Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
As expected, the plywood seat I put on the Step2 Garden Seat for Mary’s Vassar Farms plot lasted about a year before the wood rotted away around the screws. In the meantime, we’d acquired a stack of SiLite cafeteria trays, so we applied one to the cause of better seating:
Step2 Seat – tray variant
Various eBay listings value that slab of BakeliteMelamine up to $20, which is far more than Mary paid for the entire stack at a local tag sale. They also call that color “rich brown”, which is certainly better than what immediately came to mind when I saw them.
The stylin’ asymmetric design happened when I realized the squared-off handle end of the cart didn’t demand a rounded-off end of the seat. I cut off the raised tray rim before sketching the rounded outline using the rotted seat as a template; some of the sketch remains over on the right-front corner. A session with Mr Belt Sander put the remaining rim edges flush with the surface, no matter what the picture suggests.
The tray being 2 mm thinner than the plywood, I tried printing the hinges in a different orientation with different built-in support:
Rolling Cart Hinges – solid model – build
The perimeter threads pulled up far too much and, although fiddling with cooling would likely help, I think the original orientation was better:
Rolling Cart Hinges – solid model – bottom
Given that the post-apocalypse breakfast will be served on similar trays, the seat should survive for quite a while in the garden. We think the sun will convert the brown surface into a bun warmer; a coat of white paint may be in its future.
The original OpenSCAD code is still out there as a GitHub Gist.
Even linearized, the inchworm was barely 20 mm long; it’s the thought that counts.
The stamens mature in concentric rings, each stamen topped by a pollen grain. Apparently, those grains are just about the most wonderful food ever, as the inchworm made its way around the ring eating each grain in succession:
For whatever reason, a two-outlet junction box stands outside the Credit Union:
Outdoor Junction Box – angled conduit
The slanted conduit certainly looks in need of an elbow to line it up, doesn’t it?
It seems whoever installed it, many years ago, simply forced the conduit to line up, no matter the consequences:
Outdoor Junction Box – open wiring
The threaded entries on the die-cast outlet box were never intended to cope with that much misalignment; half the bottom has vanished. I think the round box on the top originally held a floodlight to wash the (uninspired) building facade at night, but those days are long gone.
If the conduit has horizontal underground runs, both are certainly full of water by now. The white(-ish) “Romex” cable insulation looks like ordinary indoor wiring, not the grayish direct-burial sheath, but it may be sun-bleached after years of exposure.
Just before Tropical Storm Isaias rolled through, my hygrometer reached a new high:
Pre-Isaias humidity
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:
EonSmoke vape stick
It turns out to be an aluminum tube holding a lithium cell and a reservoir of oily brown juice:
EonSmoke – peeled open
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:
EonSmoke – 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:
EonSmoke – reservoir heater
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:
Shuttles Game pegs – tapered – solid model
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:
Mesh Shelter Frame – assembled
The solid model shows the structure with no regard for proportion:
Mesh Shelter Frame – show view
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:
Mesh Shelter Frame – non-hulled corner model
Shrink-wrapping them with a hull() adds plenty of strength where it’s needed:
Mesh Shelter Frame – hulled corner model
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:
Mesh Shelter Frame – build layout
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:
rotate(acos((BaseVector*Nadir)/(norm(BaseVector)*norm(Nadir))),
v=cross(BaseVector,Nadir)) // aim belly side downward
Corner();
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:
Mesh Shelter Frame – corner underside
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.
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The Smell of Molten Projects in the Morning 