This is what we are trying to build. Building the housing for an LED bike light is usually the hardest phase (next to gathering all the parts) I've tried to simplifiy things a bit with this light, as compared to my all-aluminum design. I'd seen some other builders using the copper pipe end caps to house the LEDs and optics, but most of the them seemed to lack an adequate body to house the electronics. This design takes care of that as well as providing additinonal heatsink area using the aluminum body. I've added some heatsink fins as well, but they are optional, as I believe the light would run cool enough without them as long as you keep air moving around the light.
This design is about 35-40 grams heavier than my all-aluminum design, but it is easier to build, and I believe it will be more waterproof.
Note: Click on photos for full size close up view!
(with links to suppliers I used- where possible)
Electronics/Optics
3 x Seoul Semiconductor P4 (U-bin) LEDs on Star MCPCB
2 x 20mm L2 Medium (15 degree) lenses
1 x 20 mm L2 Spot (5 degree) lens
3 x Lens holders (Lux III or V Star) for 20mm L2 lenses
1 x 3023 Wired Buckpuck Controller DC, 1A with dimming
1 x 5k potentiometer + knob
1 x DC power connector
Misc
Heat shrink tubing - Radio Shack
Solder - Radio Shack
Arctic Alumina Adhesive
JB Weld - Lowes
22 ga wire - mostly used wire from Buckpuck
1 x 1" square aluminum tubing (3") - Lowes
3 x 3/4" copper end pipe caps - Lowes
1 x piece of Lexan or Plexiglass (enough to make 3, 7/8" circles) - Lowes
2 x pieces of 1/16" x 1-1/2" aluminum bar (1" length for each) - Lowes
1 x piece of 8-32 threaded rod (about 3-3/4") - Lowes
2 x 8-32 cap nuts - Lowes
optional:
3 x pieces of 3/8" aluminum C channel (1-3/4" length for each) for heatsink fins - Lowes
The main components of this light consist of one 3 inch length of square aluminum tubing (1") and 3, 3/4" copper pipe end caps. The end caps actually measure about 7/8" (22mm) across the inside diameter. Unfortuantely, the caps must be cut off in length, as they are too long and would cut off too much of the sidespill light if they were not shortened. Mine ended up being about 3/4" long after cutting them. They can be cut with a hacksaw, a Dremel tool , or sanded down with a belt sander... careful, they will get hot!
1 - piece of 1" square aluminum tubing, cut to 3" length
3 - 3/4" copper pipe end caps
I had some spare 3/8" aluminum C channel lying around and I decided to shape 3 heatsink fins. I cut the aluminum with my bandsaw, but a hacksaw would work, and then I shaped the curves with a belt sander and a Dremel tool. This is optional, but I figured they would also provide some protection to keep from knocking off the copper caps, which are just glued onto the aluminum body using Arctic Alumina Adhesive. So although optional, I thought they looked cool as well... kind of intimidating! Actually I've found that the most bike lights will stay cool enough as long as you keep moving, but keeping the LEDs cool is important.
So at this point the parts are all just sitting there so we can kind of see how this might look.
The first thing I did was use Arctic Alumina Adhesive to attach the three copper caps to the square aluminum tubing. Actually, it might be advisable to drill any holes in the back of the light body before doing this, just in case the body gets caught in the drill bit and slung around. I glued first, and drilled my back hold later. It's not too big of a concern if you can hold the light in a vice while you drill.
AAA is a thermally conductive, electrically non-conductive, epoxy adhesive. It has a very strong bond, but it is important to clean both surfaces with alcohol and sand both surfaces with some 60-100 grit sandpaper to prepare the surfaces for bonding.
It is possible that in a crash, one or more of these caps could be jarred loose. I have some other lights with AAA'd on heatsink fins and I've never knocked one off. I will be testing out the durability by mounting this light on my handlebar, where it will receive quite a pounding on the trail terrain.
Since it's nearly impossible to solder down inside the copper caps, wires need to be solder on before inserting them into the caps. I soldered on long enough wires that I could pull them out the body ends to join the LEDs in series and connect to the Buckpuck. Then I used heatshrink to cover the bare connections.
So at this point it looked like this. I made sure the wires would all pull into the body of the light and let each of the 3 LEDs sit flat onto the bottom of the copper cap. The other consideration is that you are able to paint some AAA onto the bottom of each star. If all of the above is good, go ahead and attach the stars (one at a time) to the bottom of the copper caps with AAA. You'll need to find a way to hold the star firmly against the base of the cap until the AAA kicks. It's pretty fast drying, and usually starts to set in 5 minutes. I didn't take a photo, of this stage as there is not much time between mixing the AAA and getting the star in place and holding firmly until dry. I just placed one of the lens holders on top of the star and pressed firmly until set. Did this for each of the 3 stars.
This photo shows one of the stars glued in place at the bottom of the copper cap. I tried to position the wires and solder connections on top of the star so that the lens holder would set flat without modification. This worked out fairly well.
Smoke Test
Once the stars are glued tight to the bottom of the copper caps, it's a good time for a second check of all wiring. I usually shine a light inside the case and make sure I don't see any bare wires shorting out againt the housing or each other. I try to use heatshrink on most things, but sometimes I forget.
This photo shows how the 3021 Buckpuck is positioned inside the housing. It is slid right up next to the DC power connector.
Since we passed the power test and things looked good, I proceeded to use AAA to attach the aluminum heatsink fins that I'd made from 3/8" aluminum C channel. When I'd glued on the copper caps, notice that I aligned them with the top edge of the body so that the heatsink fins would make contact. I ran a small line of AAA along the top of the caps to fasten the fins to them as well. This will help provide support for the copper caps and provides a little more heat transfer, although this is minimal I'm sure given the small contact area.
Although optional, the fins provide 3 things:
- additional heatsink area
- security against knocking off copper caps
- a cool look :)
I traced the outside of one of the lens holders onto some plexiglass, and cut out 3 lens covers. This requres a good bit of sanding. Having a belt or disc sander is great for this and the Dremel tool with a 60 grit sander accy works well also. Generally, I cut out squares first, cut the four corners off, then proceeded to round the shape using my belt sander.
As you can see here, there is a little space around each lens cover... this is intentional so that there is room for silicone caulking to squeeze in around each lens cover.
After the caulking it looks a little messy, but the white caulking that you see here turns clear.
I've found it best to use the clear silicone caulking to attach the lens covers. The kind I use starts out white, then turns clear as it dries. Use a toothpick to put a little caulk all along the edge then place inside. Be sure not to get caulk on the inside, and use ammonia-based window cleaner to clean the outside before the caulking dries. Do NOT use alcohol on the plexiglass.
End plugs for the rear housing were made from a piece of 1x1-1/2"x1/16" aluminum on which I rounded the front corners. A piece of 1/8" aluminum bar was cut to fit snugly inside (7/8" square) the rear housing then glued onto the 1/16" piece as shown in the photo. I used the AAA to glue, but you could use JB Weld.
A hole was drilled to accept an 8-32 threaded rod. The placement of the threaded rod inside the light body is tricky, but if you insert the buckpuck vertically against the rear of the body, you should have room. I had to rotate my DC connector and bend one of the solder connectors on the potentiometer in order to get it to pass through. The hole was drilled 1/4" in from the lower front corner of the 1/8" insertion plug.
Note: I had previouly made some end plugs using 1/8" stock (it was all I had on hand at the time) and molded the insertion plug using JB weld. The 1/8" stock looked too thick, so I went and bought some more 1/16" aluminum bar and made these ends, deciding to fabricate instead of molding this time.
I made two feet from the one inch square tube. Just take a one inch section and cut the diagonal corners, yielding two angle pieces. A hole was drilled 3/4" up from the bottom and centered.
When you put it all together, you have a system as shown in the photo to the right. The threaded rod must be cut to the proper length to accomodate the thickness of all of the assembeled parts and washers. I used some heatshrink on the threaded tube to prevent any shorts, since it was close to some of the connectors on the pot and power connector.
A non-skid rubber bottom is placed on the feet to help keep them from slipping around on your helmet. These are sold as Grippers for furniture feet in the hardware section of Lowes. They have a peel-and-stick adhesive on one side.
A couple of cap nuts finish it off and hold everything together. You end up with a nice looking helmet light that weighs in at about 175 grams. It's a little heavier than my all-aluminum design, but it is much easier to build, and more waterproof. This design really seals up well.
Light on the Helmet
I mount the light to my helmet using two Velcro straps.
Note: this photo shows the first version that I made with the 1/8" end plugs. I felt that the thick end panel looked a little off balance and also the foot extend past the edge of it, so I made the ned ends from the 1/16" stock and let them extend 1/2" forward on each side. It adds a more balanced look and also helps further protect the copper caps from being knocked off.
Finally, I made this mount using a Mawri Nightpro Handlebar Mount QR. I cut off the funky offset arm and used a couple small bolts to fasten an aluminum platform with rubber non-slip areas to sit the light upon and fasten with the same Velcro fasteners.
This shows what the light looks like when it's sitting on the handlebar mount. The Mawrri is adjustable to point the light left or right, which I like for a handlbar light. The light on it's feet can be adjusted up and down.
