CNC housing with angled fins- Mtbr.com
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  1. #1
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    CNC housing with angled fins

    I think that there is a possibility to improve the thermal performance of CNC housings by using angled fins.

    Here is a quick example for 4 MC-E


    In my opinion the angle of the fins will increase the air turbulence and thus increase the heat transfer.

    Any suggestions on this idea?

  2. #2
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    Looks like a good idea to me. If it was done right, you'd be able to use the un-finned section to mount the switch?

  3. #3
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    I plan a separate compartment for the driver (hipflex), switches, cable glands.
    This is a rear view of another prototype:

  4. #4
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    Great idea. It strikes me that angling the fins might also increase surface area too?

  5. #5
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    Quote Originally Posted by zendlodj
    Great idea. It strikes me that angling the fins might also increase surface area too?
    Good find! But only for the top and bottom parts of the housing. The rear is a more difficult section.

  6. #6
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    interesting concept.....i like the angled fins
    extra cooling if the fins are taller too
    4 x MC-E it`s the only way to go!
    ...Scun.thorpe, UK

  7. #7
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    Quote Originally Posted by HEY HEY ITS HENDO
    interesting concept.....i like the angled fins
    extra cooling if the fins are taller too
    4 x MC-E it`s the only way to go!
    Come on guys 4 mce has been done already do some thing rad and go for 6 mce

    or should I do a monster Trout light and upscale the xpe housing to fit 6 mce and square optics no that is crazy .

    though my brother wants something like that for a chopper he is building

  8. #8
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    Quote Originally Posted by troutie-mtb

    though my brother wants something like that for a chopper he is building
    A chopper with SIX MC-Es?? Now that's something I'd like to see!

  9. #9
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    It would probably increase the air turbulence but not the surface area. Granted some fins would be longer but others will be shorter.

    Is it worth it? I doubt it...
    Last edited by Calina; 04-23-2009 at 01:54 PM.
    When you think that life is though, keep a positive attitude : remember that it is short ;-)

  10. #10
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    I would think you want less turbulence and more airflow for max cooling. that's just my guess though.

  11. #11

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    Turbulence is bad. You want clean airflow over the surfaces. having turbulence and vortex type airflow would create more "stale" air. There is a reason why all heat sinks are designed like they are

    Even if it DID make a small increase in cooling you would not notice a difference in this application. Consider the additional machining steps as well. Not worth the time to get nothing back.

  12. #12
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    Quote Originally Posted by ash240
    Turbulence is bad. You want clean airflow over the surfaces. having turbulence and vortex type airflow would create more "stale" air. There is a reason why all heat sinks are designed like they are

    Even if it DID make a small increase in cooling you would not notice a difference in this application. Consider the additional machining steps as well. Not worth the time to get nothing back.
    Turbulence should destroy the laminar layer on the fins.
    Most efficient CPU heatsinks have bumps or cuts to break the laminar airflow.

    Heatsinks have straight edges because they are manufactured by extrusion, not CNC machining and extrusions can have only straight fins.

    I have asked a CNC machinist and he said that straight or angled fins made no difference for him. In general I agree that the efficiency gain can be small but I wish someone could make a CFD simulation of this design.

  13. #13
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    in most instances when riding the bike there is enough airflow to cool even the poorest designed light so fins of any kind will aid that cooling . the problem is then when you stop and the light is not getting any airflow so vertical fins on the back of the leds would be ideal for convection cooling , but this hampers the light design as the back is the ideal place for the driver and controls .

    We are not into formula 1 racing here and fins in any direction will be better than no fins

    the chevron style fins could look pretty cool and as the cnc machine does not care then we could even have wavey curly fins then it comes down to asthetics .

    but as most of us are not blessed with cnc acess then straight fins are our weapon of choice. or radial fins on the round housings


    keep up the inovating

  14. #14
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    Quote Originally Posted by troutie-mtb
    in most instances when riding the bike there is enough airflow to cool even the poorest designed light so fins of any kind will aid that cooling . the problem is then when you stop and the light is not getting any airflow so vertical fins on the back of the leds would be ideal for convection cooling , but this hampers the light design as the back is the ideal place for the driver and controls.
    keep up the inovating

    +1... Amen Troute!

  15. #15

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    Quote Originally Posted by zemike
    Turbulence should destroy the laminar layer on the fins.
    Most efficient CPU heatsinks have bumps or cuts to break the laminar airflow.

    Heatsinks have straight edges because they are manufactured by extrusion, not CNC machining and extrusions can have only straight fins.
    Turbulence is bad. It interrupts the air flow and causes "stale" air and hot spots. Even high end copper machined or "spot" welded heat sinks are designed as normal ones are.
    It would be quite possible to cast heat sinks in the designs you want for quite low costs IF there was a point. If you have any factual basis for making fins like you want to, in particular that there is ANY real world increase in thermal efficiency I would love to see it.
    There is no issue with you wanting to bling something up or do it for looks but there is no real gain from this. It's a waste of time and $$

  16. #16
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    Technically, Zemike is correct. Turbulent flow is considerably better for heat transfer than laminar flow. There is lots of documentation on this, grab any fluids or thermodynamics textbook and it's covered in detail. <a href="http://www.aavidthermalloy.com/technical/papers/augmentation.shtml">Here</a> is a good article that discusses turbulent vs. laminar flow and how increased turbulence can improve the performance of finned heatsinks.

  17. #17
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    Well if you're going to all this trouble, I say dash the whole thing and go straight to liquid cooling. Just wear a second camelbak as a reservoir, stick in a little high volume pump, problem solved. And in the winter you could make cocoa in it. Man I'm awesome
    Haha but yeah. One thing I've wondered is why nobody uses fans. I've got some little guys that are 40x40x10mm from old computer parts, and they're about silent. It seems like if you had one somehow on the inside blowing straight on the driver/optics it would keep things nice and chilly.

  18. #18
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    Quote Originally Posted by CheeseSoda
    One thing I've wondered is why nobody uses fans.
    I think nobody uses fans because:
    1) they need a separate 12V supply
    2) they are mechanical and can fail (dirt, mud, water)

    I have googled for efficient heatsinks and looks like for forced cooling the most efficient are "staggered bonded fins"



    Thanks to StevelKnivel i have found this interesting document:
    https://www.embeddedtechnology.com/a...nk-Design-0001

    It shows that at low air speeds (200 ft/min - 4 kmh) the difference is negligible, but at high speed (1200 ft/min - 24 kmh) the difference is 40%

  19. #19
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    Quote Originally Posted by zemike
    It shows that at low air speeds (200 ft/min - 4 kmh) the difference is negligible, but at high speed (1200 ft/min - 24 kmh) the difference is 40%
    But the problem is opposite: you need better cooling in still air.

  20. #20
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    Quote Originally Posted by Itess
    But the problem is opposite: you need better cooling in still air.
    Partially right, but I suppose that the hipflex can handle this problem.

    My design goal is to make as lightest housing as possible.

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