First, the final assembly: Convoy M21F TIR version
I always hated the beam shape of M21F with XHP70. Narrow spill, big donut hole in the hotspot, tint shifted corona. After M21H is out it sparked my interest to mod my M21F using the TIR optics that come with the M21H. I asked Simon if the TIR optic will fit and the answer was no. I hence started to research on how to make this mod happen. I measured everything:
M21F reflector: 33x25.1
M21H TIR: 35x17.8
In order to make this mod work, I need to find a way to elevate the emitter in M21F and reduce the diameter of the TIR from M21H. I found a flat piece of aluminum from an old CPU heatsink that has the perfect height (5.3mm) so I cut a rectangular piece off the corner and drilled 4 holes for the screws and wires on the MCPCB. I sanded down a spare MCPCB and used it and the XHP70.3 MCBCP to sandwich the aluminum slab in the middle. The total height plus an emitter gasket and TIR is the same as the original MCBCP plus gasket and reflector so it should all fit well.
One sanded copper MCPCB and one hand made aluminum spacer to make the emitter match the the optics height:
L: 5mm aluminum sheet sandwiched between two copper MCPCBs + 8 degree TIR
R: original MCPCB + reflector
Reassembled MCPCB with spacers:
Then I had to sand down the outer lip of the TIR because it is too big to fit into the head of M21F. The outer lip servers no optical function and is only used to position the optic so it can be sanded down without affecting the optical performance. I used an electric drill with a screw bit and plenty of Teflon tape (plumber’s tape) and inserted it into the center hole of the optic so it can be fixed firmly onto the drill without being scratched. With the drill set to slow speed, I used 400 grit wet sandpaper to gradually sanded down the outer edge, until it measures to 33.2mm with a caliper.
Rotary tool with teflon tape inserted into the center of TIR and use sand paper to sand down the TIR lip. Diameter reduced from 35mm to 33.2mm:
L: Original reflector
R: 8 degree TIR after sanding gives exact same diameter of 33.2mm
The final assembly is easy. The optic drops right in. The glass and rubber seal goes as originally designed. Only the reflector cup being replaced by the TIR. I added the original 7070 gasket on the emitter so the optics would be pressed against the MCPCB tightly to increase heat transfer.
Drop in test: perfect
Moonlight mode test. This 8-degree TIR has a beautiful pattern:
The beam profile is beautiful. Smooth, throwy with a wide spill. It’s the ideal EDC beam profile that many of my other lights have, but with XHP70.3 HI it gives plenty of power and efficiency.
Final assembly:
Beam profile: smooth, throwy and wide spill. Perfect for EDC:
