The cut is just in front of the PCB and went slowly to avoid clobbering the SMD resistors very near the edge.
The cataract turned out to be crud adhered to the LED lens:
Brutal surgery removed the LED and installed a replacement:
The PCB had two 150 Ω SMD resistors for use with 12-ish V automotive batteries. While I had the hood up, I removed one and shorted across its pads to make the LED work with the 6 V switched headlight supply from the Bafang motor.
In round numbers, 6 V minus 2.2 V forward drop divided by 150 Ω is about 25 mA. The original LED ran at 35-ish mA, but it’s close enough.
Glue the lens back in place:
The bubbly stuff is solid epoxy from the original assembly, which is why removing the PCB is not an option.
The new LED is no more off-center than any of the others:
It does, however, sit much closer to the lens, due to the ring of plastic I cut away to get inside. As a result, the beam is mostly a single centered lobe with only hints of the five side lobes; there isn’t much waste light from the side of the LED into those facets.
With the Bafang BBS02 and all its gimcrackery on the Terry Symmetry buttoned up and ready to go, I took a few closeout pictures for future reference.
The motor has a sheaf of wires sticking out of the bottom crying out for a protective covering:
Although cameras tell only the truth they’re allowed to see and can be made to lie by omission, sometimes their latent truth was completely invisible to eyewitnesses in real time.
I only noticed the mis-routed shift cable when I looked through the last set of pictures.
It should pass through the plastic channel under the metal tab holding the cable guide to the bottom bracket shell:
Normally, aiming the cable into the channel is no big deal. In this case, I had to undo the shift cable, remove the left crank, loosen the motor and rotate it out of the way, nudge the cable with a small screwdriver, then reinstall in reverse order.
The motor evidently vibrates enough to propel the block forward, shearing the double-sticky foam tape which was never intended to resist force in that plane. I thought the block was located at the point where the motor casing was tangent to the frame tube, so as to equalize the forces in both directions, but … nope.
A revised design based on measurements informed by new knowledge:
The upper curve is now symmetric and the whole block mounts more rearward under the bottom bracket lug, where some tedious work with a machinists square located the real tangent point:
The motor sure doesn’t look like it’s tangent, but a dry fit showed all the curves laid against the case and tubes.
The brazing fillet means the step fitting the downtube can’t sit snug against the edge of the lug, but most of the reaction force should go through the section into the lug, near the center of the block.
A crude marker will keep track of any motion:
I think the symmetric curve against the motor has enough projection to keep the block from wandering off, even if I haven’t gotten the location exactly right.