Step 2: Housing
Similar to the last light project, you will need to trim down a pipe cap and drill holes in it to mount and wire the LED star. Leave a light shoulder on the pip cap protruding beyond the lens to protect it from damage, 2mm is fine.
The lengths of the 3/4" pipe and coupler section aren't critical. You'll need to have the smaller 3/4" pipe section stick out of the coupler enough to epoxy on the rear cap, about 1/4" is fine.
Take a section of bare 12GA solid copper wire and bend it up as shown in the photos using your hands, feet, and teeth or a handy pair of jewelers pliers. This wire will serve as the mount. Size it according to the handlebars on your application.
Test fit everything before soldering. Then deburr, sand, clean, and flux the LED pipe cap, the coupler section, the inner 3/4" pipe section, and the wire cleat. Use a clamp to hold the pipe cap and other tubes in place while you heat and solder. Balance the cleat on the top and solder it while the rest is still hot.
The back cap has to be the last to go on and can't be soldered since there are sensitive electronics on board at that point. You will want to drill a hole in the back pipe cap to hold the waterproof cable gland and trim the length of the pipe cap to match the amount of reveal you left on the 3/4" section of pipe. Depending on the size of the cable gland nut you might need to trim the nut or leave more pipe cap to get it to fit.