2D Mag modded with an MT-G2

Hi all, i have now completed my first flashlight mod ever, using a 2d maglite as the host and adding an MT-G2 driven at about 3 amps. I know i could drive it a lot harder but this being my first mod I decided to run a lower current until i get used to how hot these things get. I opted for a design where i could make up a couple pills and pull them and drop them in tool-free and i think it turned out pretty good.

I started with the battery tube. It is made of 4 3/4” slip X male threaded PVC pipe fittings, with the points filed down to make it fit snugly into the tube. 1.375 is the ID of the mag tube, so not much has to be removed.

2 of these fittings fit an LG chem 18650 I had lying around that I borrowed from an apple ibook with a blown hard drive. These are unprotected flat top cells. I would use some 26650s but that’s more money than a broke 17 year old has to spare.

The heatsink was made by my lifelong machinist uncle, in his shop which has not been used for more than an odd job in about 6 years. We haven’t bought any cutters for the lathes in about as long so the machining was done with worn out tools, it still turned out pretty good though.


(overkill much? lol its actually not chucked, just sitting in it. The tube is too small for that chuck and the bent rod is an abomination of a chuck wrench)

I have fully potted the zener modded Qlite driver from Mountain electronics (great store btw) in JB weld.

The pill is a tight sliding fit in the tube. Tight enough that it wont fall out under it’s own weight, but loose enough that you can (if you try hard enough) pull it out barehanded.

The lip machined around the edge keeps it from falling too far.

This is what the inside of the tube looks like

The abrasions in the anodizing were from me aborting the idea of sanding it down inside for a better ground. the spring i had laying around and it has some copper braid stuffed in it.

Well that’s pretty much it, the emitter star is being held on by Arctic Silver, and i already have the tailcap spring modded for when i use the 18650s that i have on the way.

Beamshots are coming as soon as i work out all the reflector kinks, and find my standalone camera. Sorry for the poor iphone photos, but its the best i have right now and a lot of this was built at too late o’clock during exam week, so poor photos are to be expected.

My uncle also agreed to make more of those heatsinks, and even some in copper to sell if anyone is interested.I just need a reason to justify buying a couple hundred dollars worth of machine tools lol.

Hope you like it ! Thanks for reading.

It sounds like you have had a nice time with your uncle. The pill looks really nice. If you have trouble with your reflector try searching Old-Lumens D mag for some hints Or go through his threads.

http://budgetlightforum.com/user/2120/cmf

I've built quite a few lights running MTG-2 leds under 3 amps and more than happy with the light output.

Has the bug bitten and if so whats next? I believe that with your uncles help that you could build a complete light from scratch. Theres heaps of threads about them here. Yell out if you need a hand.

The bug bit about a year ago actually….I had just been lurking around the forums and decided to build a light and get an account.

As for what’s next, I think I’m going to improve this design and make a few other pills that I can swap out with an XM-L2 and an XP-G2 thrower.

My main concern is heat, and I think I’m just being paranoid about my $20 emitter, but after having it on high for ~10 seconds, I can’t touch the star. How much can these things tolerate ? I really don’t want to cook my emitter lol.

With the star installed on the heatsink or free-air?

EDIT: FWIW, we can’t measure temps over 45c or so by touch anyway. I don’t go around touching my stars while they are running so I didn’t think about that at first! The LED is good to way above that. Cree’s datasheet lists 150c as the “Maximum” junction temperature, so max star temp will be somewhere below that… but way, way above your tolerance for pain as well as way, way above the temp where flash will scald.

EDIT2: Also -

  • Welcome.
  • thanks for posting your build
  • looks like you’ve got quite a resource there in your uncle!
  • no need to use worn out tooling: sharpened bits are a matter of watching a couple of videos on youtube and walking over to the bench grinder.

Amazing for your first build. I can’t wait to see what you come up with next.
Maglites are not the easiest to work with

Lightgecko,

I really like your modular design. You obviously put a lot of thought into your contact arrangement. I really doubt the heat from an MT-G2 at 3 amps will be an issue as long as you can feel the body and head of the maglite getting warm. If the host isn't getting warm then you may need to tighten the fit of the heatsink in the neck of the tube. Wrapping the heatsink in scraps of aluminum or copper foil could achieve that end. The heatsink will be more difficult to pull out that way but adding a pair of threaded holes in the outside front face of the heatsink could allow you to add a temporary "handle" for pulling purposes.

I, for one, would welcome a reliable domestic source for reasonably priced mag heatsinks.

Just my unsolicited two cents,

Brian

Nice work! A 2D MagLight with MT-G2 is a very nice light. 3A is a good bit of light output, reasonable run time, and a very nice first build.

The MT-G2 can take quite a bit more than that. 5 x that, if necessary. :wink:

What would you consider a reasonable price ?

When the star is on the heatsink. I thought that the light output might be what I was feeling, but I just wanted to be sure.

And that’s actually what I meant, we are completely out of tool steel and this was done with the last passable carbide cutter left. And when this was a functioning machine shop, it was mostly making paper mill rollers, and repairing 1 foot plus diameter ball bearings. With some occasional large pipe fittings. The point is, we don’t have the setup for small parts at the moment. But that can change.

Out of curiosity though, how long do you think it would last only on the star in open air @ 3A ?

Pretty much the worst case scenario would be the solder melting and allowing the MT-G2 to slide or twist and short out. That’s about the only way your’e gonna kill it.

Well, the mag body did get warm, but it took quite some time. I was looking It over last night, and I realized the emitter star was loose on the pill.
Apparently I bought arctic silver grease, not adhesive. Whoops. Newbie mistake
At any rate, a drop of JB weld in the other 2 holes and clamping the head down on it overnight did the trick. It’s put in place now and the body starts getting warm in ~40 seconds on high, vs ~70 seconds before.

And Welcome to BLF!

Love the looks of that old lathe, that’s when they built things to last 100 years or more.
Later,
Keith

One of the easiest things to figure from the Cree site is junction temperature. Thermal resistance is listed for each and every Cree led and for MT-G2 is 1.5 C/W. This means the led junction will be 1.5C hotter than the solder point for every watt you pump through it. At 3A the Vf is around 6.25V so close to 19W which means the led junction will be ~30C hotter than the solder point. Copper DTP stars are fantastic at spreading out that point of heat and with good contact sharing it with the host. Anything less than enough to boil water (100C) in the star is well below the 120 limit(150C-30C).

I for one would like to find a copper pill that I can put in a maglite that is does not require a destructive mod to get it to work.

What I mean is maglits come with that handy thread in contact I took one of thoes drop in led adapters (10mm I think) and “upgraded” the emitter to an xml2 but I am pretty sure the circut is holding the xml2 back.

I keep thining that a solid copper pill that allows us to DD the emitters would be a marketable item. I know Venture used to make drop in with big heat sinks and I know malkoff used to make them also but both required to start hacking away at the light.

If you and or your uncle is open to it I bet a buch of folks here dont have ready access to machinists (other then at market rate).

It could be a good way to start generating funds for your lumen addiction?

.02