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Old 07-12-2007, 09:28 PM   #1
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Exterior Temperature differences

On our recent trip to Osoyoos two of our group had the temperature guns radiator shops and others use to determine more accurately the temperature of the engine/radiator in comparison to what the gauge indicate. Once we had checked all the various hot rod engines and gauges using both guns we found that in most cases the gauges tended read hotter than the engine and radiator actually were, following the instructions that came with the guns as to where to check for this comparison. Most were at the 10 degree level higher on the gauge and in one case 30 degree difference and these were not cheap gauges. Surprisingly, being the thrifty one of the group (or so I'm told) my elcheapo Wally World gauges were almost dead on.

Now to the really interesting part. After we'd done all the fooling around, and with the sun shining directly on the trailers, we checked the outside temperature of the various trailers. They started with my Flying Cloud as the sun was just blasting off it and there were smirks from the fiberglass crowd as they expected the worst. The temperature that day at 9 AM was 75 degrees and the FC reflection came up at 87 degrees (heh, heh, heh). Next to it was a smaller but round fiberglass trailer painted orange and it was 132 degrees. Next to it a similar trailer but painted white and it rang in at 107 degrees. Ah, life is SWEET!

Next year our buddies will hopefully have their FC done and ditch their fiberglass trailer and we will have two Airstreams to compare to the others. Mine, and his much shinier one (I never, ever, ever should have found the nicer one for him - dang).

We thought it was quite interesting that the unpainted aluminum was cooler than the painted fiberglass trailers by so much. Since those trailers actually have less insulation than the Airstream they were getting pretty hot inside during the daytime and their A/C units were working pretty much full time. We had our new to us 1957 TravelAire Swamp Cooler and it worked like a charm - we were very comfortable. They all hate me now

Barry
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Old 07-12-2007, 10:23 PM   #2
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We use those IR temp sensors at the shop every day. One of the most versatile tools ever invented.
Stuck thermostat, sticking brakes, A/C, seat heaters, funky radiator? Does it all.
Just bought a "cheapy " from the 3M jobber and it’s got more bells and whistles than the $80 one I got from Snap-On a few years ago. Think I’ll bring the "good" one home.
Accuracy seems to depend on how close the gun is to the measured surface. However, we’re more interested in temperature differentials than the actual temp.
Never thought about pointing at the GT. Does IR heat radiate off the aluminum? I would think it does. Yet another esoteric project for the weekend.

Tom.
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Old 07-12-2007, 11:00 PM   #3
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Quote:
Originally Posted by Tom Nugler
Does IR heat radiate off the aluminum? I would think it does. Yet another esoteric project for the weekend.
I think the emissivity of aluminum introduces some real errors in IR themography. If you have an IR sensor with adjustable emissivity, set it at 0.1 for polished aluminum, and 0.3 for dull oxidized aluminum. The setting for painted surfaces is probably 0.9 or higher.
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Old 07-13-2007, 11:31 AM   #4
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Quote:
Originally Posted by markdoane
I think the emissivity of aluminum introduces some real errors in IR themography. If you have an IR sensor with adjustable emissivity, set it at 0.1 for polished aluminum, and 0.3 for dull oxidized aluminum. The setting for painted surfaces is probably 0.9 or higher.
Wow Mark, I never thought about it quite in this way. We were not very scientific about our approach - every one with a coffee in their hand excepting the two with IR testers as we walked from trailer to trailer. If I start using the above mentioned terminology they will start asking my wife who I am and what has she done with Barry. They will think it's the drugs I'm on and I'm back to reading something other than hot rod magazines and Robert Ludlum books. Or even more likely I'll end up taking an unexpected swim in the lake.

Barry
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Old 07-13-2007, 11:41 AM   #5
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Unfortunately the temp of the skin isn't the whole story. From real life I can tell you that my old white SOB reflected a lot more heat than my new Safari did. In a side by side camping situation in extreme full sun heat. My SOB was 10 degrees cooler inside than my Airstream. Same size A/C BTU's. Same length of trailer. The A/C unit on my Safari was pronounced working properly by both the dealer and Jackson Center. Temp drop across the coils was right on specs. Problem was that the aluminum was absorbing more heat than my white SOB was. Lesson learned, new Classic was ordered with a 15K unit. No problems now.

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Old 07-14-2007, 12:26 PM   #6
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Well I won't be sharing any of the above info with the car club guys with their SOB's.

I'm quite frankly enjoying the perception on their part that they have deficient trailers relative to an Airstream and I think if that's the decision they've come to based on the information we all had at the time then they will just have to live with it

Barry
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Old 07-14-2007, 01:28 PM   #7
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Rivet IR Issues

I think the reflective nature of polished aluminum confuses the IR issue, too. I have gotten readings below ambient in certain areas of mine. Obviously out of the question. I feel better about shooting the blue stripes on my Excella.

Agree that the IR thermometers are great tools. Use mine for everything from adjusting my gas grill to ensuring that my beverage is at its preferred temp of 25 degrees.

Vaughan
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Old 07-14-2007, 05:49 PM   #8
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OK, now I simply have to get an IR thermometer. Now that I know they are great for not just the BBQ but as well the even more important drink it has now moved up my required tool list to second spot (behind the dual head orbital polisher and ahead of the 25 ton press and tig welder).

Barry
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Old 07-14-2007, 07:07 PM   #9
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Rivet IR Thermometers

Quote:
Originally Posted by safari57
OK, now I simply have to get an IR thermometer. Now that I know they are great for not just the BBQ but as well the even more important drink it has now moved up my required tool list to second spot (behind the dual head orbital polisher and ahead of the 25 ton press and tig welder).

Barry
Hi Barry,

I bought a Fluke Mini 62 when I post formed the WilsonArt laminate for some new countertops, at least that the excuse I used. Itís $84.35 at meter superstore.com:

http://metersuperstore.com/Merchant2...=AND&Offset=13

You can find some for less, but Fluke is the gold standard of measuring instruments. This is the first Fluke instrument of any kind I have ever seen for under $100. Iíll pay an extra $20 or so for Fluke vs. Chefís Choice, itís a real instrument.

Bad news right now, just returned from store and havenít had time to properly chill my ďantifreeze.Ē I am only able to get my beverage down to 27.

Vaughan
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Old 07-15-2007, 12:42 AM   #10
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Quote:
Originally Posted by vswingfield
Hi Barry,

I bought a Fluke Mini 62 when I post formed the WilsonArt laminate for some new countertops, at least that the excuse I used. Itís $84.35 at meter superstore.com:

Fluke 62 Mini IR Thermometer, -20 To 932 Degrees Fahrenheit: metersuperstore.com

You can find some for less, but Fluke is the gold standard of measuring instruments. This is the first Fluke instrument of any kind I have ever seen for under $100. Iíll pay an extra $20 or so for Fluke vs. Chefís Choice, itís a real instrument.

Bad news right now, just returned from store and havenít had time to properly chill my ďantifreeze.Ē I am only able to get my beverage down to 27.

Vaughan
Thank you Vaughan, this is very helpful. I already have several thoughts on the justifications, I just need to voice them appropriately over breakfast when I overheat my wife's coffee and a few other things I'm thinking about to prove the need.

Barry
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Old 07-15-2007, 06:45 AM   #11
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Vaughn,

Thanks for the tip. The Fluke 62 looks like a great general purpose IR thermometer. I did spot an error in the advert on the metersuperstore description.

Specs: Backlit display for use in dimly lit areas; Adjustable emissivity setting for more accurate measurements. Display Hold: 7 seconds; Laser sighting: Single point, offset; Response time: 500m Sec. Includes: Batteries, plastic storage case or holster, operators guide and user manual. Two-Year Conditional Warranty.

The Model 62 does not have adjustable emissivity. Tthe model 66 does, but it is more expensive.
For 99% of thethings you need an IR sensor for, the fixed setting (.95) works fine. It works great on masonry, shingles, dirt, paint stripes, asphalt, wood, and the planet Jupiter. It just doesn't work well for reflective surfaces.

I don't want to be anal about this, but some previous threads reported results on temperature gain for painted vs polished aluminum. I think the posted results may have misled some readers because the meter wasn't calibrated for the difference in emissivity.

GIGO
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Old 07-15-2007, 08:44 AM   #12
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Quote:
Originally Posted by markdoane

I don't want to be anal about this, but some previous threads reported results on temperature gain for painted vs polished aluminum. I think the posted results may have misled some readers because the meter wasn't calibrated for the difference in emissivity.

GIGO
Shhhh on this part. I wouldn't want any of my buddies to think less of my Airstream, or more about theirs , but thanks for catching that Mark. I'll take another look at the models, but for the sake of staying ahead of the "boys" and their fiberglass trailers probably stick with the original recommendation.

Barry
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Old 07-15-2007, 08:56 AM   #13
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Wink ?

Not sure what I learned here but it's an interesting post. Those guns are good for finding high resistance electrical connections and should be an maintenance item on your list.
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