The New Hotness

We negotiated the Belmar Bridge ~~connection~~ stairway from the Allegheny River Trail to the Sandy Creek trail:

Belmar Bridge Stairs - Overview — Belmar Bridge Stairs – Overview

We’re maneuvering Mary’s bike, but you get the general idea. Our bikes aren’t built for stairways, particularly ones with low overheads:

Belmar Bridge Stairs - Low Overhead — Belmar Bridge Stairs – Low Overhead

The front fender clip on my Tour Easy snapped (at the expected spots) when the mudflap snagged on one of the angles:

Belmar Bridge Stairs - First Turn — Belmar Bridge Stairs – First Turn

For some inexplicable reason, I didn’t have a roll of duct tape in my packs, so the temporary repair required a strip of tape from a battery pack, two snippets of hook-and-loop tape, and considerable muttering:

Tour Easy front fender clip - expedient repair — Tour Easy front fender clip – expedient repair

It was good for two dozen more miles to the end of our vacation, so I’d say that was Good Enough.

The new version has holes in the ferrules ten stay diameters deep, instead of six, which might eliminate the need for heatstink tubing. I added a small hole at the joint between the curved hooks and the ferrules to force more plastic into those spots:

Front Fender Clip - Slic3r — Front Fender Clip – Slic3r

I also bent the hanger extension to put the fender’s neutral position closer to the wheel.

We’ll see how long this one lasts. By now, I now have black double-sticky foam tape!

The OpenSCAD source code as a GitHub Gist:

	// Tour Easy front fender clip
	// Ed Nisley KE4ZNU July 2017

	Layout = "Build"; // Build Profile Ferrule Clip

	//- Extrusion parameters must match reality!

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

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

	//———————-
	// Dimensions

	// special case: fender is exactly half a circle!

	FenderC = 51.0; // fender outside width = chord
	FenderM = 21.0; // height of chord

	FenderR = (pow(FenderM,2) + pow(FenderC,2)/4) / (2 * FenderM); // radius
	echo(str("Fender radius: ", FenderR));
	FenderD = 2*FenderR;

	FenderA = 2 * asin(FenderC / (2*FenderR));
	echo(str(" … Arc: ",FenderA," deg"));

	FenderThick = 2.5; // fender thickness, assume dia of edge

	ClipHeight = 15.0; // top to bottom, ignoring rakish tilt
	ClipThick = IntegerMultiple(2.5,ThreadWidth); // thickness of clip around fender
	ClipD = FenderD; // ID of clip against fender
	ClipSides = 4 * 8; // polygon sides around clip circle

	BendReliefD = 2.5; // bend arch diameter
	BendReliefA = 2/3 * FenderA/2; // … angle from dead ahead
	BendReliefCut = 1.5; // factor to thin outside of bend

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

	StayDia = 3.3; // fender stay rod diameter
	StayOffset = 15.0; // stay-to-fender distance
	StayPitch = -5; // angle from stay to fender arch

	DropoutSpace = 120; // stay spacing at wheel hub
	StayLength = 235; // stay length: hub to fender
	StaySplay = asin((DropoutSpace – FenderC)/(2*StayLength)); // outward angle to hub

	echo(str(" … Pitch: ",StayPitch," deg"));
	echo(str(" … Splay: ",StaySplay," deg"));

	FerruleSides = 2*4;
	Ferrule = [StayDia,3FenderThick/cos(180/FerruleSides),10StayDia + StayOffset]; // ID = stay rod OD
	FerruleHoleD = 0.1; // small hole to create solid plastic at ferrule joint

	//———————-
	// 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);
	}

	//———————-
	// Clip profile around fender
	// Centered on fender arc

	module Profile(HeightScale = 1) {

	linear_extrude(height=HeightScale*ClipHeight,convexity=5) {
	difference() {
	offset(r=ClipThick) // outside of clip
	union() {
	circle(d=ClipD,$fn=ClipSides);
	for (i=[-1,1])
	rotate(i*BendReliefA) {
	translate([ClipD/2 + BendReliefD/2,0,0])
	circle(d=BendReliefD,$fn=6);
	}
	}
	union() { // inside of clip
	circle(d=ClipD,$fn=ClipSides);
	for (i=[-1,1])
	rotate(i*BendReliefA) {
	translate([ClipD/2 + BendReliefCut*BendReliefD/2,0,0])
	circle(d=BendReliefD/cos(180/6),$fn=6);
	translate([ClipD/2,0,0])
	square([BendReliefCut*BendReliefD,BendReliefD],center=true);
	}
	}
	translate([(FenderR – FenderM – FenderD/2),0]) // trim ends
	square([FenderD,2*FenderD],center=true);
	}

	for (a=[-1,1]) // hooks around fender
	rotate(a*(FenderA/2))
	translate([FenderR – FenderThick/2,0]) {
	difference() {
	rotate(1*180/12)
	circle(d=FenderThick + 2*ClipThick,$fn=12);
	rotate(1*180/8)
	circle(d=FenderThick,$fn=8);
	rotate(a * -90)
	translate([0,-2*FenderThick,0])
	square(4*FenderThick,center=false);
	}
	}
	}
	}


	//———————-
	// Ferrule body

	module FerruleBody() {

	translate([0,0,Ferrule[OD]/2 * cos(180/FerruleSides)])
	rotate([0,-90,0]) rotate(180/FerruleSides)
	difference() {
	cylinder(d=Ferrule[OD],h=Ferrule[LENGTH],$fn=FerruleSides,center=false);
	translate([0,0,StayOffset + Protrusion])
	PolyCyl(Ferrule[ID],Ferrule[LENGTH] – StayOffset + Protrusion,FerruleSides);

	}

	}

	//———————-
	// Generate entire clip at mounting angle

	module FenderClip() {

	difference() {
	union() {
	translate([FenderR,0,0])
	difference() { // angle and trim clip
	rotate([0,StayPitch,0])
	translate([-(FenderR + ClipThick),0,0])
	Profile(2); // scale upward for trimming
	translate([0,0,-ClipHeight]) // trim bottom
	cube(2*[FenderD,FenderD,ClipHeight],center=true);
	translate([0,0,ClipHeight*cos(StayPitch)+ClipHeight]) // trim top
	cube(2*[FenderD,FenderD,ClipHeight],center=true);
	}
	for (j = [-1,1]) // place ferrules
	translate([Ferrule[OD]sin(StayPitch) + (Ferrule[OD]/2)sin(StaySplay),j*(FenderR – FenderThick/2),0])
	rotate(-j*StaySplay)
	FerruleBody();
	}
	for (i=[-1,1]) // punch stiffening holes
	translate([FenderThick/2,-i*(FenderR – FenderThick/2),Ferrule[OD]/2])
	rotate([0,-90,i*StaySplay])
	PolyCyl(FerruleHoleD,Ferrule[OD],FerruleSides);

	}
	}

	//———————-
	// Build it


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

	if (Layout == "Ferrule") {
	FerruleBody();
	}

	if (Layout == "Clip") {
	FenderClip();
	}

	if (Layout == "Build") {
	FenderClip();
	}

view raw Front Fender Clip.scad hosted with ❤ by GitHub

As a bonus for paging all the way to the end, here’s the descent on the same stairway:

Belmar Bridge Stairs - Descent — Belmar Bridge Stairs – Descent

No, I wasn’t even tempted …

The New Hotness

Tour Easy Front Fender Clip: Longer and Stronger