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Old 12-13-2011, 12:22 PM   #109
JoelWisman
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Joined: Apr 2009
Location: STL, MO, USA
Oddometer: 1,392
Quote:
Originally Posted by JRWooden View Post
Since the oil cools the cover, and the coolant cools the oil, I would hope that whole mess should never exceed 200F?

As a high-side estimate I would guess (hope?) that the side cover never exceeds ~250F / 120C.

There is going to be some radiant heat gain from the exhaust which is going to be hard to estimate.

Maybe someone with an IR temperature gun could shoot a reading on the bottom-side of their stator cover after a good hard ride?
Hi JRWooden. An IR gun isn't going to tell you squat about the surface temperature of the stator cover owing to the subject of emissivity. It also won't tell you squat owing to laws of reflectance.

I know IR guns look neat and have a pleasant number of buttons and big lCD digits that seem all high tech, but they are perhaps the most grossly misused tools on the planet.

IR thermometers are for highly trained professionals and novices that have studied hard to take QUALITATIVE readings of prepared surfaces that can not easily be measured by direct contact. IR thermometers are never for taking QUANTITATE readings unless the instrument costs thousands of dollars and the user has a masters or better in thermodynamics.

In addition to the laser pointer, stun-gun, and torch lighter, IR guns are fun toys, but thats all they are unless you know a hell of a lot about how to use them.

I don't say this to be arrogant, but because I see IR guns cause needless worry when they are continuously misused.


An ir thermometer reads emitted infrared energy in a given portion of the EM spectrum. Cheepo IR guns are not well calibrated and read outside of the bandwidth of heat. In addition, different substances radiate at higher and lower bandwidths at the same temperature. Thickness of a substance also affects the radiated wave length. this is just for starters.

The biggest affect to an IR guns reading is going to be how the surface differs from a black body. Chepo IR guns are usually calibrated loosely and inaccurately to an emissivity of 0.95. This works well with many organic objects but won't be accurate at all for our stator cover surface which is glossy enamel paint usually having an emissivity of around 0.8.

Further, there is reflectance. The surface of our stator is reflective and is going to reflect a lot of IR energy from near by emitters such as the exhaust down tubes.


Back to the subject at hand which is the stator cover temperature. Using an accurate CONTACT probe after a hard ride in a 36 F ambient, the surface of the stator cover was 213 F and varied just 4 degrees in the 8 places I measured it.

Back to the subject of IR guns, using my upper end toy IR gun it varied from 189 to 257 degrees. The IR gun is not wrong. I have little doubt that it is accurately measuring emitted IR, but emitted IR is of no relevance to the question of the stator cover temperature nor most of the other things people use IR guns for.

Heres an accurate surface probe http://www1.mscdirect.com/cgi/NNSRIT...-SearchResults

1/4 the price and reads temperature, not emitted IR :)
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