I was looking on ebay for some large copper heat sinks for emitter testing and possibly a mega bike light build. I wanted something with a thick large mounting plate so heat would be dispersed evenly throughout the sink no matter where the emitter array was placed. I also wanted it to be symmetrical, fairly rugged and versatile.
Besides browsing photos online, I couldnt find much info regarding dimensions or weight without asking a vendor.
For now, here’s what Ive come up with:
Sun Micorsystems 371-0291 heat sink. It supposedly weighs in at over 2 lbs of copper and has heat pipes to transfer heat throughout the cooling surfaces. I have a pair of them on the way.
Does anyone have other suggestions for heat sinks in the 2-3 lb category?
For the emitter testing, have you thought about taking one of the good PC CPU heatsinks, with a (or two) fans, and turning it upside down, putting your emitter on the plate that normally is in contact with the CPU?
Or, doing something similar with maybe one of the water cooled units?
What in the world do you need a heatsink that big for??? My C9000 (which runs at over 100 watts) has a much smaller heatsink (albeit with a fan) and the heatsink stays cool enough to touch...
Thanks for the link. If the heat pipes don’t have an internal wicking mechanism, they (the heat pipes) probably won’t contribute much to the cooling other than the copper in them conveying heat. My guess though is that the heat pipes do have wicking and will contribute as heat pipes even upside down.
Must be some build - given that the later generation of P4 CPUs generated over 100W and were kept under control by a relativey simple heatsink and fan.
This is for a bike light which I assume wouldn't be running on "turbo" for extended periods while standing still.
What on earth are you building - a quad MT-G2 or perhaps a stove for heating your soup on cold winter rides?
I am using heatsinks from a Dell Precision 1950 server (part number JC867) on a 50w LED and it keeps the junction temp below 60c with only room currents. The heatsink is not mounted directly to the LED though, there’s an aluminum reflector dish, waterjetted mounting plate, and 1.5lb of solder fill between the two.
The benefit from these heatsinks (to me) is that they stick out to the side. In my case this was necessary as I did not have any room for mounting to the rear and they would then not be in the path of any airflow.
Of course the optics are completely inadequate for actually using them on the road (BLINDING!), this was just something fun to play around with because the high wattage LEDs are addictive
Be aware that some of those heat pipe units only work in one orientation (i.e. base down). Also, you are likely to drill into a heat pipe if you drill and tap into that surface. I would go with a fan cooled CPU heatsink. The one that I used in this can handle over 150 watts and barely gets warm. It is the same one that Scaru is using. The fan is quite the little screamer, though:
AFAIK from a quick google search, all the large sun microsystems rack mounted server copper cpu heatsinks with heat pipes (of that vintage) utilize a thermal wick. There are multiple patents listed.
If it gets hot during bench tests, a fan should cool it down in a hurry. I wanted something I wont have to buy twice in the future and would provide a lot of surface area for mounting multiple emitters. Being made of copper was prerequisite.
For the bike light build, I havent quite decided the direction yet. Its a back-burner project I’ll eventually piece together. Id like to cool the sink passively, although by adding a small scoop to each side would force air through the core while peddling along. The areas I ride are mostly devoid of ambient light and people, so I usually run my lights in high mode for most of the duration. I was impressed by several of trouty’s mtbr posts, especially the 5 x xml array he posted for us. While mtg2 has its place, they didnt test well in the several bike light builds Ive seen. They just dont seem to have the surface brightness to throw well, so my solution will likely be 7-8 xml’s simultaneously utilizing more than one reflector design… who knows what I’ll find when the time comes.
My current bike light is an SRK (with the good driver) fed by a large remote battery pack. The entire light and battery tube get hot feeding 2A to each XML after 30 minutes while traveling @ 15-20 mph. Not so hot that it will burn you, but hot enough that I wouldnt want to add more amps to the system. Without the remote pack (additional 9 x 18650), the voltage sags enough on 4 x 18650’s before the 30 minute mark that it doesnt overheat. But 13 x 18650’s keep it running at high voltage and it does get quite hot in that configuration. Thats what got me thinking about a remote mounted dedicated heat sink for the emitters… fun stuff.
Thanks Pyro. I didnt realize that. The sinks have already been shipped, so I will test them with a thermocouple in different orientations once I get them. If the base appears to contain a fluid path where I intend to drill & tap a mount, I will JBWeld something as an attachment point instead. At least I got a good enough deal on these that I can resell without a loss if necessary. Whew!
