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.
Making the world a better place, one piece at a time
Kai and Yen stayed with us over the weekend; they’re about 18 months into a two-year trip around the world. Kai was pulling an interesting single-wheel T2 trailer. Unlike my BOB Yak, the rear wheel has what looks like an active torsion-spring suspension:
They’re taking the northern route across the US and Canada on their way back to Taiwan:
They make our bicycling adventures fade to pale gray… which is OK with us!
Well, that fix didn’t take long to fail; they sure don’t make ’em like they used to:
The “new” fan’s bearing failure sounded more like an owl than a dog, but it was certainly not what we wanted to hear in the middle of the night. A replacement fan costs on the order of $60, which seems like an absurdly high number for what’s basically a clock motor, a plastic fan blade, and some stamped steel.
After mulling the situation for a bit, I concluded that the refrigerator has reached that age where stuffing more money into it doesn’t make much sense: the compressor will drop dead in fairly short order. It’s time for a gonzo fix that also slightly reduces the clutter in the Basement Laboratory Warehouse: stick a PC case fan and wall wart into the freezer, ignore their temperature ratings, and see what happens.
A polycarbonate sheet, a band saw, some step drills, a big hole saw, and an hour of Quality Shop Time produced a perfectly serviceable space transformer to mate the fan to the airflow director:
The plate surrounds the squishy foam washers from the OEM motor mount, with the fan on its own rubbery posts: there won’t be any vibration transmitted to the plastic air flow director! The obligatory Kapton tape on the right holds a closed-cell foam wrap around the wires to prevent rattling; I’d done much the same when I tore the thing apart after the first OEM fan failure.
The air flow is toward you out of the screen: the fan draws air from the refrigerator compartment through the evaporator coils, then directly into a square duct that leads back to the refrigerator. Whatever doesn’t make it into the duct flows into the freezer compartment through the row of vents at the top of the picture.
I assume some serious modeling went into choosing the OEM fan blade configuration and spacing so as to optimize the distribution. I hope just moving some air in roughly the right direction will suffice; I have no way to measure any interesting numbers, so this is entirely cut-and-try.
The PC case fan expects 12 VDC, which comes from a standard wall wart conspicuously labeled “For Indoor Use Only”. Well, this is certainly indoor, even if it’s not quite what they expected. The wart plugs into a cobbled-together extension cord receptacle with male 1/4 inch quick-disconnect tabs that match the female QD connectors on the OEM wiring harness that originally plugged into the fan:
All that fits into the space behind the rear panel, with the wart wrapped in a sheet of closed-cell foam to prevent rattling and provide a bit of protection:
The rear panel covers the mess, exposing only the row of vent holes along the top. The air flow is upward through the evaporator coil and fins, through the fan, and back to the two compartments.
One question remains: will the fan continue to start below 0 °F (-20 °C)?
Given the ball bearings in the fan, it ought to remain quiet, but I’ve thought that before. Now, however, I have a generous supply of case fans and wall warts that plug into the mechanical and power adapters, so I can replace fans for a long time.
I finally broke down and bought a Kindle Fire last week, with the intent of having my accumulation of datasheets and manuals where I need them when I need them, and it works reasonably well. One ergonomic blunder: the power button stands just slightly proud of the edge:
That’s exactly where my little finger rests when I’m supporting the slab in my left hand. Past experience has also shown that any opening will admit dust that eventually accumulates behind the screen, so a small protector seemed in order:
Printed with zero added shells and 1.0 infill produced a solid block of plastic that required very little cleanup:
The zittage serves to improve the fit: the protector should require a bit of fingernail persuasion to remove.
It took two tries to get the Micro-B USB connector slab offset from the centerline just right, but eventually everything lined up correctly:
My pudgy finger squeezes into that opening just enough to turn the thing on and off, but pressing on the green plastic bar has no effect. There’s not enough plastic to allow chamfering the edge in the solid model, but a bit of riffler file action worked wonders on those sharp edges.
The OpenSCAD source code:
// Kindle Fire Power Button Protector
// Ed Nisley KE4ZNU April 2012
include </home/ed/Thing-O-Matic/lib/MCAD/boxes.scad>
//- Extrusion parameters must match reality!
// Print with +0 shells and 3 solid layers
ThreadThick = 0.25;
ThreadWidth = 2.0 * ThreadThick;
HoleWindage = 0.2;
function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
Protrusion = 0.1; // make holes end cleanly
//----------------------
//- Dimensions
PlugDia = 3.5; // audio jack
PlugLength = 5.0;
PlugOffset = -10;
USBThick = 1.0; // Micro-B USB jack
USBWidth = 6.8;
USBLength = 4.0;
USBOffset = -0.25;
ButtonDia = 5.2; // power button
ButtonOffset = 10.0;
PlateWidth = 7.5;
PlateLength = 30.0;
PlateThick = 1.0;
PlateRadius = 2.0;
//----------------------
// Useful routines
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,
$fn=Sides);
}
module ShowPegGrid(Space = 10.0,Size = 1.0) {
Range = floor(50 / Space);
for (x=[-Range:Range])
for (y=[-Range:Range])
translate([x*Space,y*Space,Size/2])
%cube(Size,center=true);
}
//-------------------
// Component parts
//-------------------
// Build things...
ShowPegGrid();
union() {
translate([PlugOffset,0,0])
cylinder(r=PlugDia/2,h=(PlugLength + PlateThick),$fn=8);
translate([0,USBOffset,(PlateThick + USBLength)/2])
cube([USBWidth,USBThick,(PlateThick + USBLength)],center=true);
difference() {
translate([0,0,PlateThick/2])
roundedBox([PlateLength,PlateWidth,PlateThick],PlateRadius,true,$fn=4*4);
translate([ButtonOffset,0,-Protrusion])
rotate(360/(2*8))
PolyCyl(ButtonDia,(PlateThick + 2*Protrusion));
}
}
I loves me my 3D printer…
I’ve always liked flip-top toothpaste tube caps, which Colgate tubes have and Crest tubes don’t. I’m sure there’s a reason why they use different threads; perhaps there’s a standard for toothpaste tube threads that encompasses both?
Anyhow, after years of pondering this dilemma, I jammed a Colgate cap and the top of a Crest tube onto a length of 5/16″ drill rod and eased some epoxy into the joint:
It turns out that the minor diameter of the Colgate cap is just slightly smaller than the major diameter of the Crest tube, so they don’t quite slide together. The epoxy makes for a perfect, zero-clearance fit that’s so tight you must crunch the tube to unscrew it:
For what it’s worth, that buttress thread form provides a leakproof seal in the original tube.
I have no idea whether this will actually work, because the closet has a three-pack of Colgate that should last for quite a while. Yes, we tend to buy whatever toothpaste seems cheapest on a per unit basis when we’re restocking the closet…
That tea ball (OK, infuser) hasn’t killed me yet, but it was looking rather grody despite a more-or-less monthly run through the dishwasher. So when Mary made up a bleach solution to sterilize her plant starting pots, I tossed it into the bottom of the pan for half an hour:
Zowie! All the organic schmutz vanished, leaving it as good-looking as new.
No before picture, alas, but maybe next time…
Memo to Self: Do that more often.
After decanting the homebrew vanilla extract from those bottles, I added enough vodka to cover the spent beans, ran them through the blender, and drained the liquid:
It’s rather muddy and probably not worth keeping, but we’ll see what settles out:
The Good Stuff looked like this before it went into a dark corner of the Basement Laboratory Storage Warehouse:
It turns out you (well, I) cannot run vanilla extract through an ordinary coffee filter: it just doesn’t drain well at all. Cheesecloth didn’t seem worth the effort, so I combined all the clear liquid in a single jar, let it settle for a few days, then decanted it back into those three bottles again. The bottom of the rightmost bottle has a layer of what Breyers calls “real vanilla bean specks” in their ice cream.
In round numbers, $20 for half a pound of beans and $16 for a 1.75 l bottle of 80 proof vodka adds up to $36 for maybe 1.4 l of DIY vanilla extract = $26/l. Commercial vanilla extract runs about $72/l, so that’d be $100 in those bottles.
One could drive the DIY price down by processing more beans at a time, but this should keep us in vanilla for quite a while; that cup of hot cocoa in the afternoon smells really good now!
A week or so ago, the scroll ring on the Kensington Expert Mouse trackball at my left hand failed completely. Unlike the previous repair attempts, tweaking the IR emitter-detector pair positions did nothing. Tried it on three different PCs and five different operating systems with the same result: the ring stayed dead.
Fortunately, this one was a warranty replacement for the dead Unit 1 I bought some years back and was still within its 5 year warranty, so when I contacted Kensington tech support with the story they immediately shipped a replacement. It just arrived and works fine.
The scroll ring detents seem much smoother on this one, so I haven’t taken it apart to remove the magnetic latch and don’t know if they’re using a different quadrature sensor. One can but hope.
For what it’s worth, an absolutely brand new ball barely moves on those three jeweled bearings (one marked with the yellow oval in the picture). Just rub the ball on one side of your nose to add some skin oil: shazam it spins like glass on ice.
They don’t mention that trick anywhere in the meager instructions…
Update: Eight years in the future, a real fix appears!
The Smell of Molten Projects in the Morning 