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Old 09-10-09, 04:18 PM   #1
Novakane 
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Cooling Halogen mounted in PVC?

After a recent accident painfully reminded me of the need for good lighting, I have dug out my box of parts to get back to building my halogen headlight. (if anyone is paying attention to such things, I'm onto about year three of making this stupid thing... lol)

The general design is a standard mr16 type Halogen bulb (12v/20w) fit into a few PVC pipe fittings. I beveled the opening to accommodate the bulb and sealed it in (originally with silicon, but recently reattached with hot glue...)

I recently acquired a pair of 7.2v R/C car batteries and have connected them in parallel to the bulb. I know I can get extreme brightness with them in series, but it drains the batteries way too fast this way. When I get a second charger and another pair of these batteries I'll make it run off two banks of two in series.

As I write this I'm about 40 minutes into initial testing and it's still going strong at the same brightness as when I started. About 5-10 minutes in, the bulb got hot enough to turn the hot-glue into liquid, and I slid the bulb right out of the casing. This didn't seem to happen on a previous test with the silicon, so I'll be re-attaching it with that.

My question for anyone who has made one of these with PVC piping before, is the airflow over the light while riding adequate to cool the bulb before it heats the PVC to melting point?
I was considering cutting a section of aluminum heatsink (with fins) from an old computer and recessing it into the enclosure. The flat metal section would be above the light and the fins sticking out into the open air.

Am I over-engineering this, or will it work OK without the fancy cooling? I just don't want the enclosure melting or catching fire.
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Old 09-10-09, 07:54 PM   #2
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I made one like this and have used it for 2 years with no heat issues as long as the bike is moving.
http://www.instructables.com/id/E5TXSGFT7ZEP286N78/

No glue needed!
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Old 09-17-09, 01:15 PM   #3
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Interesting. I like the no-glue aspect, but I think the silicon should hold it fine in my case. I'll have to post pictures as soon as it's done.
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Old 09-17-09, 01:24 PM   #4
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I wouldn't suspect that a 12V/20W bulb undervolted to 7.2V would get very hot (or bright) at all.
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Old 09-17-09, 03:39 PM   #5
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I built mine by using a rubber union (the kind with hose clamps to tighten it) of the right size for an MR16, with a PVC plug shoved in the back.
It's not pretty, but it costs $5 and takes 3 minutes to make, and it lasted me a year and would have lasted forever if I hadn't decided to go to an HID (these days I'd go straight to the MS P7 that I'm using now for $90) I ran this one at 12V but these days I'd overvolt it.
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