Edit: Since a bunch of people asked, if you pay for parts I will make you one.
The TL:DR: 170 lumen, built in USB rechargeable li-ion battery with 3-12 hours of run time
Here is the ‘triangle’ cover. People have some strong feelings about which is better, and not knowing which my friend would prefer, I made both.
Not under a shirt.
Here is the circle version.
Here it is not under a shirt.
Literally built out of a box of scraps, but not in cave. One wire went to the battery pack, which I put in my pocket. The other went down my sleeve and controlled brightness and on/off. After using it, it was pretty clear that the wires had to go.
The new design
I began with the PCB (printed circuit board). The battery, charger, brightness and on/off would all be integrated. Using surface mount components on a real PCB meant I could increase the led brightness to just over 170 lumens peak. The big open space on the back side is for the battery.
Some sketches to get a feel for proportions.
While the PCB was being made, I worked on the case. Almost every time the arc reactor is shown in the movies, it’s different from the last. I settled on modeling the two I though were most iconic, the 10 spoke circle and triangle (Mark 1 and Mark 3 respectively, I believe).
The board arrived, and I soldered the 31 components on.
I had the case components 3D printed using a selective laser sintering (SLS) process.
Stereolithography (SLA) would have been smoother, but it lacks the strength for some of the smaller geometries and is particularly temperature sensitive.
The back cover is curved and smooth on the outside so it’s comfortable to wear.
Once the case parts were cleaned, they coated with a special primer.
After giving the primer a day to dry and harden, the parts were spray painted a metallic chrome. 3D printed metal would have allowed me to skip this step, but at 3-4x the cost of plastic, it was too pricey.
The laser cut light diffuser was the most difficult part to get. I talked to nearly a dozen companies before I found one who would do it for an affordable price. There are multiple layers needed, this is the piece for the white layer.
The end is near! Here it is charging, getting ready for testing. (This picture was taken before the final paint coat)
There are holes in the top to thread a string through so it can be worn as a necklace. I’m holding it by this thread and spinning it.
360 degree view on lowest brightness.