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.

Category: Machine Shop

Mechanical widgetry

Fiskars Bypass Pruner Rehabilitation

Mary found a rusted Fiskars bypass pruner in the trash pile near her Vassar Farms plot and brought it home for proper disposal. The nuts and screws responded to an overnight penetrating oil treatment and it came apart easily:

Fiskars bypass pruner – as found

The movable jaw may have once sported a PTFE coating, but it’s likely just a different steel alloy.

After scrubbing the pieces with an abrasive pad, a little diamond filing, and (at the insistence of the Squidwrench chorus) some Dremel wire-wheel action, it looks almost new:

Fiskars bypass pruner – restored

The blades sport a few nicks from their previous life, but work well enough.

2021-08-02
Amber Side Marker Light Hackery

Start with the amber side marker light sporting a cataract and distorted beam:

Side Marker – beam test – E

Part off the lens:

Side Marker E – cutting case

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:

Side Marker E – LED cataract

Brutal surgery removed the LED and installed a replacement:

Side Marker E – replacement LED

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:

Side Marker E – clamping case

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:

Side Marker E – new LED – front

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.

Replace the one I originally put in the new fairing mount:

Side Marker E rebuilt – installed

However, it’s still not much more than a glowworm in the daytime, so we need more firepower …

2021-07-22
Bafang Charger Cord Anchor

The Bafang battery charger uses an AC line cord “binocular” connector with what must be the weakest spring contacts ever made, which finally annoyed me enough to fix:

Bafang charger – AC line cord anchor

Also, the case now sports four thick fuzzy felt feet to keep it from sliding around quite so easily.

Another customer-does-the-last-ten-percent product …

2021-07-20
The Value of Closeout Pictures

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:

Bafang BBS02 – wire bundle cover

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:

Bafang BBS02 – wire bundle vs shift cable

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.

Dang, that was close …

2021-07-13
Bafang BBS02: Improved Motor Reaction Spacer
The original BBS02 reaction spacer for Gee’s Terry Symmetry didn’t work quite the way I expected:

Bafang BBS02 – reaction block displacement

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:

Terry – Bafang motor spacer – improved – solid model

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:

Bafang BBS02 – reaction block improvement

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:

Bafang BBS02 – reaction block marker

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.

Stipulated: H ope is not a strategy.

The OpenSCAD source code:
```
MotorOD = 111;              // motor frame dia
MotorOffset = 10.0;         // motor OD tangent wrt lug edge
ShiftSpace = 6.0;           // motor to frame space

LugLength = 25.0;           // length of section over BB lug

Spacer = [5.0 + LugLength,DownTube[ID]/2,4*ShiftSpace];
SpaceAngle = 0*atan(1.8/Spacer.x);            // tilt due to non-right-angle meeting
echo(str("Spacer angle: ",SpaceAngle));

module MotorSpacer() {

    difference() {
        translate([LugLength - Spacer.x/2,0,0])
           cube(Spacer,center=true);
        translate([0,0,DownTube[ID]/2])
            rotate([0,90 + SpaceAngle,0]) rotate(180/FrameSides)
                cylinder(d=DownTube[ID],h=DownTube[LENGTH],$fn=FrameSides,center=true);
        translate([DownTube[LENGTH]/2,0,DownTube[ID]/2 - DownTube[LENGTH]*sin(SpaceAngle)/2])       // concentric with ID
            rotate([0,90 + SpaceAngle,0]) rotate(180/FrameSides)
                cylinder(d=DownTube[OD],h=DownTube[LENGTH],$fn=FrameSides,center=true);
        translate([MotorOffset,0,-(MotorOD/2 + ShiftSpace)])
            rotate([90,0,0]) rotate(180/48)
                cylinder(d=MotorOD,h=2*Spacer.y,$fn=48,center=true);
    }

}
```
Nothing like actual riding to reveal what needs more thought!
2021-07-12
Vacuum Tube Lights: Urethane Coated Plate Cap

With a generous dollop of JB Plastic Bonder left over from a set of Bafang brake sensor magnets, I tried coating the ersatz plate cap of a triode tube:

Triode – urethane coated plate cap

That’s the result after leaving it hanging upside-down while it cured to push all the drips to the top.

For comparison, the uncoated cap back in the day:

Triode – plate cap plug

Seeing as how the urethane is an adhesive, not a coating, I’d say it looks about as bad as expected.

As with all 3D printed things, one must embrace imperfections and striations, rather than endlessly strive for perfection.

Now, if I had a resin printer …

2021-07-09
Side Marker Beam Patterns: FAIL
The truck side marker lights I’m thinking of using as daytime running lights have a pentagonal lens, so they should have a pattern with a bright central beam surrounded by five lobes. The one on Mary’s Tour Easy produced an oddly shaped blotch on the garage wall, so I ran the others though a simple test setup:

Side Marker – beam test setup

The lights sit horizontally in a small vise to keep them level and in the same position, although in no particular rotational orientation, and 100 mm from the graph paper. It’s running at 6 v to keep the brightness down enough to avoid blowing out the image. All of the images were exposed based on the central spot, so the surrounding paper gives some idea of the relative brightness: darker paper = brighter LED spot.

The front view of the lights comes from the stereo zoom microscope, with the wires gripped in a Third Hand and rotated to put the (inverted) TOP label where you’d expect it. They’re all roughly at the same position and pretty nearly lined up with the lens axis. The bubble-looking thing behind the central pentagon is the lens on the Piranha LED package, which should be centered but rarely is. You can see the dark orange square of the amber LED chip in some of the pictures.

Without further ado, the nine truck side marker lights that aren’t on her bike:
- Side Marker – beam test – A
- Side Marker – beam test – B
- Side Marker – beam test – C
- Side Marker – beam test – D
- Side Marker – beam test – E
- Side Marker – beam test – F
- Side Marker – beam test – G
- Side Marker – beam test – H
- Side Marker – beam test – I
Side Marker Light – Beam tests
Side Marker E has a blob that looks like a cataract atop the LED lens, but it might be a mold imperfection.

Obviously, paying a buck a light doesn’t get you much in the way of build quality these days.
2021-07-08