The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Author: Ed

Another CatEye Cadence Sensor Magnet Mount
The stock Bafang pedal cranks measure 170 mm on centers between the bottom bracket shaft and the pedal spindle. Having grown accustomed to the 165 mm cranks from Mary’s bike, I got a set of cheap 160 mm cranks to feel if there was any difference:

Bafang vs ProWheel crank forging

The bottom crank has a quick-and-dirty adaptation of the magnet mount for the Lekkie Buzz Bar offset cranks, but, of course, the 160 mm cranks have an entirely different profile. They are also heavier and more crudely forged, which is about what you’d (well, I’d) expect.

Also unlike the Lekkie cranks, neither the Bafang nor the Prowheel cranks correct the Bafang motor’s offset, so I’m using the left-side Kneesaver from the old cranks, which turns out to be close enough.

Modeling the profile started with an infrequently used contour gauge:

CatEye Magnet holder – ProWheel crank profile tests

The black 3D printed mount in the upper right fit the Bafang crank and appears in the top photo.

Transferring the new contour to paper and applying the Chord Equation got the radius of the not-quite circle:

CatEye magnet crank adapter – chord radius

Knowing the size of the magnet and the radius of the circle, drawing the profile in LightBurn was straightforward:

CatEye magnet crank adapter – framed

Applying the laser cutter to MDF produced the two successive test-fit pieces in the picture while figuring out how much stickout the magnet needed beyond the inner crank face to reach the sensor. LightBurn’s Node Editor simplified adjusting the size: drag-select a group of nodes, then move them in precise increments with the arrow keys.

Export the profile from LightBurn as an SVG file, import it into OpenSCAD, and extrude it to the proper length:
```
module CatEyeMagnet() {

Magnet = [19.0,14.0,8.5];

translate([0,75,0])
    linear_extrude(height=Magnet.y)
        import("CatEye magnet crank adapter.svg");

}
```
The translate puts the profile approximately at the XY origin. The center = true option moves the profile elsewhere on the XY plane, but does not center it, which may have something to do with the viewport used by LightBurn, the OpenSCAD version I’m using, or something else entirely.

In any event, the 3D printed mount fits the crank and puts the magnet where it will do the most good:

CatEye Magnet holder – ProWheel crank – installed

What looks like an obvious curvature mismatch comes from having the tape edge not quite squashed against the crank.

I should poke a channel through it for a cable tie around the crank, but that 3M foam tape is really good stuff and hasn’t failed me yet.
2023-04-03
Canon LiDE 120 Scanner vs. Sane vs. Networking: FAIL
The Canon LiDE 120 scanner on Mary’s desk gets considerable use by both of us, until a recent update of something killed network access to it. The usual searches revealed comments suggesting the sane scanner program has deliberately disabled network access to USB scanners which use the net back end, apparently to prevent loops when one instance shares a networked USB scanner already shared by another instance.

I have no clue how all that works, nor why the change has apparently taken half a dozen years to reach our scanner.

The workaround required downgrading sane on the “server” PC (the one with the Canon scanner) to the most recent version that doesn’t enforce the prohibition:
```
sudo pacman -U /var/cache/pacman/pkg/sane-1.1.1-2-x86_64.pkg.tar.zst
```
And preventing further upgrades with a stanza in /etc/pacman.conf:
```
IgnorePkg = sane
```
The pamac GUI interface now shows sane as eligible for an upgrade, then reports that it won’t do the deed. That’s survivable.

At some point, not updating the sane package will cause other problems. Perhaps by then we’ll have moved the hulking Epson ET-3830 printer/scanner upstairs and can recycle the Canon scanner.
2023-03-31
Under-cabinet Dell Sound Bar Mount

Another bedroom rearrangement ejected the Raspberry Pi streaming media player in favor of a phone and Bluetooth speaker, which meant I could convert the under-shelf mount into an under-cabinet mount:

Under-cabinet sound bar mount

It’s basically ten identical identical spacers cut from 3 mm plywood, with a side benefit of dramatically reducing my scrap plywood stash, then skewered by a pair of absurdly long 4 mm self-tapping metal screws into holes drilled half an inch into the ¾ inch solid wood cabinet floor.

It clears some clutter atop the microwave and, at least to my deflicted ears, sounds much better. At some point I must screw the Raspberry Pi under the cabinet, too, but that awaits further rearrangement.

2023-03-30
The Early Opossum

Having just deployed a trail camera to see what might be skulking about in the middle of the night, this appeared just before the (not fresh) batteries died:

The Early Opossum

It’s hard to tell with possums, but I’d say that critter is on a mission!

I’m still figuring out proper distances; the possum is about two feet away, which is obviously much too close. Great focus on the water barrels standing by the garage, though.

2023-03-29
Bafang DPC-18 Button Mollyguard

I got the Bafang DPC-18 display for my Tour Easy specifically to put the control buttons on the handgrip, rather than the buttons on the left of the 500C display on Mary’s bike:

Tour Easy Bafang – display 26 mi

The first pass put them on the left handgrip, just behind the thumb throttle:

Bafang DPC-18 control buttons – initial mount

This turned out to be a catastrophically bad position, because the “buttons” extend all the way to the edge of the mount and trigger when pressed a fraction of a millimeter: the dark line visible under the light gray top is the entire range of motion.

My resting hand position on the grip put the edge of my gloved index finger along the buttons, where it would inexorably nudge the + button until I was riding in assist level 9 (Rocket Sled) mode.

One ride was enough to convince me those buttons needed a Mollyguard:

PXL_20230321_233854755 – Bafang DPC-18 button Mollyguard – rear view

It is, of course, a laser-cut piece of 1.5 mil black acrylic, held in place with hot-melt glue. Because the button housing isn’t mounted symmetrically on the handlebar, I cut a few paper templates before getting the position and size right.

A view from the front shows the lip sticking up over the buttons:

Bafang DPC-18 button Mollyguard – front view

FWIW, the asymmetric mount put the buttons on the rider’s side of the flat handlebars found on contemporary upright city-rider style bikes. It makes perfect sense in that context, but didn’t help me in the least.

With the Mollyguard in place, I rotated the whole button assembly around the handgrip to allow pushing the buttons with my thumb in its natural position.

Now the assist level changes only when I want it to!

2023-03-28
Stonework Pillar: Brace for Impact

Sometimes fake stones fall off on their own accord, but this is impact damage:

Fake Stone Pillar – Impact Damage

Judging from the displaced stones near the top of the picture, that pillar got hit rather firmly by something heavy.

One wonders what the front of the pickup (it’s gotta be a hulking pickup) looked like and how much that repair cost.

I’d bet substantial money on the culprit driving away without offering to pick up the pillar repair bill.

2023-03-27
LED Shoplight Conversion: First Failure

Having started replacing the fluorescent shop lights with LED tubes back in 2016, this was only a matter of time:

Shop Light – failing LEDs

The next morning the dead section lit up again, albeit with a dim ring at its right end. I think one LED in that string failed open and darkened the whole string, then failed short under the voltage stress, and is now quietly simmering in there with slightly higher than usual current.

The lights over the workbench weren’t in the first wave of conversions, so they may be only four years old.

For sure, they have yet to approach their 50000 hour lifetime …

2023-03-24