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Discussion Starter · #1 ·
I'm diving in for my second home-brewed light. This is a mash-up of an achesalot and troutie-styled light; both of which I find very interesting. My design goals for this wearable headlamp project are as follows:

-Sub-100g including battery and strap
-200 lumens with 2 to 3 hours capacity
-Max case temp of 50 ° C in still air/light breeze
-A head size that is as small or smaller than Apex Pro
-Preferably no exterior fins

Components:
2 x Cree XPG (wired in parallel)
1 x 18650
1 x LFlex driver
1 mm walled, 25 mm square tubing

Which of the following is likely to provide greater cooling capacity:

2mm holes in the case,


Total volume of metal removed 88 cm3

Flat surface area removed (175 mm2)
Side surface area gained 229 mm2
Net surface area gained 53 mm2

or 2mm slots in the case?

Total volume of metal removed 200 cm3

Flat surface area removed (400 mm2)
Side surface area gained 204 mm2
Net surface area lost (196 mm2)

The piece of angle shown inside the case will have a series of heat sink fins mounted between the holes or slots, so that I can get some extra heat dissipation.

Thank you for taking the time to consider this.
 

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a bit more info on why you've chosen a particular option would be helpful. Eg.
why 2 XP-G if you only want 200lms? 1 XP-G can do that easily (and up to 400lms if necessary).
Why the 10mm optics? they have a bad rep for being very floody with not much throw - a single XP-G and Regina would be far better.
Where's the battery going to go? Why only 1 cell? A 2P battery isn't going to be that much more noticeable on your helmet, if this is where the light is destined for.
If you want to use 25mm OD tubing, you can do this easily by simply cutting a U shape from the tubing, stick LED on one end, switch and power cord on the other, with the lflex in the middle. Then slide into a 44mm long piece of tubing, attach with screw through a cateye clip, then use a cateye helmet mount.

That plus a 2P battery should get you in around 120-140g (or 80-100g for a 1P battery) and 350lm/2h. It'll be a lot simpler to make too :)
 

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matthemuppet - if he's going to use an Lflex then wouldn't it make even more sense to use an xm-l and drive it at low amps? You would have the ability to drive it higher if needed and the Lflex/xm-l will be designed to work at 3.7v.
The reason I ask is that is the light I want to build using your design along w/ troutie's suggestions w/ his "1". How would you connect the sled w/ a screw through a cateye clip? If the Lflex is sitting on the middle section of the sled, wouldn't that make the screw go through the same section of aluminum that the Lflex is on?
Also, how would you add more surface cooling to run that puppy at 2.8 amps?
thanks in advance.
andy
 

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Discussion Starter · #4 ·
Thanks for the questions, guys.

I want a very floddy light, at 90 CRI, which is what led me to the XPG and 10mm (XML is out due to color and CRI).

I want to stay inside th 25mm x 25mm box size for use as a working/playing headlamp on a strap.

The 1s1p choice is strictly weight/size driven.

The 2 XPG v. 1 XPG is to squeeze just a touch more efficiency.

200 lumens is the average expected output. The 18650 should be good up to 2C draw, and the housing should be good for just a few minutes of "high beams."

Temp regulation is an absolute requirement to avoid a toasty forehead.
 

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So are you looking at using the xp-g Q2 to achieve the 90CRI

As for cooling I would go for fins. That way when you are stopped, natural convection will cool much better as the air travels upwards through the fins. I think there would be too much turbulence in the drilled holes to be efficient.

Brad
 

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Discussion Starter · #7 ·
Makes sense, Brad, thanks. Slots are easier, too.

Yes, the HI CRI Q2s are currently making their way from OZ.

As an aside, my absolute favorite light beam of all time is a Surefire C3 with the P91 incan module, which is what I am trying to duplicate here.

Seeing the beamshots posted here, I do agree with Matt that I would prefer a Regina, but I just don't have the room in this one.
 

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I prefer your slotted version.

The 10mm Carclos will give you the floody beam you are looking for.

The sub 100 gram mark seems to me a bit tough to hit. I have 2 dual XPG designs that weigh 26.4 grams using Reginas, and 27.1 grams using 10mm Carclos. Neither of those has the driver in the head, it lives in the battery pack. The Carclo version could be lighter if it were not designed to run at 1A (fewer/thinner fins). If your lamp assembly comes in somewhere around that weight and an 18650 is about 50 grams, the remaining 25 grams for head strap, cable, switch, etc. seems tough. Good luck, I am looking forward to seeing this project progress.
 

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ah, gotya, understand now :) I'm guessing that you need that tint because of what you're working on?

Re Andy13 - the lflex will go like so:

switch II__ __lflex II LED

so that it's on the opposite side of the piece of metal the LED is screwed to (screws cut flush of course). Sending the LED wires through will be a bit of a squeeze, but there should be enough room in the corners, either side of the lflex.
Then the bolt from the Cateye bracket would go through the bottom of the U to hold everything in place. I'd love to make a single XM-L for myself, but there's no way I'd be able to sneak it past my wife when I already have a very nice helmet light and I'm working on a twin XM-L bar light :)
 

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Discussion Starter · #11 ·
Matt, I just saw the design you are describing. I like it.

New question:

Is it OK to rivet the 10mm star (PCB) to the heat spreader instead of gluing, screwing or taping it down?

Like this:


I will, of course, put silver 5 thermal compound to put under the PCB before applying the 3 mm aluminum rivets.

I have some arctic epoxy inbound with the XPGs, but now I don't want to commit to these optics 100%. I might be able to squeeze a 1 XPG and a Regina into this box, and use the other LED for ???????
 

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Put the second rivet into the hole before you start to apply pressure / tighten the first rivet. This should help locate the star properly and stop it from being pushed sideways. If you are confident enough I would then also give the first rivet a single squeeze on the gun, slide the gun off and put it on the other rivet and do the same thing. This will snug them up without getting too tight. Once you're happy with the positioning of the star and that it hasn't moved then do them up tight enough that the rivet shaft snaps off as per normal.
 

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A correctly formed rivet will be fully waterproof. Sometimes the rivet shank can pull through, check you have the correct nose on your rivet gun. Also make sure the hole is the correct size. A rivet is designed to expand in the hole, as well as on either side. The amount of rivet sticking out should be the same as the diameter of the rivet. is, a 3.2mm dia rivet should have 3.2mm poking though your work.

We use a mix of solid and 'pop' rivets on the aircraft and they are all water proof.

In addition to Emu26, apply pressure onto the rivet head when you give it a squeeze, this will ensure it's nice and tight in there!
 

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P220C said:
Matt, I just saw the design you are describing. I like it.
thanks! Though it's a collaborative thought exercise with Ofroad'bent, so I can't take all the credit. I think he's planning on making a single XM-L/ lflex that way, so hopefully we'll see a build report up in the near future.
 

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Discussion Starter · #19 · (Edited)
Work Progresses - (Is it an extra gravity day?)

Work progresses on my "thinking inside the box" project. Still trying to maximize surface area at minimal weight gain without resorting to exterior fins.

The box size is 25 mm x 32 mm, and I calculate a total of 10 sq. inches of surface area. I added texture to the fins by running a file on edge at 45 degree angles. Looks like really small diamond plate, if the diamond plate factory workers were dropping acid on plate making day.


It's really hard to win this game, when the strap alone weighs 28 grams.


On the positive side, the strap, and most of the body weighs 46 grams.


I don't know how much weight the 2 x 10mm PCBs w/ XPGs, Carclo optics, and LFlex are going to add, but it seems pretty evident that I am going to have to either concede on my 100g, or 3 hours (i.e. go with a 14500 battery in lieu of 18650). I will probably just make up one battery "pack" of each (one for running with, and one for working with).
 

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P220C said:
I don't know how much weight the 2 x 10mm PCBs w/ XPGs, Carclo optics, and LFlex are going to add, but it seems pretty evident that I am going to have to either concede on my 100g
2 XPGs on 10mm round MCPCBs, 2 trimmed down Reginas, 100 mm length of 4.3 dia.cable, .75mm lexan lens cover and o-ring seal add up to 8.5g. The 10mm squares will be a bit lighter as they are thinner than the rounds.
 
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