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  1. #1
    Singletrack Daydreamer
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    Scar inspired homebrew

    I started this project in late October, but delays in receiving the optics slowed the process a bit. The LEDs are Cree Q5.


    Machined housings and other bits


    Routing wires between the housings


    More bits in place. The copper heatsink is designed to pull heat outside the housing as quickly as possible.


    One LED in place, wired and ready, one to go.


    Modified lens ready to go in place.


    Despite the plan to use micro pots, the area is just too small to be able to cram in all the wiring and bits, so I resorted to two resistors. One is 1k ohms, the other is 470 ohms. The on-off-on toggle switch gives a low (about 200 lumens), high (about 500 lumens), medium (about 350 lumens) option at the flip of a switch.


    Heat shrink tubing prevents wiring from grounding out on the body of the light.


    Assembly completed, heatsink in place.


    Completed unit lit up and ready to mount. I still have to mount it to a helmet mount, but it's tested and impressive.

    Cree Q5s (ones shown from cutter, but can be had from DX) (2): $9.75 (ea)
    Optics from Cutter (2): $3.95 (ea)
    BuckPuck from LEDSupply: $13.99 (caught on sale)
    Switch from Radio Shack: $2.95
    Heatsinks from Radio Shack (2): $1.30 (ea)
    Screws from Home Depot: $5.00
    Aluminum & Copper stock from local metal sales: $5.00
    Wires, solder, heat paste, silicone sealant & misc.: $10.00
    Broken double end 1/8" mill bits from Shars (3): $3.95 (ea)
    Time invested: 10-14 hours
    Total weight (w/o battery): 218g
    Joy gained from a light I can be proud of: Priceless

    I'd definitely buy a prewired puck next time and could make it about 1/2" shorter body. It took a lot of figuring to get the wire routing right and such, so next time I'd suspect it would only take about two or three hours for manufacture and assembly.

    Thanks for the inspiration Scar.
    Train 'til you puke. Cheat to win. Party like a rockstar. We miss you, Jan!

  2. #2
    Light freak
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    rockymtnway - Excellent looking light. Very creative solution for the heatsink!!

  3. #3
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    Brilliant, I love it. I'm assuming you had to do a lot of sealing around the copper inserts?

  4. #4
    Singletrack Daydreamer
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    Thanks guys. I used some but not enough to make it truly water tight. I wanted to basically dry fit it, ride a little with it so see if the lenses provided the spread and spill that I wanted before sealing it up for submarine duty. The final build will have a lot more silicone sealant and I'll use thermal epoxy instead of thermal grease.

    I just did a still air heat test and got the following results:
    Start temp 5 minute 10 minute
    Low 74.5F 81.4F 83.9F
    Mid 73.4F 85.9F 89.0F
    Hi 71.0F 86.0F 102.1F

    Temp taken with a non-contact thermometer set to record the highest temperature and moved across the top of the entire unit. Little doubt the temperature was running away at the end of the Hi test, as 30 seconds later it was 106.0. However, the copper coming out of the unit was the hottest part of the unit, so mission accomplisted for getting the heat out of the housing. The other two tests seemed to be reaching an equilibrium.
    Train 'til you puke. Cheat to win. Party like a rockstar. We miss you, Jan!

  5. #5
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    How did you assemble the front and back plates?

  6. #6
    Singletrack Daydreamer
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    I drilled and tapped #8 screw threads from the bottom through the base plate and into the light bodies. The rear switch plate started off as a 3/8" aluminum box that I trimmed down to only 3/16" thick where I installed the switch, but where it is tapped, it's still full thickness giving it some good thread contact. I also went into two similar blocks that are essentially insulators behind the copper heat conduits. I used 1/4" and 1/2" set screws (headless w/ 2mm allen heads in the thread) to hold the whole thing together. A little locktite once I'm done swapping out lenses (going for a 4 degree and a 15 degree rather than two 4 degrees currently set up) and some silicone around the edges and it should be good to go. I'll post a picture from the bottom as soon as I can find my camera again (probably buried under a pile of wire, scrap aluminum and resistors).

    I will be swapping out the resistors, as I did a little testing and wasn't getting the power I thought I was getting. With a 470 ohm resistor I was only putting out about 134ma and with the 1k ohm resistor I was putting out about 460ma. After some experimentation, I figure I need to be using a 700 ohm and 2k ohm to get the 350ma and 750ma output that I was looking for. I'll post all the data I gathered on how to get the right bang from your puck (pun intended).
    Train 'til you puke. Cheat to win. Party like a rockstar. We miss you, Jan!

  7. #7
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    So you have a set screw coming from the bottom, and that presses the base of the lens, and for the back, presses the base of the aluminum block?

  8. #8
    Singletrack Daydreamer
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    In the case of the lens, yes, the set screw just presses it in place. In the case of the back and middle blocks, their also threaded, so the set screws are actually screwed into them. Since I needed some way of holding the base plate that holds the two together and provides the foundation for the mount, the set screws work well enough with some locktite. It's not like you can really torque on them (with barely a full thread in the 1/8" thick aluminum tubing), but they do a fair job of pinning it all in place. At least with the internal 3/8" block I have over a half inch of thread to screw into.
    Train 'til you puke. Cheat to win. Party like a rockstar. We miss you, Jan!

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