Re: Post#13
crnkin,
“_So thats 115,260 lux at 1m at 2.85a (7x.35s and 1 .38)
was 99,000 lux at 1m at 2.50a (7x .35’s)._”
I see 1807 from the lux meter, please advise how you got 115,260 Lux.
Also on your first post, you have 68,200 Lux at 8M, is it 68,200 data from the Lux meter at 8 meters?
As discussed on A Little More Machining Video, pure Al and Cu are too plastic for practical machining, and casting is not a practical alternative for a budget light. It might be possible to forge a soft metal pill, but not without a lot of development. So we are talking about relatively pure alloys that are machinable but still good conductors versus alloys like aircraft aluminum and brass that are optimized for machinability and strength.
Don’t have a scale to weigh them, but the C12 doesn’t feel much heavier in hand.
The Wikipedia article on 6061 aluminium alloy says “The typical value for thermal conductivity for 6061-T6 at 80°C is around 152 W/m K.”, whatever those units are. For pure Al, it lists numbers around 220 in what appear to be the same units, in the article List of thermal conductivities. Pure copper is around 390 and brass 120 in the same table.
So brass is nearly as conductive as hard Al alloy and suitable for pills when it is easier to fabricate, while alloys with higher Cu content have superior heat conductivity.
Heat conductivity of metals is loosely related to electrical conductivity, so alloys used for ground busses and such in electrical devices are good.
If I manage to find C12 somewhere with nice discount I’ll get one for experimenting :- ) It just looks like it has a better heat management than C8
P.S. (talking to everyone): have you seen this:
I would have to say your being pretty dammed anal to worry about the thermal conductivity of a brass pill over alu alloy tbh.
I have two similar sized, similar mass lights driven roughly the same, one, the emitter is screwed to the head - direct bonding, one has a brass pill, I defy you to feel a difference in how they heat up.
I certainly am not convinced you could measure a difference between a brass pilled c8 and an alu alloy pilled c8, interesting experiment though it would be.
me? I’ll take ease of assembly thanks
I even got a true copper pill (from VOB) in a LightMalls UF C8 and really can't tell the difference in heat and output between this light and others I have with brass and aluminum pills. Originally it had aluminum w/copper discs, upgraded to brass w/copper discs, and now just the copper pill - can't tell a difference.
The stock light would drop output as it warmed up like crazy - direct drive gone a-muck.
The difference would be seen in how fast the outside of the light heats up. It may not affect the overall ‘hotness’ of the light since that is determined by the external features of the light and ambient temperature and not the pill. Honestly, I don’t know how much of a difference there is but personally, I prefer an Aluminium pill vs Brass.
Ive got 8 of VOB’s copper pills sitting here.
I’m not going to use them until ive found the best setup, 4 will be for my personal use, 2 each for my hunting buddies.
The biggest improvement you can make is going from alloy star with silk screen to a sinkpad. Straight away its got to be 30% plus much more stable, and longer life.
Artic silver has been amazing too, the lights get so much hotter, so much quicker than even Artic alumina.
Someone mentioned why the meter said 1801 lux and I have rated it at more. I don’t have time to play google but basically light intensity reduces at the inverse square per distance. So I measure at 8m, and multiply the reading by 64 (8x8).
Any more would be to spoon feed 
Chris
Good stuff Chris.
Have a bunch of C8s (and a C12), XP-G2s, Intl-outdoor copper boards (16mm) and the Sinkpads sitting around… still waiting on drivers, glue and XM-L2 U2s (and maybe a XM-L2 U3). Will flick my measurements up once they are all together.
XP-G2s on copper at 3 amps are awesome!!! (and cheap).
I think the ultimate would be a XinTD V4* with de-domed XM-L2 U3 on copper with one of PilotPTKs upcoming drivers… modded for up to 4 amps of cause. 
Can anyone confirm the XinTD has a deeper reflector then a standard C8?
You could email Hank from IO and ask him. He used to have a photo on his site of the V3 vs typical C8 reflector.
Not quite sure in that! It would be a US$60 - $70 C8!
Looking in Wikipedia reminded me that heat conductivity is limited by lattice defects (such as atoms of other metals). Some metals are supplied in a heat treated or work hardened form. This extra hardness is caused by lattice defects (They interfere with slipping along crystal planes). So heating the pill after it has been shaped and letting it cool slowly my make a significant improvement in its heat conductivity.
This is the opposite of the way knives are made, at least sometimes. The annealed metal is worked, such as by filing and grinding with abrasive belts and then it is hardened, tempered and polished. I am pretty sure budget light manufacturers wouldn’t bother with this step.
The conduction mechanism is that more energetic conduction electrons move to cooler parts of the metal and vice versa. The rate depends on the mean free path, as for atoms in a gas.
if your driving your emitters hard enough, pills should soon get heat treated…… :bigsmile:
Might make a small difference, but Copper and Brass don’t need to be cooled slowly like a lot of other metals. You can anneal it by dropping it in a bucket of water, or cooling it 1 degree an hour, it will still end up metallurgically the same.
Id say the brass gets pretty hot in flashlights, would have to be over 100 deg C in a hard driven light I would think. Not quite enough to anneal it though
Ben, sounds awesome.
Graeme came around last night and picked up some xml2 c8’s, the ones in the first post.
Took him outside with the 125k xpg, and a stock xml u2.
It didn’t look 6 times brighter, but I guess thats colour temps playing with you! Im thinking about dropping even on more colour bin for the next lot, the 6500 de domed is perfectly neutral to me, but I think going one more down will be better with tracking blood etc.
Working on a DD at the moment, its all hinging on if the factory switch can hold 4.something amps going through it.
Hoping for 100k XML2!
Chris
I didn’t get any reply from crnkin, can anybody help me understand his readings.
The highest I can get from my C8 is 25,000 Lux from my Lux meter at 1m.
How he got 115,260 lux at 1m where he shows 1807 from the meter.
measured at 8 meters? that would be 115648 cd
Answered it a few days ago
Chris
Thanks Chris. Somehow I missed your reply or else I’ll not post again about this.
Not that familiar at all with this Lux data and still learning.
No worries buddy!
Chris