BLF recoil über-thrower

Of course, but my initial goal was to reflect as much light as possible and out throwing everything else with the same ‘light engine’ and hotspot size.
Now i’m not so sure if this will be better than a multi lens set up (with which i have gotten some impressive (at least to me) results)…
We’ll see.
Soon the mirascope will arrive, then i can get an idea.

Recoil is definitely the best way to get almost all the light, I have a flashlight using a 100mm aspheric which has awesome throw and 1M lux, but there is over 50% light wasted even with a Wavien collar, so it's about 500lm or less actually coming out the front.

I'm not a fan of multi-lens setups due to the inefficiency at each lens, and imperfections/error gets multiplied every time making the collimation worse. 1 or 2 lenses is the optimal configuration. or a single reflector.

Currently I'm doing some tests with an aspheric+spherical lens, I got about 1 960 000 lux on the last test (no collar) which is pretty impressive, although the thing is as big as a garbage can and weighs like 5kg xD

I'm looking forward to seeing your reflector results, if you can get at least 500k lux I will also buy one :D

If heat is a concern, what if the arm was (at least in part) a heatpipe as opposed to solid metal?

It could be drilled. I’m talking about pumped fluid, not a liquid salt. Other options are good, I’m thinking aloud about how to use these fancy mills.

Guys, he already bought a heat pipe to do the initial testing, he knows its better than solid copper :P I think it was discussed on page 2 or 3 or something.

More than one of us can make things.

Yes? And how is that relevant to the fact that heatpipes instead of solid copper was already suggested back in page two?

Bending heat pipes is difficult (wick must not be crimped, probably can’t bend multiple times due work hardening/embrittlement) and so is ensuring a tight fit to a heat sink. Fitting an U shaped pipe would require very precise bending while probably resulting in a larger head/more complicated heat sink design due to the required radius in the bend, an L piece would be slightly easier to mount but still tricky for the same reason and I guess centering of the mounted LED.
With an angled design there would be no radius to take into consideration and fit would basically be limited to lining up the contact surface of the HS to the rim of the reflector:

Imagine a cover over the heat pipe/heat sink contact area. My vector drawing skills aren’t too great :stuck_out_tongue:

Zebralight head lamp: https://eu.nkon.nl/magento17/media/catalog/product/cache/7/image/9df78eab33525d08d6e5fb8d27136e95/h/5/h52w_3.jpeg obviously much smaller light, it’s about the general idea.

This is interesting too:

https://www.aliexpress.com/item/4mm-Outer-Diameter-x-1mm-Thickness-Soft-copper-tube-metal-hose-air-conditioner-pipe/32685875240.html?scm=1007.12873.37803.0&pvid=cfb748f2-bba0-4a91-865c-46e7f8908574&tpp=1

No bending if used with a copper bezel, the heat pipe could be soldered/brazed to it, give the bezel a few fins and there is your cooling, also by using three pipes (merc symbol) it would not matter how it was orientated and give it the ability to hold the led at the focal point during rough use.
As far as using a large reflector the pipes would block less light % than using a smaller one :wink:

Cheers David

I think it's not hard to bend heat pipes, I have seen people just wrap them around a solid metal cylinder to get nice 90 degree angles.

With flat heat pipes it's even easier than round, all you need to do is check the minimum bend radius (usually mentioned by the manufacturer) based on the width and thickness, and then bend it a bit bigger than that.

There is always the risk of kinking it if not bent correctly, but doing a 90 degree large radius bend should require minimal skill.

I really like the idea of using an aluminum/metal cylinder as the body and just binding the heatpipe to that using thermal adhesive, makes it a lot sleeker on the outside while still having good cooling :)

Whether a ‘bezel with a few fins’ would be sufficient depends on the power consumption of the LED. Remember that the heat pipe itself does not provide substantial cooling, it just transfers heat from A to B.
Soldering is possible afaik although you can see how easy that is by trying to solder something to bare copper and then multiplying by ~10. Brazing will probably cause the pipe to burst. Thermal epoxy is viable and common but you still need a tight fit between HP and HS, arctic silver epoxy has a thermal conductivity of about 8W/mK, even small (<1.5 mm thickness) heat pipes have conductivities in the range of 700W/mK and higher.
Another reason why a decent heat sink is important: If you’re using something like an MTG2 the LED itself can stomach junction temps well over 100C. The heatpipe can’t, because water is a gas at 100C (assuming the whole HP/HS circuit reaches 100C or close enough).

A page from the link I posted on page two, note they contain H2O.

Soldering is not only possible with a finished pipe but also gives optimal results :wink:

I should of said brazing can be done during manufacturing while it is still just a pipe not a heat-pipe.

Water boils at 100c at sea level pressure, contain it and the pressure rises as does the boiling point, think of a steam engine the fire produces enough heat to instantly melt lead yet the water is held just below boiling point, at the other extreme water will both boil and freeze at the same time in space :smiley:

Cheers David

I did a series of throw tests last evening on the cheapo plastic optical illusion reflector (mine is even unbranded chinese, I read above that there's quality differences even in these toys). I used a dedomed XP-E2 on 10mA current as light source and found that with the full size reflector there is not one focus, the middle part of the reflector does something completely different than the edge. Which is of course not good for throw. I wonder if this is inherent about a parabolic reflector used at these steep angles or that these optical illusion reflectors are particularly bad?

But this is the reflector I'm going to make a light out of, so I checked the hotspot brightness while varying which part of the reflector is used, from full size down to just 50mm diameter. I did this by laying the reflector upwards on the table and pointing the beam to the ceiling, and by placing pieces of cardboard with varying holes on top of the reflector I varied the reflector size. The led was positioned in the optimal focus point (that gave the highest spot brightness) using my XYZ-table. The highest luxreading in the hotspot was measured each time with a luxmeter.

Here are the luxvalues that I found, the numbers themselves have no exact meaning but they are a measure of spot brightness:

Full size (139mm) 946
90mm 898
80mm 881
70mm 865
60mm 858
50mm 663

As you can see, in this reflector it is quite pointless to go larger than 60mm (huge size increases with hardly any throw gain), the focal distance being 48mm this is about a 60 degrees cone of the led-beam. I was a bit surprised a this and I wonder if this is a general thing with recoil throwers, or that it is just a sign of using a bad reflector.

Fact is that 1) the (dedomed!) led has the highest brightness straight forward and clearly less close to 90 degrees to the side (it is in the led datasheets but I illustrated it a bit more visually below by positioning the used dedomed XP-E2 in the middle point of a piece of paper bended in a circle), and 2) that the imaging quality of the reflector is decreasing when going from the middle to the edge (I checked that by blocking defined parts of the reflector and watching the effect on the hotspot). In other words, it is a challenge to get enough light that is reflected by the edge of the reflector in the direction of the hotspot.

Extrapolating these results to the bigger 9-inch Mirascope reflector, a 90mm diameter section of that one should make the best size if a recoil thrower would be made with it.

I'm still overthinking what the influence has been of using the very small die dedomed XP-E2 (which was at hand) compared to leds with bigger dies.

Thanks for the testing! :)

Did you test out the mirasope before using it for the tests?

If the image of the mirasope (when used as intended) is highly distorted that could indicate problems with the reflector quality.

The mirasopes are supposed to be perfectly parabolic, so if your luxmeter was centered when you were doing your measurements the outside of the parabolic reflector would be reflecting light straight forward which would land outside the luxmeter. Basically the larger mirasope diameter should be making a larger spot, not a higher intensity spot, unless you measure with the reflector focused to a point at several meters distance.

Do you have any pics of the spot with the different sized holes we could take a look at?

The mirascope worked fine, my six year old son was amazed by it and demanded that I would not destroy it and make a flashlight out of the reflector :person_facepalming:

I have to think about the ray direction coming from the edge of the reflector compared to the centre. If what you suggest is indeed going on, the contribution of the edge of the reflector to the hotspot brightness would increase with imaging distance (which was just 2 meter in the test).

The recoil reflector should work in the same way, in principle, to a standard orientation reflector.
This thread has relevant discussion: Reflector width vs depth for throw?

The beam of a parabolic reflector can be thought of as an image of the LED, sort of the same as the beam from a aspheric lens light. Except the reflector has different focal lengths and so the beam is actually a superposition of the different sized and oriented images of the LED produced by the different parts of the reflector.

The light reflecting from the outer diameter of the reflector should produce the smallest beam since the focal length there (distance from LED to reflector) is the largest (see demonstration done by djozz in the above linked thread). The fact that the reflector in djozz’s present experiments is behaving differently for the inner and outer sections is indicative of the reflector just not being perfectly parabolic.

Well Djozz, that all sounds a little disappointing… :frowning:
Let’s say i hope your mirror works better as a mirascope…

I expect mine in the mail tomorrow, i hope it may be better, but they all look rather identical, maybe there’s only one factory in China that makes them. (?)

If mine is bad too, it’s probably the end of this project for me, unless miraculously a source of proper affordable parabolic mirrors suddenly pops up…

In your last picture is see that your LED does shine about 135° wide, with the ‘best’ light within some 90°.
But it’s hard to really tell by the picture.
But i think it explains why a zoomy has a brighter hotspot (in focus) than a regular light.

Anyway, thanks for the effort.

If you do a ray trace of a parabolic reflector you will see that when focused to infinity (aka not converging or diverging) the LED is at the focal point, and all rays are collimated.

In this case, a larger reflector will make a larger spot (eg. a 6" diameter reflector will make a 6" spot, a 9" diameter reflector will make a 9" spot)

In either case the intensity will be the same, but more of the light is being collected in order to make the spot bigger with higher lumen output overall (same intensity, more area = higher lumens)

I would definitely suggest doing tests at large distances (eg 5m or 10m or around there), the converging beams should be a lot more accurate and form a smaller point. Pictures of the projected spot or beam would also be able to show if te reflector is collimating correctly.

One trick I love to use to make sure by optics are collimating is spraying the air with a water sprayer (fine mist) which allows me to see exactly which rays are going straight forward, which are converging, etc...

Very convenient way of checking the collimation that doesn't require a foggy night :P

In practice it does not work this way, probably because LEDs are not points. Please see demonstration done in the thread I linked above.

In practice this is definitely not true. See this thread: Flashlight Optics - Dome, Dedoming and Throw