Headlight Temps

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Dan116i
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Headlight Temps

Post by Dan116i » Tue Mar 06, 2018 5:05 pm

Is anyone able to give a rough idea on how hot the inside of a headlight gets? I’ve got some carbon, but the resin is only rated to 65c and high temp resin is naturally more yellow than clear
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Re: Headlight Temps

Post by Nottsknots » Wed Mar 07, 2018 8:10 pm

I suspect 65 degrees is not going to be enough, assuming you're referring to halogens; you can use a halogen bulb to desolder surface mounted chips, and that's over 180 degrees C (admittedly a headlight has some volume, so would not get THAT hot).

If no-one else gives a definitive answer by the weekend, I've got a thermocouple temp sensor I can stick in and measure for you at the weekend.
E87 118d, stock, plus PDC control unit drain, Parrot, debadged, Mothercare baby shades (but no babies), and occassionally a good layer of wax. Instantly forgettable, and thats the way I like it.

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Re: Headlight Temps

Post by Dan116i » Thu Mar 08, 2018 6:32 pm

Brilliant :) cheers. I’ve got a feeling 65c isn’t going to be enough sadly. Long story short, I’m making some custom depos and looking to carbon skin the inside...
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Re: Headlight Temps

Post by Nottsknots » Sat Mar 10, 2018 3:42 pm

Dan116i wrote:
Thu Mar 08, 2018 6:32 pm
Brilliant :) cheers. I’ve got a feeling 65c isn’t going to be enough sadly. Long story short, I’m making some custom depos and looking to carbon skin the inside...
Well, its good news and bad.

It took half an hour on full beam, but I got it from ambient at 13c up to 65c. Given longer, amd potentially higher summer temps, I reckon it would probably go up to 70, maybe 75 - the last 5 were really slow, but still climbing. That was with the thermocouple placed on the plastic at the bottom of the main beam bulb surround (where the light is strongest, just behind the lip to the bit that slopes down at the front); it MIGHT be hotter at the top, but I'd guess the direct incident light is going to be the greatest contributor to heating. Also, with the plastic hatch to access the bulbs clipped shut, so not artificially cool.

It depends what happens at the 65c rated temp; if the glue softens, or it starts to yellow a bit, or it bursts into flames, will colour your decision.

Also dont forget that halogens generate a shed load of UV; behind the glass its pretty safe for mere mortals, but inside the headlight unit, its going to be intense - make sure whatever carbon look-alike you're using is UV stable. Whilst genuine carbon fibre composite degrades, its only in its structural strength rather than cosmetics (as its really the resin thats changing). I'm guessing you're not using genuine cfc though.

All that said, low beam on its own generates a lot less heat, as there is less light incident on the interior surface; who has full beam on for a full half hour :?:

In the immortal words of "Blind Date", "The choice is yours".

https://imgur.com/gallery/GwI0w
E87 118d, stock, plus PDC control unit drain, Parrot, debadged, Mothercare baby shades (but no babies), and occassionally a good layer of wax. Instantly forgettable, and thats the way I like it.

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Re: Headlight Temps

Post by Dan116i » Sat Mar 10, 2018 6:14 pm

Nice one :) cheers. Unfortunately I have HID's, so this is very bad news :lol: better I find out now though as I didn't want to destroy the carbon once the headlight is sealed again

Cheers :)
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Re: Headlight Temps

Post by Nottsknots » Sat Mar 10, 2018 7:05 pm

Hmmm....

HIDs themselves operate hotter, but may direct the light differently; I'll see what I can do with the wifes HIDs tomorrow. Dont give up hope yet; I was surprised how low the halogens got the light; I dont thiink this one is easily predicted.
E87 118d, stock, plus PDC control unit drain, Parrot, debadged, Mothercare baby shades (but no babies), and occassionally a good layer of wax. Instantly forgettable, and thats the way I like it.

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Re: Headlight Temps

Post by Dan116i » Sat Mar 10, 2018 7:24 pm

Be great if you could :) I’m just after doing something unique :)

I’ve got projector lenses to focus the beam better. But it’s the overal headlight temp that worries me :)
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Re: Headlight Temps

Post by Octavius » Sat Mar 10, 2018 8:21 pm

MY SIGNATURE STOPPED WORKING AFTER AN UPDATE.

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Re: Headlight Temps

Post by Dan116i » Sun Mar 11, 2018 10:15 am

I’ve already spoken to them and the resin sets yellowish. Thanks any way :)
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Re: Headlight Temps

Post by Octavius » Sun Mar 11, 2018 12:25 pm

How noticeable would it be over the black. Wonder if they could send you a sample to try ?
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Re: Headlight Temps

Post by Nottsknots » Sun Mar 11, 2018 2:52 pm

Sorry Dan, couldnt get into the HID units easily, so unable to measure for you.

Octavius' DIY option might just work; its not like you're after strength, so that would defo handle the heat. You might even get away with laying a thin coat of epoxy on a surface, and just laying the carbon sheet on top; you wouldnt need the epoxy to soak all the way through, so no risk of yellowness showing, just RAW carbon.

If you dont want to epoxy straight into the headlight surface, you could make a mould first; mask off an area with card and tape, lightly spray PTFE (GT85 or similar) onto the area to be moulded, wait for it to level across the surface or wipe and wait, then spray on builders expanding urethane foam. When set, remove the negative mould, wrap in stretchy cling film (so no creases), and repeat to get a positive mould, on which to form the surface you want. For larger panels it helps to drop a piece of plywood on the back edge of both parts of the mould, so the foam doesnt disintegrate, but for a headlight size I dont think you'd need that. Then you can be sure its right before sticking in place with a final dab of epoxy. Everything can be trimmed with a craft knife, so its no more complicated than an Airfix kit. I've made a few replacement glass-fibre panels for boats that way, but It should work for carbon as well.
E87 118d, stock, plus PDC control unit drain, Parrot, debadged, Mothercare baby shades (but no babies), and occassionally a good layer of wax. Instantly forgettable, and thats the way I like it.

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Dan116i
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Re: Headlight Temps

Post by Dan116i » Sun Mar 11, 2018 4:35 pm

Cheers guys :)

Good shout about using a thin layer of epoxy to minimise the yellowing. This is the look I'm aiming for

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Without M Badge :lol:
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Now: 2006 130i with even more goodies ;)
Gone: 2008 116i with goodies :)

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