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

Punched Cards: Paper Matters

Using different card colors makes it easy to find your program deck in the Comp Center’s output bins:

Punched Cards – paper color vs smoke stains

The smoke stains on the bottom orange card came from the same LightBurn settings used with the purple (violet?) and blue (teal?) cards: 400 mm/s, 35% power, and assist air enabled.

The conventional wisdom is that you *do not* use assist air while engraving, to avoid pushing the smoke / soot down onto the material, and I’ve generally followed that rule. Apparently evaporating holes in the other colors doesn’t generate much smoke and I had no reason to notice the air was enabled.

The upper orange card differs from the lower one only in having the assist air turned off, so I have definitely learned my lesson!

Readers of long memory will recall the dual-path assist air setup that pushes 2 l/m through the nozzle when the LightBurn layer has AIR disabled, specifically to keep smoke out of the nozzle and away from the lens; that gentle breeze doesn’t push smoke into the paper.

FWIW, that’s why I run a set of test cards before I do anything fancy for the first time.

2026-02-27
Snow Tensile Strength

Spotted on a grocery store cart corrall:

Roof Snow Curl – bottom

If you had to make snow do this, you couldn’t:

Roof Snow Curl – top

I was tempted to touch it, but left it for the next person to admire …

2026-02-26
Blackout

Some weeks ago Mary heard a loud bang just as the lights went out. Central Hudson crews arrived shortly thereafter and began examining the transformer serving the group of houses around us. I wandered over to ask questions and learned the bang came from a high-voltage fuse atop a pole 800 feet from our house.

With all the power cables underground, the crews were locating the transformer just upstream of the problem, with the intent of disconnecting it and restoring power to everybody else. That took a few hours for our service, but folks up the hill remained in the dark maybe six more hours.

The paint on the transformer enclosures has been weathering for many decades, but I spotted this one up the hill that looks different from all the rest:

Scorched utility transformer housing

The scorched half of the enclosure pivots upward to reveal the high-voltage disconnect switch, fuses, and low-voltage connections. This one is across the street from our house:

Neighborhood distribution transformer

I think something went badly wrong in there and the transformer overheated to the point of insulation failure, whereupon the short circuit blew the HV fuse half a mile away down the hill.

I hope it’s not the beginning of a trend …

2026-02-25

Crosman BB Bottle Cap

Mary made a frame weight to maintain tension on the fabric in the HQ Sixteen longarm:

It’s a sturdy cloth tube filled with BBs, somewhat like a grossly overweight door snake (a.k.a. draft stopper).

The bottle of 6000 copper-plated steel BBs arrived in an overwrap bag of the sort Amazon applies to all bottled products. This was a Good Thing, because the scrap of packing paper did nothing to cushion the bottle in an otherwise empty box. The bag contained most of the shattered cap and a few BBs, with escapees rattling around inside the box and surely a few left along the way.

So I conjured a replacement cap from TPU:

Crosman BB bottle cap - solid model - build view — Crosman BB bottle cap – solid model – build view

It fits around the bottle neck and snaps onto the spout just like the original:

Except this one is unbreakable.

The strapless TPU cap was a quick test to verify the fiddly shoulder snapping onto the bottle snout:

Crosman BB bottle cap - solid model - section view — Crosman BB bottle cap – solid model – section view

As it turned out, we poured all 6000 BBs (minus those few lost-in-transit strays) into the cloth tube, but the bottle will come in handy for something someday.

The OpenSCAD source code as a GitHub Gist:

	// Crosman BB bottle cap
	// Ed Nisley – KE4ZNU
	// 2026-02-22

	include <BOSL2/std.scad>

	Layout = "Show"; // [Show,Build,Section]

	/* [Hidden] */

	ID = 0;
	OD = 1;
	LENGTH = 2;

	HoleWindage = 0.2;
	Protrusion = 0.1;
	NumSides = 634;

	$fn=NumSides;

	WallThick = 1.0;

	Heights = [1.2,2.0,13.0,WallThick]; // for easy tweaking

	Ring = [34.5,39,WallThick];

	Strap = [70.0,5.0,Ring[LENGTH]];

	CapOAL = sum(Heights);

	//—–
	// Conjure it with magic numbers

	module Cap() {

	tube(Heights[0],id=16.8,wall=WallThick+0.6/2,anchor=BOTTOM) position(TOP)
	tube(Heights[1],id=17.4,wall=WallThick,anchor=BOTTOM) position(TOP)
	tube(Heights[2],id1=17.4,id2=14.0,wall=WallThick,anchor=BOTTOM) position(TOP)
	cyl(Heights[3],d=14.0+2*WallThick,rounding2=WallThick/2,anchor=BOTTOM) position(BOTTOM)
	cuboid(Strap,anchor=BOTTOM+LEFT) position(BOTTOM+RIGHT)
	left(1.0)
	tube(Ring[LENGTH],id=Ring[ID],od=Ring[OD],anchor=BOTTOM+LEFT);
	}

	//—–
	// Build things

	if (Layout == "Show") {
	Cap();
	}


	if (Layout == "Section") {
	difference() {
	Cap();
	down(Protrusion)
	cuboid(2*Strap.x,anchor=BOTTOM+LEFT+FRONT);
	}
	}

	if (Layout == "Build") {
	back(Strap.x/2)
	zrot(90)
	up(CapOAL)
	yrot(180)
	Cap();
	}

view raw Crosman BB bottle cap.scad hosted with ❤ by GitHub

2026-02-24

HQ Sixteen: Fabric Rod Bearings

The rods (a.k.a. tubes or poles) holding & guiding the quilt top / batting / backing fabric on Mary’s HQ Sixteen longarm quilting machine span the eleven feet of the table:

HQ Sixteen - table overview — HQ Sixteen – table overview

The two end plates are 1/4 inch steel plate with four punched holes for the rods / tubes, which look remarkably like EMT. The machine is two decades old and Mary is (at least) the third owner, so it’s no surprise the rods long ago wore through the white powder-coat paint on the plates and, during the course of a long quilting project, now deposit black dust on the table.

Black dust not being tolerable near a quilt-in-progress, Mary asked for an improvement.

The tube OD is 28.7 mm (so it’s probably 1 inch EMT) and the plate hole ID is 31.2 mm (likely a scant 1-¼ inch punch), leaving barely a millimeter of clearance all around. I wanted to make a bearing from suitably slippery Delrin / acetal, but figured 3D printed PETG would suffice for at least while.

The proper term is “bushing“, because it has no moving parts:

Rod Bearing Sleeve - solid model - show view — Rod Bearing Sleeve – solid model – show view

On the right side, the bushing rim must fit between the sprockets and the plate:

HQ Sixteen rod - right front — HQ Sixteen rod – right front

The spring-loaded pin holding the tube in place (visible on the inside bottom) sets the maximum length:

HQ Sixteen rod - right outer — HQ Sixteen rod – right outer

The left side has none of that, so I made the bushings a little longer:

HQ Sixteen rod - left inner — HQ Sixteen rod – left inner

The left-side bushings will need a better design should normal back-and-forth sliding push them out of place.

A touch of silicone grease around the plate holes makes those bushings / bearings turn sooo smooth.

The OpenSCAD source code as a GitHub Gist:

	// Bearing sleeve for HQ Sixteen table rods
	// Ed Nisley – KE4ZNU
	// 2026-02-20

	include <BOSL2/std.scad>

	Layout = "Show"; // [Show,Build]

	/* [Hidden] */

	ID = 0;
	OD = 1;
	LENGTH = 2;

	HoleWindage = 0.2;
	Protrusion = 0.1;
	NumSides = 832*4;

	$fn=NumSides;

	Rod = [25.0,28.7,100.0]; // very short rod

	Sleeve = [Rod[OD] + 0.3,31.2 – 0.2,9.0]; // LENGTH = overall
	Rim = [Sleeve[ID],Sleeve[OD] + 6.0,0.6];

	IdlerLength = 15.0;

	NumSlots = 2*4;
	Kerf = 1.0;

	Gap = 5.0;

	module Bearing(oal) {

	difference() {
	union() {
	tube(oal,id=Sleeve[ID],od=Sleeve[OD],anchor=BOTTOM);
	tube(Rim[LENGTH],id=Rim[ID],od=Rim[OD],anchor=BOTTOM);
	}
	for (a=[0:NumSlots-1])
	zrot(a*360/NumSlots)
	up(oal/4 + Rim[LENGTH])
	right(Sleeve[ID]/2)
	cuboid([Sleeve[OD],Kerf,oal],anchor=BOTTOM);
	}

	}


	//—–
	// Build things

	if (Layout == "Show") {
	color("Gray",0.5)
	xcyl(Rod[LENGTH],d=Rod[OD]);
	right(Rod[LENGTH]/3)
	yrot(90)
	Bearing(Sleeve[LENGTH]);
	left(Rod[LENGTH]/3)
	yrot(90)
	Bearing(IdlerLength);
	}

	if (Layout == "Build") {
	right(Rim[OD]/2 + Gap/2)
	Bearing(Sleeve[LENGTH]);
	left(Rim[OD]/2 + Gap/2)
	Bearing(IdlerLength);


	}

view raw Rod Bearing Sleeve.scad hosted with ❤ by GitHub

2026-02-23

Google Pixel 6a Battery Performance Program: Just Take The Money
Our Google Pixel 6a phones qualify for their “Battery Performance Program”, which involves severely limiting the battery charge and discharge levels to avoid “potential battery overheating”. After the mandatory capacity limit kicked in, I must now let the phone suck a socket by the middle of the afternoon so that it will survive until bedtime; if I had a more active lifestyle, it’d be flat dead by noon.

My options under the Program are thus:
- Have the battery replaced by the local iFixit shop, without a warranty covering “Whoops, broke your phone. Too bad, so sad.”
- Get a $100 check
- Get $150 off a new phone at The Google Store
Even though I do not have a deep emotional attachment to the 6a, the first option is obviously a bad deal. Somewhat against my better judgement, I opted to take the $150 discount on a shiny new Pixel 10a.

Redeeming the $150 from the Battery Program involves (their words + my bullets & emphasis):
- visit store.google.com,
- add the desired item(s) to the cart,
- then enter discount code during checkout for an instant $150 discount on your purchase.
- Promotional code is for one-time use only with no residual balance;
- can be combined with other offers
So I set up an order with the cart looking like this:

Pixel 10a order form

The alert reader will note the inability to enter the “discount code” associated with the Battery Program.

Two hours of chat-typing with Google Customer Support over the course of two days established the hard fact that “can be combined with other offers” does not apply in this case, because the $100 discount precludes any additional offers.
```
6:16:15 PM Ed Nisley: There is no way to add a second discount code.
6:16:59 PM Ed Nisley: So I cannot add the $150 battery code to the order
6:19:38 PM Ed Nisley: But quoting the email with the battery code: "can be combined with other offers"
6:20:01 PM Ed Nisley: How do I include the battery code in this order?
6:21:17 PM Stella:  Got it  , let me check with my resources.
6:22:47 PM Stella: I have checked the details with my team, and unfortunately, you cannot apply two promo codes at the same time. You may use only one code per order. I apologize for any inconvenience this may cause.
6:24:57 PM Ed Nisley: So Google saying the battery code can be combined with the other offers is a lie?
6:26:46 PM Stella: I apologize for the inconvenience this has caused.
6:27:08 PM Ed Nisley: It's not an inconvenience, it's $150 I'm not getting.
6:27:28 PM Ed Nisley: Despite having it be Google's fault in the first place for the bad batteries.
6:28:14 PM Stella: I understand your point. While the Pixel 6a promo code can be combined with ongoing store promotions, it cannot be used in conjunction with another promo code. Per our policy, two promo codes cannot be combined for a single order. I hope you understand.
6:28:47 PM Ed Nisley: This is contradictory: "can be combined with ongoing store promotions, it cannot be used in conjunction with another promo code"
6:29:09 PM Ed Nisley: If it can't be combined with another promo code, how can it be combined with ongoing store promotions?
6:29:47 PM Stella: I understand your point here.
6:29:53 PM Stella: I do understand that the provided resolution doesn't meet your expectations. But, please understand that I cannot go beyond the system restrictions.
```
Thus whittling the $150 battery discount down to $50, because I can have either $100 or $150, but not both.

There is obviously no recourse. I will definitely take the cash-in-hand $100 when we do this dance with Mary’s phone.

Google doesn’t care, because they’re bigger than the phone company ever was and they know it.
2026-02-20
Punched Cards: Layered Apollo Eagle
What with punching the Apollo 11 CSM source code into the cards, converting the mission’s eagle into a layered shape made some sense.

The original Apollo 11 mission patch:

Apollo 11 mission patch – rescaled

After considerable faffing, a few of the fifteen layers look like this in GIMP:

Apollo 11 Patch – eagle layers

Each layer is a connected white region defining the cut perimeter, which will expose some part of the layer(s) below it in the stack. The small squares in the corners provide a bounding box to make all the layers snap to the same location.

Then:
- Select each layer’s shape + corner boxes with GIMP’s Color Select tool
- Convert the selection to a path
- Export paths as SVG files (all fifteen of them!)
- Import SVGs into LightBurn & arrange neatly
- Put outlines on a cut layer, corner squares on a tool layer
- Burn each layer separately
Testing the concept with packing paper looked surprisingly good:

Apollo 11 Eagle – layer test piece

A few key layers on punched cards:

Apollo 11 Eagle – card partial test piece

The changes for each of those iterations required tweaking the original layer images to eliminate obvious-in-retrospect problems, recreating the SVG files, and importing into LightBurn. This is a relentlessly manual process.

Then I ran a full-up test of all fifteen layers on cards punched with the Apollo source code.

Cutting the head layers from face-down cards made them sufficiently white, although it’d be nice to have a different beak color and darker eyes :

Apollo 11 Eagle patch – layer test – head

I must arrange the cards with text to put more holes in the wings, although too many will cause fragile feathers:

Apollo 11 Eagle patch – layer test – wing

The white tail should be also done with face-down cards, more holes, and the three-way joint between the cards shifted under the tail layers to its left:

Apollo 11 Eagle patch – layer test – tail

The feet and olive branch were a total faceplant, as successive layers did not register accurately enough to overlay the leaves:

Apollo 11 Eagle patch – layer test – feet

Not to mention those ug-u-lee claws.

The wing layers need more rounding along their edges, perhaps with some thin cuts to emphasize the feathers.

On the whole, though, I think it turned out well.

Things to do:
- Registration holes / pins up to the top layer
- Remove speckles on all the layers
- Arrange cards for more hole density where needed
- Better glue application
- Different card colors?
2026-02-19