Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
So I picked up a cheap digital scale at Harbor Freight because it can count parts based on weight. After all the dust settled, it was on sale for about $8, which tells you just about all you need to know, and the “5 Year Warranty” looked generous on the box:
Harbor Freight 1 kg Scale
Alas, the fine print taketh away (clicky for more dots):
Warranty
Ah, well, all this stuff is disposable anyway, right? Nobody’d ever try to fix it…
The instructions for the Count function omit a step. In order to invoke the Count function, do this dance:
Turn it on
Count exactly 10 pieces on the scale, wait for stabilization
Press-and-hold PCS until the display shows 10
Release PCS
Press PCS briefly; the pcs annunciator turns on (they omitted that)
The display will still show 10, which is the number of pieces
Now you can weigh stuff and read off their counts
The scale resolution is 0.1 gram, so SMD resistors just aren’t going to count properly at all. It’s best if you add the entire group at one time, rather than trickle parts into the pan.
Scaling the cubes to about 15 mm on a side puts a 6×6 array neatly on the build plate. Takes nigh onto four hours to print all 36 of them at 30 mm/s print and 100 mm/s move… a bit over 6 minutes each.
The print quality is Good Enough. The bottom surface of the front cubes faces forward and reflects the scale markings:
When confronted with a zombie horde, though, nothing exceeds like excess:
Finned CO2 Cartridge Array
In real life, they’re 12 gram CO2 capsules, of the type used in tire inflators and air pistols. I knew I’d find something to do with the box of empties I’d been accumulating: they became (somewhat threatening) tchotchkes. This was inspired by that thing, although that STL file doesn’t render into anything and, as with many interesting Thingiverse things, there’s no source code.
These fins were an exercise in thin-wall printing: the outer square is one thread thick, the diagonal struts are two threads, and the ring around the nozzle has just a touch of fill inside, with a one-thread-thick base below the cartridge nozzle:
Fin Array on build platform
The solid model looks about like you’d expect:
Fin Assembly- solid model
The teeny little quarter-cylinders in the corners encourage Skeinforge to do the right thing: build each quadrant in one pass, leaving the corners unfinished. The diagonals must be exactly two threads wide to make that possible: each strut thread connects to the corresponding single-thread outer edge.
It turns out that my box has several different types of CO2 cartridges and the nozzle ends are all different. To get it right, there’s a template for matching the curves:
Cartridge nozzle template
That end of the cartridge consists of a cylinder for the body, a sphere mated to a tangential conic section, another conic fillet, and then the cylindrical nozzle. Basically, you twiddle with the parameters until the template comes pretty close to fitting, then fire off a few trial fins until it comes out right.
CO2 Capsule Nozzle – solid model detail
They were a big hit at the Long Island Linux Users Group meeting…
The OpenSCAD source code:
// CO2 capsule tail fins
// Ed Nisley KE4ZNU - Oct 2011
Layout = "Show"; // Show Build FinBlock Cartridge Fit
include
//-------
//- Extrusion parameters must match reality!
// Print with +0 shells and 3 solid layers
ThreadThick = 0.33;
ThreadWidth = 2.0 * ThreadThick;
HoleWindage = 0.2;
Protrusion = 0.1; // make holes end cleanly
function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
//-------
// Capsule dimensions
BodyDia = 18.70;
BodyRad = BodyDia/2;
BodyLength = 53.0; // between hemispherical endcap centers
BodyBaseLength = 21; // tip to endcap center
TipDia = 7.40;
TipRad = TipDia/2;
TipLength = IntegerMultiple(4.0,ThreadThick);
FilletLength = 5.0; // fillet between tip and cone
FilletTop = TipLength + FilletLength;
FilletBaseDia = 8.60;
FilletBaseRad= FilletBaseDia/2;
FilletTopDia = 9.5;
FilletTopRad = FilletTopDia/2;
ConeTop = 16.0; // tip to tangent with endcap
ConeLength = ConeTop - FilletTop;
echo(str("Cone Length: ",ConeLength));
IntersectZ = ConeTop; // coordinates of intersect tangent
IntersectX = sqrt(pow(BodyRad,2) - pow(BodyBaseLength - ConeTop,2));
echo(str("IntersectZ: ",IntersectZ));
echo(str("IntersectX: ",IntersectX," dia: ",2*IntersectX));
//-------
// Fin dimensions
FinThick = 1*ThreadWidth; // outer square
StrutThick = 2*FinThick; // diagonal struts
FinSquare = 24.0;
FinTaperLength = sqrt(2)*FinSquare/2 - sqrt(2)*FinThick - ThreadWidth;
FinBaseLength = 2*TipLength;
//-------
module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes
Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
FixDia = Dia / cos(180/Sides);
cylinder(r=(FixDia + HoleWindage)/2,h=Height,$fn=Sides);
}
module ShowPegGrid(Space = 10.0,Size = 1.0) {
Range = floor(50 / Space);
for (x=[-Range:Range])
for (y=[-Range:Range])
translate([x*Space,y*Space,Size/2])
%cube(Size,center=true);
}
//-------
// CO2 cartridge outline
module Cartridge() {
$fn = 48;
union() {
translate([0,0,BodyBaseLength]) {
cylinder(r=BodyDia/2,h=BodyLength);
translate([0,0,BodyLength])
sphere(r=BodyRad);
}
intersection() {
translate([0,0,BodyBaseLength])
sphere(r=BodyRad);
union() {
translate([0,0,(TipLength + FilletLength+ConeLength)])
cylinder(r=BodyRad,h=(BodyBaseLength - ConeLength));
translate([0,0,(TipLength + FilletLength)])
cylinder(r1=FilletTopRad,r2=IntersectX,h=(ConeLength + Protrusion));
translate([0,0,TipLength])
cylinder(r1=FilletBaseRad,r2=FilletTopRad,h=(FilletLength + Protrusion));
}
}
translate([0,0,FilletTop])
cylinder(r1=FilletTopRad,r2=IntersectX,h=ConeLength);
translate([0,0,TipLength])
cylinder(r1=FilletBaseRad,r2=FilletTopRad,h=(FilletLength + Protrusion));
translate([0,0,-Protrusion])
PolyCyl(TipDia,(TipLength + 2*Protrusion));
}
}
//-------
// Diagonal fin strut
module FinStrut() {
rotate([90,0,45])
translate([0,0,-StrutThick/2])
linear_extrude(height=StrutThick)
polygon(points=[
[0,0],
[FinTaperLength,0],
[FinTaperLength,FinBaseLength],
[0,(FinBaseLength + FinTaperLength)]
]);
}
//-------
// Fin outline
module FinBlock() {
union() {
translate([0,0,FinBaseLength/2])
difference() {
cube([FinSquare,FinSquare,FinBaseLength],center=true);
difference() {
cube([(FinSquare - 2*FinThick),
(FinSquare - 2*FinThick),
(FinBaseLength + 2*Protrusion)],center=true);
for (Index = [0:3])
rotate(Index*90)
translate([(FinSquare/2 - FinThick),(FinSquare/2 - FinThick),0])
cylinder(r=StrutThick,h=(FinBaseLength + 2*Protrusion),center=true,$fn=16);
}
}
for (Index = [0:3])
rotate(Index*90)
FinStrut();
cylinder(r=IntegerMultiple((FilletBaseRad + StrutThick),ThreadWidth),h=TipLength);
}
}
//-------
// Fins
module FinAssembly() {
difference() {
FinBlock();
translate([0,0,ThreadThick]) // add one layer to close base cylinder
Cartridge();
}
}
module FinFit() {
translate([0,0.75*BodyBaseLength,2*ThreadThick])
rotate([90,0,0])
difference() {
translate([-FinSquare/2,-2*ThreadThick,0])
cube([IntegerMultiple(FinSquare,ThreadWidth),
4*ThreadThick,
1.5*BodyBaseLength]);
translate([0,0,5*ThreadWidth])
Cartridge();
}
}
//-------
// Build it!
ShowPegGrid();
if (Layout == "FinBlock")
FinBlock();
if (Layout == "Cartridge")
Cartridge();
if (Layout == "Show") {
FinAssembly();
color(LG) Cartridge();
}
if (Layout == "Fit")
FinFit();
if (Layout == "Build")
FinAssembly();
I cable-tied the mic/earphone cable on Mary’s bike helmet to a rib on the fancy air vents near the back end, hoping that would reduce the inevitable flexing. Alas, it didn’t work out that way and the cable lasted only two seasons. This cut-away view shows the pulverized shield braid inside the jacket:
Fatigue-failed helmet cable
The symptoms were totally baffling: the mic worked perfectly, but the earphones cut out for at most a few syllables. Of course, I can’t wear her helmet and it only failed occasionally while riding. I barked up several wrong trees, until it got so bad that I could make it fail in the garage while listening to the local NWS weather radio station.
I spliced in a new USB male-A connector and (re-)discovered that the braid seems to be aluminum, rather than tinned copper. In any event, the wire is completely unsolderable; I crimped the braid from the new connector to a clean section of the old braid. The braid serves only as an electrostatic shield, as it’s not connected to anything on the helmet end. That should suffice until I rebuild the headsets this winter.
As part of sawing a kitchen countertop apart to fit it into the bathroom, this happened:
Sawed-off sawhorse
I’d very carefully checked the clearance for the first two cuts, but …
The sawhorse is polyethylene, which cannot be glued, so I drilled holes in the internal bulkheads, slobbered JB Industro-Weld epoxy through them, and filled the gaps with wood blocks:
Wood-epoxy PE repair
The goal being to not have metallic fasteners where the saw blade can find them.
This should work for a while:
Sawhorse cap repaired
If that’s never happened to you, I’d say you aren’t doing enough circular saw work…
I finally got around to replacing the sink in the front bathroom, which required a surprising number of tools:
Bathroom tool midden heap
As with the three other sinks I’ve replaced over the years, this one was a beautiful cast-iron monster made by the American Regulator & Standard Sanitary company, back before the name mushed into American Standard. This casting shows the original typography:
Bathroom sink by American Regulator and Standard Sanitary
A thin stainless steel trim ring and 16 (!) clamps held the sink in place on the countertop. Harsh experience taught me to support the sink while removing the clamps, because without the clamps there is nothing holding the sink up and I no longer enjoy stopping the tailpiece of a cast-iron sink with my chest…
Supporting the old sink
As it turned out, the sink required two pumps on the jack to break it free from the gunk gluing it in place; I was pleased to be wrong. I toted it to the end of the driveway, put a FREE sign on it, wherefrom it vanished within two hours. We’ll never know if it became someone’s precious antique or just a source of heavy brass fittings at the scrap metal recycler.
The original vanitory countertop had been recessed into the corner walls before the tiles went up, so I sawed out a chunk of the front edge and bent the plywood enough to tap it out without destroying anything. The countertop rotated around the left-front corner and the right-rear corner looked like this when the dust settled:
Extracted vanitory countertop
Half a century ago, the tile installers did a lovely mud job; the tiles adjoin and the grout is barely 1/16 inch wide. The vanitory case top was dead level, but the tiles weren’t quite aligned and my carefully applied and very neat 5 mm stripe of new caulk looks downright amateurish.
For what it’s worth, the new countertop started life as a stock kitchen countertop. I sawed off the backsplash, trimmed the length, cut a pair of notches to match the recesses, sawed a hole for the sink, rotated it into place, and screwed it down. You can go the custom-top route, but given that you only see about two square feet when you’re done, dropping $400 for 6 ft2 of fancy material with a gaping sink hole or over a kilobuck for a countertop with built-in recessed sink didn’t make enough sense to us.
And, no, vanitory is not a misspelling; I learned a new word during this project:
Vanitory job label
After we sell the house, the new owners will rip all this out without a second thought. After all, Dusky Rose went out of style a long time ago, a perfect hand-set array of 3/4 x 1-5/8 inch floor tiles isn’t attractive, and nobody cares about mud jobs. We’d rather keep that nice work around (even if we’re willing to put up with a simple countertop), but that’s just us; we’re the type of people who think keeping the original spring-loaded turned-wood dowel in the toilet paper holder is charming.
They’ll junk that space heater recessed into the wall, too: it has a long coily 120 V heating element strung inside, easily within the reach of questing little fingers. I added a GFI to that circuit, but I can’t imagine anybody else tolerating it. Times change.
My buddy Mark One asked me to make a golf-ball sized Thing that’s the intersection of three mutually orthogonal cylinders. He claims I (subtractively) machined one from solid plastic, many many years ago, but I cannot imagine I ever had that level of machine shop fu; right now, I’m not sure how I’d fixture the thing.
Cylinder Thing – solid model
It’s much easier with a 3D printer…
Of course, spheroids aren’t printable without support, but you can chop one in half to reveal the nice, flat interior surfaces, then add holes for alignment pegs. Using 0.50 infill makes for a compact mesh inside the ball:
Cylinder Thing – building
Smooth a few imperfections from the mating surfaces and add four pegs (the other two are busy propping the right-hand half off the countertop). Somewhat to my surprise, the alignment holes came out a perfect push fit for the 2.9 mm actual-OD filament with my more-or-less standard 0.2 mm HoleWindageFinagle Constant. This also uses the 1.005 XY scale factor to adjust for ABS shrinkage, not that that matters in this case:
Cylinder Thing – alignment pegs
Then solvent-bond everything together forever more:
Cylinder Thing – clamped
The seam is almost imperceptible around the equator, perhaps because I didn’t slobber solvent right up to the edge. I did print one without the alignment pegs and demonstrated that you (well, I) can’t glue a spheroid without fixturing the halves; that one goes in my Show-n-Tell heap.
The 0.33 mm Z resolution produces sucky North and South poles; the East, West, Left, and Right poles are just fine, as are the eight Tropical Vertices. After mulling for a bit, I rotated a cylindrical profile upward:
Cylinder Thing Rotated – solid model
The obvious contour lines fit the cylinder much better, although you can see where better Z resolution would pay off:
Cylinder Thing – rotated
This was at 0.33 mm x 0.66 mm, 200 °C, 30 & 100 mm/s, 2 rpm. No delamination problems; I applied a wood chisel to persuade those big flat surfaces to part company with the Kapton tape.
The OpenSCAD source code:
// Three intersecting cylinders
// Ed Nisley KE4ZNU - Oct 2011
Layout = "Build"; // Show Build
//- Extrusion parameters must match reality!
// Print with +1 shells and 3 solid layers
// Use infill solidity = 0.5 or more...
ThreadThick = 0.33;
ThreadWidth = 2.0 * ThreadThick;
HoleWindage = 0.2;
Protrusion = 0.1; // make holes end cleanly
//------ Model dimensions
CylDia = 2*IntegerMultiple(40.0/2,ThreadThick);
CylRad = CylDia/2;
echo(str("Actual diameter: ",CylDia));
Angle = [45,0,0]; // rotate to choose build orientation
$fn=128;
AlignPegDia = 2.90;
//-------
function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes
Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
FixDia = Dia / cos(180/Sides);
cylinder(r=(FixDia + HoleWindage)/2,h=Height,$fn=Sides);
}
module ShowPegGrid(Space = 10.0,Size = 1.0) {
Range = floor(50 / Space);
for (x=[-Range:Range])
for (y=[-Range:Range])
translate([x*Space,y*Space,Size/2])
%cube(Size,center=true);
}
//------- Model bits & pieces
module OneCyl() {
cylinder(r=CylRad,h=CylDia,center=true);
}
module ThreeCyl() {
intersection() {
OneCyl();
rotate([90,0,0]) OneCyl();
rotate([0,90,0]) OneCyl();
}
}
module HemiThing() {
difference() {
rotate(Angle)
ThreeCyl();
translate([0,0,-CylRad])
cube(CylDia,center=true);
for (Index = [0:3])
rotate(Index*90)
translate([CylRad/2,0,-Protrusion])
PolyCyl(AlignPegDia,5+Protrusion);
}
}
//---------
ShowPegGrid();
if (Layout == "Show")
ThreeCyl();
if (Layout == "Build") {
translate([CylRad,CylRad,0])
HemiThing();
translate([-CylRad,-CylRad,0])
HemiThing();
}
The Smell of Molten Projects in the Morning 