This is the slightly smaller mount corresponding to the OpenSCAD code there for the two-section inspection mirror shaft, hot from the printer:
It’s about the same as the previous version, despite trimming a few millimeters from the diameters and spacings:
I’ll print the next one in a darker color. At least it’s not pink…
The OpenSCAD source:
// Helmet mirror mount
// Ed Nisley KE4ZNU June 2011
include </home/ed/Thing-O-Matic/lib/MCAD/units.scad>
include </home/ed/Thing-O-Matic/lib/MCAD/boxes.scad>
include </home/ed/Thing-O-Matic/lib/visibone_colors.scad>
//-- Layout Control
Layout = "Build"; // Build Fit Show None
Examine = "None"; // AzMount ElMount ElBody ElPlate HelmetPlate None
//-- Extrusion parameters
ThreadThick = 0.33;
ThreadWT = 2.0;
ThreadWidth = ThreadThick * ThreadWT;
HoleWindage = 0; // enlarge hole dia by this amount
//-- Useful sizes
Tap2_56 = 0.070 * inch;
Clear2_56 = 0.082 * inch;
Head2_56 = 0.156 * inch;
Head2_56Thick = 0.055 * inch;
Nut2_56Dia = 0.204 * inch;
Nut2_56Thick = 0.065 * inch;
Tap3_48 = 0.079 * inch;
Clear3_48 = 0.096 * inch;
Head3_48 = 0.184 * inch;
Head3_48Thick = 0.058 * inch;
Nut3_48Dia = 0.201 * inch;
Nut3_48Thick = 0.073 * inch;
Tap4_40 = 0.089 * inch;
Clear4_40 = 0.110 * inch;
Head4_40 = 0.211 * inch;
Head4_40Thick = 0.065 * inch;
Nut4_40Dia = 0.228 * inch;
Nut4_40Thick = 0.086 * inch;
//-- Azimuth Mount
AzMountDia = 12.0;
AzMountLength = 14.0;
AzFacets = 30;
echo(str("Azmuth mount dia: ",AzMountDia," length: ",AzMountLength));
//-- Mirror sizes
MirrorShaftDia = 3.60;
MirrorShaftOffset = -1.5; // vertical offset from center of AzMountBody
MirrorShoulderLen = 3*MirrorShaftDia;
MirrorShoulderDia = min(AzMountDia,MirrorShaftDia + 6*ThreadWidth);
MirrorStudDia = Tap3_48;
MirrorStudLen = 2.0;
//-- Elevation Mount / Body / Plate
ElMountDia = AzMountDia;
ElMountLength = 2.0 + ElMountDia;
ElMountBase = 2.0;
ElMountRounding = 2.0;
ElMountFacets = AzFacets;
ElBodyWidth = ElMountDia;
ElBodyBlockLength = ElMountLength + AzMountLength/2 - MirrorShaftOffset;
ElBodyThick = 8.0;
echo(str("Elevation body overall: ",(ElBodyBlockLength + ElBodyWidth/2)," width: ",ElBodyWidth));
ElPlateTall = ElBodyBlockLength + 0.70*ElBodyWidth;
ElPlateWidth = 1.25 * ElPlateTall;
ElPlateThick = Nut3_48Thick + 3*ThreadThick;
ElPlatePlusX = ElPlateThick + (ElMountDia/2 + ElMountBase) + ElBodyThick;
echo(str("Elevation plate tall: ",ElPlateTall," width: ",ElPlateWidth));
ElArcRadius = (3/4) * ElBodyBlockLength;
ElArcThick = 4*ThreadWidth;
ElArcHeight = (1/2) * ElBodyThick;
ElArcAngle = 35;
ElArcFacets = 32;
ElPlateFacets = 52;
//-- Helmet Interface Plate
HelmetCX = 60.0;
HelmetMX = 4.0;
HelmetRX = (pow(HelmetMX,2) + pow(HelmetCX,2)/4)/(2*HelmetMX);
HelmetPlateC = max(ElPlateTall,ElPlateWidth);
HelmetPlateTheta = atan(HelmetPlateC/HelmetRX);
HelmetPlateM = 2*HelmetRX*pow(sin(HelmetPlateTheta/4),2);
HelmetPlateThick = ThreadThick*(ceil(HelmetPlateM/ThreadThick) + 1);
//-- Bearing Interfaces
BearingWidth = 3*ThreadWidth;
BearingOverlap = 3*ThreadThick;
BearingClearance = 1*ThreadThick;
BearingStudDia = min(AzMountDia,ElBodyWidth) - 2*BearingWidth;
//-- Convenience values
Protrusion = 0.1; // make holes look good
//----------------------
// Useful routines
module PolyCyl(Dia,Height) { // based on nophead's polyholes
Sides = ceil(Dia) + 2;
FixDia = Dia / cos(180/Sides);
cylinder(r=(FixDia + HoleWindage)/2,
h=Height,
$fn=Sides);
}
PegSize = 1.0;
module ShowPegGrid(Size) {
for (x=[-5:5])
for (y=[-5:5])
translate([x*10,y*10,Size/2])
cube(Size,center=true);
}
//----------------------
// Azimuth Mount
module AzMount() {
difference() {
union() {
cylinder(r=AzMountDia/2,h=AzMountLength,$fn=AzFacets); // body
translate([0,0,AzMountLength/2 + MirrorShaftOffset])
rotate([-90,0,0])
cylinder(r=MirrorShoulderDia/2,
h=MirrorShoulderLen,$fn=AzFacets); // mirror shaft shoulder
if (Layout != "Fit")
for (y=[0:1]) // shoulder support
translate([-AzMountDia/2,(4*y + AzMountDia/2 + ThreadWidth),0])
difference() {
cube([AzMountDia,2*ThreadWidth,AzMountLength/6]);
translate([AzMountDia/2,-Protrusion,AzMountLength/2 + MirrorShaftOffset])
rotate([-90,0,0])
cylinder(r=MirrorShoulderDia/2,h=ThreadWidth + 2*Protrusion);
}
}
translate([0,-Head3_48/2,AzMountLength/2 + MirrorShaftOffset])
rotate([-90,0,0])
PolyCyl(MirrorShaftDia,(AzMountDia + MirrorShoulderLen)); // mirror shaft
translate([0,-(Head3_48/2 - Protrusion),AzMountLength/2 + MirrorShaftOffset])
rotate([90,0,0])
PolyCyl(MirrorStudDia,MirrorStudLen+Protrusion); // mirror stud
translate([0,0,
Head3_48Thick - (AzMountLength - MirrorShaftDia)/2 + MirrorShaftOffset - Protrusion])
PolyCyl(Head3_48,AzMountLength + Protrusion); // mounting screw head
translate([0,0,-Protrusion])
cylinder(r=(Clear3_48 + HoleWindage)/2,
h=(AzMountLength + 2*Protrusion),
$fn=ceil(Clear3_48)+2); // mounting screw clearance
translate([0,0,AzMountLength/2 + Head3_48Thick + MirrorShaftDia/2 + MirrorShaftOffset - Protrusion])
cylinder(r1=(Head3_48/cos(180/7) + HoleWindage)/2,
r2=Clear3_48/2,
h=(3*ThreadThick + Protrusion),
$fn=7); // overhang support
translate([0,0,AzMountLength/2 + MirrorShaftOffset])
rotate([0,90,0])
PolyCyl(Tap2_56,AzMountDia/2 + Protrusion); // setscrew hole
translate([0,0,AzMountLength - (BearingOverlap + BearingClearance)])
PolyCyl(BearingStudDia,
BearingOverlap + BearingClearance + Protrusion); // bearing surface
}
}
//----------------------
// Elevation Mount
module ElMount() {
difference() {
union() {
translate([(ElMountDia/4 + ElMountBase/2),0,(ElMountLength/2 + BearingOverlap)])
rotate([0,90,0])
cube([ElMountLength,ElMountDia,(ElMountDia/2 + ElMountBase)],
center=true); // mounting block
translate([0,0,BearingOverlap]) {
// color([0.4,0.3,0.3,0.7])
cylinder(r=ElMountDia/2,
h=ElMountLength - ElMountDia/2,
$fn=ElMountFacets); // cylinder to Az
// color([0.3,0.4,0.3,0.7])
translate([0,0,ElMountLength - ElMountDia/2]) { // curved interface
intersection() {
cylinder(r=ElMountDia/2,h=ElMountDia/2,$fn=ElMountFacets);
translate([0,ElMountDia/2,0])
rotate([90,0,0])
cylinder(r=ElMountDia/2,h=ElMountDia,$fn=ElMountFacets);
}
}
}
cylinder(r=(BearingStudDia - HoleWindage)/2,h=BearingOverlap); // bearing stud
}
translate([0,0,-Protrusion])
PolyCyl(Tap3_48,(3/4)*ElMountLength + BearingOverlap + Protrusion); // AzMount screw
}
}
//----------------------
// Elevation Body
module ElBody() {
difference() {
union() {
translate([-ElBodyBlockLength,-ElBodyWidth/2,0])
cube([ElBodyBlockLength,ElBodyWidth,ElBodyThick]);
translate([0,0,ElBodyThick])
cylinder(r=(ElBodyWidth - 2*BearingWidth)/2,h=BearingOverlap);
cylinder(r=ElBodyWidth/2,h=ElBodyThick,$fn=ElMountFacets);
}
PolyCyl(Clear3_48,ElBodyThick + BearingOverlap + Protrusion);
translate([0,0,-Protrusion])
PolyCyl(Head3_48,Head3_48Thick);
translate([-ElArcRadius,0,ElBodyThick - ElArcHeight/2])
rotate([0,-90,0])
PolyCyl(Tap2_56,ElBodyBlockLength - ElArcRadius + Protrusion);
translate([0,0,ElBodyThick - (ElArcHeight + BearingClearance)])
difference() {
cylinder(r=ElArcRadius + (ElArcThick/2 + BearingClearance),
h=ElArcHeight + BearingClearance + Protrusion,
$fn=ElArcFacets);
cylinder(r=ElArcRadius - (ElArcThick/2 + BearingClearance),
h=ElArcHeight + BearingClearance + Protrusion,
$fn=ElArcFacets);
}
}
}
//----------------------
// Elevation Plate
module ElPlate() {
union() {
difference() {
translate([ElBodyWidth/2 - ElPlateTall/2,0,0])
scale([ElPlateTall,ElPlateWidth,1.0])
cylinder(r=0.5,h=ElPlateThick,$fn=ElPlateFacets);
translate([0,0,-Protrusion])
PolyCyl(Tap3_48,ElPlateThick + 2*Protrusion);
translate([0,0,ElPlateThick - (BearingOverlap + BearingClearance)])
PolyCyl(BearingStudDia,(BearingOverlap + BearingClearance) + Protrusion);
translate([0,0,-Protrusion])
cylinder(r=Nut3_48Dia/2,h=(1.1*Nut3_48Thick + Protrusion),$fn=6);
}
translate([0,0,ElPlateThick])
difference() {
cylinder(r=ElArcRadius + ElArcThick/2,
h=ElArcHeight,
$fn=ElArcFacets);
cylinder(r=ElArcRadius - ElArcThick/2,
h=ElArcHeight + Protrusion,
$fn=ElArcFacets);
rotate([0,0,90 - ElArcAngle])
translate([ElArcRadius + ElArcThick,0,ElArcHeight/2])
cube([2*ElArcRadius + ElArcThick,
2*ElArcRadius + ElArcThick,
ElArcHeight + Protrusion],
center=true);
rotate([0,0,-(90 - ElArcAngle)])
translate([ElArcRadius + ElArcThick,0,ElArcHeight/2])
cube([2*ElArcRadius + ElArcThick,
2*ElArcRadius + ElArcThick,
ElArcHeight + Protrusion],
center=true);
}
}
}
//----------------------
// Helmet Interface Plate
module HelmetPlate() {
difference() {
scale([ElPlateTall,ElPlateWidth,1.0])
cylinder(r=0.5,h=HelmetPlateThick,$fn=ElPlateFacets);
translate([0,0,HelmetRX + HelmetPlateThick - HelmetPlateM])
sphere(r=HelmetRX,$fn=256,$fs=0.1);
}
}
//----------------------
// Lash it together
if (Examine == "AzMount")
AzMount();
if (Examine == "ElMount")
ElMount();
if (Examine == "ElBody")
ElBody();
if (Examine == "ElPlate")
ElPlate();
if (Examine == "HelmetPlate")
HelmetPlate();
if ((Layout == "Build" || Layout == "Show") && Examine == "None") {
translate([-10,-20,0])
rotate([0,0,90]) // mis-align top fill from ElMount
AzMount();
translate([-10,20,ElMountLength + BearingOverlap])
rotate([0,180,-90])
ElMount();
translate([0,0,0])
rotate([0,0,0])
ElBody();
translate([10,15,0])
rotate([0,0,215]) // mis-align top fill from ElBody
ElPlate();
translate([20,-20,0])
rotate([0,0,-45])
HelmetPlate();
if (Layout == "Show")
ShowPegGrid(PegSize);
}
if ((Layout == "Fit") && Examine == "None") {
translate([0,0,-(AzMountLength/2 + MirrorShaftOffset)])
color(MFG) AzMount();
translate([0,0,AzMountLength/2 - MirrorShaftOffset - BearingOverlap])
color(DHC) ElMount();
// color([ 0/255, 204/255, 204/255,0.5]) ElMount();
translate([ElMountDia/2 + ElMountBase,0,0])
rotate([0,90,0])
color(DFC) ElBody();
translate([ElPlatePlusX,0,0])
rotate([180,90,0])
color(LHC) ElPlate();
translate([ElPlatePlusX,0,ElPlateTall/2 - ElBodyWidth/2])
rotate([0,90,0])
color(LWM) HelmetPlate();
}
The Smell of Molten Projects in the Morning 
Comments
3 responses to “Helmet Mirror: Smaller Mirror Shaft”
So, just how crashworthy do you think this design is? Because it looks to my naïve eye like a rather larger chunk of mostly-solid ABS than I really want punching a hole through the skin of my helmet over my temple…
Fair to middlin’, methinks.
One 3-48 screw and a barely captive nut holds the elevation mount to the plate, so I expect it to peel off if I scrape it on the pavement. That leaves a few millimeters of flexy plastic that isn’t any more irregular than the usual pavement around here.
In my usual graceful zero-speed rollover, my shoulder hits first and the helmet never touches the ground. That’s an advantage of a recumbent: about three feet less elevation to fall from.
If I did manage to whack that lump directly, the plate would crush the foam over a fairly broad area, which is one reason for having such a big plate. Given enough force to completely crush the foam, yeah, then it’d get ugly, but I haven’t had an accident that bad in four decades (and that was a direct shot to the occiput, anyway, long before bike helmets were invented, back when I was young and even more stupid than I am now).
Helmets aren’t useful in high-speed car-on-bike collisions: you could be wearing a Styrofoam shako and have the same outcome. So in a higher-energy crash, it basically doesn’t matter.
But, yeah, I’d still like to shave that lump down, too. I’d like to try a close-set double-45-degree pivot, but I think that requires enough precision for a snap-together joint without a screw and I’m not there yet.
[…] other news, the 3D-printed fairing mounts, blinky light mounts, and helmet mirror mounts continue to work fine; I’m absurdly proud of the mirrors. Mary likes her colorful homebrew […]