Just before Tropical Storm Isaias rolled through, my hygrometer reached a new high:
The National Weather Service reported 99% at the airport a few miles away, so the meter’s calibration seems about right.
Shortly thereafter, the humidity dropped to the mid-70s as the wind picked up and, over the next few hours, falling branches took out vast swaths of Central Hudson’s electrical infrastructure. My little generator saved our refrigerator & freezer during 15 hours of outage; three days later, thousands of folks around us still have no power.
A confluence of other events, none nearly so dramatic, will throttle my posting over the next two weeks.
Being the type of guy who uses metal bits & pieces, I thought this might be a useful aluminum rod:
It turns out to be an aluminum tube holding a lithium cell and a reservoir of oily brown juice:
The black plastic cap read “EonSmoke”, which led to a defunct website at the obvious URL. Apparently, EonSmoke went toes-up earlier this year after ten years of poisoning their customers, most likely due to “competitor litigation”.
The black cap held what looks like a pressure switch:
Suck on the icky end of the tube to activate the switch, pull air past the battery (?), pick up some toxic vapor around the heater, and carry it into your lungs:
Maybe there’s a missing mouthpiece letting you suck on the icky end, activate the switch, pull vapor through the heater, and plate your lungs with toxic compounds. I admit certain aspects of my education have been sadly neglected.
The lithium cell was down to 1.0 V, with no overdischarge protection and no provision for charging, so it’s a single-use item. I’m sure the instructions tell you to recycle the lithium cell according to local and state regulations, not toss it out the window of your car.
As is all too common with 3D printed replacement parts done remotely, the first Shuttles game pegs didn’t quite fit into the game board’s holes. Fortunately, living in the future means rapid prototyping and quick turnaround:
They’re slightly smaller, tapered toward the bottom, and take slightly less time to print.
The OpenSCAD code in the GitHub Gist now has has the tweaks.
Plant seedlings started in pots require some hardening off time outdoors before being transplanted. Veggie seedlings also require protection from critters regarding them as a buffet, so Mary covers them with a sheet of floating row cover, which must be both suspended over the plants to give them growing room and tucked under the tray to keep the bugs out. She asked for a frame to simplify the process:
The solid model shows the structure with no regard for proportion:
The 5 mm fiberglass rods come from our decommissioned six-passenger umbrella, cut to length in the Tiny Lathe™ by applying a Swiss Pattern knife file around the perimeter, over the ShopVac’s snout to catch the glass dust. I started with a pull saw (also over the vacuum) during the weekly Squidwrench v-meeting, whereupon Amber recommended either a Dremel slitting wheel or a file, so I mashed everything together and it worked wonderfully well, without producing any errant glass-fiber shards to impale my fingers.
The corners consist of three tubes stuck together at the origin:
Shrink-wrapping them with a hull() adds plenty of strength where it’s needed:
I decided putting the belly side (facing you in the picture) downward on the platform and the peak upward would distribute the distortion equally among the tubes and produce a nicely rounded outer surface for the mesh fabric:
Which led to some Wikipedia trawling to disturb the silt over my long-buried analytic geometry, plus some calculator work to help recall the process; back in the day I would have used a slipstick, but I was unwilling to go there. Although I could special-case this particular layout, the general method uses Euler’s Rotation Theorem, simplified because I need only one rotation.
Should you need concatenated rotations, you probably need quaternions, but, at this point, I don’t even remember forgetting quaternions.
Anyhow, the Euler rotation axis is the cross product of the [1,1,1] vector aimed through the middle of the corner’s belly with the [0,0,-1] target vector pointing downward toward the platform. The rotation amount is the acos() of the dot product of those two vectors divided by the product of their norms. With vector and angle in hand, dropping them into OpenSCAD’s rotate() transformation does exactly what’s needed:
v=cross(BaseVector,Nadir)) // aim belly side downward
Dang, I was so happy when that worked!
Because the corner model rotates around the origin where all three tube centerlines meet, the result puts the belly below the platform, pointed downward. The next step applies a translation to haul the belly upward:
translate([ArmOAL,0, // raise base to just below platform level
ArmOC/sqrt(3) + (ArmRadius/cos(180/SocketSides))*cos(atan(sqrt(3)/2)) + Finagle])
This happens in a loop positioning the four corners for printing, so the first ArmOAL as the X axis parameter translates the shape far enough to let four of them coexist around the origin, as shown above.
The mess in the Z axis parameter has three terms:
Raise the centerline of the ends of the tubes to Z=0
Raise the rim of the tube to Z=0
Add a wee bit to make the answer come out right
The 0.18 mm Finagle constant fixes things having to do with the hull() applied to miscellaneous leftover angled-circles-as-polygons approximations and leaves just a skin below the platform to be sheared off by a huge cube below Z=0, matching the corner bellies with the bottoms of the feet.
Because the corners have awful overhangs, the results look a bit raggedy:
That’s after knocking off the high spots with a grubby sanding sponge and making a trial fit. They look somewhat less grotendous in person.
If we need another iteration, I’ll think hard about eliminating the overhangs by splitting the corner parallel to the belly, flipping the belly upward, and joining the pieces with a screw. What we have seems serviceable, though.
My favorite half-teaspoon measure hit the floor with a surprising sproing:
The weld lasted far longer than anyone should own a spoon, I suppose, but it wasn’t much to begin with:
Having had much the same thing happen to a measuring cup from the same set, I cleaned the back of the spoon and the front of the handle with a stainless steel wire brush in the Dremel and gingerly re-bent the handle to remove any inclination it might have to break free again:
Some 60% silver solder (the formula evidently changed in the last few decades), nasty flux, and propane torch work produced a decent fillet:
It looks a bit worse on the far side, but I’ll never tell.
Rinse off the flux, wire-brush the joint, wash again, and it’s all good.
I thought about excavating the resistance soldering gadget, but the torch was closer to hand and a bigger fillet seemed in order.
Mary took on the task of finishing a hexagonal quilt from pieced strips, only to discover she’ll need several more strips and the myriad triangles required to turn hexagons into strips. The as-built strips do not match any of the standard pattern sizes, which meant ordinary templates were unavailing. I offered to build a template matching the (average) as-built hexagons, plus a triangle template based on those dimensions.
Quilters measure hexes based on their finished side length, so a “1 inch hex” has sides measuring 1 inch, with the seam allowance extending ¼ inch beyond the sides. It’s difficult to measure finished sides with sufficient accuracy, so we averaged the side-to-side distance across several hexes.
Some thrashing around produced a quick-and-dirty check piece that matched (most of) the stack of un-sewn hexes:
That one came from a knockoff of the circle template, after some cleanup & tweakage, but failed user testing for not withstanding the side force from the rotary cutter blade. The inside and outside dimensions were correct, however, so I could proceed with some confidence I understood the geometry.
Both the pattern width (the side-to-side distance across the inside of the hex) and the seam allowance appearing in the Customizer appear in inches, because that’s how things get measured outside the Basement Laboratory & Fabrication Facility:
You feed in one side-to-side measurement and all other hex dimensions get calculated from that number; quilters default to a ¼ inch seam allowance. Remember, standard quilt hexes are measured by their side length, so just buy some standard templates.
Both templates have non-skid strips to keep the fabric in place while cutting:
I should have embossed the size on each template, but this feels like a one-off project and YAGNI. Of course, that’s how I felt about the circle templates, so maybe next time I’ll get it right.
As it turned out, Mary realized she needed a template for the two half-triangles at the end of each row:
It’s half of the finished size of the equilateral triangle on the right, with seam allowance added all around. The test scrap of fabric on the left shows the stitching along the hypotenuse of the half-triangle, where it joins to the end-of-row hexagon. Ideally, you need two half-triangle templates, but Mary says it’s easier to cut the fabric from the back side than to keep track of two templates.