Really all I have done so far turn the outer diameter of the battery tube to see how it looks, I like it so far. Unfortunately the x-axis on the lathe DRO has gone whacky, so I’m back to using the knobs and measuring manually.
I’m also drawing some parts in solidworks and looking around Kaidomain for lenses, reflectors and switches. I’m considering a few different optics too.
Anyone know where I can buy a Samsung INR21700-30T? I realized I don’t even have a 21700 battery to check the tube sizing.
Been awhile since I updated this. Ordered some tools from China almost 2 months ago, and they finally came in last week. So had a chance to do a bit more work.
As of now, plans have changed, I decided a tube light on this scale just wouldn’t look right with the Khatod quad optics I want to use, so instead it will have a slightly larger head and tailcap than battery tube.
Speaking of battery tube, I finally figured out how to thread on my lathe, so the tube is done! Final dimensions are 25.4mm OD, 21.5mm ID, 75mm long. Threads are a weird mix of metric and inch since I couldn’t get the metric pitches to work right. Its a 25mm major diameter, 22.9mm minor diameter, and 18 threads/inch.
Next I will probably try to get the tailcap machined, and will see how internal threading goes. Now, on to the pics
One side threads about done, first time cutting threads on this lathe.
Shaved to length and threaded the other side, as you can see a 21700 fits nicely.
Sandblasted to clean it off, and because I just like the finish that way.
Had a little bit of time today so I made the copper insert for the light engine and started the head. Cut my first internal threads on any lathe ever, and they actually work!
Right now the plan is to have the head be mostly aluminum, then have a press fit copper insert that holds the MCPCB and driver so I can solder the driver in rather than having to make a retaining ring setup. Not sure my tooling could even do threads fine enough for that. On to the pics!
Quick update for this morning’s progress. Machined out the front of the head and pressed in the copper insert. It has a 0.01mm ish interference fit, and if I had thought ahead some I would have frozen the copper and heated the aluminum, because holy cap was it tough to get in there. I actually bent the handle on my vice beating it with a hammer. But it’s in, and it won’t be going anywhere. If I were to do it again I would just press a copper slug into the aluminum tube, then do the driver and emitter pockets, and the head threads after, was nervous about messing up my previous work, but it worked out.
Once it was in I made a quick pass with the boring bar to clean up the scuffs and open the hole up enough so the optics can drop in. For the first time I think I can actually see this maybe becoming a flashlight.
Copper insert pressed in, look at those score marks! Thing won’t be moving anywhere, plus thermal and electrical contact won’t be an issue.
Cleaned up and optics dropped in, now I just need to cut the head down to length and figure out the bezel. And of course give it some style. Starting to be able to picture it as a light though!
Lots more progress today. Head is done! Just need to fill it with the electronics. The bezel ended up being deeper than I wanted, which means the optics sit pretty far back from the face (about 3.5mm), but on the plus side it should be more resistant to something breaking the lens.
I’m getting really excited now, it actually looks like a flashlight, and seems like everything should fit well. All I have left is to build the tailcap and switch.
Bezel made and the top of the head threaded. Fitment of everything is good, should hold the MCPCB to the head nicely for thermal transfer. I lost a bunch of pictures between these and the next one.
Completed head! I shaved the outside down to 27mm, and shortened up the bezel as much as I could, then added the grooves. Grooves are mostly just for looks, not deep enough to make a huge impact on heat transfer. Finally I sandblasted it all aside from the bezel threads, and screwed the tube on. Really excited to see this thing light up.
I also did start the tailcap by making the brass insert ring I will solder the driver to. I figured I would employ a classic Old-Lumens method, and make something out of plumbing hardware, so an extra fitting from my bathtub install was used as the material.
Switch is a nice beefy Omten PBS-101 on a 20.5mm board. Bonus of having the larger diameter cell is you can easily use the larger Omten switches. I was originally going to go with a 22mm PCB, but I found this assembly so went with it.
Well I sort of made the decision to just say forget all the plans and drawings, I’m just gonna build the thing and solve the problems as they come. As a result I’ve spent a lot more time actually making the light and less trying to figure out how I can make it perfect. Along the way I’ve learned a lot, and could probably make a second one much nicer.
I’m hoping to have it done by the end of this week or early next week, then I’m going to enjoy the heck out of it because it’ll have lots of run time and beautiful tint. Plus I may have the only light designed specifically for a 21700 right now.
Little bit more progress today. Got the tailcap mostly done, all the internal geometry is cut and the threads are cut. I spun the outside down to size to match the head.
Hoping tomorrow I can finish up the outside profile on the back, as it is a little bit long, and I want it to tailstand, so I need to recess the switch boot. After that I just need to make the switch washer and put the brass insert into it. Then the host will be complete!
Making some chips. The inside is already done at this point, just taking down the OD.
Can see how much extra material I left on the back. That small hole on the bottom is what the switch boot goes through.
Light is done! Really happy with it, a nice 4000k color temperature, guessing around 2000 lumens, beautiful beam from the khatod 10 degree quad optic and RMMs quad board, and lots of runtime from that almost 5Ah 21700 cell. The host doesn’t look half bad either. Lots more details with the pics.
Finished up the machining on the tailcap first. Some grooves to match the head and give it a little style. Sand blasted finish of course.
Tailcap assembled. Brass ring was a very tight fit, but not interference fit like the insert in the head, so I used a center punch to peen it into the tailcap around the edges. Won’t be going anywhere. After that it is a standard tailcap assembly, boot, washer, switch. Then soldered in place. Measured it at about 5 milli-ohms at 10A with the big Omten.
Now to take care of the driver. I used a heavily modified H2-C from kaidomain. First I removed the reverse input protection FETs on the bottom and bridged them with lots of copper braid and solder. Should help with heat from the IC too. I have covered this more in my thread on buck and boost converters here.
After that I changed the spring for a convoy spring and bypassed it with solder braid. I also replaced the short wire off the inductor from 24ga to 20ga, and replaced the output wires with nice short 20ga as well. That was the easy stuff. Next, using the schematic I posted (also in the driver thread above), and the MP3428 datasheet I did some resistor mods to change a bunch of parameters.
Once the inductor is off we can see the circuit. The purple circle is the current sense resistor, stock is 2XR100 in parallel, giving about 1.5A on high. I replaced these with an R025, R075, and R500 in parallel to give me about an R018, which I measured at 4A on high. In the green circle we have the high side FB resistor (R1 in my schematic) for setting the output voltage. Stock the driver is setup to run an XHP35, but to help efficiency I wanted to run 2P2S emitters so I needed a 6 volt type output. I swapped the 200k resistor for an 82k, giving me about 7.5V OCV, which is decent for 2S emitters. Finally, in the blue circle is the high side resistor for the battery voltage divider (R11 in my schematic), this is used for driver LVP. Stock is setup to reduce current and eventually cut out at 3.0V, I wanted to get a lower cutoff, so I stacked a 130k resistor on top of the stock 33k resistor to give me a 26.3k resistor for a roughly 2.7V cutoff. Put it all back together and it worked great. 4A on turbo to the emitters, after 60 seconds it starts dropping to about 2.8A over another 60 seconds. Low mode is about 20mA to the emitters, nice and low.
Next up was emitters, since it was a quad I would need 4, and Nichia is my go-to, after using the 90 CRI Nichias, nothing else seems good enough. I used one of RMMs MTN Quad boards which I slightly modified. It is setup for Carclo quad optics, the khatod has the same emitter spacing, but the standoffs are further out, so I turned the optic leg holes into slots, the khatod optics hit the edge of the board to press it to the head once the bezel is tight. Since i am a fan of tint mixing and Vf mixing with boost drivers, I decided to go with 4 separate emitters, and get as much red as I could at 4000k. I went with a 219B SW45k R9080 in parallel with a 219B SW40 R9080, then those were in series with a 219C SM4070e and a 219C SM353 in parallel. The net tint is about 4000k, with a nice rosy hue. The reason I decided to stick the two pairs of emitters in parallel is so that I should be able to keep running if any 2 emitters fail.
Finally time to assemble the head. First I dropped the driver in, perfect fit, and soldered it around the entire ring. Next up was the emitters, some AS5 thermal paste for the MCPCB, solder the driver wires, then just stack on the khatod optics, Kaidomain AR lens, and screw down the bezel. Now there is just one thing left, screw the parts together, pop in a battery, and turn it on. And….
Hope you all can follow that long post! I really enjoyed building this, and it feels really special to hold a light I made myself from a piece of aluminum and copper rod, and a random bathtub fitting. Time for me to sit down, enjoy my light, and have a nice homebrew hard cider.
He did a review of those: 
