
I thought I'd share my first mod, a SSC P4 (unknown bin) powered by a 9.6v RC car battery and a LM317 set at 700ma. Along with the cut reflector, I stuck a convex lens from my telescope that happened to fit perfectly.
While the emitter and and drive aren't anything special, what's interesting is the heatsink I used:

For me, funds are scarce, so ordering a $20 mag heatsink wasn't really an option for me. The first thing I thought to try was a copper plumbing end cap, specifically a 1" one from Home Depot a ~$2 each.
[copper endcap]
The ID of the mag (~34mm) is larger than the OD of the endcap (~28mm), so they won't work without a bit of modification. I used a rotary cutting device to make 8 equally spaced cuts down the sides, so I could flatten the endcap out (I made sure to let the "arms" keep their curvature, as this leads to better contact with the inside of the mag). After, I bent the arms back perpendicular, but at a larger diameter, so it would fit into the mag perfectly. (unfortunately, I didn't take picture of the entire build process)

The result was a heatsink that worked and barely cost anything. The copper is only 1/16" thick, so I used an LED on a star to help distribute the heat a little more. Before, the LED got really hot because the heat had no where to go; now, it barely gets hot even after long periods of on time.
Overall, the combination of parts comes together to form a nice flashlight. The battery pack is a bit of a hassle and the heatsink for the LM317 gets way too hot, but for ~$8 in parts ($4 for the regulator, $4 for the heatsink, and the LED was salvaged; I had the mag and the battery pack is for my car), it works well.



Future improvements include placement in a cut down mag for use as a bike light, and a different regulator/battery combination.
If there's an interest in this I'll make a more formal guide on making these.
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