpret color. The most believed THEORY is that of reflected light and light absorption, as demonstrated by examining color temperatures throughout the spectrum.

When a white light hits a surface, the pigment absorbs all of the wavelengths (i.e., colors) of the visible (and invisible) spectrum and reflects back the wavelengths you see. So for a green, it's abosorbing red, blue, yellow, some UV - but reflecting back only the wavelength of light we interpret as green. This leads to the statement you always hear in reference to color theory - "every color is there except what you see." That's not really **it,** but it's close enough to it. :D

So now we get to why black objects get hot. Black is the complete absence of the ability to reflect light. The closest reflective benchmark that science has come up with for a reflective black point is a pure graphite box into which they shoot a white light: zero reflectivity.

Since black cannot reflect light, it absorbs all of the wavelengths in the spectrum. Light is energy; the energy stimulates electrons, stimulated electrons generate heat. This is why your black objects get hotter than white ones: white reflects nearly all the wavelengths in the spectrum in equal proportions.

So. If you have a black engine head or cooling heat sink, if it's exposed to any light at all, it would only stand to reason that if anything, it's temperature could only increase. But in the context of a 100 degree ESC cooling heat sink or 220 degree engine head, it's not enough to make a real difference.

In the case of your black body, yeah, it's going to drive your temp up, but if the color of your body has significantly added enough heat to push your electronics over the top, you were probably running at the threshold anyway.

[LEMMEDRIVEIT!!]

Wow. You really know what your talking about lol.

What I was gonna say is that if you ever notice when you go to the beach, or out in the sun on a really hot day, if you wear a black or very dark T-Shirt, you die of heat. Now if you wear a white T-Shirt, the heat is a little more bearable. Its not that much of a difference, but its still there.

[trw]

i would imagine though since T-shirts are made of some sort of fabric and not metal, that would make quite a difference such results.

[rocknbil]

lemmedriveit - it actually makes a **big** difference when you're talking about body heat. Note how desert-dwelling societies have turbans, capes, and other clothing that's almost always a light or white color to repel heat absorption. Your second best tool for survival in the desert - a white hat. :D

[G10products]

We did an experiment on this in physics last year, its been awhile but darkness DOES make a difference.
I will ask my physics teacher tommorow to double check, but black cools faster. Since as mentioned above, black is good at storing enegry from light, it is also the best at dispersing heat. It is a better "conductor", if you see what I mean. Black heats faster and cools faster, white takes longer to heat but stays hot longer.

You can take two coke cans, paint one black and one white, fill them with an equal amounts of the same temperature water and put them and equal amout of distance away from a heat source, watch the temps and see what happens.

[BJoeHandley]

Some of my experiences tend to agree with what G10 just said. I bought my first car, an all black '85 Lebaron GTS hatchback (also had alot of windows too!), just before the Heatwave of '95 that killed a large number of elderly here in the Chicago area. I was working for a local drug store at the time and of course the car was always hot during the day, but when I'd go to leave the store at midnight (I was 18 at the time and working any extra hours to pay for the insurance on the car, they figured out it was a factory turbo car) the car was actually cooler inside that Lebaron than ambient air temp, which was still pretty hot for being midnight. Not too long before I actually had the original overheating issues with my Fusion (maybe a year or two), I had read in a Mopar magazine that one of the teams that ran a factory sponsored Dodge Ram in the NASCAR Craftsman Truck series had asked Chrysler for permission to flip the trucks color scheme from Black/White to White/Black to help reduce running temps of their race engines. I also mentioned this to my father last night before I put up this thread. he told me that his first car, a '50 Plymouth Business Coupe, had the flathead I-6 that was painted silver from the factory had a tendancy to run hot, so he stripped the silver paint off of the engine and repainted the block black and it made a suprising difference in how hot the flathead ran, no matter if was sitting with the engine running, or on the move. Now in this case I will say, he was living in rural Iowa in the 50's and 60's, not suburban Chicago here in the late 90's and now 21st century, that motor would not have liked the kind of traffic we've had to deal with. I also seem to remember in a 1/1 car magazine there was a discusion about this and somebody mentioned that the reason radiators are painted black and large coffee machines are polished stainless or aluminum is the same as the experiment G10 did in physics class was ment to teach. The black will tend to pull heat out of the radiator/coolant cooling the engine, while the polished finish will tend to retain the heat in the coffee machine keeping the coffee hot till somebody is ready to drink it. Can't wait to hear what you old Physics teacher has to say about this G10, I think it might be a bit of a suprise. I just might paint my next engine for my Nitro 4-Tec (I've got both types of 4-Tecs, so no you haven't misread anything) black, if I don't get the Fantom .18 for it.

[G10products]

It is correct, just watch the paint too thick a layer will do more harm than good.