heat and electric motors.
01-01-2006, 05:37 PM
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heat and electric motors.
i thought i would post this here as it is very informative!
Posted by Steve Shepperd.
"Gentlemen : I have conducted a test to determine the difference in the temperatures of two identical electric motors, one blackened, and the other one plain, shiny metal.
Under the supervision of the physics professor at the University of Hawaii, Hilo, I strapped a brand-new Bladerunner helicopter to the work surface, and ran the motors at WOT for 5 minutes. At the beginning of the test, the ambient room temperature, and the motor cans were at 70*F.Before each test, I charged the battery to 4.2V., to ensure equal voltage and current to each motor. One motor had the surface scratched up (to increase surface area), and blackened. with a sharpie pen. The other motor was plain, shiny, as it came from the factory. A Fluke pyrometer was used, fitted with a contact thermocouple. After running for 5 minutes, the black motor can was at 90*F., and the plain one was at 120*F. The motors were measured at 4 different places and the readings averaged out. This test was run three more times, in order to eliminate possible variables. Total variation between tests was <2*F.
A second series of tests was done, but the plain motor was blackened with gun blue. (blue, actually, but black to the eye.) this time the blued motor registered 85*F. This difference in temps is not insignificant, in these tiny motors.
Here are a couple of websites to test your knowledge of thermodynamics.
http://www.savenrg.com/efactorfacts.htm
http://www.eng.auburn.edu/~wfgale/u...on1_4_page2.htm
http://www.eng.auburn.edu/~wfgale/u...on1_4_page3.htm
http://sol.sci.uop.edu/~jfalward/he...attransfer.html
http://www.efunda.com/formulae/heat...n/blackbody.cfm
http://www.eng.fsu.edu/~alvi/EML430...xperiment_1.htm
I hope these lessons in physics will quell all the nay-saying being vented here by persons who have no education in physical sciences.
Note : You cannot use just any ordinary paint to achieve positive results. Most paints are a thermal blocker - automobile radiators are coated with a special heat-transferring paint.
Air-cooled aircraft engines have black cylinder fins, as do Volkswagen engine cylinders. Some heat sinks on the market are anodized in exotic colors, just because beight colors sell better than black onexs. Heat-radiating surfaces that are not blackened at the factory rely on mass, rather than radiation to get the heat away from the combustion chambers.
If you need more information about how black surfaces radiate heat better than shiny metal surfaces do, I am ready and willing to present you with a plethora of info.
Lastly, I have been exhorting Bladerunner folks to blacken their motors, and those who have tried it and reported back have UNANIMOUSLY reported good results - cooler
motors and much longer flight times and motor and battery life.
Let this be the final word on this subject ! Those of you who know nothing are confusing the minds of those who know even less!"
Posted by Steve Shepperd.
"Gentlemen : I have conducted a test to determine the difference in the temperatures of two identical electric motors, one blackened, and the other one plain, shiny metal.
Under the supervision of the physics professor at the University of Hawaii, Hilo, I strapped a brand-new Bladerunner helicopter to the work surface, and ran the motors at WOT for 5 minutes. At the beginning of the test, the ambient room temperature, and the motor cans were at 70*F.Before each test, I charged the battery to 4.2V., to ensure equal voltage and current to each motor. One motor had the surface scratched up (to increase surface area), and blackened. with a sharpie pen. The other motor was plain, shiny, as it came from the factory. A Fluke pyrometer was used, fitted with a contact thermocouple. After running for 5 minutes, the black motor can was at 90*F., and the plain one was at 120*F. The motors were measured at 4 different places and the readings averaged out. This test was run three more times, in order to eliminate possible variables. Total variation between tests was <2*F.
A second series of tests was done, but the plain motor was blackened with gun blue. (blue, actually, but black to the eye.) this time the blued motor registered 85*F. This difference in temps is not insignificant, in these tiny motors.
Here are a couple of websites to test your knowledge of thermodynamics.
http://www.savenrg.com/efactorfacts.htm
http://www.eng.auburn.edu/~wfgale/u...on1_4_page2.htm
http://www.eng.auburn.edu/~wfgale/u...on1_4_page3.htm
http://sol.sci.uop.edu/~jfalward/he...attransfer.html
http://www.efunda.com/formulae/heat...n/blackbody.cfm
http://www.eng.fsu.edu/~alvi/EML430...xperiment_1.htm
I hope these lessons in physics will quell all the nay-saying being vented here by persons who have no education in physical sciences.
Note : You cannot use just any ordinary paint to achieve positive results. Most paints are a thermal blocker - automobile radiators are coated with a special heat-transferring paint.
Air-cooled aircraft engines have black cylinder fins, as do Volkswagen engine cylinders. Some heat sinks on the market are anodized in exotic colors, just because beight colors sell better than black onexs. Heat-radiating surfaces that are not blackened at the factory rely on mass, rather than radiation to get the heat away from the combustion chambers.
If you need more information about how black surfaces radiate heat better than shiny metal surfaces do, I am ready and willing to present you with a plethora of info.
Lastly, I have been exhorting Bladerunner folks to blacken their motors, and those who have tried it and reported back have UNANIMOUSLY reported good results - cooler
motors and much longer flight times and motor and battery life.
Let this be the final word on this subject ! Those of you who know nothing are confusing the minds of those who know even less!"
