Seedling Shelter Frame

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
Mesh Shelter Frame – assembled

The solid model shows the structure with no regard for proportion:

Mesh Shelter Frame - show view
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
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
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
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
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.

The OpenSCAD source code as a GitHub Gist:

Lending a Hand

This being repotting season, Mary trimmed a pair of leaves from a bay tree and wanted to dry them for cooking, so I offered to lend a hand:

Bay leaves drying in helping hand fixture
Bay leaves drying in helping hand fixture

Two hands, in fact.

The whole affair now sits on a kitchen windowsill, shriveling by the day, and the leaves should be ready in a month or two. Yum!

Garden Soaker Hose Repairs In Use

Just for completeness, here’s what the various soaker hose clamps look like in the garden, as solid models only let you visualize the ideal situation:

Soaker Hose Connector Clamp - Show view
Soaker Hose Connector Clamp – Show view

This one prevents a puddle in the path to the right:

Soaker hose repairs in situ - clamp
Soaker hose repairs in situ – clamp

Bending the hoses around the end of a bed puts them on edge, with this clamp suppressing a shin-soaking spray to the left:

Soaker hose repairs in situ - end-on clamp
Soaker hose repairs in situ – end-on clamp

The clamp at the connector closes a leak around the crimped brass fitting, with the other two preventing gouges from direct sprays into the path along the bottom of the picture:

Soaker hose repairs in situ - clamps and connector fix
Soaker hose repairs in situ – clamps and connector fix

All in all, a definite UI improvement!

As far as I can tell, we have the only soaker hose repairs & spritz stoppers in existence. Hooray for 3D printing!

Robin Nest: Fledging Day

The robin nestlings fledged fourteen days after we spotted the first eggshell on the driveway below the nest. The first one may have flown away the previous evening, leaving three increasingly restless siblings behind:

Robin Fledging Day - three nestlings
Robin Fledging Day – three nestlings

They’re recognizably robins now, covered in young-bird speckle camouflage.

Feeding continued apace:

Robin Fledging Day - feeding
Robin Fledging Day – feeding

After feeding, robin nestlings produce fecal sacs, which the parents either eat or carry away:

Robin Fledging Day - fecal sac
Robin Fledging Day – fecal sac

Robins aren’t big on facial expressions, but, speaking from personal experience, anything to do with diapers isn’t the high point of a parent’s day.

And then there were none:

Robin Fledging Day - empty nest with parasites
Robin Fledging Day – empty nest with parasites

The gazillion black dots on the soffit are pinpoint-sized insects / mites / ticks infesting the nest and, presumably, the birds. The earlier pictures don’t show them, so perhaps these missed the last bird off the nest and are now regretting their life choices.

Go, birds, … gone!

Robin Nest: Nestlings!

All four nestlings emerged on schedule:

Garage Robin - four nestlings
Garage Robin – four nestlings

The oldest nestling was ready for feeding almost immediately, even with unopened eyes:

Garage Robin - Nestling begging
Garage Robin – Nestling begging

As any infant will tell you, holding your head up is hard work:

Garage Robin - Nestling dozing
Garage Robin – Nestling dozing

But doing only half the job won’t get you fed:

Garage Robin - Nestling recovering
Garage Robin – Nestling recovering

They’re just starting to make little chirps, so this isn’t nearly as raucous as you might think:

Garage Robin - Nestlings begging
Garage Robin – Nestlings begging

The adults seem to have no trouble bringing an endless stream of worms, insects, and unidentifiable organisms from the yard and garden.

Go, birds, go!

Soaker Hose Clamps

Having figured out the geometry for two- and three-channel soaker hoses, I cranked out more clamps:

Soaker Hose Clamps - production
Soaker Hose Clamps – production

Actually, those are the remainder of two production runs devoted to reducing the amount of water sprinkling the garden paths. A 50 foot hose runs along both sides of one 14 foot bed, crosses the path, then continues along the adjacent bed. The hoses have (deliberate!) sprinkler holes along their porous rubber body and sometimes the layout puts a hole where it waters the path.

The blue silicone rubber strips provide a bit of sealing to prevent the absurdly high pressure water from streaming through the orange PETG clamps. It’s OK if the clamp leaks, but less flow is better!

I’m getting really good at making those aluminum backing plates and, in fact, I think it’s faster to run the blanks past the disk sander, then drill the holes, than to CNC-machine them. Could be wrong, but Quality Shop Time is not to be sniffed at.

Garden Hose Valve Wrench: Reinforced

After five gardening seasons, my simple 3D printed wrench broke:

Hose Valve Knob - fractured
Hose Valve Knob – fractured

Although Jason’s comment suggesting carbon-fiber reinforcing rods didn’t prompt me to lay in a stock, ordinary music wire should serve the same purpose:

Hose Valve Knob - cut pins
Hose Valve Knob – cut pins

The pins are 1.6 mm diameter and 20 mm long, chopped off with hardened diagonal cutters. Next time, I must (remember to) grind the ends flat.

The solid model needs holes in appropriate spots:

Hose Valve Knob - Reinforced - Slic3r
Hose Valve Knob – Reinforced – Slic3r

Yes, I’m going to put round pins in square holes, without drilling the holes to the proper diameter: no epoxy, no adhesive, just 20 mm of pure friction.

The drill press aligns the pins:

Hose Valve Knob - pin ready
Hose Valve Knob – pin ready

And rams them about halfway down:

Hose Valve Knob - pin midway
Hose Valve Knob – pin midway

Close the chuck jaws and shove them flush with the surface:

Hose Valve Knob - pins installed
Hose Valve Knob – pins installed

You can see the pins and their solid plastic shells through the wrench stem:

Hose Valve Knob - assembled
Hose Valve Knob – assembled

Early testing shows the reinforced wrench works just as well as the previous version, even on some new valves sporting different handles, with an equally sloppy fit for all. No surprise: I just poked holes in the existing model and left all the other dimensions alone.

The OpenSCAD source code as a GitHub Gist: