BLF recoil über-thrower

It's honestly not that conductive due to the distance the heat has to travel, liquid cooling work work far better but cost far more.

Maybe if you can find some heat pipes from china that would work a lot better? They transfer heat a lot better than just solid copper.

Hmmm… I guess i overestimate the copper boom…
What’s in those heat pipes anyway?
I assume you mean those copper tubes used in laptop cooling etc…

Heat pipes have some sort of liquid inside

If I remember right a bar of 3 heatpipes of about 5x6mm could cool my 85W Laptop CPU they were like 15cm long

They are used in big cpu coolers because they can transport heat a lot better than way thicker solid copper

I am sure a bar of 3 smaller heatpipes can easily handle 20-40W of LED power

8x2.5mm Heatpipe
https://www.aliexpress.com/item/1PCS-LOT-YT257-Flat-Copper-Heat-pipe-100-8-2-5mm-Laptop-CPU-GPU-Video-Card/32732898661.html?spm=2114.01010208.3.10.2tHVLI&ws_ab_test=searchweb0_0,searchweb201602_2_10091_10090_10088_10089,searchweb201603_1&btsid=06e24f7f-d7e2-4aaf-ad55-47d434e59670

Cool! :+1:
(pun not intended)

It will only need one pipe to handle a 50w light as roughly half is converted to light and half generated as heat, a 8mm x 2.5mm pipe will handle that with room to spare, however I would suggest two for rigidity and also the cooler a led is the more efficient it is.
Have a read of this pdf from Digi-Key.

Cheers David

Still that much?
If an XP-L HI is used at 6A @ 3,9 V, would that not mean a total energy of 23,4 Watts of which the majority is transformed into light?
Please correct me if I’m wrong, these kinda calculations are not my strong suit.

So maybe one small copper bar with one small heat pipe inside?

Grtz
Nico

The reflector that I’m checking out atm is a cheap plastic reflector used in those optical illusion discs, like this one: http://www.ebay.com/itm/Toysmith-3-D-Mirascope-6-Inch-/162165285686?hash=item25c1cde336:g:5XQAAOSw9NdXq7Kw The focal length of this reflecor, as EasyB noted, is short, just as needed for this kind of set-up, just a bit above the edge of the reflector. I have a 6 inch version that I’m trying out, but there is a 9 inch version that should work better and have better throw. But here in The Netherlands I can not buy one for cheap, in the States they are plenty available. I think that optically the reflectors in these toys are not bad (or they would not work for the optical illusion) but I suspect that the surface does not reflect optimally, there’s more light loss there than is desirable.

In a test set-up with a XP-G2 S3 3d dedomed and direct drive (I used a 14500 zoomie flashlight without lens, so as a mule), and blocking the outer edge of the beam so that a 90mm diameter section of the reflector is used, I get 310kcd. But it is running from an Efest 14500 and the flashlight and clamp are blocking quite some light, in a better build I expect over 400kcd from this. Considering that 90mm of the reflector is used, there is room for improvement, probably with a better reflector, but it is fun anyway to see the principle working so well.

Alright, if you guys manage to build a recoil thrower with active liquid cooling I’m definitely in :money_mouth_face:

Would a heat pipe behind the LED a good idea?

Apparently, yes.
I ordered one today, hope it will arrive soon so i can check it out.

…you mean with a pump and a radiator? :smiley:

heat pipes by themselves can not handle anything, they only move heat, not dissipate it.
there is always a heatsink and fan on the other side of heatpipes, also heatpipes work well only when hot end is lower than cold end, with something stationary like a computer, you can have radiator\heatsource mounted with height difference, but a flashlight that is not stationary it is not the best solution at all.

I think a heatpipe is probably a good solution for getting heat away from the LED. Even if it is not oriented optimally, it’s probably a lot better than a solid piece of Cu of the same size. I could be wrong about that, but heatpipes in laptops, for example, are not oriented vertically.

I think everyone is aware that the heatpipe is just a way to transfer heat and not dissipate it. Of course it would be connected to a heatsink.

Heatpipe is the best solution to cool a led above 15W

I’m going to make my test light without active cooling: the XP-G2 will be producing about 14W of heat, let’s see if I can get that guided away fast enough, I think I can :slight_smile:

To make this a bit more quantitative:
The thermal resistance of a piece of material with cross sectional area A, length x, and thermal conductivity k, is
R=x/(A*k)

So for a copper bar 0.5cm x 1cm and 7cm long, with k=385 W/m*K, the thermal resistance is 3.6 K/W. This is quite high when compared to other flashlight shapes/designs. For example, I did some thermal testing of a couple flashlights and found their thermal resistances (from MCPCB shelf to outside of flashlight head) were almost 10x less. Whether it’s too high depends on the power of the LED and the size of the heatsink and how hot we allow the heatsink to get.

It’s supposed to transfer the heat from the LED to the head (and body) of the light in this case.

I didn’t know that it uses height differences.
If so, the drawing in opening post is upside down. :slight_smile:

I think i should have ordered more than one heat pipe maybe…
(edit) Just ordered a 2nd one.

Dang, i wish i had a mirror i could use…
…but when you say the XP-G2 will produce 14 Watts of heat, you’re apparently gonna push some 7 Amperes through it…??

I think the height difference is not necessary, it just helps. If the hot side is lower, the liquid that recondenses on the cold side then doesn’t have to diffuse/wick back to the hot side against gravity. Just a guess.

That's really high. Could you post a picture or link of your setup plz? :)

OP is not going to do that for costs reasons and convenience, but when I do in the future, I'll definitely put a build log on the forum ;)

The actual light efficiency of an LED drops when you give it more current, so even if the LED is 150lm/W at stock it might only be 100lm/W or less when running near max.

https://en.wikipedia.org/wiki/Luminous_efficacy

So you get about 15-20% efficiency.

I think people overestimate how efficient LEDs are, there is still a ton of energy being turned into heat.