Join Date: Aug 2006
Location: Canada's Capital
Bikes: Sekine RM40 1980, Miyata 1000LT 1990, Raleigh Mixte Sprite 1980, Raleigh Grand Prix 1979
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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.