The New Hotness

The objective being to reduce the number of onion maggots in Mary’s Vassar Farm plot without chemical agents, I conjured sticky trap screen frames from the vasty digital deep:

Sticky Trap - first production run — Sticky Trap – first production run

Each one contains half a sheet of yellow sticky plastic, which is easy enough to cut before peeling off the protective covering sheets. The cage is half-inch galvanized hardware cloth snipped with hardened diagonal cutters. A bead of acrylic adhesive around the base holds the cage in place

Although you can deploy sticky sheets without cages, they tend to attract and affix beneficial critters: butterflies, small birds, furry critters, toads, gardeners, and the like. We don’t know how effective the cages will be, but they seemed better than nothing.

They mount on ski poles cut in half:

Sticky Trap - ski pole installed — Sticky Trap – ski pole installed

And on fence posts around the perimeter:

Sticky Trap - angle bracket installed — Sticky Trap – angle bracket installed

To my untrained eye, some of those doomed critters are, indeed, onion maggot flies. The rest seem to be gnats and other nuisances, so IMO we’re applying population pressure in the right direction.

Each base-and-cap frame takes about three hours to print, so I did them one at a time over the course of a few days while applying continuous product improvement.

The sheets rest on small V blocks intended to keep them centered within the cage:

Sticky Sheet Cage - angle bracket - solid model — Sticky Sheet Cage – angle bracket – solid model

The ski pole attachment must build with the cap on top, but it bridges well enough for the purpose:

Sticky Sheet Cage - ski pole - solid model — Sticky Sheet Cage – ski pole – solid model

The overhanging hooks on the blocks (just barely) engage the grid to keep the lid in place, while remaining short enough to not droop too badly. You could probably delete the hooks from the bottom plate, but they align the cage while the adhesive cures.

The sheets tend to bend in the middle, so I’ll stick a thin slat or two vertically to keep them straight.

The OpenSCAD source code as a GitHub Gist:

	// Sticky Sheet Cage
	// Ed Nisley KE4ZNU May 2021

	Layout = "Build"; // [Build, Show, Cap, Attachment]

	Bracket = "Ski"; // [Angle, Ski, Post]

	//- 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;

	ID = 0;
	OD = 1;
	LENGTH = 2;

	function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);

	//———————-
	// Dimensions

	Sheet = [1,100,150]; // sticky sheet

	Grid = 0.5*inch;

	Cage = [2Grid + 5.0, 8Grid + 5.0, 12*Grid + 2.0]; // grid wire cage bent around sheet
	CageRad = 2.5; // wire bending radius
	CageThick = 2.0; // grid thickness

	WallThick = 3.0; // min wall and bottom thickness
	Recess = 5.0; // inset to capture cage edge

	Plate = [Cage.x,Cage.y,Recess] + [2WallThick,2WallThick,WallThick];
	PlateRad = 5.0;

	SkiPole = [20.0,20.0 + 2*WallThick,50];
	AnglePlate = [30,30,50];

	ScrewClear = 5.0;

	BuildGap = 5.0;

	//———————-
	// 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);
	}

	//———————-
	// Pieces

	module Cap() {

	union() {
	difference() {
	hull()
	for (i=[-1,1], j=[-1,1])
	translate([i(Plate.x/2 – PlateRad),j(Plate.y/2 – PlateRad),0])
	cylinder(r=PlateRad,h=Plate.z,$fn=12);
	translate([0,0,Plate.z – Recess])
	hull()
	for (i=[-1,1], j=[-1,1])
	translate([i(Cage.x/2 – CageRad),j(Cage.y/2 – CageRad),0])
	cylinder(r=CageRad,h=Plate.z,$fn=12);
	}
	difference() {
	Strut = Cage.x – 2*CageThick;
	Latch = [Cage.x,WallThick,0.75*Plate.z];
	union() {
	for (j=[-1,1])
	translate([0,j2.5Grid,Plate.z])
	cube([Strut,WallThick,2*Plate.z],center=true);
	for (j=[-1,1])
	translate([0,j2.5Grid,2*Plate.z – Latch.z/2])
	cube(Latch,center=true);
	}
	translate([0,0,2*Plate.z + (Cage.z – Sheet.z)/4])
	rotate([0,45,0])
	cube([Strut/sqrt(2),Plate.y,Strut/sqrt(2)],center=true);
	}
	}
	}

	module Attachment() {

	if (Bracket == "Angle") {
	translate([0,Plate.y/2,0])
	rotate(45)
	difference() {
	union() {
	cube(AnglePlate,center=false);
	rotate(-45)
	translate([0,WallThick,Plate.z/2])
	cube([Plate.x – 2PlateRad,4WallThick,Plate.z],center=true);
	}
	translate([WallThick,WallThick,-Protrusion])
	cube(AnglePlate + [0,0,2*Protrusion],center=false);
	translate([AnglePlate.x/2,-Protrusion,2*AnglePlate.z/3])
	rotate([-90,0,0])
	PolyCyl(ScrewClear,2*AnglePlate.x,6);
	translate([-Protrusion,AnglePlate.x/2,1*AnglePlate.z/3])
	rotate([90,0,90])
	PolyCyl(ScrewClear,2*AnglePlate.x,6);
	}
	}
	else if (Bracket == "Ski") {
	translate([0,Plate.y/2 + SkiPole[OD]/2,0])
	difference() {
	union() {
	PolyCyl(SkiPole[OD],SkiPole[LENGTH],24);
	translate([0,-3*WallThick,Plate.z/2])
	cube([Plate.x – 2PlateRad,4WallThick,Plate.z],center=true);
	}
	translate([0,0,-2*WallThick])
	PolyCyl(SkiPole[ID],SkiPole[LENGTH],24);

	}
	}
	}

	//———————-
	// Build it

	if (Layout == "Cap")
	Cap();

	if (Layout == "Attachment") {
	Attachment();
	}

	if (Layout == "Show") {
	translate([0,0,Sheet.z/2 + Plate.z])
	color("Yellow")
	cube(Sheet,center=true);
	Cap();
	Attachment();
	translate([0,0,Sheet.z + 2*Plate.z])
	rotate([180,0,0])
	Cap();
	}

	if (Layout == "Build") {
	translate([-(Plate.x/2 + BuildGap),0,0]) {
	Cap();
	Attachment();
	}
	translate([(Plate.x/2 + BuildGap),0,0])
	Cap();
	}

view raw Sticky Sheet Cage.scad hosted with ❤ by GitHub

The New Hotness

Sticky Trap Screen Frames