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.

Tag: Repairs

If it used to work, it can work again

EBL Bucked Lithium AA and AAA Cells

A new kitchen scale eats a quartet of AAA alkaline cells every month, so a set of bucked lithium AAA cells make sense:

EBL AAA first charge – 2024-09-11

The cells claim 1200 mA·hr capacity, because it looks much more impressive than 1.2 A·hr, and deliver 900 mA·hr at 500 mA, likely higher than the scale’s actual load current.

The old Sony DSC-H5 works well with the light box and gets a pair of bucked lithium AA cells to replace the tired Eneloops:

EBL AA first charge – 2024-10-17

They claim 3000 mA·hr and deliver 2.5 A·hr at 500 mA: nearly perfect, considering some of the junk I’ve gotten over the years.

Now, to see how they behave in real life …

2024-10-22
Gizo Spiders: Leg Splice

This being the season for decorative spiders, two more appeared:

Gizo spider assortment

Wedding photographers have trouble getting the proper exposure for both the bride and the groom, too.

Only one of the 32 legs came loose from the platform:

Gizo spider – failed leg

The upper part of the leg captured the loose segment and glommed it into a blob:

Gizo spider – failed leg – detail

Fortunately, one of the clearance test pieces was an isolated leg and joint, so I amputated the grisly mess, matched the cut in the test piece, and hot-melt-glued the pieces together:

Gizo spider – spliced leg

Not quite perfect, but good enough for the purpose.

Given the 3% failure rate, I think the legs show such small contact areas really do justify a brim. Adding a brim to the main body would mess up the joints, but I think PrusaSlicer can add brims to specific parts. More study is needed.

Orange eyes for the win!

2024-10-21
Seasonally Appropriate Teapot Knob
Long years ago, the Bakelite (or some such) lid on our rarely used teapot disintegrated, whereupon I replaced it with an aluminum sheet and metal knob. Admittedly, a metal knob was not the brightest idea I ever had, but it sufficed for a few uses over the intervening decades.

Mary hosted this month’s quilting bee and, after having someone else bring a larger teapot for the occasion, suggested I Make. A. Better. Knob. After a bit of searching, this statue seemed appropriate for the season:

Skull teapot knob

It’s printed with PETG filament that should easily withstand the no-more-than-boiling-water temperatures found atop a teapot.

I imported the original model into PrusaSlicer, shrank it to 50 mm tall and simplified the mesh, exported it as an OBJ file, imported it into OpenSCAD, mashed it together with a 1/4-20 threaded_nut from BOSL2, added the finger protector, and got a suitable model:

Teapot Knob – solid model bottom view

The as-printed threads were a bit snug with $slop=0, but running the screw in with a dot of silicone grease to ease the way worked fine.

I should rebuild the whole lid in PETG-CF sometime.

The OpenSCAD code stitches the parts together:
```
// Teapot Knob
// Ed Nisley - KE4ZNU
// 2024-10-11

include <BOSL2/std.scad>
include <BOSL2/threading.scad>

StackHeight = 50.0;
ThreadLength = 25.0;
HeatbreakOD = 40.0;
HeatbreakThick = 3.0;

    intersection() {
        union() {
            cylinder(d=HeatbreakOD,h=HeatbreakThick,$fn=2*4*9);
            up(HeatbreakThick)
                translate([-121,-105])      // totally eyeballometric
                    import("stackofskulls - 50mm.obj",convexity=10);
        }

        union() {
            threaded_nut(100,INCH/4,ThreadLength,INCH/20,        // flat size, root dia, height, pitch
                                     bevel=false,ibevel=false,anchor=BOTTOM);
            up(ThreadLength)
                cylinder(d=100,h=StackHeight);
        }
    }
```
2024-10-16
SJCAM M20 Dashboard Camera: NP-BX1 Battery Deterioration

A year of limited use (a little over 3000 miles) after setting up the SJCAM M20 action camera as a dashcam in the Forester has killed the junk-as-delivered Batmax NP-BX1 battery:

Batmax NP-BX1 – 2022-H in 2024-11

Although the total capacity remains about the same as before, the voltage depression causes the camera (which expects to run from a high-voltage lithium cell) to crash immediately after the car’s USB power jack shuts off, preventing it from properly closing the video file.

Another Batmax battery from the same batch works fine, so we’ll see if it can survive for another year.

2024-10-11
Ceiling Lamp Nuts
While cleaning dead bugs out of the ceiling lamps, we discovered the kitchen light was missing one of the three nuts holding its cover in place. While spare nuts might be available, this seemed like a quicker & easier solution:

Ceiling Lamp Nut – bottom view – solid model

The stepped interior fits a brass insert with 8-32 threads (not metric, to my utter astonishment) rammed in place with a heat-set tool:

Ceiling Lamp Nut – insert staking

Using the nominal diameters seems to work fine, although I’m sure some finesse will be needed with smaller inserts.

Printed four just to be sure, rammed three inserts, and they’re ready:

Ceiling Lamp Nuts – as-built

The curved cap matches the original nut through the use of the Chord Equation to get the cap radius as a function of its height (sagitta) & base diameter. Admittedly, it looks kinda grotty with only a dozen layers, but it’s the thought that counts.

The original nuts are heavy knurled steel and the new ones are cheap plastic, but nobody will ever know:

Ceiling Lamp Nut – installed

Bonus: now I have two spare steel nuts for the next time …

The OpenSCAD source code:
```
// Nuts for LED ceiling light fixture
// Ed Nisley KE4ZNU
// 2024-09-27

KnurlLength = 7.4;
KnurlOD = 9.0;

CapOD = 9.0;
CapHeight = 2.0;
CapRadius = (pow(CapHeight,2) + pow(CapOD,2)/4)/(2*CapHeight);
echo(CapRadius=CapRadius);

NumSides = 1*(2*3*4);
$fn = NumSides;

Protrusion = 0.1;

difference() {
    union() {
        intersection() {
            translate([0,0,KnurlLength + CapHeight - CapRadius])
                sphere(r=CapRadius);
            translate([0,0,KnurlLength])
                cylinder(d=2*KnurlOD,h=KnurlLength);
        }

        cylinder(d=KnurlOD,h=KnurlLength);

    }

// Ad-hoc 8-32 brass insert sizes

    cylinder(d=5.5,h=8.0);
    cylinder(d=5.9,h=5.7);
    cylinder(d=6.2,h=2.2);
    translate([0,0,-Protrusion])
        cylinder(d=6.2,h=2.2);

}
```
2024-10-01
Subaru Upholstery Peg
One of the flat-topped pegs anchoring the fuzzy black upholstery / carpet to the back of the rear seats went walkabout a while ago, but the situation only became critical after I vacuumed the crud out of the car.

Living in the future simplifies things:

Upholstery Peg – solid model

Rather than getting all fancy with barbed ends and suchlike, I just slathered the stem with hot-melt glue, jammed it in place, and waited a few breaths:

Upholstery peg – installed

The vivid yellow stuff is seat cushion foam.

3D printing is wonderful for simple parts like that.

The OpenSCAD source code is simple enough:
```
// Upholstery pin for Subaru back seat
// Ed Nisley KE4ZNU
// 2024-09-13

HeadThick = 1.5;
HeadOD = 25.0;

PegLength = 10.0;
PegOD = 8.0;
SlotWidth = 1.5;

rotate_extrude(angle=360,$fn=32)
    polygon(points=[[0,0],[HeadOD/2 - 1,0],[HeadOD/2,HeadThick],[0,HeadThick]]);

difference() {
    rotate(180/8)
        cylinder(d=PegOD,h=10.0,$fn=8);

    translate([0,0,HeadThick ])
        cylinder(d=PegOD/2,h=PegLength,$fn=8);

    for (a=[0,90])
        rotate(a)
            translate([0,0,PegLength/2 + HeadThick + 1.0])
                cube([SlotWidth,10.0,PegLength],center=true);

}
```
2024-09-26
Improvised Garden Gate Latch Staple

For reasons not relevant here, I ended up making a field-expedient repair to a garden gate latch:

Improvised gate latch staple – installed

The hole in the post just to the left of the obviously improvised staple shows where the Original Staple had vanished, never to be seen again. It looks like the gate has shifted an inch or so to the right (or the post to the left), which would explain why the staple gradually worked loose.

The improvised staple is a length of coat hanger wire bent into a square U, with the ends snipped off at an acute angle:

Improvised gate latch staple – cut wire

Those points do look scary, don’t they?

Then I gently tapped it into place, driving maybe ¾ inch of wire in the wood, flattening the loop a little more than I wanted, but not enough to make me try again.

Not our gate, not Mary’s garden, but deer pose a threat to all veggies within, without regard to ownership.

I have *a lot* of coat hanger wire for repairs like this …

2024-09-25