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// Pride wheelchair brake lever mods
// Ed Nisley KE4ZNU 2020-11
/* [Layout options] */
Layout = "Build"; // [Build, Show, Fit, TabCap, Handle, Knob, Support]
// Hold up the knob's inside
Support = true;
/* [Extrusion parameters] */
/* [Hidden] */
ThreadThick = 0.25;
ThreadWidth = 0.40;
HoleWindage = 0.2;
function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
function IntegerLessMultiple(Size,Unit) = Unit * floor(Size / Unit);
Protrusion = 0.1; // make holes end cleanly
inch = 25.4;
ID = 0;
OD = 1;
LENGTH = 2;
//----------------------
// 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,$fn=Sides);
}
//* [Basic dimensions] */
WallThick = 4.0; // min wall thickness
Screw = [3.0,5.5,20.0]; // thread, head, length under head
Insert = [3.0,4.1,8.0]; // thread, knurl, length
//----------------------
// Brake tab cap
BrakeTab = [15,21,3.1]; // length to wheel, width, thickness
BrakeTabSagitta = 8.0; // height of curved endcap
CapOAL = [BrakeTab.y + 2*WallThick,BrakeTab.y + 2*WallThick,BrakeTab.z + 2*WallThick];
module TabCap() {
difference() {
rotate(180/8)
cylinder(d=CapOAL.y,h=CapOAL.z,center=true,$fn=8);
translate([BrakeTab.x/2,0,0])
cube(BrakeTab,center=true);
rotate(180/8)
cylinder(d=BrakeTab.y/cos(180/8),h=BrakeTab.z,center=true,$fn=8);
}
}
//----------------------
// Brake lever handle
// Soft covering with rounded sides that we square off for simplicity
HandleRibs = [15,34,14]; // ignoring slight taper from end
HandleCore = [50.0,24.0,12.0]; // straight section of lever to top of ribs
HandleTipWidth = 30.0; // ignoring actual sector height
module Handle() {
union() {
hull() {
rotate(180/8)
cylinder(d=HandleTipWidth/cos(180/8),h=HandleCore.z,center=true,$fn=8);
translate([-HandleCore.x/2,0,0])
cube(HandleCore,center=true);
}
translate([-(3*HandleCore.x/2 - Protrusion),0,0]) // extend base for ball trimming
cube(HandleCore,center=true);
translate([-HandleRibs.x/2,0,0])
cube(HandleRibs,center=true);
}
}
//----------------------
// Support structure for handle cavity inside knob
// Totally ad-hoc tweakage
// Remember it's lying on its side to match the handle
NumRibs = 2 + 1; // must be odd
RibSpace = floor(HandleCore.z/(NumRibs + 1));
module KnobSupport() {
color("Yellow") { // support overlaps in the middle
render(convexity=3)
intersection() {
for (k=[-1,1])
translate([0,k*ThreadThick,0]) // shrink inward to break adhesion
Handle();
translate([(HandleCore.x - HandleRibs.x)/2 - HandleCore.x - Protrusion,0,0])
cube([HandleCore.x - HandleRibs.x,HandleRibs.y,HandleCore.z],center=true);
union()
for (k=[-floor(NumRibs/2):floor(NumRibs/2)])
translate([0,0,k* RibSpace])
cube([2*HandleCore.x,HandleRibs.y,2*ThreadWidth],center=true);
}
translate([(HandleCore.x - HandleRibs.x)/2 - HandleCore.x,0,0])
cube([HandleCore.x - HandleRibs.x,4*ThreadWidth,NumRibs*RibSpace],center=true);
}
}
//----------------------
// Brake handle knob
// Largely built with magic numbers
// Includes support because it's not really optional
KnobOD = 55.0;
KnobOffset = HandleRibs.x/1;
KnobSides = 2*4*3;
module Knob() {
difference() {
hull() {
resize([0,HandleRibs.y + 4*WallThick,HandleCore.x + HandleTipWidth/2 + WallThick])
sphere(d=KnobOD,$fn=KnobSides);
}
translate([0,0,KnobOffset])
rotate([0,-90,0])
Handle();
for (i=[-1,1],k=[-1,1])
translate([i*KnobOD/4,0,k*KnobOD/4]) {
rotate([90,0,0])
PolyCyl(Insert[OD],1.5*Insert[LENGTH],6);
translate([0,-Screw[LENGTH]/2,0])
rotate([-90,0,0])
PolyCyl(Screw[ID],KnobOD,6);
translate([0,Screw[LENGTH] - Insert[LENGTH],0])
rotate([-90,0,0])
PolyCyl(Screw[OD],KnobOD,6);
}
}
if (Support)
translate([0,0,KnobOffset])
rotate([0,-90,0])
KnobSupport();
}
//----------------------
// Lash it together
if (Layout == "TabCap") {
TabCap();
}
if (Layout == "Handle") {
Handle();
}
if (Layout == "Support") {
KnobSupport();
}
if (Layout == "Knob") {
Knob();
}
if (Layout == "Show") {
translate([60,0,0])
TabCap();
Knob();
}
if (Layout == "Fit") {
translate([60,0,0])
difference() {
TabCap();
translate([0,0,CapOAL.z/2])
cube(CapOAL,center=true);
}
difference() {
Knob();
translate([KnobOD + KnobOD/4,0*KnobOD,0])
cube(2*KnobOD,center=true);
translate([-KnobOD,-KnobOD,0])
cube(2*KnobOD,center=true);
}
}
if (Layout == "Build") {
translate([KnobOD/2,0,(CapOAL.y*cos(180/8))/2])
rotate([0,-90,90])
TabCap();
for (j=[-1,1])
translate([0,-j*0.75*HandleCore.x,0])
difference() {
rotate([j*90,0,0])
Knob();
translate([0,0,-KnobOD])
cube(2*KnobOD,center=true);
}
}
@ednisley

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@ednisley ednisley commented Dec 7, 2020

More details on my blog at https://wp.me/poZKh-9Et

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