BLF recoil über-thrower

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.

I think people don’t realise how totally inefficient incandescent lights are. :slight_smile:

That too.

10x better efficiency than 2% is still only 20% :P

I thought LEDs did better than 20% though, Djozz’s XP-G2 will probably survive then. :slight_smile:

The led will be reflowed on the middle of a copper bar, 3mm thick, on average 15mm wide, and 90mm long, so the heat can go in two directions 45mm far. After that it is spread out over an aluminium plate. I’m ok with the led running at 100degC I guess….

Sounds like it is made already but I have done nothing yet :stuck_out_tongue:

But 95mm isn't even close to the diameter of the reflector?

A 95mm heatpipe would be good from the center to the edge, but not the full diameter, if you're talking about the 6" one.

BTW thanks for the info on these cheap mirascope reflectors :) checking some out right now.

I’m not going to use the full 6 inch, but a 9mm section (~3.5 inch). I have a feeling that that is a sort of optimal size/throw combination for this reflector.
So for the 9inch version the optimal size would be 135mm, and that may even get close to the 1 Mcd (well, 900 kcd). But as said, can’t get that one for cheap, let’s first try this one.

I hope you’ll try if more will work too, because the idea is to collect / catch as much light as possible / sensible / worthwhile.

Collecting that last bit of light (the less intense light) will not add that much extra light (lumens), but the extra area of the reflector (going from 90 to 120mm) will add a lot more throw, assuming the reflector is shaped well enough to be focused. The light reflected from the outer portions of the reflector would make a very small hotspot.

I did try what the complete reflector did, but as I was sort of playing around I did not write it down. I did give more throw but not much more, and the light will be a whole lot bigger.

I understand, and that’s why in my mind it should catch about, hmm… 120° probably, but not less.
But i have no idea of the measurements of your parabole, but i think you’re around 90° with your idea (?)

:slight_smile: I just wish i had a prab. reflector to experiment with and see for myself…

Indeed, because the distance to the LED is biggest around the rim.

I did some research, it seems like the best cheap option for a parabolic reflector is these "3d mirascope" toys that djozz brought up, which come in 6 and 9 inch sizes.

They are not perfect, there are a lot of complaints about easy scratching and cheap plastic, but the coating seems pretty good as long as you handle it carefully (as you always should).

The two best ones are the mirascope 6 inch https://www.amazon.com/Toysmith-79747-3-D-Mirascope-6-Inch/dp/B000N5T8KA

And the mirage 3-D 9 inch https://www.amazon.com/Mirage-3-D-Instant-Hologram-Maker/dp/B0002W3J7M

From the reviews, these have the clearest image and least aberrations.

I put in the measurements into a ray tracer and it captures slightly over 120 degrees from the focal point, which is almost perfect for using with an LED.

I plan to buy the 9" one some time and test things out myself, if it works as expected (the other guy said he got 300-400kcd) then I will try to buy a professional glass reflector for myself with similar size and focal point.

$7 is a great deal for a reflector of this kind, and 6" is pretty close to what you were looking for so I highly recommend you try the 6" mirascope one out :)

I just decided to order one, i hope i can find one of similar quality / the same product for under 20 bucks shipped. (i’m not exactly Bill Gates…)
120° sounds great to me.
6 inch is bigger than i had in mind originally though, but so be it.
Thanks.

Wait. Did you guys miss what happened? Djozz says that with the complete reflector, the throw was greater and the beam was larger… not or, and! How could this be a bad thing?

The Ultrafire UF-007,is not sold out. Shop by Category | eBay