Rather than poke things into the undamagedcharge port of our battery, I built a quick-and-dirty mechanical duplicate:
Bafang battery – charge port simulator
The “center pin” is a snippet of what’s almost certainly 5/64 inch brass tube measuring Close Enough™ to 2.1 mm, with a few millimeters of 3/32 inch tube soldered on the end to simulate the nugget.
The aluminum rod has a 5.5 mm hole matching the coaxial jack’s diameter and depth, with a smaller through hole for the “pin” and a dab of Loctite bushing adhesive.
Then I turned the end of a 3/8 inch acetal rod down to a 5.5 mm bushing that completely fills the jack:
Bafang battery – guide bushing – dummy jack
It has a 3 mm hole down the middle to aim homebrew shell drills directly at the pin, while preventing a short to the side contact.
The first test looked encouraging:
Bafang battery – shell drill – test results
The nugget in the damaged jack is definitely larger than my soldered brass tube, but this was in the nature of exploratory tinkering while mulling the problem.
Because the tubes get epoxied into the adapters, there’s no particular need for a smooth surface finish and, in fact, some surface roughness makes for a good epoxy bond. The interior of a 3D printed adapter is nothing if not rough; the epoxy in between will be perfectly happy.
Turning the tubes started by just grabbing the conduit in the chuck and peeling the end that stuck out down to the finished diameter, because the conduit was thick-walled enough to let that work.
The remaining wall was so thin that the chuck would crunch it into a three-lobed shape, so the white ring in the chuck is a scrap of PVC pipe turned to fit the tube ID and provide enough reinforcement to keep the tube round.
The conduit ID isn’t a controlled dimension and was, in point of fact, not particularly round. It was, however, smooth, which counts for more than anything inside a tube carrying airborne fuzzy debris; polishing the interior of a lathe-bored pipe simply wasn’t going to happen.
The fixture on the other end started as a scrap of polycarbonate bandsawed into a disk with a hole center-drilled in the middle:
Pipe end lathe fixture – center drilling
Stick it onto a disk turning fixture and sissy-cut the OD down a little smaller than the eventual tube OD:
Pipe end lathe fixture – turning OD
Turn the end down to fit the tube ID, flip it around to center-drill the other side, stick it into the tube, and finally finish the job:
Dirt Devil adapter – pipe fixture
The nice layering effect along the tube probably comes from molding the conduit from recycled PVC with no particular concern for color matching.
A family portrait of the fixtures with a finished adapter:
Dirt Devil adapter – fixtures
A fine chunk of Quality Shop Time: solid modeling, 3D printing, mini-lathe turning, and even some coordinate drilling on the Sherline.
A smear of epoxy around the interior holds the tube in place:
Dirt Devil adapters – assembled
Building the critical dimensions with a 3D printed part simplified the project, because I could (and did!) tweak the OpenSCAD code to match the tapers to the tools. Turning four of those tubes from a chunk of PVC conduit, however, makes a story for another day.
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It’s basically the same as the lower blade guide, except coming from a stick of 5/8 inch acetal. A scant 6 mm stem goes into the vertical square rod, with a flat matching the setscrew coming up from the bottom to hold it in proper alignment.
I came within a heartbeat of cutting the slot parallel to the flat.
It worked OK while cutting a chunk of stout aluminum tube: so far, so good!
The impressive chunk of hardware is the OEM blade guide, with the brass tube for coolant flow all over the bearings. It’s mostly intended for use with the diamond blade, so I’ll swap it back in when I finally get around to cutting some slate for base plates.
Because the rear running light will have a higher duty cycle than the front light, I made the (admittedly too small) heatsink slightly longer, with a deeper recess to protect the lens from cargo on the rear rack:
Tour Easy Rear Running Light – boring LED recess
Boring that nice flat bottom is tedious; I must lay in a stock of aluminum tubing to simplify the process.
Drilling the holes went smoothly:
Tour Easy Rear Running Light – drilling LED heatsink
Those two holes fit a pair of pins aligning the circuit plate, with a screw and brass insert holding it to the heatsink. Scuffing a strip across the aluminum might give the urethane adhesive (you can see uncured globs on the pins) a better grip:
Tour Easy Rear Running Light – circuit plate attachment
The screw / insert /pins are glued into the plate to permanently bond it to the heatsink. The screw occupies only half of the insert, with the longer screw from the end cap pulling the whole affair together.
The same lathe fixture and double-sided duct tape trick I used for the amber running light’s end cap should have worked for this one, but only after I re-learned the lesson about taking sissy cuts:
Tour Easy Rear Running Light – end cap fixture – swirled adhesive
Yet another snippet of tape and sissy cuts produced a better result:
Tour Easy Rear Running Light – end cap
Protip: when you affix an aluminum disk bandsawed from a scrap of nonstick griddle to a lathe fixture, the adhesive will grip the disk in only one orientation.
The Smell of Molten Projects in the Morning 