Question: Temp reached by black anodized aluminum in direct sun

I am working on product that is comprised of aluminum sleeves affixed to carbon fiber tubes with structural adhesives. We have tensile tests that show we have more than
enough strength for normal use. However, I am looking at the 200 degree service limit for the adhesive and wondering just how hot this part might get say, sitting in the sun out in Phoenix in the middle of summer..... It's winter here in Calif. so hard to collect data. I might ship some parts off to a friend in OZ to collect data as it's summer there. But thought I'd ask if anyone here might have done any testing of this nature and know.
I have approx 3/4"dia by 2" long aluminum, bonded to 1/2" carbon fiber. This resides near an engine, so worst case would likely be a hard run through the desert, then being parked with this part in direct sunlight while taking in heat from the engine.
Once I have an good idea what temps we might see, I can specify in the next tensile test that the parts be heated to this temp before being pulled.
Thanks,
Jon
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On Sat, 19 Jan 2008 09:03:46 -0800, Jon Anderson wrote:

200F or 200C? One inch away from the engine or one foot?
My gut feel is that if it is more than four inches away from the top end of the engine, or more than 10 inches away from the exhaust it'll get "ouch" hot but not "sizzle" hot. For most people, "ouch" hot is about 50C (so about 120F). "Sizzle" hot can be taken as a bit above boiling, or 110C (230F) (I wonder just what "sizzle" hot really is...).
If the critical temperature is 200F you should probably stop now -- it'll fail often enough in service to make you look bad, even if it usually works fine. If the critical temperature is 200C, you're probably fine -- but I'm not a mechanical engineer, so don't go quoting _me_ on that!
--
Tim Wescott
Control systems and communications consulting
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May I assume the aluminum sleeve is part of the mounting system. If so, will it move the heat to a cooler piece of metal, or will it conduct heat from something toward the carbon tube?
Since you mentioned desert, how does your adhesive and carbon tubes react to UV? That is are real problem in the high desert.
Paul
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Tim Wescott wrote:

If this is on an air-cooled engine, they spew an amazing volume of air at 400 F or so, and will likely fill the enclosure with that hot air, unless it is carefully rigged for the engine to suck air from the enclosure and direct it outside with little leakage back to the interior. The exhaust is WAY hotter, and the radiation from exhaust pipes carrying 1500 F exhaust is really strong.
Jon
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When I was testing materials for my solar collector I saw 190F on some samples.
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Anodized aluminum has a good IR emissivity, and black anodize has a good visible absorptivity. So you are balancing two high values. Thus the resulting temperature is hard to calculate- you must have exact values of solar reflectance and IR emissivity. Slight changes to value of either has a big impact on radiant temperature.
That being said, the radiant temperature will only be really important in a vacuum. With a material like that, conduction and especially convection will be the dominant drivers on equillibrium value of temperature.
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Jon Anderson wrote:

Phoenix??!!!!! Summer!!! Black metal sitting in the SUNNNN??
I think you are in trouble. I can't absolutely guarantee a flash to steam, but if I took a black aluminum plate and set it on my driveway on a hot summer day in St. Louis, I think I could get close to sizzle.
If your adhesive BEGAN to lose strength at 200 F, You might have a chance. If it must NEVER exceed 200 F, I'd say you're sunk. No WAY can you guarantee it will hold (whatever) together under these conditions.

There are outfits that can supply "sun simulators" for this kind of testing. You can probably set up a couple 1000 W mercury vapor lamps at the right distance and do it yourself. There ought to be some kind of reference to this on the net.

What? You are throwing in heat from an IC engine, too? Hell, the exhaust can get to maybe 1500 F!
Jon
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Bit more data. Temps are all F. Part is near base of cylinders on V-twin motorcycles, in air stream, nowhere near exhaust. My partner has had one on his bike for year, but various things kept him from riding anywhere near as much as he wanted. However he did get one good freeway run in and gave the aluminum the bare hand check, was easily able to hold his hand on the part though it was hot.
UV should not be a huge problem, only a very small portion of the glue joint is exposed.
We're going to build a test rig and see just what's the worst tensile load we can foresee the most ham fisted pissed off drunken yahoo applying.
I think I will just go ahead and ship some parts out to my friend in Oz and let him collect some temp data from solar radiation. I'll fab a fixture to hold the part a ways from a decent scrap of aluminum to account at least partially for heat coming off the engine.
Does anyone know of a source for temp recording strips? That would be easiest. I know I looked for something like this a year or so ago, never really found what I was looking for.
I'm referring to the ones that change color based on temp, and they don't change back when cooled.
We might be just worrying about nothing, but without the ultimate tensile load and temp data, we just don't know. I am 90% certain we don't have a problem, but don't want to hang the reputation of a new company and product on that 10%....
Jon
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I used to live in Tucson and took these measurements some years ago. I know it's not black anodized aluminum but it is some quantified data. All measurements were made on surfaces in full sun except where noted. A thermocouple was placed on the surface and covered with a 12x12x1" piece of styrofoam. The measurement was recorded when the reading stabilized. The grass was watered the previous evening. Art
Tucson temperatures 25July96 2PM Air 109F Tap Water (cold) 80F Grass 106F Grass, full shade 82F Swimming pool cool deck 125F Concrete sidewalk, light grey 163F Dirt, bare (light tan color) 158F Roof, flat (silver paint) 145F Asphalt, medium grey color (seal coated) 176F
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Artemus wrote:

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cavelamb,

No kidding! I grew up in the SF bay area, about 2 miles from the bay. 90F was considered hot. Visited relatives in Phoenix in the late 70's, and saw temps over 110. I know one can acclimate to such temps, but that doesn't happen over the course of a one week stay. Made the mistake of tubing down the Verde river to cool off and was rewarded with half dollar size blisters all over my legs. Worst sunburn I've ever had. Thank God drinking age was 18 out there, at least I could anesthetize myself....
Jon
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Artemus,
Thank you for the data. Doesn't help directly, but sure supports 200F as probably well within reach.
I finally found the stick on temp recording strips I knew were out there. Two different strips will cover 171F to 360F, and that ought to cover us. Soon as they arrive, I'm shipping some black and polished aluminum to my friend in Oz. Nice thing about these strips is they record max temp reached and do reset. So my friend can just leave them out in direct sun for a week, and tell me what he got. We can also stick them to test samples on a bike and know we are getting a valid peak reading, and don't have to worry about wires or anything coming loose.
Source I found for these is: <http://www.tiptemp.com/ProductList.aspx?CategoryID 3>
Jon
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On Sat, 19 Jan 2008 21:57:47 -0800, Jon Anderson wrote:

If you have one mounted on a bike you should be able to go ride the thing hard, then park it in the shade for a bit and measure the temperature of the part, and the air temperature. What you want to get is the temperature rise above ambient.
Then get your data from your friend in Oz, and make sure he gets some idea of the air temperature there, too.
Then take the two temperature rise numbers, add them, and add them to the 110F (or more?) air temperature that you expect in Phoenix. That should be pretty close to what you'll see in real life, but I'd add another 20% to 40% rise to be on the safe side.
--
Tim Wescott
Control systems and communications consulting
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On Sat, 19 Jan 2008 21:57:47 -0800, Jon Anderson

temp indicators: http://www.mcmaster.com/nav/enter.asp?pagenumT5 if your source can't do small quanities, Mcm can.
Worst case test for your part would be city traffic or parked running bike. I.E. no air flow. Get bike good and hot with hard ride then park bike with sun hitting the side of the running bike that has your part and let idle for 30 minutes.
That should be a good test, add in a run through death valley for good measure.
YMMV
Thank You, Randy
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the black tinted rear window of my vette will get hot enough that it can't be touched with bare skin in the summer. i have to wear an oven mitt to close it. i'd say it would be at least 150F.
regards, charlie cave creek, az
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On Mon, 21 Jan 2008 12:54:34 -0700, with neither quill nor qualm,

When I attended UTI in Phoenix in '72, I came out to go to school one fine December morning. It was 17 degrees. When I came out at noon to go to lunch, I couldn't touch my white Ford Ranch Wagon. It was 110F in the shade. That's the desert for ya: one helluva range in weather in one day.
-- You cannot depend on your eyes when your imagination is out of focus. -- Mark Twain
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Jon Anderson wrote:

Yup, heat soak after the bike is shut off may be the worst.

Tempil makes the Tempi-label. I think you can get small quantities of a similar device through Omega, the place for all things temperature-related, called the Omegalabel. You probably want the non-reversible ones that permanently show the highest temp reached. See www.omega.com
Jon
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As I recall, sunlight is around 1000 watts per square meter. Add that heat load to your ambient minus any heat conduction.
But I'd expect that your worst enemy will be heat cookoff after you shut it down, park it in a confined or otherwise no air flow situation. I think you will be up near your 200F limit on a regular basis.
You could probably get a good feel for the temp rise by doing a hot run, stick a thermocouple lead on the part, see what kind of temp cycle you get. Add that temp to the ambient, make the assumption that the temp difference will be the same on a 120 degree day. If you don't have a thermocouple handy, the digital cooking thermometers are pretty accurate, just stick the tip to the part with a lump of clay.
Jon Anderson wrote:

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On Sat, 19 Jan 2008 09:03:46 -0800, Jon Anderson

To make informed comments, we really need to know a bit more... Not-so-Wild Guess: This is carbon-fiber engine shrouding and/or cladding, with the aluminum tubes being the mounting tab points to the engine block and the frame?
You'll have heat conduction from the block, through the tube, through the glue, to the carbon fiber. This can be blocked to a degree with plastic or ceramic washers or some other sort of heat break at the mounting bolt. And there will only be a few "hot" mount points to worry about, most can be "cold" in comparison.
You'll have radiant heat from the engine. And especially from the upper cylinders and heads and the exhaust headers - this can be significant, but you can wrap the exhaust in ceramic compounds to hold the heat in the gases.
But you'll also have significant convection cooling helping after shutdown, especially if you plan for clear vertical airflow paths. It won't be blistering hot with no airflow for too long.
One thought: I wouldn't count on adhesive alone to hold the CF tube to the AL tube. Drill at the join and put a pin or screw, or some other mechanical connection to provide positive backup for those short periods where the glue gets hot enough to soften.
--<< Bruce >>--
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Bruce L. Bergman wrote:

Not quite ready to discuss exact details. But it's not shrouding and does not bolt to the engine. It's out in free air flow while riding, but is near the crank case. While a few true customs sometimes have exhaust on the left side of a Harley engine, that's pretty rare. This mounts on the opposite side so exhaust is not an issue.
It's the combination of radiant heat from the engine and absorbed heat from direct sun that I am looking to account for. The first test unit has been in use for a year, and several times during 100 degree heat. It was just checked by grabbing, after a decent highway run, and was not hot enough that it couldn't be held. But we didn't account for it sitting in direct hot sun while soaking up heat from the engine.
We are 90% confident we're OK, just looking to verify. And switch adhesives if we have to. We've now located adhesives good to over 400F which most certainly is overkill, but at least in the worst case, we have that option.
Nothing quite like this exists at present, since we're starting small we are a bit secretive about the specifics. There are accessory manufacturers that have national or global distribution that could beat us to market if they knew what we had and thought it could sell. If we are successful we know we will be copied, we just want to make sure WE get credit for being the first to market.
Jon
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