I had originally planned on something a bit different than my current revised plan but was unable to find a critical component that’s hiding here somewhere. Fortunately I was able to find one of these (random google photo).
The heatsink is from a dell dimension 4300. Since the p4 rated at just below 70 watts was passively cooled effectively I decided this should do the job. I had originally planned to re-purpose heat pipes from other heatsinks and build an external radiator but have since switched to an internal radiator with active cooling. I removed six fins to make the heatsink square, soldered two to cap the top, and removed the alloy base. This reduction still provides over 2 square feet of surface area and should be reasonably effective with or without a fan.
Heatsink with base removed. Heat spreaders will be attached here to mount stars and brass disc for mounting and assembly will also be attached.
Top of the heatsink with two of the removed fins mounted to seal the top and stabilize the fins. A brass disc will be attached here for mounting and assembly.
The heat spreaders will be made from pieces of 1/2 inch copper water line. I cut pieces about 1 1/2” long using a tubing cutter then made a cut lengthwise with a hacksaw. I then used a claw hammer to open the slit and expanded it with scraps of bone from another project. When wide enough I flattened them using the vise on my drill press. After flattening they were heated to relieve stress and will be pressed between two slabs of a2 steel in a bench vise. Both the stars and spreaders will be lapped to insure smooth copper to copper contact.
Revision: I cut a piece of 3/4 inch water line, flattened it as described above, and soldered it to the base of the heatsink. The pieces of copper previously intended as heat spreaders will be used for another purpose. Photos of heatsink with heat spreader ready for mounting disks.
More soon. edit: this light was partially inspired by old-lumens desire to see an improved srk style light. I wanted more. The goal of this project is a light that will produce 1M candella (or as close as possible - 750k is perfectly acceptable). more to come
A little info: this will be a quad emitter light powered by 2s4p 18650 built of copper and brass. It will allow replacement of cell pairs without shutting it off. The heatsink will be oriented to allow convection cooling if the fan is absent. It will use a blf srk v2 fet driver and if I can figure out how to do it the fan will be controlled by a thermal sensor. A major goal is to make the head and battery compartment waterproof (with fan removed and power connector sealed). The head will be around 100 mm in diameter. More to come.
With the surface area of the head and radiator housing added it would be close to 3 square feet including the interior of the radiator housing but since thermal conductivity of brass is significantly lower than copper I didn’t add it to the total.
Further progress delayed pending arrival of additional materials. I have decided to make the radiator housing and internal support structure out of copper to increase the surface area for cooling and improve appearance. If I use the 4x xhp70s as planned I’ll need as much cooling surface area as possible.
Head: 1mm (.040 in) brass sheet
Heat spreader: 3.175mm (.125 in) copper sheet
Radiator housing: 1.27mm (.050 in) copper sheet
Wiring pass-thru tubes: .250 in dia .030 wall brass tubing
Battery tube: 3/4” copper water line and 1mm thick brass sheet
It seems like the motto for this build is “If it’s flat make a tube and if it’s a tube make it flat.”
The head will have copper and silver (lead-free solder) for contrast at the seams and the radiator housing will have brass and silver (solder) at the seams. The copper battery holders will be assembled using brass sheet with visible silver (solder) seams. Still debating inclusion of a led voltmeter display activated by a momentary switch. Not much benefit in a 2s4p cell setup but a rotary switch to isolate pairs for checking might make it worth having.
Agreed it won’t be easy but I got lucky and found something that will work as a form for bending the sheet for the head - an empty 46 oz Sacramento vegetable juice can. Current plan is to fill it with mortar, heat and bend the sheet, wrap it with wire to hold it in shape and position, then solder the joints. Head and housing will be four segments with seams aligned with copper visible on the battery holders. Still looking for something a bit smaller than the veggie juice can to use as a form to bend and assemble the rad housing. Maybe a large tomato sauce can…
For soldering aluminum cans work great as the solder won’t wet to it but for brazing, aluminum melts below brazing temp and steel is a problem as the silver solder will wet to both the can and the wire.