## Wednesday, September 21, 2016

### 3D printed cable guide for X-Peria tandem fork

In my original entry about the X-Peria tandem, I noted that the fork did not have an obvious method for routing the cable to the disc brake, but that there was a screw hole on the inside of the left fork blade. My solution was a 3D-printed bracket designed to attach to the screw hole and reach around behind the fork blade where the cable would pass through it.

Note that the hole for the screw mount has a flared shape to accommodate an angle-head screw, so as to minimize the amount the screw protrudes into the space inside the fork. The OpenSCAD source code for this design is below:

``````guidelength = 20;
width = 15;
cablesize = 5;
thickness = 1.5;
screwhole = 5;
len1 = 5;
len2 = 5;
th2 = 2.5;
angle = 70;

\$fs=0.01;
\$fa=3;

r2 = screwhole/2+4;
cr = cablesize/2;
ofs = width/2-r2;
d = (guidelength-width)/2;

rotate(angle) {
difference () {
union () {
// cable guide outer
translate([0, 0, -d]) cylinder(guidelength, r=cr+thickness);

// connector section 1
translate([0, -th2/2, 0]) cube([len1, th2, width]);

// connector bend
translate([len1, -th2/2-bendradius, 0]) rotate([0, 0, 90])
rotate_extrude(angle=-angle) {
}
}

// cable guide hole
translate([0, 0, -d-0.01]) cylinder(guidelength+0.02, r=cr);
}

// connector section 2
translate([len1, -bendradius-th2/2, 0]) rotate([0, 0, -angle])
translate([len2, bendradius+th2/2, width/2]) rotate([90, 0, 0])
translate([0, 0, -th2/2])
difference() {
hull() {
cylinder(th2, r=r2);
translate([-len2/2, -ofs, 0]) cylinder(th2, r=r2);
translate([-len2/2, ofs, 0]) cylinder(th2, r=r2);
translate([-len2-1, -width/2, 0]) cube([1, width, th2]);
}
translate([-len2-r2, -width/2-0.05, -0.05]) cube([r2, width+0.1, th2+0.1]);

// Screw hole
translate([0, 0, -0.05]) cylinder(th2+0.1, r=screwhole/2);

// flared hold for angle head screw
translate([0, 0, -1]) cylinder(screwhole/2, screwhole, screwhole/2);
}
}``` ```

The part was printed in white ABS plastic by Shapeways. I have produced other parts using Shapeways before and have found the results to be very high quality. A couple of weeks after placing my order, the cable guide arrived.

The hole for the cable was actually just a little too tight for the cable to fit, so I widened it slightly with a drill. This is actually the second version of the design, the result of some changes I made to my first design after I had a chance to test it on the bike. Here is the final product, installed on the bike.