Rear Running Light: Tour Easy Seat Clamp

With the amber front running light blinking away, it’s time to replace the decade-old Planet Bike Superflash behind the seat:

Superflash on Tour Easy
Superflash on Tour Easy

The new mount descends directly from the clamps holding the fairing strut on the handlebars and various hose clamps:

Rear Running Light Seat Clamp - solid model
Rear Running Light Seat Clamp – solid model

The central block has two quartets of brass inserts epoxied inside:

Rear Running Light Seat Clamp - sectioned - solid model
Rear Running Light Seat Clamp – sectioned – solid model

That means I can install the light, then mount the whole affair on the bike, without holding everything together while fiddling with overly long screws.

A trial fit with the not-yet-cut-to-length 25.3 (-ish) PVC pipe body tube:

Rear Running Light - Tour Easy seat clamp trial fit
Rear Running Light – Tour Easy seat clamp trial fit

The aluminum plates have the standard used-car finish: nice polish over deep scratches.

Although I’ve been thinking of mounting the light below the seat rail, as shown, it can also sit above the rail.

Mary hauls seedlings and suchlike to the garden in a plastic drawer bungied to the rack, with the SuperFlash serving as an anchor point; this light may need fine tuning for that purpose.

The OpenSCAD source code as a GitHub Gist:

// Rear running light clamp for Tour Easy seat strut
// Ed Nisley - KE4ZNU - 2021-09
Layout = "Show"; // [Show,Build,Block]
Section = true;
/* [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
// Light case along X axis, seat strut along Y, Z=0 at strut centerline
LightOD = 25.4 + HoleWindage;
StrutOD = 5/8 * inch + HoleWindage;
PlateThick = 1/16 * inch;
WallThick = 2.0;
Kerf = ThreadThick;
Screw = [3.0,6.8,4.0]; // M3 OD=washer, length=nut + washers
Insert = [3.0,5.4,8.0 + 1.0]; // splined brass insert
RoundRadius = IntegerMultiple(Screw[OD]/2,0.5); // corner rounding
ScrewOC = [IntegerMultiple(StrutOD + 2*WallThick + Screw[ID],1.0),
IntegerMultiple(LightOD + 2*WallThick + Screw[ID],1.0)];
echo(str("Screw OC: ",ScrewOC));
BlockSize = [ScrewOC.x + Insert[OD] + 2*WallThick,
ScrewOC.y + Insert[OD] + 2*WallThick,
LightOD + StrutOD + 3*WallThick];
echo(str("Block: ",BlockSize));
BaseOffset = -(WallThick + LightOD/2); // block bottom to centerline
StrutOffset = LightOD/2 + WallThick + StrutOD/2; // light centerline to strut centerline
echo(str("Strut screw min: ",IntegerMultiple(PlateThick + WallThick + StrutOD/2 + Insert[LENGTH]/2,1.0)));
echo(str("Light screw min: ",IntegerMultiple(PlateThick + WallThick + LightOD/2 + Insert[LENGTH]/2,1.0)));
NumSides = 2*3*4;
//----------------------
// 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,
$fn=Sides);
}
// Block with light along X axis
module Block() {
difference() {
hull()
for (i=[-1,1], j=[-1,1])
translate([i*(BlockSize.x/2 - RoundRadius),j*(BlockSize.y/2 - RoundRadius),BaseOffset])
cylinder(r=RoundRadius,h=BlockSize.z,$fn=NumSides);
for (i=[-1,1], j=[-1,1])
translate([i*ScrewOC.x/2,j*ScrewOC.y/2,BaseOffset - Protrusion])
rotate(180/8)
PolyCyl(Screw[ID],BlockSize.z + 2*Protrusion,8);
for (i=[-1,1], j=[-1,1])
translate([i*ScrewOC.x/2,j*ScrewOC.y/2,0]) {
translate([0,0,-Protrusion])
rotate(180/8)
PolyCyl(Insert[OD],Insert[LENGTH] + 1*Protrusion,8);
translate([0,0,(StrutOffset - Insert[LENGTH] - Kerf/2 + Protrusion)])
rotate(180/8)
PolyCyl(Insert[OD],Insert[LENGTH] + 1*Protrusion,8);
}
translate([-BlockSize.x,0,0])
rotate([0,90,0])
cylinder(d=LightOD,h=2*BlockSize.x,$fn=NumSides);
translate([0,BlockSize.y,StrutOffset])
rotate([90,0,0])
cylinder(d=StrutOD,h=2*BlockSize.y,$fn=NumSides);
translate([0,0,StrutOffset])
cube([2*BlockSize.x,2*BlockSize.y,Kerf],center=true);
cube([2*BlockSize.x,2*BlockSize.y,Kerf],center=true);
}
}
//- Build it
if (Layout == "Block")
if (Section)
difference() {
Block();
rotate(atan(ScrewOC.y/ScrewOC.x))
translate([0,BlockSize.y,0])
cube(2*BlockSize,center=true);
}
else
Block();
if (Layout == "Show") {
Block();
color("Green",0.25)
translate([-BlockSize.x,0,0])
rotate([0,90,0])
cylinder(d=LightOD,h=2*BlockSize.x,$fn=NumSides);
color("Green",0.25)
translate([0,BlockSize.y,StrutOffset])
rotate([90,0,0])
cylinder(d=StrutOD,h=2*BlockSize.y,$fn=NumSides);
}
if (Layout == "Build") {
translate([-1.2*BlockSize.x,0,-BaseOffset])
difference() {
Block();
translate([0,0,BlockSize.z])
cube(2*BlockSize,center=true);
}
translate([1.2*BlockSize.x,0,StrutOD/2 + WallThick])
difference() {
rotate([180,0,0])
translate([0,0,-StrutOffset])
Block();
translate([0,0,BlockSize.z])
cube(2*BlockSize,center=true);
}
translate([0,0,StrutOffset - Kerf/2])
rotate([180,0,0])
intersection() {
Block();
translate([0,0,StrutOffset/2])
cube([2*BlockSize.x,2*BlockSize.y,StrutOffset],center=true);
}
}

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