Critique my Light Design- Mtbr.com
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  1. #1
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    Critique my Light Design

    Greetings oh gurus of the LED light. Newbie here from VA, USA that has been infected with MultiXledluminitis.

    What do you all think of the light I'm considering building?

    It's an 8 XPE run in 4S2P configuration using 1.5" square tubing.



    I'm planning to use an 18V LiIon battery from my cordless Milwaukee impact wrench. It's labeled as 50Wh which I calculate to be 2777mah. The driver is planned to be a 1000ma 3023 buckpuck to keep the wiring simpler. This should yield 500ma through each LED.

    Power connector and switch is still tbd, but not critical to the design.

    I'm guessing somewhere around 900 lumens, but will it be enough surface area to dissipate the heat? I've considered cutting shallow grooves in the body (only 1/8" thick) to increase surface area some.

    The main heat sink is 3/4" thick square of alum that will be an interference fit in the body.

    Any input is appreciated.

    ndrordr

  2. #2
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    It will certainly be bright .
    I am glad you are leaving the middle on out shame you cant have a hole down the middle
    for extra cooling . you may need it ,
    I would say give it a go and if it overheats then you can allways add some fins from memory heatsinks .
    You have a big buffer in there but it needs to be able to shed the heat fast .

  3. #3
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    Thanks for the input Troutie. I was planning to use the center position for the wire pass-through, but I could possibly fit a piece of 1/4" alum tube through the center with a hole in the front cover and rear cover to get some air flow through the center. There's not quite enough room for a 3/8" tube with the buckpuck in there.

  4. #4
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    The light on the left is 1/8 wall with small cuts made in it with a table saw. It does get fairly warm when running.
    The light on the right gets just a little warm.

    The heat sink is T channel available on ebay. The picture is of 1 inch stock JB Welded to the square tube. It does come in 1.5 inch so would work for your design.
    Last edited by odtexas; 02-27-2009 at 08:37 AM.

  5. #5
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    If i understand your graphic correctly - why do you have such a thick piece of metal behind the LEDs? That really is overkill - it could be 1/8" thick and still be plenty. Also, how well that fits into your square tube is critical for heat transfer - it should be a press fit. Your light will be dissipating somewhere around 12-15W on high, which is a lot of a little square tube. Troutie already covered that possible problem, though.

    Good luck

  6. #6
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    The 8x XPE is probably overkill, but none the less I wanted some feedback. Thanks everyone.

    I'm also considering making one (or two) very similar to Odtexas in a 4xXPE R2.

    it would look like this:


    I'm planning to use it when riding my dirtbike (ktm200) for the couple times a year that I need to be out in the woods pre-dawn.

    So here's another question, would it be better from a thermal transfer standpoint to have a thinner heatsink to try to "wick" the heat away from the leds? I always thought that you wanted the leds mounted to something with some thermal mass to keep them from heating rapidly.

  7. #7
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    Thermal mass is a good thing. It also means better contact with the outer housing. The less chance of a thermal bottleneck from LEDs to surface area the better!

  8. #8
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    Quote Originally Posted by ndrordr
    So here's another question, would it be better from a thermal transfer standpoint to have a thinner heatsink to try to "wick" the heat away from the leds? I always thought that you wanted the leds mounted to something with some thermal mass to keep them from heating rapidly.
    From a thermal transfer standpoint (as in trying to get heat into the air) it doesn't make any difference. All it does is make it take longer for the LEDs to get to the same hot. It is generally better thermal design to provide finning to reduce the maximum temperature. However, if you are riding, the air does a ton to keep things cool, and maybe all you need is the thermal mass for when you are stopped (if for only a few minutes).

    Regardless, it'll be super bright, and i'm sure you'll like the results. Just remember that if a housing like that gets too hot to touch after a couple minutes (in still air), that is a good thing. Heat is getting to the outside surface. Just keep riding to keep it cool.

  9. #9
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    ndrordr, I was looking at the way that you are going to fit the back and it got me thinking.

    I hope you don't mind but I've had play with you drawing.

    Fins otional
    Last edited by yetibetty; 03-23-2009 at 10:23 AM.

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