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Light Engines: to use thermal grease or not?

tylerdurden

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Is there a consensus on whether using thermal grease on the threads of the light engine is of enough benefit to outweigh the mess and inconvienence it causes when transferring the LE from one head to another?
 

ErickThakrar

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I would use something even if it only was silicone grease. Even the silicone grease should aid in thermal transfer. I would stay away from something like Arctic Silver though. That stuff is messy as all hell. Ceramique or the Nanotherm compounds should be fine.
 

Haesslich

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Say, how little Ceramique should be used for the thermal transfer part? I've handled thermal compounds for CPUs, where a little goes a long way, but I'm wondering how to handle it here... and also how to get the LE out of the head when the time comes. /ubbthreads/images/graemlins/grin.gif Suggestions on that end? I have a pair of needlenose pliers that should be up to the task, but any suggestions on technique?
 

tylerdurden

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I just use a very tiny bit, as little as possible to go all the way around the threads on the inside of the head. I generally squeeze a little dab on the end of a toothpick, then spread it on the threads all the way deep inside the head, then repeat as needed to go all the way around. Next time I do this, I'll take pictures so you can get an idea of how much I use (it's really not very much).
 

Haesslich

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Just a dot or two, then? Any suggestions on how to get the bugger out of the head afterwards, to make sure I don't damage anything important? I've heard Ceramique does 'set' quite well, so that's my main concern. However, it IS less runny than AS 3 or 5, so that's a big bonus. Ditto the non-conductivity.
 

tylerdurden

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I've found that a good pair of needlenose pliers is enough to grab the light engine by the bottom of the ecan lip. Even with the ceramique, it doesn't take much torque to get the LE out.
 

Haesslich

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Looks like this 8" will be overkill, then. Light twist, then just keep turning till it's loose? A bit of isopropyl alcohol on the threads afterwards to clean off any remaining ceramique before doing the same for the head and switching to a new one?
 

tylerdurden

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Yep, I think it will be best to use new thermal paste each time a LE is removed from a head and re-installed in another. Just wipe the threads (both in the head and on the LE) with an alcohol-soaked cotton bud.

It should not take much force at all to unscrew the light engine. If you use just a bit of ceramique, even after it dries it won't be any trouble to loosen it.
 

Haesslich

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I don't think I'd want to REUSE Ceramique, given that it's the way it settles to fill in all the gaps to transmit heat that make it so effective. /ubbthreads/images/graemlins/grin.gif As long as I keep the heads and the threads clean with a cotton-swab or rag dipped in alcohol between switches, and apply a little with a toothpick in between the threads, I should be okay, then?

Either way, I've got needlenose pliers ready for the job... and hopefully Canada Post'll have the package in tomorrow so I can test it out after work. Aleph 3 head first, I think... or I could just test out the Aleph 2. Decisions, decisions....
 

tylerdurden

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I think you'll be fine. Of course, I started this thread to answer a similar question.

I wouldn't be surprised if Luxeon-III light engine did just fine without any grease or gunk at all, at least for relatively short runtimes (five minutes or less). I don't think I'd want to try any five-watt light engines without some thermal gunk, though.
 

Haesslich

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As long as the alcohol doesn't damage the inner reflective surfaces, I'll be content. The grease is mostly there, IMO, just as insurance - why take chances with it?

With a larger body and head (Aleph 3, 2x123 or Balrog BE4), I probably wouldn't worry TOO much about the heat, as long as the light was reasonably used and gunked to allow transfer into that nicely massive body. /ubbthreads/images/graemlins/grin.gif
 

ErickThakrar

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I just thought of something when it comes to Arctic Alumina. This may not mean anything at all when it comes to surfaces that are in stationary contact like heatsinks and such, but when it comes to threading you're dealing with a different animal. Arctic Alumina has a large percentage of aluminum oxide in it. Which as you probably know is an abrasive. Using this stuff on a light engine that sees frequent removal may cause premature wear on the threads. I don't know for sure how much if any effect the AA will have, but I think it's a valid enough concern that I felt I should give everybody a headsup.
I kinda feel bad for suggesting the Ceramique in the first place /ubbthreads/images/graemlins/frown.gif
 
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