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Thread: Help: Using copper pipe cap as heat sink

  1. #1

    Help Help: Using copper pipe cap as heat sink

    Since another has opened the door on design input, I also seek counsel.

    (Mad! Completely nuts!, No NOT that sort of counsel, or a lot of us would be in trouble, right?)


    You can skip to the bottom to the issue and refer to the following sections to understand why I am asking, or where I messed up.

    Background on why I want to use copper end caps at all (FYI):
    I would prefer a CNC aluminum head light unit for the minimal number of thermal interfaces and the 'look' but those are beyond my budget at the moment. I also wish to try a unique arrangement of XPG's to double up a usable light and an experimental platform for road beam testing. I want the finished lights to look like a commercial setup and be amenable to redesign later. Lastly, in case one or a few readers wished to follow the same path, I thought at least a limited supply of reasonably priced bits would be good to base these lights on.

    So I decided to try two of EL34's stash of MR11 (not MR16 as listed) bullet Marwi metal halogen light heads, and an array of matching handlebar and helmet mounts to add mounting positions to the mix of testing. He also has the older funnel or bell shaped head units and a reflector/heatsink machined to fit a P7, and you can piece out a P7 light kit as you like, as some of you know. However, I wanted a multi XP-G design with the new LISA2 pin lenses. I wanted room for either a Bflex or Maxfflex driver board behind the light engine array so the bullet style is it.

    That leads to the reason for considering the copper pipe end cap as the starting point for the MCPCB mounting and heat spreader to the aluminum shell.

    For those interested, Google this forum for copper and aluminum and read away. The summary is that copper is as much better at conducting heat from hotter to cooler zones compared to aluminum as aluminum is compared to steel. Silver is a bit better than copper but no where near the cost differntial. Since we are concerned with long term steady state and not short-term transient heat storage as in some flashlight applications, the higher heat storage per unit volume of copper is not particulary useful.

    Copper is more expensive and heavier than aluminum. But pipe caps are mass produced and you can buy just what you need and not 4' or aluminum tube when you need 50 cm, so at the DIY level of cost, copper can be cheaper. The weight can be a deal breaker for some cycling applications. For non-competition or training use, as long as we aren't talking a solid copper CNC light, a copper heatsink is a worthy alternative to aluminum.

    And so, we arrive at the use of copper pipe end caps. It so happens, that a 1" pipe end cap is a good first approximation of a nesting heat sink for the Marwi light with a wall to mount the led and flanges to move the heat to the body of the light and at least one builder has used this method successfully it in a triple Q5 application with some cut away to allow for the mounting slot.

    http://forums.mtbr.com/showthread.php?t=295664

    Go to post 24.

    LED thermal management 101 (background for issue):
    However, if you Google this forum on lapping heat sinks or stars, there is an issue with the end cap and MCPCB mounting that needs to be addressed for optimal thermal path. Although the thermal path from the mounted LED to the MCPCB is the most critical, I have elected to trust Cutter for my mounted XP-G's (as so many here have, so they are what they are, but I hope there are some VIAs from the thermal pad to the bottom surface). That leaves me with the MCPCB to heat sink and heat sink to body interfaces to optimize. It is the first interface that isn't as simple as it first appears.

    The MCPCB is a heat spreader and metal-metal contact between the spreader and heatsink is an order of magnitude better than thermal glues or greases, which are orders of magnitude better than an air gap. So you want as much metal to metal contact as possible, the thinnest layer of thermal compound or epoxy, and no air gaps.

    MCPCB's are punched or cut and by definition are not flat. Some DIY's have lapped these while being careful not to rock them and flare the edges. (if anyone has lapped the 10 mm round ones and has a good technique, now's the time to come forward).

    Even new heat sinks may not be ruler flat. Even if flat, unless they are carefully polished, they have microscopically large peaks and valleys (polished equals microscopicaly smaller peaks and valleys). Thermal compounds and epoxies fill these gaps and fill the air gaps between the heat sink and MCPCB. But if the layer is thick in order to compensate for a considerable lack of flatness, then the thermal resistance at this interface will be high and can prevent heat leaving the MCPCB as fast as needed to keep the LED in operating range let alone as close to ambient as possible.

    Finally: The copper end cap issue:
    This is true for all heat sinks, so why am I reviewing all this for the copper end cap? First, for anyone familiar with these, the end wall or floor of the cap is far from being planar, let alone polished. Second, is the teacher in me: I spent a lot of time tracking all this down and thought it would be nice for onter newbies and not so newbies to know. Last, I need any misunderstanding to be corrected and there are willing parties here.


    I have two manufacturers' examples, and though this is a small non-random sampling, 100% is a high frequency, so it may be a common problem. I have two different logos stamped in the copper and ghostly images of them clearly visible inside the cap bottom. Copper is maleable and ductile which means it can be molded and bent to shape, handy to modify the end cap to fit the inside of a bullet-shaped light body. It also means the pressing has pushed up the center bottoms of these caps. I can detect the raised parts around these logos inside the pipe caps and the recessed circumference near the side wall. Not even close to flat, let alone polished.

    So has anyone addressed this issue to get a flat mount for the MCPCB?

    The XP-G has a high thermal limit and a slower heat decay, so is this is a lot of fuss over a slight reduction if lumens/watt?

    Does this solution sound feasible:
    Unless I learn better here, I plan to cut off the bottom of one 1" end cap, remove any 'edge' of the former 'wall' remaining, then sand the inner side of the bottom flat and lap it to a mirror finish. Then, lap the MCPCB's. Mark, drill , and tap mounting holes for screws, and use minimal thermal paste on the MCPCBs.

    As it happens, I need a slightly larger diameter than a 1" pipe end cap to meet the inner wall of the body from just behind the former seating for the M11 bulb to the plane of the LED and lens mounting and a little beyond. So I plan to use that the removed wall, (which is a short cylinder after the bottom is cut off). It will be cut lengthwise to make a split cylinder that can be expanded and used to make the heat sink larger in diameter to meet the inside of the body at that point.

    I am also mounting the LED's asymetrically, so I need a thicker thermal path to the opposite side of the light. (Cross section of heat sink should be about 1/4-1/2 the distance from the LED to the body, a rule of thumb in this forum, under heat sink size rule of thumb thead, I think) I will use a second pipe cap's bottom for this added thickness and it's walls will be beveled to match and meet the bullet shape towards the rear of the light to help heat flow through that part of the light's body.

    Assuming I am a sucker for all the hand work, any thoughts?

    I can assemble the heat sink in two ways:
    Each light will use about 3.5 watts on the street on 'highs' (350 mA) and 10 on the trails (1 A), about 80% of that, as heat.

    I can solder the the heat sink as one assembly and have difficulty mounting the MCPCB's and thinning out the thermal paste for best thermal path because they are close to the sides at the bottom of a 8 mm deep 'well'.

    Or I can make the end cap bottom a removeable part of the heat sink bolted and thermal pasted to the second part with lapped mating surfaces, rather than soldered in place. Then the MCPCBs and lens can be mounted in the open to aid thinning out the thermal paste.

    In the first case, I get the excellent thermal path of solder through the heat sink but likely a poorer path at the MCPCB's. In the second design, I get easier modification, likely much better MCPCB thermal path, but I add another resistance interface to the thermal path to the body.

    In both cases, I plan to hone the heat sink to the body and use thermal paste to reduce the resistance at the last thermal interface before the air. (CNC will start to look good, during this process, I'm sure).

    Does anyone have experience or a gut feeling about how the 2-piece heat sink would work compared to the 1-piece?

    My gut says the smaller and hotter interface needs the most attention. So the 2-piece is the better solution thermally and for future mods.

    What do you think?

  2. #2
    Flashaholic* Szemhazai's Avatar
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    Default Re: Help: Using copper pipe cap as heat sink







    Cree XR-E emitter glued directly into the cap and ledil 21,6 mm diameter optics - the wiring this is hard but it is small and reliable lamp.
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  3. #3
    Flashaholic* znomit's Avatar
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    Default Re: Help: Using copper pipe cap as heat sink

    Leave out the end caps. Just bash one wall of the pipe flat and mount the leds to it.




  4. #4
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    Default Re: Help: Using copper pipe cap as heat sink

    Hi BrianMc I have been using copper end caps for all my lights from 3/4" through to 1 1/4" with great success.
    Here is a picture of 9 XPE's being mounted on a copper end cap it has been sanded by wet and dry sandpaper on a flat glass table top(when my wife is not looking). A thin layer of Arctic Silver is applied and then the MCPCB's are screwed to the end cap.
    file:///C:/Documents%20and%20Settings/All%20Users/Documents/Bike%20light%20parts/IMG_0013.jpg
    For all the smaller lights ie 3 or 4 up and MCE Pipe Lights I then cut vertical slots with a hacksaw after sanding and drilling as one cannot hold it in the vise properly once this is done
    file:///C:/Documents%20and%20Settings/All%20Users/Documents/Bike%20light%20parts/IMG_0350.jpg
    Here's an example of an MCE Arctic Silvered and screwed to the copper end cap. The copper end cap is a very tight push fit into the pipe coupling and provides excellent heat transfer to the brass chrome plated tube.
    Here is a selection of the lights built with the same technique.
    file:///C:/Documents%20and%20Settings/jim/My%20Documents/My%20Pictures/LED%20light%20JF1234/LED%20light%20JF1234%20158.jpg

  5. #5
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    Default Re: Help: Using copper pipe cap as heat sink

    Can some one explain to me how to post these pictures please?

  6. #6

    Default Re: Help: Using copper pipe cap as heat sink

    looks like the pics are on your pc hard drive......
    you will need to use a photo hosting site eg photobucket or imageshack, etc
    and upload your pics to them
    then you can post a link here, to the hosted pics ..
    click on this icon when posting your reply and paste the url (adress) of the pic
    Last edited by HEY HEY ITS HENDO; 12-12-2009 at 04:28 PM.
    .......

  7. #7
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    Default Re: Help: Using copper pipe cap as heat sink

    Thanks I thought this forum had the same or similar upload functions as MTBR but obviously not.

    Will try again.

  8. #8

  9. #9

    Default Re: Help: Using copper pipe cap as heat sink

    Hey jim ... remember there is a limit here on pic size
    i`ll try find it

    when you upload, resize to 800 x 600
    Last edited by HEY HEY ITS HENDO; 12-12-2009 at 05:13 PM.
    .......

  10. #10

    Default Re: Help: Using copper pipe cap as heat sink

    .......

  11. #11

    Default Re: Help: Using copper pipe cap as heat sink

    click on this icon when posting your reply and paste the url (adress) of the pic
    .......

  12. #12

    Default Re: Help: Using copper pipe cap as heat sink

    Thanks all. I have the pipe caps. The lights arrive Monday or Tuesday. So I can get started sanding and lapping.

    Szemhazai:

    Are the bottoms of the pipe caps you get (in Poland, right?) flat? Do you do anything to them to prepare them to accept a star? BTW I enjoy reading your posts.

    znomit:

    Your light was one of the first I read about and it helped convince me to build my own, and loved the Kiwi flavor of it. Even the cheap DX P7 with Geomangear support could not stop me after reading posts like yours. You sir, are a bad influence. Keep it up.

    Remind me. Did you do anything special to prepare the heat sink/case and star interface to help heat transfer?

    I also like the amber side light from the stray light that doesn't get out the lens. I almost designed amber markers on the headlights inspired by your design, but decided side markers were going to be a later build, front and rear. The amber 1/2 watt XP-E's at Cutter look too good not to try out.

    formantjim:

    I feel your pain. I had trouble too. Had to google this forum to find out how to do it. And will have to my next time, too. Your 'one more time' links took me to the host but no pictures. I don't know why.
    Could you try again? Please? It soulds like I really do need to see them.

    You do sand and lap the cap bottoms for mounting. Do you lap the stars, too?

    If I understand you correctly, you are saying I need to think about the order of certain tasks or I won't be able to hold the sink in the vise to do it later, and that you found a good interference fit between sink and body was more than enough to get good heat transfer to the body.

    I have been giving the order some thought. I will be out a lot of work if I have an essential step to do that I can no longer do. Like the chocolate cake I forgot to put sugar in. A bit late after its baked. It is one of the reasons for this discussion, I won't be able to foresee everything and just seeing another light or talking about it can be a big help.

    In the Marwi lights, the front bezel tightened against the former MR11 lamp to seat it firmly. I am going to use that same force to push the sink firmly against the body. So that should do the trick without thermal paste? The shapes of the sink and body are compound curves, but I will get the match between them right.

    I have a number of free panes of glass salvaged from picture frames that I plan to use over a plywood base to keep the marital peace.

    HEY HEY ITS HENDO:

    Quad die. P7 or MC-E but looks like the MC-E reflector. Was the inside bottom of your cap flat? Did you prepare either the pipe end cap or the star before fastening them together?
    Last edited by BrianMc; 12-12-2009 at 09:08 PM.

  13. #13
    Flashaholic* znomit's Avatar
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    Default Re: Help: Using copper pipe cap as heat sink

    Quote Originally Posted by BrianMc View Post
    znomit:

    Remind me. Did you do anything special to prepare the heat sink/case and star interface to help heat transfer?

    I also like the amber side light from the stray light that doesn't get out the lens. I almost designed amber markers on the headlights inspired by your design, but decided side markers were going to be a later build, front and rear. The amber 1/2 watt XP-E's at Cutter look too good not to try out.
    Nothing special, and given that it was hammered flat probably not a particularly good interface. I guess I used some brasso to polish it.
    I don't know how important the lapping is. I've never bothered dressing stars.

    Go easy with the side lights, unless you can mount the light clear of your eyesight.

  14. #14
    Flashaholic* Szemhazai's Avatar
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    Default Re: Help: Using copper pipe cap as heat sink

    BrianMc, it is 22mm pipe end cap, bottom in the center of the cap is flat. I've used emitters (no stars), if you want to use the stars you will have to cut them on the corners.
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  15. #15
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    Default Re: Help: Using copper pipe cap as heat sink

    OK BrianMc.
    Yes I do indeed sand and lap both the copper end cap and stars.
    Yes the sequence of the tasks is important mark and drill the holes first, sand and lap the face then cut the slots. Using the face glass to finally push the copper in so an interference fit is obtained. [IMG][/IMG]



  16. #16

    Default Re: Help: Using copper pipe cap as heat sink

    Thanks all for your feedback.

    The take-home lesson here appears to be that if you are not fastidious about the interface does not mean the light won't work, but doing so (lapping etc) may still be a best practice.

    formantjim

    Thanks a lot for persevering pic posting.

    We were right. Tell you sister you were right, Luke... oops Star Wars moment there! I really did need to see them.

    Those are chromed brass sink u-bend parts? They do make for a compact package. And rugged. Look like a fun build. Hmmm: high power tailight?



    Your cap's triangle-M logo is the same as on two of my caps from the local pumbing supply house. The two 'NIBCO' caps are a little shorter in height, larger in diameter, and came from Lowes. At one point, I was thinking of using slits in the side to allow splaying and contracting to follow the bullet shape better. Glad to know this method has real world testing behind it. Combined with a bit of bend in each leg this will do the milder front curve. For the legs aimed rearward, wider cuts (with double blades) near the edge to allow for the increased curve, and some sanding, I should be able to get the shape needed. There should be just enough spring left to push the legs against the body with the push from the bezel. I just really like the shape of these old Marwi heads and would like to find a DIY way other than a CNC aluminum heatsink to use them.

    I have a project step-by-step list and Excel spreadsheet used instead of MS Project to keep things in order. A light recipe, I guess.

    First I need to clear up my workspace for pics. My vise is about as photogenic as yours. My foot less so.


    Szemhazai:

    Sorry. Missed the emitter driect comment in your first post, too amazed by the barbell design, I guess. So you used something like Acrtic Silver Epoxy to fasten the emitter to the bottom center of the copper cap? Did you rig up a way to apply pressure to the emitter but not the dome to squeeze the layer of epoxy thin, or did you apply it to the back of the emitter scrapping it to a thin layer and sort of 'smoosh' it in place to get the layer thin?

  17. #17
    Flashaholic* Szemhazai's Avatar
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    Default Re: Help: Using copper pipe cap as heat sink

    BrianMc, I'm using my favorite 3M 467MP thermal adhesive tape - it is 0,05 mm thick and it is giving very good results for XR-E emitters.
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  18. #18

    Default Re: Help: Using copper pipe cap as heat sink

    Sanding the bottom outside is not a problem.

    I can feel the embossed brand stamp in both brands, and the centers of both are raised relative to the outer edges of the inside bottoms of the heat sinks/copper caps, and sanding is really not an option.

    If you cut the sides mostly away as shown for one light, you could get a decent sandig job. I could take the sides off and resolder them back on.

    I could go the tape or thermal compound route and hope the higher thermal conductivity of copper helps a fair bit. Three XR-E R2's and three XP-G R5's are about the same sized heat source, so the light will work.

    Another idea is that liquids (except liquid helium near absolute zero) seek level. Gravity works. So what if I just places a coil of high silver content solder and some flux in the cap bottom and heat the cap up until the solder melts and flows into a flat surface and then let it cool? High silver content solders flow best. Silver is even a little better than copper in thermal conductivity so the mixed solder should be pretty close to copper, Maybe a bit better. No sanding. Just mount the MCPCBs and go.

    Anyone have experience melting solder in a similar fashion to form a pad?

    I'll have a go, but if there are tricks or pitfalls I'd like to know.

    Wait! I mismeasured the bottom thickness, I thought two caps back to back would put be close to 1/4", but that's 1/8". Solves the lapping issue: I cut off an end cap bottom, lap it, and solder it in the bottom of the front cap before drilling and other mods.
    Last edited by BrianMc; 12-14-2009 at 08:24 PM.

  19. #19
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    Default Re: Help: Using copper pipe cap as heat sink

    If you use copper fittings like this I would suggest using type K fittings. Copper comes in three thicknesses K, L, and M. M is the common thinner wall stuff and K is the thickest. I don't think I've ever seen L copper before but it probably falls in between.

  20. #20

    Default Re: Help: Using copper pipe cap as heat sink

    NigelBond:

    Thanks.

    I googled K and L copper pipe and it seems to apply to residential (L thinner walled copper pipe) and K commercial. I can attest that the 3/4" copper pipe and 3/4" end caps that I also have, are only 1/32" thick whereas the 1" caps have 1/16" thick side walls and bottoms.

    I am planning two caps back to back with extra soldered in because the LED's are on one side. A crude rule of thumb says heatsink thickness should be about 1/4 to 1/2 of LED distance to the body for flashlights. So 1/16 would be fine for the near side but, the rule suggests 1/4" to move heat to the far side. It is copper though so being at the low end of the rule should be fine. Once at the body, 1/16" of copper lines the inside of the body to dump the heat into almost the entire aluminum housing. The housings arrived today:

    http://www.el34world.com/Misc/bike/BikesLights42.htm

    I may be wrong, but I think that 3 XP-G's at 9.9 Vf and max current of 1 A, are likely dumping about 8 watt, if I keep them cool, the same amount of heat as a P7 at 2.4 A, or close enough. This housing has about the same surface area as a certain 'MS' P7 light, too.

    I don't have a scale, but a hand test of the ViewPoint housings with 10 watt MR11 in place, say they are close to the weight of two unmodified pipe caps. Both caps will be shortend some, but will have the thicker bottom. I think that should be ample. Better be: they'll be heavy enough.

  21. #21

    Default Re: Help: Using copper pipe cap as heat sink

    Thanks for all the input.

    My pipe cap solutions for the two Marwi/ Viewpoint Bullet shaped housings are shown here:

    http://www.candlepowerforums.com/vb/...70postcount=27

    When the lenses and LED's arrive, I will post the completed units with beamshots. I'll use the MTB settings.

    Google works well so no need to post all links to pipe caps here. So I guess we could close this thread.


  22. #22

    Default Re: Help: Using copper pipe cap as heat sink

    Quote Originally Posted by BrianMc View Post
    [long quote removed - DM51]
    I think the easiest solution is to cut another disk of copper, lap that, and drop it into the cap and solder it. Then, drill it for your wires( being careful to dremel the burrs around the holes.
    Last edited by DM51; 04-23-2010 at 04:37 PM.

  23. #23

    Default Re: Help: Using copper pipe cap as heat sink

    Quote Originally Posted by BrianMc View Post
    [long quote removed - DM51]
    I have tried cutting notches to follow the interior shape and it works but I have found that for me a better way is to heatpipe with copper nails to a copper band on the outside of the housing works even better and is much less work. I use ordinary metal epoxy with the lens, cap, and star in place to exactly locate the copper cap. Then, after it has cured, I remove the lens and star and drill through the band, housing, and copper cap, solder in a few copper nails and dremel off the excess. I also create a separate copper slug heatsink with a separate path to ambient for the driver in the same manner. This method ensures perfect alignment for the optic as well as even pressure on the star for optimal heat transfer. In still air the copper gets warm well before the aluminum housing. This is important for me as I use the old Vistalite housings with a plastic part that houses the switch. When in motion the copper conducts well enough that niether my triple cree q5 at 1A nor my quad xpg at 1.3A is more than luke warm. The quad is using a Maxflex 5 ( Kudos to Georges at Taskled for building great drivers) and it has yet to cutoff with the thermal set at 60 C. The triple cree(actually, two of them) uses one of the $12 kd p7 super output drivers which are supposed to also have a thermal cutoff but I don't know at what temperature they are set. The quad has only been finished for two weeks but I have been using the other two for the last year and can say (imho) they have been a great success and have not failed yet. My earlier attempts with closely fitted copper, a common heatsink for driver and led(mce) were less than satisfying as it resulted in a toasted led which while it lasted produced a beam not nearly as smooth as the multiple leds I am currently using. I admit I am going against common practise by running the q5s in parallel but even now I haven't been able to locate a driver anywhere close to as inexpensive capable of running 3 crees in series that I could simply pop into the vistalite using the same switch and no pot to achieve dimming. In any case, I can heartily attest to the ability of a cheap copper pipe cap as a means for those of us without access to a lathe to make more light. Mod-on
    Last edited by DM51; 04-23-2010 at 04:38 PM.

  24. #24

    Default Re: Help: Using copper pipe cap as heat sink

    Quote Originally Posted by rufusbduck View Post
    I think the easiest solution is to cut another disk of copper, lap that, and drop it into the cap and solder it. Then, drill it for your wires( being careful to dremel the burrs around the holes.
    Good idea.

    I am not sure that the 4-6% gain in thermal resistance at the interface is worth the effort I put in to that as both lights run cool enough. But for those wanting to have the copper pipe cap work at its very best, I add the following:

    I solved the issue of polishing inside the caps by just using the caps reversed so I could lap their bottoms. One was made into a pill like in flashlights held in a copper liner by a ridge and valley keyway system shown here at the top of the post:

    http://www.candlepowerforums.com/vb/...0&postcount=27

    The other was a pipe cap fit into the back of the body shown in the botttom of the same post.

    I melted a pool of silver solder in the back of the last version to increase the radial thermal path to the light body and the solder obligingly made a negative miniscus thinnest in the center. Nice surprise. (The pill has a thick copper insert, (heavy and overkill), but it slows warm up.)

    I used a hot plate to melt the solder in the cap. Worked like a charm. So I might suggest that the hole in the cap be made before the polished copper plate is soldered so excess solder can exit and not well up at the edges. Put a spiral of solder wire under the plateand place the plate/solder/cap on a hot plate. With the hole between the heating element courses. Any leaked solder will lift off the pan underneath when you are done.

    If you need to enlarge the copper cap to get a good interference fit in the Marwi Bullet housing, I'd add the copper wire and solder wire around the outside of the cap to do this at the same time in one step, (if you aren't goin to use the flower petal method to expand the cap as used to shrink the backside of both my heat sinks). Drill the hole through the new added bottom from its side to reduce burrs. Then file and sand the enlarged cap cicumverence to get a nice snug fit. Some Arctic Alumina, and all will be well.

    Or for the Marwi Bullet light, just cut a 5 mm thick slab of aluminum bar a bit bigger than the ID about 32 mm for a slug. Drill a hole for wiring and any screws then sand to fit and polish as much as you want. Arctic Epoxy it at the depth you need it up to 20 mm. Done.
    Last edited by BrianMc; 04-23-2010 at 04:25 PM.

  25. #25
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    Default Re: Help: Using copper pipe cap as heat sink

    rufusbduck, it is unnecessary to quote entire posts, especially where they are lengthy ones. A brief extract is usually sufficient.
    Resistance is futile...

  26. #26

    Default Re: Help: Using copper pipe cap as heat sink

    Quote Originally Posted by rufusbduck View Post
    I have found that for me a better way is to heatpipe with copper nails to a copper band on the outside of the housing ... less work. I use ordinary metal epoxy with the lens, cap, and star in place to exactly locate the copper cap. Then, after it has cured, I remove the lens and star and drill through the band, housing, and copper cap, solder in a few copper nails and dremel off the excess. I also create a separate copper slug heatsink with a separate path to ambient for the driver in the same manner. In any case, I can heartily attest to the ability of a cheap copper pipe cap as a means for those of us without access to a lathe to make more light. Mod-on
    Great addition to this thread for others building lights.

    +1 on Pipecaps. Also search CuLite on MTBR for making the entire light of copper pipe fittings.

    I can attest to the hours spent dremeling and grinding copper heat sinks for a tight fit with Arctic Alumina to fill voids. Definitely a drawback of the tight fit method, but it too made cool running MR11 lights (about 7 square inches of air interface) with minimal air interface.

    The radial distance the heat has to go has an effect. More smaller sources of heat closer to the outer part of the light are going to move heat better than one hotter on at the center. Taskled recommends the LED and MAxflex not share a common thermal path. Based on my lights you could have stuck with the tight fitting pipe caps and been succesful, but less work is a very nice benefit.

    Is the Vistalight an MR11 or is it larger? Any pics to help others do this too? How many copper nails? Did you concentrate them in line with the LEDs? What was the total cross section of copper heat pipes/nails? Did you do an entire ring for the Maxflex heat sink or just the one point? The list goes on. Please, we want some more!

    For those reading this thread for ideas on using pipe caps, a blend of the two would also be possible, though the nails alone can make for successful heat management. You could solder segments of straightened copper pipe straps (Mueller makes them about $1 for five) outside the pipe cap running axially at the points where the LEDs will be radially. Then you only need sand these wider heat pipes to fit the case, not an entire enlarged pipe cap. Much easier. Much less work. The nails could be used as rivets/heat pipes to an outside copper ring and/or an aluminum motor heatsink for some mods. Use silver solder, it conducts heat better.

  27. #27

    Default Re: Help: Using copper pipe cap as heat sink

    I use Vistalite housings for a few reasons which I will cover as they come up.
    For a quad xp-g mod I used one 1" cap and several sections of 3/4" copper pipe. I cut around the cap~ 5/16" up the wall and soldered inside a smooth piece of copper flashing cut a little undersized as a disc to fit inside the cap. Then I cut the remaining section up one side and opened it into a u - shape and soldered slugs cut from female thread copper fittings(the curve of the threads already fits the housing shape) inside the ends of the 'u'. I set these parts aside and make the heatsink for the driver next(Maxflex 5A in this case).
    Using a small copper pipe cutter, I cut several 3/16" sections of 3/4" pipe(six or so) and a couple more of 1/2" pipe. Then I remove sections of the pipe so that I can reduce the radius and make two nests of copper rings( one goes inside the housing, one outside). If you heat the copper with a torch it looses its temper and gets more pliable. With the torch again I heat the slugs and solder them up. for this I use plumbing solder as it's cheaper than electrical solder and easier to apply in somewhat larger quantities.The Vistalites have a ring in the bottom which helps center the exterior slug if you allow on of the rings to protrude from the nest. Next I grind away as much of the interior aluminum ribbing as I can with a dremel leaving enough to secure the interior base nut and the switch support. I again use the dremel to fit the interior slug over the base nut and remaining aluminum. I epoxy the two slugs in place with jb-weld and drill two 1/8" holes all the way through both slugs and the housing and solder in two copper nails and cut the excess of inside and out. A small copper tab sized to fit the Maxflex soldered in completes this part( and raises the pcb to clear the pcb solder connections.
    Back to the led heatsink. With the interior slug in place, I grind enough of a bite shape out of the pipe so the sink, star (quad xp-g r5 32mm from cutter) and focusing fit loosely behind the lens retaining ring. I drill a 5/16" hole in the center of this part along with two 1/8" holes that line up with the screw holoes in the housing and smooth this with the flat surface of the dremel grinding disc (I keep an assortment with various states of ware to fit in small places) and some wet/dry paper. Butter up the outside edge of this part with jb-weld and drop into place, add star, lens, and retaining ring and apply pressure frome the inside out(toward the retaining ring) until its set. Fit and epoxy the u-shaped hoop to the indents on the outside of the housing (looks like it's wearing earmuffs). Then drill a 1/8" hole through each 'ear' and solder in a nail. The jb-weld conducts heat less well than the copper nails thus somewhat isolating the two heatsinks and by allowing the led sink to fit loosely there should be a small space between the two.
    The switch is another reason I like the Vistalites. The stock switch will work with most of the dx and kd drivers to change modes and power on/off and digikey has an exact fit replacement for a momentary n/o switch to operate Taskleds UI Uni software. The wiring is difficult in such a small case but possible if you cut away the mr-11 plug base part of the switch module.
    Before assembly I throw on some undercoat and flat black paint and start cramming. The switch wired to the maxflex goes first with some aa to that tab I mentioned before. After that sets, preload the screws in the case and reattach the back of the case using the two 1/8" holes drilled for this purpose. With some thermal grease on the sink(not the star or it could foul the led leads) carefully slip the leads and star into place(twist the star back and forth to spread the grease thin). Solder, add lens, cover and power and you're ready to rock.
    I use the original 6v nightsticks for the kd drivers but for the maxflex I made up a pack of nimh cells in an 8s 2p arrangement for 9.6 v to get as close to the minimum voltage for 4 xp-gs as possible. Level 1 is ~ 40-50 ma which corresponds to a forward voltage of 2.5-2.6 v. So, 4 x 2.5 is 10v so even at the lowest setting the maxflex should regulate(and does) and still keep me ~ 2a to the driver on high running at 1.3a to the leds.
    I am 50 and my night vision ain't so good anymore and these lights make all the difference. I wanted to do this to see if I could make something pretty nifty for not much $ without having access to a lathe. Don't get me wrong, I drool with the rest over some of the awsome work that shows up on this site but I couldn't help myself. Does this make me a flashaholic?
    If you're curious there are some pics on the mtbr site in the homemade lights database and I'll be posting some here soon if there's a need.

  28. #28

    Default Re: Help: Using copper pipe cap as heat sink

    Quote Originally Posted by rufusbduck View Post
    I use Vistalite housings for a few reasons which I will cover as they come up....I am 50 and my night vision ain't so good anymore .... I wanted to ...make something pretty nifty for not much $ without ...a lathe. Don't get me wrong, I drool ..over ...the awsome work ...on this site but I couldn't help myself. Does this make me a flashaholic?
    If you're curious there are some pics on the mtbr site in the homemade lights database and I'll be posting some here soon if there's a need.
    Closer to 60 than 50 here, I'm afraid. Legally blind without glasses. I also need more light!

    Many of us are tool deprived or challenged yet want something in alight tht no one is making. Or recycle a faithful friend which has lighted the way. Copper plumbing parts are a very viable route.

    You can just copy the shortcut(s) of your post(s) in MTBR to your edited post above to add pictures, if that would be easier for you. (Right click the post number in the thread and copy shortcut and past it where you want it in case you did not know).

  29. #29
    Flashaholic pe2er's Avatar
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    Default Re: Help: Using copper pipe cap as heat sink

    I Think this is the RufusBDuck posting: http://forums.mtbr.com/showpost.php?...4&postcount=60



    Except that this is a triple, not a quad...

  30. #30

    Default Re: Help: Using copper pipe cap as heat sink

    Yeah, that's one of the earlier models but it 's still going strong and kicks butt on even a 20 w halogen bulb that tends to cook the plastic in these lamp heads. The quad xp-g is only just finished and I wanted to test it on a ride or two before I showed pics. The copper tabs that you can see above notched through the pcb are where the copper nails are drilled and soldered all the way through from the outside. This one was modified without epoxying the inside copper before soldering and this made it very difficult to achieve good pressure on the pcb with the lens and holder.
    I am a fan of medium beam lenses and the old halogen bulbs lit up just too small of an area with the spot and flood bulbs were too dim. I was running one of these vistalite mods on the bars with a ledil cute-3 med and one on my helmet with a cute-3 ss but now I have both of these on the bars with medium lenses and the quad xpg on my head. I figure 6 xr-e q5 at ~ 200 lumens each plus 4 xp-g r5 ~ 420 lumens each at 1.3 A means I'm in th vicinity of 2800 -2900 lumens with some pretty inexpensive lights.
    Here are some numbers on the cost:

    Q5 Triple
    kd driver $12
    3 q5 from dx ~$17( I bought 5 packs)
    pcb from Cutter $3-4(price has gone up)
    1 " copper cap $4
    3/4 " copper pipe $free for me but only $1-2 for a foot
    awg 20 Teflon wire $5 will get you plenty
    solder ~$5

    Total $46

    For the quad xpg I purchased the leds preloaded from cutter with a gt4-xp lens ~$45 with shipping and a momentary switch from digikey for ~$2 and a Maxflex 5A from Taskled for $35 so the cost for the quad was a bit more at around $85-90 as I already had the solder and wire.

    One thing I should mention about those inexpensive kd drivers is that I am unable to run them using a remote switch as interference causes the lamp to cycle between high and low every few seconds. I solved this problem by separating the driver from the lamp head but the idea was to minimize the crap on the bars while making it easy to switch levels without taking my hands off the grips to reach the lamp. Georges at Taskled mentions a pullup resistor on his flex drivers to allow for longer switch wires but his switches don't control main power. I have a Hipflex that I can use to drive both lamps if it comes to that but was hoping to avoid gutting the drivers from the lamps. Ideas anyone? I have two nightstick batteries from which I removed the five 2200 mahr sub-c cells and replaced with seven 2000 mahr 4/5 sub-c cells so I have the power for the hipflex already.
    It should be pretty obvious that the copper is an insignificant part of the price but as far as I'm concerned makes this particular mod work. Would love to hear any suggestions for improvement as I these sets still show up frequently on ebay.

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