Does anyone have experience making a custom taillight?

Posted by anon_sir@reddit | projectcar | View on Reddit | 18 comments

I need to keep this led board from moving around and I was thinking I could cast it with resin.

Should I use polyurethane resin or epoxy resin?

Should I use mold release and keep the led board separate from the lens, or scuff the inside of the lens and make it one piece?

Thanks in advance for any help!

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hhrsspanelman@reddit

Resin will hold it just fine, but keep in mind on some cars switching to LED brake lights can be screwy with the cruise control.

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anon_sir@reddit (OP)

It’s actually going on a motorcycle. 1981 Harley sportster chopper.

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silic0n_jesus@reddit

I have built so many Harley taillights Alumalite. dm me for tips.

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texan01@reddit

Even non computerized cars like 1970s GM can get weird with LES bulbs in front sidemarkers since it’s an alternate ground for the front turn signals.

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Some cars, like 2000s gm, use resistance through the brake lights to control the cruise pause/reset option. So when you step on the breaks the cruise control is paused and pressing resume sets it back up.

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DC2-@reddit

Ahh gotcha, thank you sir. That makes sense.

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Gwendolyn-NB@reddit

Ok few options; done a lot of this stuff for decades.

- Design and 3D print a rear cover, then it's not potted and looks more factory; I do this a lot if I've got a factory piece I'm trying to replicated/update and want to use the factory mounting locations.

- Epoxy fill the whole thing - make sure you use one that is UV stable and won't yellow over time. I do this quite a bit for other lights; but it becomes 100% non-serviceable, so it works for smaller lights where it's cheap/easy to make another one.

- Use some silicone and make a positive mold of the void between the LED bar and housing; then make a negative mold of that; so one silicone mold off another... then cast the first part in Epoxy; then just tack the corners/edges. More work than #2, but makes it serviceable if you need to replace the LEDs or lens. Also allows for doing some funky stuff with the epoxy/resin with colors/sections/blocking/sectioning.

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anon_sir@reddit (OP)

The pot metal piece is gone, I made a bucket with a backing plate.

Now that I think about it, I could probably super glue some neodymium magnets to the led board and call it a day. That should keep it from jiggling around and be easy to take back apart if I need to replace the leds.

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ItWorkedInCAD@reddit

I would suggest 3D printing a backing plate that you can attach the LED board to and attach to the lens. Will make it a lot easier to service, you don’t have to check resin compatibility with the lens and (in my opinion) will make it look a lot better.

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anon_sir@reddit (OP)

There’s a bucket the whole assembly will fit into with a backing plate and a grommet for the wires to fit through.

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Substantial_Ant_2662@reddit

I repurposed some lights from my OEM bumper

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silic0n_jesus@reddit

I have built several custom tail lights with custom LEDs for motorcycles where they are polished into the paint the product you want is Alumalite easy to pour the solvent is rubbing alcohol fantastic product.

https://alumilite.com/

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Threedawg@reddit

Yes! Specifically how to make it look solid red instead of like a strip of LEDs.

Two thin layers of bright red UV resistant paint inside the lens do the trick.

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