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Our Larval Engineer practiced fencing for several years, learning the fundamental truth that you should always bring a gun to a knife fight:

Fencing - taking a hit — Fencing – taking a hit

It’s time to pass the gear along to someone who can use it, but we discovered one of the ear grommets inside the helmet had broken:

Blue Gauntlet M003-BG Helmet - broken ear grommet — Blue Gauntlet M003-BG Helmet – broken ear grommet

The cylinder in the middle should be attached to the washer on the left, which goes inside the helmet padding. It’s a tight push fit inside the washer on the right, which goes on the outside of the padding. Ridges along the cylinder hold it in place.

Being an injection-molded polyethylene part, no earthly adhesive or solvent will bother it, soooo… the solid model pretty much reproduces the original design:

Fencing Helmet Ear Grommet - show — Fencing Helmet Ear Grommet – show

The top washer goes inside the padding against your (well, her) ear, so I chamfered the edges sorta-kinda like the original.

There are no deliberate ridges on the central cylinder, but printing the parts in the obvious orientation with no additional clearance makes them a very snug push fit and the usual 3D printing ridges work perfectly; you could apply adhesive if you like. The outside washer has a slight chamfer to orient the post and get it moving along.

The posts keep the whole affair from rotating, but I’m not sure they’re really necessary.

Printing a pair doesn’t take much longer than just one:

Fencing Helmet Ear Grommet - build — Fencing Helmet Ear Grommet – build

It doesn’t look like much inside the helmet:

Blue Gauntlet M003-BG - replacement ear grommet - installed — Blue Gauntlet M003-BG – replacement ear grommet – installed

The OpenSCAD source code as a gist from Github:

	// Fencing Helmet Ear Grommet
	// Ed Nisley KE4ZNU December 2015

	// Layout options

	Layout = "Show"; // Base Cap Build Show

	//- Extrusion parameters must match reality!
	// Print with +1 shells and 3 solid layers

	ThreadThick = 0.20;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

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

	Protrusion = 0.1; // make holes end cleanly

	//———————-
	// Dimensions

	NumSides = 12*4;
	$fn = NumSides;

	//———————-
	// 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);
	}


	//——————-
	// Parts

	// Base on outside of liner

	PostOD = 15.5;
	PostLength = 8.0;

	BaseOD = 26.0;
	BaseLength = 3.4;

	module Base() {
	difference() {
	union() {
	cylinder(d=BaseOD,h=2.0);
	cylinder(d=20.0,h=BaseLength);
	for (i=[0:5])
	rotate(i*360/6)
	translate([11.5,0,0])
	rotate(180/6)
	cylinder(d1=2.5,d2=3*ThreadWidth,h=4.0,$fn=6);
	}
	translate([0,0,-Protrusion])
	// PolyCyl(PostOD,4.0,NumSides/4);
	cylinder(d=PostOD,h=PostLength,$fn=NumSides/4);
	translate([0,0,(BaseLength – 4*ThreadThick)])
	cylinder(d1=PostOD,d2=(PostOD + 2ThreadWidth),h=(4ThreadThick + Protrusion),$fn=NumSides/4);
	}
	}

	// Cap inside liner

	CapID = 12.0;
	CapOD = 28.0;
	CapThick = 3.0;

	module Cap() {
	difference() {
	union() {
	rotate_extrude(convexity=2)
	polygon(points=[
	[CapID/2 + CapThick/3,0.0],
	[CapOD/2 – CapThick/3,0.0],
	[CapOD/2,CapThick/2],
	[CapOD/2,CapThick],
	[CapID/2,CapThick],
	[CapID/2,CapThick – CapThick/3]
	]);
	translate([0,0,CapThick – Protrusion])
	cylinder(d=PostOD,h=(PostLength – (CapThick – Protrusion)),$fn=NumSides/4);
	}
	translate([0,0,-Protrusion])
	PolyCyl(CapID,10.0,$fn);
	}
	}

	//———————-
	// Build it!

	if (Layout == "Base")
	Base();

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

	BuildSpace = 30/2;
	if (Layout == "Build") {
	for (j=[-1,1])
	translate([j*BuildSpace,0,0]) {
	translate([0,-BuildSpace,0])
	Base();
	translate([0,BuildSpace,0])
	Cap();
	}
	}

	if (Layout == "Show") {
	color("LightGreen") Base();
	translate([0,0,12])
	rotate([180,0,0])
	color("LightBlue") Cap();
	}

view raw Fencing Helmet Ear Grommet.scad hosted with ❤ by GitHub

The New Hotness

Blue Gauntlet Fencing Helmet Ear Grommet