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.
Things around the home & hearth
This appeared while we uprooted a row of forsythia along the north border:
Although FOD has killed a good share of my lawn mowers and blades over the decades, this happened long before my administration and I can’t take credit for the precision targeting.
As other folks have discovered, it’s straightforward to convert soft, soothing baby wipes into toxic sanitizing wipes by pouring harsh chemicals down the hatch:
Ending up with the proper dilution, though, requires knowing how much liquid the wipes already have, so you can account for it in whatever recipe you’re following.
Stand back, I’m going to use arithmetic!
Gut a new package of wipes: 552 g total weight, with 80 wet wipes weighing 536 g, so the packaging amounts to 15.5 g and each wet wipe weighs 6.7 g.
Hang five wipes in the breeze for a few hours to find they weigh 9.2 g. They’re still slippery, because of all the aloe & Vitamin E & whatever else Amazon specifies for the mix, but they’re dry. One dry wipe weighs 1.8 g, so all 80 weigh 150 g.
The block o’ wet wipes holds 536 – 150 = 390 g = 390 ml of water.
Should you want a 70% (by volume) isopropyl alcohol solution, pour 0.7/0.3 × 390 ml = 910 ml of 99% alcohol into the package and let it settle for a while. Each wipe will emerge dripping wet, but that’s not entirely a Bad Thing. Perhaps it’d be a good idea to start by letting the block dry out for a while, re-weigh, then calculate the alcohol dose from the reduced amount of water.
Bleach dilutions for sanitation seem wildly varied, but the jug of 8.25% sodium hypochlorite on the shelf says 1/2 cup to a gallon, a 1:32 volume ratio. Starting with 390 ml of water-like substance in the package, pour 12 ml of bleach into the hatch, let things settle, then squish it around for good measure.
None of the dosages seem particularly critical, given the slapdash way everybody applies wipes.
You should, of course, conspicuously mark the packages, so as not to apply toxic wipes to sensitive parts of you or your baby …
One of two new round rubber soaker hoses arrived with a slight crimp, enough to suggest it would crumble at an inopportune moment. Rather than return the hose for something that’s not an obvious failure, I clamped the crimp:
Unlike the clamps for the punctured flat soaker hoses, this one doesn’t need to withstand much pressure and hold back a major leak, so I made the pieces a bit thicker and dispensed with the aluminum backing plates:
The solid model is basically the same as for the flat hoses, with a slightly oval cylinder replacing the three channels:
The OpenSCAD source code as a GitHub Gist:
| // Rubber Soaker Hose Splice | |
| // Ed Nisley KE4ZNU 2020-03 | |
| Layout = "Build"; // [Hose,Block,Show,Build] | |
| TestFit = false; // true to build test fit slice from center | |
| //- Extrusion parameters must match reality! | |
| /* [Hidden] */ | |
| ThreadThick = 0.25; | |
| ThreadWidth = 0.40; | |
| HoleWindage = 0.2; | |
| Protrusion = 0.1; // make holes end cleanly | |
| inch = 25.4; | |
| function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit); | |
| ID = 0; | |
| OD = 1; | |
| LENGTH = 2; | |
| //———- | |
| // Dimensions | |
| // Hose lies along X axis | |
| Hose = [200,14.5,13.6]; // X = longer than anything else | |
| // 8-32 stainless screws | |
| Screw = [4.1,8.0,3.0]; // OD = head LENGTH = head thickness | |
| Washer = [4.4,9.5,1.0]; | |
| Nut = [4.1,9.7,6.0]; | |
| Block = [50.0,Hose.y + 2*Washer[OD],4.0 + 1.5*Hose.z]; // overall splice block size | |
| echo(str("Block: ",Block)); | |
| Kerf = 1.0; // cut through middle to apply compression | |
| CornerRadius = Washer[OD]/2; | |
| NumScrews = 3; // screws along each side of cable | |
| ScrewOC = [(Block.x – 2*CornerRadius) / (NumScrews – 1), | |
| Block.y – 2*CornerRadius, | |
| 2*Block.z // ensure complete holes | |
| ]; | |
| echo(str("Screw OC: x=",ScrewOC.x," y=",ScrewOC.y)); | |
| //———————- | |
| // 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(d=(FixDia + HoleWindage),h=Height,$fn=Sides); | |
| } | |
| // Hose shape | |
| // This includes magic numbers measured from reality | |
| module HoseProfile() { | |
| NumSides = 12*4; | |
| rotate([0,-90,0]) | |
| translate([0,0,-Hose.x/2]) | |
| resize([Hose.z,Hose.y,0]) | |
| cylinder(d=Hose.z,h=Hose.x,$fn=NumSides); | |
| } | |
| // Outside shape of splice Block | |
| // Z centered on hose rim circles, not overall thickness through center ridge | |
| module SpliceBlock() { | |
| difference() { | |
| hull() | |
| for (i=[-1,1], j=[-1,1]) // rounded block | |
| translate([i*(Block.x/2 – CornerRadius),j*(Block.y/2 – CornerRadius),-Block.z/2]) | |
| cylinder(r=CornerRadius,h=Block.z,$fn=4*8); | |
| for (i = [0:NumScrews – 1], j=[-1,1]) // screw holes | |
| translate([-(Block.x/2 – CornerRadius) + i*ScrewOC.x, | |
| j*ScrewOC.y/2, | |
| -(Block.z/2 + Protrusion)]) | |
| PolyCyl(Screw[ID],Block.z + 2*Protrusion,6); | |
| cube([2*Block.x,2*Block.y,Kerf],center=true); // slice through center | |
| } | |
| } | |
| // Splice block less hose | |
| module ShapedBlock() { | |
| difference() { | |
| SpliceBlock(); | |
| HoseProfile(); | |
| } | |
| } | |
| //———- | |
| // Build them | |
| if (Layout == "Hose") | |
| HoseProfile(); | |
| if (Layout == "Block") | |
| SpliceBlock(); | |
| if (Layout == "Show") { | |
| difference() { | |
| SpliceBlock(); | |
| HoseProfile(); | |
| } | |
| color("Green",0.25) | |
| HoseProfile(); | |
| } | |
| if (Layout == "Build") { | |
| SliceOffset = TestFit && !NumScrews%2 ? ScrewOC.x/2 : 0; | |
| intersection() { | |
| translate([SliceOffset,0,Block.z/4]) | |
| if (TestFit) | |
| cube([ScrewOC.x/2,4*Block.y,Block.z/2],center=true); | |
| else | |
| cube([4*Block.x,4*Block.y,Block.z/2],center=true); | |
| union() { | |
| translate([0,0.6*Block.y,Block.z/2]) | |
| ShapedBlock(); | |
| translate([0,-0.6*Block.y,Block.z/2]) | |
| rotate([0,180,0]) | |
| ShapedBlock(); | |
| } | |
| } | |
| } |
Our Young Engineer recently rented a house, now knows why our sinks have CNC-machined strainers, and asked for something better than the disgusting stainless mesh strainer in the kitchen sink.
Being a doting father, I turned out a pair to get a pretty one:
They’re made from the same scrap smoked acrylic as the ones in our sinks:
They’re definitely upscale from the (not watertight!) 3D printed version I built for a Digital Machinist column to explain OpenSCAD modeling:
This time around, though, I rewrote the subtractive design in GCMC, with helical milling for all the holes to eliminate the need to change tools:
They’re done on the Sherline, because it has real clamps:
Four tabs eliminated the need to reclamp the stock before cutting the perimeter, but I should have ramped, not plunged, through the final cut between the tabs:
The handles come from the same chunk of hex acrylic as before, eyeballed to length, tapped 8-32, and secured with acrylic adhesive.
The GCMC source code as a GitHub Gist:
| // Drill & mill sink drain strainer | |
| // Ed Nisley KE4ZNU — Digital Machinist 15.2 Spring 2020 | |
| // polycarbonate or acrylic sheet | |
| // External clamps at corners | |
| // Origin at center of sheet | |
| //—– | |
| // Dimensions | |
| DiskOD = 80.0mm; // usual kitchen drain = 3-1/4 inch | |
| DiskRad = DiskOD/2; | |
| PlateThick = 6.0mm; // stock thickness | |
| MillOD = 3.170mm; // measured end mill OD | |
| HoleDia = 4.75mm; // 3/16 inch drain holes | |
| ScrewOD = 0.18in; // knob screw clearance | |
| NumRings = 3; // rings of drain holes | |
| RingSpace = 1.5 * HoleDia; // .. between rings | |
| MaxZCut = 0.25 * MillOD; // max cut depth | |
| MillSpeed = 1000mm; // horizontal feedrate | |
| NumTabs = 4; | |
| TabTilt = 45deg; | |
| TabLength = 5.0mm; | |
| TabThick = 0.5mm; | |
| SafeZ = 10.0mm; // above all obstructions | |
| TravelZ = 1.0mm; // within engraving / milling area | |
| MillZ = -(PlateThick + 0.5mm); // through disk into spoil board | |
| TwoPi = 2*pi(); | |
| //—– | |
| // Mill one hole | |
| function MillHole(ctr,radius,turns) { | |
| goto([-,-,TravelZ]); | |
| goto(head(ctr,2) + [radius,-,-]); | |
| goto([-,-,0]); // kiss surface | |
| circle_cw(ctr,turns); // helix downward | |
| circle_cw(head(ctr,2)); // remove last ramp | |
| goto(ctr); // get elbow room | |
| goto([-,-,TravelZ]); | |
| } | |
| //—– | |
| // Start cutting! | |
| goto([-,-,SafeZ]); | |
| goto([0,0,-]); | |
| goto([-,-,TravelZ]); | |
| feedrate(MillSpeed); | |
| // Mill center screw hole | |
| comment("– Center hole"); | |
| ctr = [0,0,MillZ]; | |
| MillHole(ctr,(ScrewOD – MillOD) / 2,ceil(abs(ctr.z) / MaxZCut)); | |
| // Mill hole rings | |
| comment("– Drain hole rings"); | |
| repeat (NumRings; ri) { | |
| comment("Ring: ",ri); | |
| rr = DiskRad – ri*RingSpace; // ring radius | |
| comment(" radius: ",rr); | |
| nh = to_int(floor(TwoPi*rr / (2*HoleDia))); // number of holes | |
| comment(" holes: ",nh); | |
| repeat(nh; h) { | |
| a = (h – 1) * TwoPi / nh; // angle of hole | |
| ctr = [rr*cos(a),rr*sin(a),MillZ]; // center point at ending Z | |
| MillHole(ctr,(HoleDia – MillOD)/2,ceil(abs(ctr.z) / MaxZCut)); | |
| } | |
| } | |
| // Mill perimeter | |
| comment("– Perimeter"); | |
| r = DiskRad + MillOD/2; | |
| goto([r,0,-]); | |
| goto([-,-,0]); | |
| ctr = [0,0,-(PlateThick – TabThick)]; | |
| circle_ccw(ctr,ceil(abs(ctr.z) / MaxZCut)); // ramp downward | |
| circle_ccw(ctr,1); // remove last ramp | |
| goto([-,-,TravelZ]); | |
| comment("– Tabs"); | |
| ta = 360deg / NumTabs; // between tabs | |
| tsa = to_rad(TwoPi*((TabLength + MillOD) / (TwoPi * r))); // subtended tab angle | |
| repeat (NumTabs; i) { | |
| comment(" # ",i); | |
| a = TabTilt + (i – 1)*ta; // tab center angle | |
| p0 = [r*cos(a + tsa/2),r*sin(a + tsa/2),MillZ]; // entry on ccw side | |
| p1 = [r*cos(a + ta – tsa/2),r*sin(a + ta – tsa/2),MillZ]; // exit at next tab | |
| if (0) { | |
| comment(" angle: ",a); | |
| comment(" entry: ",p0); | |
| comment(" exit: ",p1); | |
| } | |
| goto(head(p0,2)); // to entry point | |
| move(p0); // plunge through | |
| arc_ccw(p1,r); | |
| goto([-,-,TravelZ]); | |
| } | |
| goto([-,-,SafeZ]); | |
| goto([0,0,-]); | |
All in all, a pleasant diversion from contemporary events …
It being the season for hacking down decorative grasses, our ancient Craftsman Hedge Trimmer woke up dead, a decade after I fixed its switch and predicted it’d be good for another decade.
After verifying the failure isn’t in the wall outlet or the extension cord, haul it to the Basement Laboratory Repair Wing, clamp the blade in the bench vise, remove a myriad screws, and pop the top:
I should have removed the screw in the extreme lower right corner and loosened the similar screw at the rear of the bottom plate; they’re two of the three machine screws engaging nuts embedded in the shell. Everything is greasy enough to let the nuts slide right out of the plastic and no harm was done, but that need not be so.
After poking around a bit and finding nothing obvious, I checked the resistance across the plug: open-circuit with the switch OFF and nearly shorted with the switch ON.
Huh.
Put the case back together with just enough screws to prevent heartache & confusion, unclamp the blade, plug into the bench outlet, discover it works fine again, reinstall the rest of the screws, and continue the mission:
We moved the Praying Mantis oothecae to nearby bushes for science!
Because the cheap batteries I use in the Sony HDR-AS30V camera provide just slightly less runtime than our longest usual ride after a year of use, I carry a spare battery in a small red felt bag. The bag also holds a USB card reader helping to make the MicroSD card somewhat less lose-able on its trips betwixt bike & desk.
Here I am, swapping batteries in Adam’s Fairacre parking lot before starting the trip home:
You can see it coming, right?
Eight minutes later, we’re turning onto the Dutchess County Rail Trail:
And then it’s gone:
Mary drove past there on her way to a distant meeting, but the little red bag was not to be found anywhere. Maybe it’ll reappear on a fence post or taped to the bulletin board; I’ve tried to return things I’ve found that way.
I expect somebody got a nice present and, if naught else, it’s good to drop happiness into the world.
There’s another reader and a quartet of batteries on their way.
Our CVS blood pressure meter (a relabeled Microlife unit) ran its pump for a few seconds this morning, gave up, and spat out Err 3, which translates into “Inflation of the cuff takes too long”. Not surprising, as the motor wasn’t running.
The AA alkaline cell quartet has plenty of mojo and no corrosion, but the motor doesn’t even turn over. The display is fine and the pressure release valve clicks, so it’s not completely dead.
This unit is sufficiently old to have the compelling advantage of transferring data through a USB (mini-B) connection, rather than a Bluetooth link through some sketchy Internet cloudy Android app, so it’s worth at least a look inside. Four screws and some internal snaps along the sides hold the case together; it’s a surprisingly easy teardown.
The business side of the PCB looks good:
The various wires and solder joints for the “high current” parts look OK, although the wires likely don’t go all the way through the PCB:
Q4 and Q5 look like they switch the compressor pump motor and pressure-release valve. D3 and D4 should tamp down the inductive energy, but they look like they’re in series with the outputs. Yes, the Valve wires are both black.
The motor has a foam vibration isolation wrap, which is a nice touch. Although you can’t see them well, all its wires & solder joints look like they’re in good shape:
The hose sticking out toward you plugs into the black right-angle fitting in the lower right corner of the picture. It’d help to have smaller fingers than mine, but I managed to get the hose off and on the fitting with only minor muttering.
Seeing nothing obviously wrong, I installed the same batteries, poked the switch to start a measurement, and the motor ran fine. Of course, the measurement failed because the cuff & pressure sensor weren’t connected.
Connect the hose, plug in the cuff & wrap it around my arm, poke the button, and everything works fine.
Reassemble everything and it still works fine.
I still think there’s a bad wire or solder joint in there somewhere, so this delightful “repair” can’t possibly last very long …
The Smell of Molten Projects in the Morning 