Copper? C8 pills for $4.30

Depends.
You could put two 16340 or 18340 in series, or try an extension tube or 2 :smiley:

Point is, i think i would prefer a copper pill and good heat paths from there to the rest of the flashlight in an extremely powerful flashlight.
You can sink the heat in a solid copper pill, but eventually heat dispersion is (more?) important.

Maybe what Hikelite is trying to point out here is that the specific heat & density of brass and copper are almost the same. Together I think they indicate that the volumetric heat capacity of copper and brass are about the same (~13x that of aluminum!).

When we build a hotrod light like the C8 you described, no amount of thermal conductivity can keep it running indefinitely with hand-cooling or convection cooling. Instead, all we can do to extend runtime is maximize the heat capacity of the light. We’ve got to take care of thermal conductivity right at the LED, this thermal junction is critical since it is so small. Beyond that, thermal conductivity may not be as important.

So the thermal capacity of copper or brass is approximately 13x that of aluminum. Aluminum has a little less than 2x the thermal conductivity of most brass. Copper has >3x the thermal conductivity of brass and a little less than 2x that of aluminum.

BTW I did check a chart and there’s no significant improvement to the radiation of heat going from copper to brass - so you may still want a thin, anodized aluminum skin on the outside of the light for radiation purposes.

I’m sure I wouldn’t want to use a brass star, but maybe a brass pill isn’t the end of the world.

I believe wight nailed down what Hikelite was probably thinking. Nice analysis and presentation of the concept by the way. If I follow you correctly, you are basically saying the brass pill will probably be an asset in a small C8 (due to increasing the light's thermal mass), but a liability in a big light that actually has the ability to shed the heat to the air (or applicable surroundings) at a rate faster than the pill can deliver.

Thanks. That's more or less the gist of what I'm thinking.

I wasn't specifically thinking about the C8 lights, but in general if you are using copper or brass and you can significantly increase the mass (which we'd detect as weight) of an unloaded light... you are probably doing something good. If you are swapping an aluminum pill out for brass (not copper) and you aren't making a big increase in the mass of the light you may be hurting yourself. ..I think.

Is it not an improvement over alum to be able to solder a copper star to the brass pill ? Is this not the most important heat transfer point.
Is that not better than alum stars and arctic alumina?

djozz tests 6 different stars, found that direct thermal path whether aluminum or copper work almost the same (until you get VERY high power)

That is the biggest thermal gain you can expect in emitters under say 5A

I think deckart is talking about the transfer point from the star (such as Notigon, Sinkpad, etc) and the pill.

I'm not aware of any testing, but I believe that you are right that a good soldered connection to the pill is superior to thermal paste/adhesive connections. I think each individual case is going to be different, but I would personally prefer reflowed to brass over thermal paste to aluminum pill. That being said, I tend to trash all my brass and aluminum pills these days and press (not thread) in home made copper pills in my high amp lights. Also copper line areas near the thread area to increase rapid heat distribution to the host.

Once you transfer the heat to the flashlight body, then getting rid of it happens by
— conduction, if you’re handholding it and carrying the heat off through your body
— convection and radiation to the air.

For radiating heat away, you want a high “emissivity”
http://www.tomshardware.com/forum/118364-29-truth-copper-heatsinks-aluminum-ones

This is somewhat off-the-wall to be my first post… I’ve been lurking for some time now. But having bought/received three of these, I can answer your questions.

1. YES - THESE FIT CONVOY C8’S —- actually…. they ONLY fit Convoy C8’s. They do NOT fit my XinTD V4 C8 or my UF C8.

2. I bought the same ones in the OP — http://www.dealsmachine.com/best_180109.html

3. They are almost certainly brass. Seem very heavy though. Significantly heavier than the standard Convoy C8 aluminum pill. Very thick walls. With some extra sanding/drilling, they should accept a 20mm star instead of the usual 16mm.

Ok now I don’t see why brass pill are not better than aluminum.

That’s a pretty good first post! :wink: :slight_smile:

Thanks for the info.

Did you read post #68? Read it, look at the data in the links, and think things over. Honestly I haven’t formed any concrete conclusions.

Ok - I was totally wrong! It certainly does fit a Convoy C8, as grantman said.

Got mine today - sure is brass. I got brass and copper C8 pills, and these are absolutely brass. It is pretty chunky pill though - nice thick pill top, but looks like the pill top is not perfectly flat, but that's common. I tried this in a UF C8 and the Convoy C8 and it fit both! Not sure how they did it, but it seems to be a good fit for both.

Along side a Convoy C8 pill. It' about 19.56 mm pill top width, so a 20 mm start needs some trimming. I use a dremel sanding drum for this - did it many times for HD2010's. The problem is the holes. They have to be widened or re-drilled, then you will hit into the inner walls of the pill inside. You can file the cutouts in the star deeper - again, I've done this many times also. Shown with a 20mm Noctigon:

Stock Convoy C8 pill, small and light:

The other common brass C8 pill, from FT and other places. I paid maybe $4-5 or so from LCK-LED I think? This one doesn't thread into a Convoy C8:

This new brass C8 pill. Nice heft, you can feel it in your hand:

Ryan's super copper Convoy C8 pill. Problem I had it was too damn good - had to drill out material to fit stacked 7135's:

I still haven received mine yet …grr :Sp can it fit 17 mm driver?

Sure fits 17mm drivers... Definitely not a total waste seeing it's so flexible. I got a couple of C8's it doesn't fit because the threads on those C8's are much wider, but that's part of the C8 game. Both of those are cheap lights/hosts.

Nice…ordered one for my Convoy C8…going to direct solder a copper sinkpad to the pill, then run it either with a BLF17DD or a Nanjg 8*7135 with 2 extra chips soldered on

very cool thanks for the info guys!

C8 coming in the male, I wish I could solder so I could use this and upgrade the driver.

Good post.

Those holes seem like a big oversight to an otherwise good brass pill. Do they line up with 16mm MCPCBs? I can’t tell from looking.

Well, close, maybe skinny wires.

Just got mine in, screws in perfect, nice little heavy pill, upgrade time :smiley:

Convoy or Ultrafire?