The New Hotness

Some years ago we acquired a free quartet of aluminum-frame patio chairs in need of new straps and feet. Eventually enough straps broke to force me to re-strap the things and I finally got around to replacing the badly worn OEM feet:

Patio Chair Foot Adapter - OEM feet — Patio Chair Foot Adapter – OEM feet

The small drilled holes let me yoink most them out with sheet-metal screw attached to a slide hammer, then apply the Designated Prydriver to the most recalcitrant / broken ones.

Some feet had worn enough to expose the aluminum tubes, but most had at least a thin layer of plastic:

Patio Chair Foot Adapter - OEM foot erosion — Patio Chair Foot Adapter – OEM foot erosion

Obviously, I should have stripped and repainted the frames (if that’s possible, as they’re probably powder-coated), but a man’s gotta know his limitations and this job needed to get done.

One might think patio furniture replacement feet are cheap & readily available, but no amount of keyword engineering produced search results with any degree of assured fit, so I conjured adapters for screw-in feet from the vasty digital deep:

Patio Chair Foot Adapters - solid models — Patio Chair Foot Adapters – solid models

This was a long-awaited opportunity to explore the BOSL2 library and it worked wonderfully well. Each adapter is whittled from a huge hex nut with threads that perfectly fit the M8×1.25 stud, which stands vertically through the middle of the (slightly oval) bottom surface parallel to the floor.

The front tubes have a 5° angle with respect to the vertical:

Patio Chair Foot Adapter - front — Patio Chair Foot Adapter – front

And the rear tubes are 15° off:

Patio Chair Foot Adapter - rear — Patio Chair Foot Adapter – rear

Each adapter has an orientation notch pointing toward the front of the front leg and the rear of the rear leg:

Patio Chair Foot Adapter - orientation notch — Patio Chair Foot Adapter – orientation notch

I expected to apply adhesive on the inside and outside of the adapters, but they tapped firmly into place inside the legs and the studs screwed firmly into them, so we’ll see how they survive in actual use. I expect the studs to rust after a while, but that might not be the most awful thing ever to happen.

The OpenSCAD source code as a GitHub Gist:

	// Patio chair foot adapter
	// Ed Nisley – KE4ZNU – 2023-06

	include <BOSL2/std.scad>
	include <BOSL2/threading.scad>

	LegAngles = [5,15];

	/* [Hidden] */

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

	Protrusion = 0.1; // make holes end cleanly

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

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

	inch = 25.4;

	//———————-
	// Dimensions

	LegTube = [18.8 – HoleWindage,22.5,0];

	Stud = [8.0,1.25,10.0]; // M8x1.25 foot stud

	FlangeBase = 3.0;

	//———————–


	for (i=[0:len(LegAngles)-1]) {

	ang = LegAngles[i];

	FlangeIncr = LegTube[OD]*tan(ang);
	Flange = [Stud[0],LegTube[OD],FlangeBase + FlangeIncr];

	translate([i1.5Flange[OD],0,0])
	difference() {
	translate([0,0,0*-FlangeIncr/2])
	threaded_nut(2Flange[OD],Stud[0],1.5Stud[2],Stud[1],
	anchor=BOTTOM,bevel=false,$slop=0.2);
	rotate([0,ang,0]) {
	translate([0,0,FlangeBase + FlangeIncr/2])
	tube(4Stud[2],2Flange[OD],LegTube[ID]/2,
	anchor=BOTTOM);
	tube(4Stud[2],2Flange[OD],Flange[OD]/2,
	anchor=CENTER);
	}
	cube([Flange[OD],ThreadWidth,2*ThreadThick],anchor=BOTTOM+RIGHT);
	}
	}

view raw Patio Chair Foot Adapters.scad hosted with ❤ by GitHub