How to Make an XHP70.2 into a Thrower

Flashlight Modding and DIY Parts
1

Here was a fun little experiment to test the effectiveness of mounting an LED in reverse, aka “recoil” configuration.

For perspective, here is a rendering of a typical 100mm wide parabola, with a 3.45mm LED at its focal point:

We normally cut off the portion behind the LED, as it is not used:

Event with a deep reflector, much light is lost to spill. Worse yet, the spill is the very best light the LED makes. Its the center of the pizza. The light from the sides is weaker and has more color aberrations. It is the crust of the pizza, burnt, dry, and no toppings, sauce or cheese.
Worse yet, the LED is very close to the base, so ratio of the die size to reflector size is very small, and we don’t get good focus from the deepest part of the reflector.
Reference djozz demo here: https://budgetlightforum.com/t/-/11947/23

If we turn the LED 180 degrees, we can capture 100% of the lumens:

Better yet, we can now drastically increase the focal length of the parabola, and get much tighter focus. By the way, this rendering is now a 7mm LED in a 150mm reflector:

It is very hard to find reflectors without holes at the vertex but I found this toy has a decent parabola. It has been around since the 1980s and is almost perfect:
3D Magic Trick

I had a 900g solid copper bar left over from an experiment several years ago, 12.7mm x 25.4mm. I mounted an XHP70.2 P2 to it:

Drilled and tapped holes for mounting bolts, glued wings to the reflector, attached buck drivers with rubber bands (my buck drivers only go to 3A, and the dropout from the 12v supply was too great, so I powered the LED as two independent 6V LEDs at 3A each:

The focus was not bad for such a non-precise reflector. At 7m, the shadow from the copper bar is gone, no corona and absolutely no spill. I think the beam spread is about 4 degrees:

My Jaxman zoomie with XHP50.2 as reference:

The Jax on the office building one street over:

The contraption. According to Texas Ace tests, 6V at 6A should be about 5000 lumens:

Hopefully someday I can go to the desert again and get some proper beam shots.

2

Interesting. I have an old XR-E flashlight like this (much smaller). I think it was coined as a recoil thrower. However there was always a shadow over the image from the bar. Also I suspect on a higher driven setup heat would have been an issue.

I’ll have to dig the host out and have a play with it. I recall messing it up when looking to mod it one time. The shape of the beam was pretty cool, but it generally under performed compared to other lights running the same LED in a regular reflector.

3

Found it. Ultrafire WF-008.




I wonder if the reason for seeing the shadow is simply down the smaller size of the reflector in this host. An interesting topic though. :slight_smile:

4

That’s cool. I think it’s the right way to go, if the heat can be shed. I found a Czech lighting company making residential fixtures with this concept:Rendl

And Hella came out with their own version last year, which is very annoying because off-road lights is what I want to make:
Hella Rallye 4000 Metal

I still want to package it up into a roof mount spotlight though. It’s so spectacular.

5

I love this, thank you for sharing. I suspect its only a matter of time before this gets picked up in the flashlight world.

6

Enderman did it…

etc.

7

Wow, I just read all 15 pages. Incredible! How did I miss that whole thread? Oh yeah, that was shortly after the new baby was born.

8

I knew it. Babies are evil.