who said sled lights were dead? Grandpa's on-and-flashing rear light- Mtbr.com
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  1. #1
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    who said sled lights were dead? Grandpa's on-and-flashing rear light

    this light is like Grandpa's axe - this is its 3rd iteration (at least), with 2 different LEDs, 3 different batteries and countless switches. It's also the most important rear light on my bike as it is both on (distance perception for approaching drivers) and flashing (to get their attention). It even has a double-double flash which I wrote the code for myself. Only took me a year to learn how!

    anyway, this is the old one - charger was failing and the switch was on the way out (turned the light off on bumps)


    starting materials

    some random alu scrap, some scavenged batteries (3 for a total of 4Ah) and a microUSB charging+protection circuit


    some 1.5in square tubing from the scrap yard

  2. #2
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    pocket for charger milled out, then hacked out with a Dremel and carbide burr, plus a couple of screws for extra security


    milling some slots in the back, plus the switch and charger hole. impromptu machinists jack stopped the whole lot from singing too badly


    sled and housing finished and polished prior to anodising


    ta da! Didn't come out bad. The mystery tubing allow didn't anodise as well, some smut and it didn't take the dye as deeply. Next time I'll anodise different parts separately so the settings are right for each part rather than the whole assembly.

  3. #3
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    starting the wiring process


    showing a whoopsie where I cut deeper than intended while carving out the charger hole and cut into that when I did the o-ring groove. Nothing a bit of JB weld can't cure


    driver holder. Fatigued solder joints has been a major source of problems with the previous versions, especially as this light sees a lot of road vibration, so this should reduce any chance of wires and parts moving relative to each other


    LED star installed. These are relatively old XP-E red LEDs. The new XP-E2 LEDs would be brighter still. The star is parallel wired so the forward voltage is the same as 1 LED (about 2.5V) and the current draw of each LED is 1/3 of the output of the driver (~1.8A).

  4. #4
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    everything installed. Didn't take pics of the finished wiring job as I was trying to get everything finished before dinner. The 3 batteries only just fit.

    Clear part is made from 2 pieces of lexan, one bored to fit the optic, 5 minute epoxied together. Then the edges were milled to send some light back and forward at an angle to increase side visibility.


    the back


    front on view


    Cateye clip on the bottom and extra screw to increase thermal transfer from the sled to the housing

  5. #5
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    on full


    I was happy to have this riding home in the rain tonight. I'm much less worried about being hit from behind with a couple of bright lights out back.

    Now to get back to the front light!

  6. #6
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    Thanks for recording what you're doing. I miss the old days when so many people were rolling their own lights. The light looks excellent, and a good rear light is certainly essential for road riding.

    Tim

  7. #7
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    thanks Tim. I miss the old days too, always lots of cool stuff going on (and more mtbing in my life!). I think it's easy to be a victim of ones own success too - once you get good at this your lights last a long time and there are only so many lights one person needs

    I'm really happy with this light I was happy with the last version until I started putting in alot more miles (50/day) and its weaknesses started showing up. Cars definitely give me a wider berth with this on that's for sure!

  8. #8
    Light freak
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    Nice job Matt, looks nice!!

    ******

  9. #9
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    thanks Scar, much appreciated!

  10. #10
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    Quote Originally Posted by mattthemuppet View Post
    ..... I think it's easy to be a victim of ones own success too - once you get good at this your lights last a long time and there are only so many lights one person needs
    That's exactly where I'm at. My last bar light was really more of a CAD/CAM exercise than it was to fill a need in my collection of lights.

    The "sled light" design is a classic in the DIY world. Probably the best design out there for folks with limited access to machinery.
    GoPro adapters for bike lights http://www.pacifier.com/~kevinb/index.html

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