Bafang BBS02: Motor Reaction Spacer

The Terry Symmetry’s rear shift cable passes along the side of the downtube and through a plastic guide channel under the bottom bracket shell. The Bafang BBS02 motor must press against the bottom of the downtube, so the shift cable rubs against the top of the motor.

The solution is a small block shaped around the point of contact to cradle the downtube, the bottom bracket shell lug, and the motor case:

Terry - Bafang motor spacer - solid model
Terry – Bafang motor spacer – solid model

A strip of double-sided foam tape holds the block to the motor and the reaction force from the motor’s torque presses the block against the downtube:

Terry Bafang - motor reaction block
Terry Bafang – motor reaction block

Seen from the other side, looking parallel to the shift cable, you can see the tight clearance:

Terry Bafang - shift cable clearance
Terry Bafang – shift cable clearance

The block holds the motor 8 mm from the downtube, just enough to give the cable some breathing room.

The block is slightly taller on its front end, because the motor doesn’t meet the downtube at a right angle:

Terry - Bafang motor spacer - tube angle - solid model
Terry – Bafang motor spacer – tube angle – solid model

I determined the proper angle by taping waxed paper to the top of the motor, sticking a trial (non-angled) block to the downtube, coating its bottom surface with hot-melt glue, then squishing the motor against the block. The cooled glue was flush with the block on the rear and 1.8 mm thick on the front, a 5° angle over the 20 mm block.

Definitely easier than correctly figuring the geometry from first principles: tweak the model to include the measured thickness, compute the angle, tilt the tube, and print another block that fits like it grew there.

With the block in place and the motor held against the downtube, tighten the retaining nut against the “fixing plate” by giving it a few gentle whacks with a hammer, then tighten the jam nut.

The OpenSCAD source code snippet:

// Motor Reaction Block
// Holds motor away from downtube enough to miss rear shift wire

MotorOD = 111;              // motor frame dia
MotorMountRad = 85;         // BB spindle center to motor center
Space = 8.0;                // motor to frame space

Spacer = [20.0,DownTube[ID]/2,4*Space];
SpaceAngle = atan(1.8/Spacer.x);            // tilt due to non-right-angle meeting
echo(str("Spacer angle: ",SpaceAngle));

module MotorSpacer() {

    difference() {
        cube(Spacer,center=true);
        translate([0,0,DownTube[ID]/2])
            rotate([0,90 + SpaceAngle,0]) rotate(180/FrameSides)
                cylinder(d=DownTube[ID],h=DownTube[LENGTH],$fn=FrameSides,center=true);
        translate([DownTube[LENGTH]/2,0,DownTube[ID]/2 - DownTube[LENGTH]*sin(SpaceAngle)/2])       // concentric with ID
            rotate([0,90 + SpaceAngle,0]) rotate(180/FrameSides)
                cylinder(d=DownTube[OD],h=DownTube[LENGTH],$fn=FrameSides,center=true);
        translate([0,0,-(MotorOD/2 + Space)])
            rotate([90,0,0]) rotate(180/48)
                cylinder(d=MotorOD,h=2*Spacer.y,$fn=48,center=true);
    }

}

Mary’s Tour Easy didn’t need this block, because all the cables run elsewhere, but I did capture a piece of closed-cell foam between its vestigial downtube and the motor to prevent chafing.

Bafang BBS02: Terry Symmetry Battery Mount Tee Nuts

The two middle mounting blocks under the Bafang battery plate have 5 mm holes for the screws going into the water bottle studs brazed to the frame. The outer blocks clamp around the frame and it seemed like a good idea to secure the plate to them, as well:

Terry Bafang battery mount - trial installation
Terry Bafang battery mount – trial installation

Those two blocks have a recess for an M5 tee nut:

Terry - Bafang battery - station 2 - bottom view - solid model
Terry – Bafang battery – station 2 – bottom view – solid model

I snipped off the prongs with hardened diagonal cutters and filed the stubs to a uniform height:

Modified M5 tee nuts
Modified M5 tee nuts

Applying a hot soldering gun to the plate melted the stubs into the block:

Terry Bafang battery mount - tee nut in place
Terry Bafang battery mount – tee nut in place

An M5 screw with a wingnut atop a big washer kept the tee nut properly aligned while pulling it into the melty plastic; I was pleasantly surprised at the lack of drama.

A ring of JB Plastic Bonder urethane adhesive glued the nut to the block:

Terry Bafang battery mount - tee nut gluing
Terry Bafang battery mount – tee nut gluing

The adhesive starts out runny and flows under the nut, so there’s more surface in play than meets the eye.

Clamping the partially cured goo to the frame atop a layer of waxed paper squashes any protruding adhesive lumps flat and prevents them from marring the tube’s paint:

Terry Bafang battery mount - tee nut adhesive molding
Terry Bafang battery mount – tee nut adhesive molding

Anchoring the battery to the bike at four spots makes it utterly immovable, which seems like a good way to ensure longevity:

Bafang BBS02 - Terry Symmetry full assembly
Bafang BBS02 – Terry Symmetry full assembly

That’s a test assembly predating the cable management cleanup …

Bafang BBS02: Terry Symmetry Battery Mount

The Bafang 48 V 11.6 A·h battery for Gee’s Terry Symmetry mounts on the downtube:

Bafang BBS02 - Terry Symmetry full assembly
Bafang BBS02 – Terry Symmetry full assembly

The battery slides onto a plate screwed to the pair of water bottle studs brazed to the tube:

Terry Bafang battery mount plate - test install
Terry Bafang battery mount plate – test install

Water bottle studs are (nominally) 65 mm on center. One stud normally appears under the plate’s center hole, with the other stud under either the upper or lower slot, depending on whether the battery fits better mounted lower or higher on the downtube.

However, the Symmetry’s downtube is so short the plate must mount with the lowest slot matching the uppermost stud, putting the lower stud beneath the metal compartment with its complete lack of mounting holes.

Well, I can fix that:

Terry Bafang battery mount - internal modifications
Terry Bafang battery mount – internal modifications

The upper hole in the metal base is 65 mm from the middle of the lower slot in the plastic baseplate, which will be (approximately) centered on the upper stud inside the black plastic mount. The location of that hole is not a free variable: it requires measuring and marking from the slot with the battery plate assembled.

The lower hole in the base puts the bottom of its plastic mount just about even with the end of the plate.

I shortened the battery side of the cable, crimped on (genuine!) 45 A Powerpole pins, and shaped the wiring to put the connector inside the metal compartment, out of harm’s way, and shielded from the weather.

The small bar of white HDPE serves as a cable clamp, held by a pair of M3 BHCS in the conveniently tapped holes.

With all that settled, the final iteration of the 3D printed mounting blocks took shape:

Terry - Bafang battery - all stations - solid model
Terry – Bafang battery – all stations – solid model

A station number from 1 through 4 identifies the blocks (station 0 is the blank block shape) and, of course, they’re all different. I refactored the OpenSCAD code used for Mary’s Tour Easy to put the feature selection into vectors, rather than convoluted logic:

Latches = [false,true,true,false,false];                // clearance for battery latch clips
Notch = [false,true,true,false,false];                  // notch for battery screw pockets
Recess = ["None","TeeNut","Bottle","Bottle","TeeNut"];  // stud or nut clearance against frame

HarnessCable = [false,true,true,true,true];             // passage for main harness cable

ShiftWire = [false,true,true,true,true];                //  .. shifter wire through sensor
Ferrules = ["None","Both","Front","None","Back"];       // ferrule and bushing ssockets

GearCable = [false,false,true,true,true];               //  .. gear sensor cable

Producing the features for a specific block is now a straightforward series of obvious choices. For example, adding the channels to clear the battery latches at stations 1 and 2 looks like this:

        if (Latches[BlkNum])
            for (i=[-1,1])
                translate([0,i*LatchOC/2,BlockMaxZ - LatchThick/2 + Protrusion])
                    cube([BossSlotOAL,LatchWidth,LatchThick + Protrusion],center=true);

Both parts of the block show the station number to avoid mixups:

Terry - Bafang battery - station 2 - solid model
Terry – Bafang battery – station 2 – solid model

Each block requires a bit under three hours of printing time, so they’re produced singly:

Terry - Bafang battery - station 2 build - solid model
Terry – Bafang battery – station 2 build – solid model

Building them sideways produces the best surface finish in all the recesses and holes. Small support structures under the rounded corners make them look Good Enough™ for their purpose.

A test assembly:

Terry Bafang battery mount - trial installation
Terry Bafang battery mount – trial installation

The two middle blocks (stations 3 and 2) sit at the water bottle studs. The rightmost block (station 1) is 130 mm from station 2, with the Bafang gear sensor on the rear derailleur cable.

An aluminum plate spreads the clamping force from the M4 screws across the bottom, as seen here below the cable stop cap holding the harness cable:

Terry Bafang - shift stop cap
Terry Bafang – shift stop cap

Those 50 mm screws are too long; a soon-to-arrive bag of 45 mm screws should fit perfectly. The final assembly will use nyloc nuts so they won’t vibrate loose.

The OpenSCAD source code for all the pieces as a GitHub Gist:

// Terry Symmetry - Bafang e-bike conversion
// Ed Nisley KE4ZNU 2021-06
Layout = "BuildClip"; // [Frame,Block,AllBlocks,BuildBlock,DispMount,BrakeMagnet,ShiftCap,BuildShiftCap,Case,NutMold,HeadClip, BuildClip]
Station = 4; // [0:4]
Support = false;
//- Extrusion parameters must match reality!
/* [Hidden] */
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);
ID = 0;
OD = 1;
LENGTH = 2;
//----------
// Dimensions
// Bike frame lies along X axis, rear to +X
FrameTube = [400,28.9 + HoleWindage,28.9 + HoleWindage]; // X = longer than anything else
FrameSides = 24;
SpeedOD = 3.5; // speed sensor cable
PowerOD = 6.7; // power cable
Harness = [6.0,13.0,30.0]; // main motor-to-handlebar cable
GearOD = 3.0; // gear sensor cable
HandlebarMax = 1*inch; // middle handlebar diameter
HandlebarMin = 24.0; // .. tape section
HeadTube = [32.0,35.0,8.0]; // ID=tube OD=lug LENGTH=clear between lugs
BottleStud = [5.0,10.0,IntegerMultiple(1.2,ThreadThick)]; // frame fitting for bottle screws
BafangClampID = 22.3; // their handlebar clamp diameter
ShiftOD = 2.0; // rear shifter cable
ShiftFerrule = [ShiftOD,6.0,10.0];
ShiftOffset = 7.5; // .. from downtube
ShiftAngle = -20; // .. from midline
BatteryBoss = [5.5,16.0,2.5]; // battery mount boss, center boss is round
BossSlotOAL = 32.0; // .. end bosses are elongated
BossOC = 65.0; // .. along length of mount
LatchWidth = 10.0; // battery latches to mount plate
LatchThick = 1.5;
LatchOC = 56.0;
// Per-block features
// first element is unadorned block
Latches = [false,true,true,false,false]; // clearance for battery latch clips
Notch = [false,true,true,false,false]; // notch for battery screw pockets
Recess = ["None","TeeNut","Bottle","Bottle","TeeNut"]; // stud or nut clearance against frame
HarnessCable = [false,true,true,true,true]; // passage for main harness cable
ShiftWire = [false,true,true,true,true]; // .. shifter wire through sensor
Ferrules = ["None","Both","Front","None","Back"]; // ferrule and bushing ssockets
GearCable = [false,false,true,true,true]; // .. gear sensor cable
// M3 SHCS nyloc nut
Screw3 = [3.0,5.5,35.0]; // OD, LENGTH = head
Washer3 = [3.7,7.0,0.7];
Nut3 = [3.0,6.0,4.0];
// M4 SHCS nyloc nut
Screw4 = [4.0,7.0,4.0]; // OD, LENGTH = head
Washer4 = [4.2,8.9,1.0];
Nut4 = [4.0,7.8,5.0];
// M5 SHCS nyloc nut
Screw5 = [5.0,8.5,5.0]; // OD, LENGTH = head
Washer5 = [5.5,10.1,1.0];
Nut5 = [5.0,9.0,5.0];
Teenut5 = [6.5,17.0,8.0,2.0]; // OD, LENGTH+1 = flange
// 10-32 Philips nyloc nut
Screw10 = [5.2,9.8,3.6]; // OD, LENGTH = head
Washer10 = [5.5,11.0,1.0];
Nut10 = [5.2,10.7,6.2];
CableTie = [150,5.0,2.0];
WallThick = 4.0; // thinnest wall
BlockMinZ = -(FrameTube.z/2 + WallThick);
BlockMaxZ = FrameTube.z/2 + max(WallThick,Teenut5[LENGTH]) + BatteryBoss[LENGTH];
Block = [25.0,78.0,BlockMaxZ - BlockMinZ]; // Y = battery width
echo(str("Block: ",Block));
Kerf = 0.5; // cut through middle to apply compression
CornerRadius = 5.0;
EmbossDepth = 2*ThreadThick; // lettering depth
//----------------------
// 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(d=(FixDia + HoleWindage),h=Height,$fn=Sides);
}
// frame downtube
module Frame() {
rotate([0,90,0]) rotate(180/FrameSides)
cylinder(d=FrameTube.z,h=FrameTube.x,center=true,$fn=FrameSides);
}
// clamp overall shape
module ClampBlock(BlkNum = 1) {
Screw = Screw4;
Washer = Washer4;
Nut = Nut4;
ScrewOC = LatchOC;
ScrewSides = 8;
ScrewOrient = 180/ScrewSides;
ScrewRecess = LatchThick + Screw[LENGTH] + Washer[LENGTH] + 1.0;
echo(str("Screw length: ",Block.z - ScrewRecess));
difference() {
hull()
for (i=[-1,1], j=[-1,1])
translate([i*(Block.x/2 - CornerRadius),j*(Block.y/2 - CornerRadius),BlockMinZ])
cylinder(r=CornerRadius,h=Block.z,$fn=4*3);
cube([2*Block.x,2*Block.y,Kerf],center=true);
Frame();
for (j=[-1,1]) {
translate([0,j*ScrewOC/2,BlockMinZ - Protrusion])
rotate(ScrewOrient)
PolyCyl(Screw[ID],2*Block.z,ScrewSides);
translate([0,j*ScrewOC/2,BlockMaxZ - ScrewRecess])
rotate(ScrewOrient)
PolyCyl(Washer[OD],BlockMaxZ,ScrewSides);
}
if (Latches[BlkNum])
for (i=[-1,1])
translate([0,i*LatchOC/2,BlockMaxZ - LatchThick/2 + Protrusion])
cube([BossSlotOAL,LatchWidth,LatchThick + Protrusion],center=true);
if (Notch[BlkNum])
translate([0,0,BlockMaxZ - BatteryBoss[LENGTH]/2 + Protrusion])
cube([BossSlotOAL,BatteryBoss[OD],BatteryBoss[LENGTH] + Protrusion],center=true);
if (HarnessCable[BlkNum])
rotate([-155,0,0]) {
translate([0,FrameTube.y/2 - Harness[ID]/2,0])
cube([2*Block.x,2*Harness[ID],Harness[ID]],center=true);
translate([0,FrameTube.y/2 + Harness[ID]/2,0])
rotate([0,90,0])
translate([0,0,-Block.x])
rotate(180/6)
PolyCyl(Harness[ID],2*Block.x,6);
}
if (GearCable[BlkNum])
rotate([-45,0,0]) {
translate([0,FrameTube.y/2 - GearOD/2,0])
cube([2*Block.x,2*GearOD,GearOD],center=true);
translate([0,FrameTube.y/2 + GearOD/2,0])
rotate([0,90,0])
translate([0,0,-Block.x])
rotate(180/6)
PolyCyl(GearOD,2*Block.x,6);
}
rotate([ShiftAngle,0,0]) {
if (ShiftWire[BlkNum])
translate([-Block.x,FrameTube.y/2 + ShiftOffset,0])
rotate([0,90,0]) rotate(-(90 + ShiftAngle))
PolyCyl(ShiftOD,2*Block.x,6);
if (Ferrules[BlkNum] == "Back" || Ferrules[BlkNum] == "Both") {
i = 1;
translate([i*(Block.x/2 - ShiftFerrule[LENGTH]),FrameTube.y/2 + ShiftOffset,0])
rotate([0,i*90,0]) rotate(-i*(90 + ShiftAngle))
PolyCyl(ShiftFerrule[OD],Block.x,6);
}
if (Ferrules[BlkNum] == "Front" || Ferrules[BlkNum] == "Both") {
i = -1;
translate([i*(Block.x/2 - ShiftFerrule[LENGTH]),FrameTube.y/2 + ShiftOffset,0])
rotate([0,i*90,0]) rotate(-i*(90 + ShiftAngle))
PolyCyl(ShiftFerrule[OD],Block.x,6);
}
}
if (Recess[BlkNum] == "Bottle") {
rotate(ScrewOrient) {
PolyCyl(BottleStud[ID],2*Block.z,ScrewSides);
PolyCyl(BottleStud[OD],FrameTube.z/2 + BottleStud[LENGTH],ScrewSides);
}
}
else if (Recess[BlkNum] == "TeeNut") {
rotate(ScrewOrient) {
PolyCyl(Teenut5[ID],2*Block.z,ScrewSides);
PolyCyl(Teenut5[OD],FrameTube.z/2 + Teenut5[LENGTH+1],ScrewSides);
}
}
translate([0,15,BlockMaxZ - EmbossDepth/2 + Protrusion])
cube([9.0,8,EmbossDepth],center=true);
translate([0,17,BlockMinZ + EmbossDepth/2 - Protrusion])
cube([9.0,8,EmbossDepth],center=true);
translate([0,-5,BlockMinZ + EmbossDepth/2 - Protrusion])
cube([9.0,30,EmbossDepth],center=true);
}
translate([0,15,BlockMaxZ - EmbossDepth])
linear_extrude(height=EmbossDepth)
rotate(90)
text(text=str(BlkNum),size=5,spacing=1.00,font="Bitstream Vera Sans:style=Bold",
halign="center",valign="center");
translate([0,17,BlockMinZ])
linear_extrude(height=EmbossDepth)
rotate(-90) mirror([0,1,0])
text(text=str(BlkNum),size=4.5,spacing=1.00,font="Bitstream Vera Sans:style=Bold",
halign="center",valign="center");
translate([0,-5,BlockMinZ])
linear_extrude(height=EmbossDepth)
rotate(-90) mirror([0,1,0])
text(text="KE4ZNU",size=4.5,spacing=1.00,font="Bitstream Vera Sans:style=Bold",
halign="center",valign="center");
}
// complete clamp block
module Clamp(BlkNum = 1) {
ClampBlock(BlkNum);
if (Support)
color("Yellow") {
NumRibs = 7;
RibOC = Block.x/(NumRibs - 1);
intersection() {
translate([0,0,BlockMaxZ + Kerf/2])
cube([2*Block.x,2*Block.y,Block.z],center=true);
union() {
translate([0,0,Kerf/2])
cube([1.1*Block.x,FrameTube.y - 2*ThreadThick,4*ThreadThick],center=true);
for (i=[-floor(NumRibs/2):floor(NumRibs/2)])
translate([i*RibOC,0,0])
rotate([0,90,0]) rotate(180/FrameSides)
cylinder(d=FrameTube.z - 2*ThreadThick,h=2*ThreadWidth,$fn=FrameSides,center=true);
/*
translate([0,FrameTube.y/2 + PowerOD/2,Kerf/2])
cube([1.1*Block.x,PowerOD - 2*ThreadWidth,4*ThreadThick],center=true);
for (i=[-floor(NumRibs/2):floor(NumRibs/2)])
translate([i*RibOC,FrameTube.y/2 + PowerOD/2,PowerOD/4])
cube([2*ThreadWidth,PowerOD - 2*ThreadWidth,PowerOD/2 - 2*ThreadThick],center=true);
translate([0,-(FrameTube.y/2 + SpeedOD/2),Kerf/2])
cube([1.1*Block.x,SpeedOD - 2*ThreadWidth,4*ThreadThick],center=true);
for (i=[-floor(NumRibs/2):floor(NumRibs/2)])
translate([i*RibOC,-(FrameTube.y/2 + SpeedOD/2),SpeedOD/4])
cube([2*ThreadWidth,SpeedOD - 2*ThreadWidth,SpeedOD/2 - 2*ThreadThick],center=true);
*/
}
}
}
}
// Half clamp sections for printing
module HalfClamp(BlkNum = 1, Section = "Upper") {
render()
if (Section == "Upper")
intersection() {
translate([0,0,BlockMaxZ/2])
cube([1.1*Block.x,Block.y,BlockMaxZ],center=true);
translate([0,0,-Kerf/2])
Clamp(BlkNum);
}
else
intersection() {
translate([0,0,-BlockMinZ/2])
cube([1.1*Block.x,Block.y,-BlockMinZ],center=true);
translate([0,0,-BlockMinZ])
Clamp(BlkNum);
}
}
// Handlebar mount for controller
module DispMount() {
ClampRing = [HandlebarMax,HandlebarMax + 2*WallThick,10.0];
ClampOffset = (HandlebarMax + BafangClampID)/2 + 6.0;
DispStudLenth = 16.5;
NumSides = 24;
Tilt = 0*atan2((ClampRing[OD] - BafangClampID)/2,ClampOffset);
echo(str("Tilt: ",Tilt));
difference() {
union() {
hull() {
cylinder(d=ClampRing[OD],h=ClampRing[LENGTH],$fn=NumSides);
translate([0,ClampOffset,0])
cylinder(d=BafangClampID,h=ClampRing[LENGTH],$fn=NumSides);
}
translate([0,ClampOffset,0])
cylinder(d=BafangClampID,h=ClampRing[LENGTH] + DispStudLenth,$fn=NumSides);
translate([-ClampRing[ID]/4,-(ClampRing[OD]/2),ClampRing[LENGTH]/2])
rotate([0,90,0]) rotate(180/8)
cylinder(d=ClampRing[LENGTH]/cos(180/8),h=ClampRing[ID]/2,$fn=8);
}
cube([Kerf,4*ClampOffset,4*DispStudLenth],center=true);
translate([0,0,-Protrusion])
cylinder(d=ClampRing[ID],h=ClampRing[LENGTH] + 2*Protrusion,$fn=NumSides);
translate([-ClampRing[ID]/2,-(ClampRing[OD]/2),ClampRing[LENGTH]/2])
rotate([0,90,0]) rotate(180/8)
PolyCyl(Screw3[ID],ClampRing[ID],8);
for (i=[-1,1])
translate([i*ClampRing[ID]/4,-(ClampRing[OD]/2),ClampRing[LENGTH]/2])
rotate([0,i*90,0]) rotate(180/8)
PolyCyl(Washer3[OD],ClampRing[ID],$fn=8);
translate([-5,25,EmbossDepth/2 - Protrusion/2])
rotate(Tilt)
cube([4.5,21.5,EmbossDepth + Protrusion],center=true);
if (false)
translate([-6,25,EmbossDepth/2 - Protrusion/2])
rotate(-Tilt)
cube([4.0,27,EmbossDepth + Protrusion],center=true);
}
translate([-5,25,0])
linear_extrude(height=EmbossDepth)
rotate(90 + Tilt) mirror([0,1,0])
text(text="KE4ZNU",size=3.3,spacing=1.05,font="Bitstream Vera Sans:style=Bold",
halign="center",valign="center");
if (false)
translate([-6,25,0])
linear_extrude(height=EmbossDepth)
rotate(90 - Tilt) mirror([0,1,0])
text(text="softsolder.com",size=2.2,spacing=1.05,font="Bitstream Vera Sans:style=Bold",
halign="center",valign="center");
}
// Mold to reshape speed sensor nut
SensorNut = [0,14.4,13.0];
SensorMold = [SensorNut[OD] + 2*WallThick,SensorNut[OD] + 2*WallThick,SensorNut[LENGTH] + WallThick];
MoldSides = 20;
RodOD = 1.6;
module NutMoldBlock() {
difference() {
translate([0,0,SensorMold.z/2])
cube(SensorMold,center=true);
translate([0,0,WallThick])
rotate(180/MoldSides)
PolyCyl(SensorNut[OD],2*SensorNut[LENGTH],MoldSides);
translate([0,0,-Protrusion])
rotate(180/8)
PolyCyl(SpeedOD,2*SensorMold.z,8);
for (i=[-1,1])
translate([i*(SensorMold.x/2 - WallThick/2),SensorMold.y,SensorMold.z/2])
rotate([90,0,0])
PolyCyl(RodOD,2*SensorMold.y,6);
}
}
module NutMold() {
gap = 1.0;
for (j=[-1,1])
translate([0,j*gap,0])
intersection() {
translate([0,j*SensorMold.y,0])
cube(2*SensorMold,center=true);
NutMoldBlock();
}
}
// Brake sensor magnet mount
// Magnetized through thinnest section
module BrakeMagnet() {
Magnet = [10.5,3.0,5.5];
Plate = 2*ThreadThick;
BrakeRad = 10.0; // brake handle curve Radius
Holder = [2*BrakeRad,7.0,Magnet.z + Plate];
difference() {
intersection() {
translate([0,-BrakeRad,0])
rotate(180/24)
cylinder(r=BrakeRad,h=Holder.z,$fn=24);
translate([0,BrakeRad - Holder.y,Holder.z/2])
cube([2*BrakeRad,2*BrakeRad,Holder.z],center=true);
translate([0,0,-2*BrakeRad/sqrt(2) + Holder.z - 3.0 + BrakeRad])
rotate([0,45,0])
cube(2*[BrakeRad,2*BrakeRad,BrakeRad],center=true);
}
translate([0,Magnet.y/2 - Holder.y - Protrusion/2,Magnet.z/2 + Plate + Protrusion/2])
cube(Magnet + [0,Protrusion,Protrusion],center=true);
}
}
// Shift stud cap
// With passage for harness cable
CapBlock = [18,18,16.5];
module ShiftCap() {
Rounding = 3.5;
CapM = 3.0;
StudBase = [12.5,12.5,4.5];
Stud = [5.0,9.3,15.5];
difference() {
hull() {
translate([0,0,CapBlock.z - 0.5])
PolyCyl(Washer5[OD],0.5,12);
for (i=[-1,1], j=[-1,1])
translate([i*(CapBlock.x/2 - Rounding),j*(CapBlock.y/2 - Rounding),0])
sphere(r=Rounding,$fn=12);
translate([-CapBlock.x/2,-Harness[ID]/2 - StudBase.y/2,StudBase.z/2])
rotate([0,90,0])
cylinder(d=Harness[ID] + 2*WallThick,h=CapBlock.x,$fn=12);
}
translate([0,0,-(FrameTube.z/2 - CapM)])
Frame();
PolyCyl(Screw5[ID],2*CapBlock.z,6);
PolyCyl(Stud[OD],Stud[LENGTH],12);
translate([0,0,StudBase.z/2])
cube(StudBase,center=true);
translate([0,-StudBase.y/2,StudBase.z/2])
cube(StudBase + [0,-StudBase.y/2,0],center=true);
translate([-CapBlock.x,-Harness[ID]/2 - StudBase.y/2,StudBase.z/2])
rotate([0,90,0])
cylinder(d=1.5*Harness[ID],h=2*CapBlock.x,$fn=12);
}
}
// Head tube clip for harness cable joint
module HeadClip() {
CableOD = Harness[OD];
difference() {
linear_extrude(height=HeadTube[LENGTH],convexity=10)
difference() {
hull() {
circle(d=HeadTube[ID] + 2*WallThick,$fn=FrameSides);
translate([0,-(HeadTube[ID] + CableOD)/2])
rotate(180/(FrameSides/2))
circle(d=CableOD + 2*WallThick,$fn=FrameSides/2);
}
circle(d=HeadTube[ID] + HoleWindage,$fn=FrameSides);
translate([0,-(HeadTube[ID] + CableOD)/2])
rotate(180/(FrameSides/2))
circle(d=CableOD + HoleWindage,$fn=FrameSides/2);
translate([0,-HeadTube[ID]/2])
square(0.75*CableOD,center=true);
translate([0,HeadTube[ID]])
square(2*HeadTube[ID],center=true);
}
translate([0,-(HeadTube[ID]/2 + CableOD + WallThick - CableTie.z/2),HeadTube[LENGTH]/2])
cube([HeadTube[ID],CableTie.z,CableTie.y],center=true);
for (i=[-1,1])
translate([i*(HeadTube[ID]/2 + WallThick - CableTie.z/2),0,HeadTube[LENGTH]/2])
cube([CableTie.z,HeadTube[ID],CableTie.y],center=true);
}
}
// Programming cable case
ProgCavity = [60.0,18.0,7.0];
ProgBlock = [70.0,24.0,13.0];
ProgCableOD = 4.0;
module ProgrammerCase() {
difference() {
hull() {
for (i=[-1,1], j=[-1,1])
translate([i*(ProgBlock.x/2 - CornerRadius),j*i*(ProgBlock.y/2 - CornerRadius),-ProgBlock.z/2])
cylinder(r=CornerRadius,h=ProgBlock.z,$fn=12);
}
translate([-ProgBlock.x,0,0])
rotate([0,90,0])
PolyCyl(ProgCableOD,3*ProgBlock.x,6);
cube(ProgCavity,center=true);
translate([0,0,ProgBlock.z/2 + ProgCavity.z/2 - EmbossDepth])
cube(ProgCavity,center=true);
translate([0,0,-(ProgBlock.z/2 + ProgCavity.z/2 - EmbossDepth)])
cube(ProgCavity,center=true);
}
translate([0,4,ProgBlock.z/2 - EmbossDepth])
linear_extrude(height=EmbossDepth)
text(text="Bafang BBS02",
size=5,spacing=1.00,font="Bitstream Vera Sans:style=Bold",
halign="center",valign="center");
translate([0,-4,ProgBlock.z/2 - EmbossDepth])
linear_extrude(height=EmbossDepth)
text(text="Programmer",
size=5,spacing=1.00,font="Bitstream Vera Sans:style=Bold",
halign="center",valign="center");
translate([0,4,-ProgBlock.z/2])
linear_extrude(height=EmbossDepth)
mirror([1,0])
text(text="Ed Nisley",
size=5,spacing=1.00,font="Bitstream Vera Sans:style=Bold",
halign="center",valign="center");
translate([0,-4,-ProgBlock.z/2])
linear_extrude(height=EmbossDepth)
mirror([1,0])
text(text="softsolder.com",
size=5,spacing=1.00,font="Bitstream Vera Sans:style=Bold",
halign="center",valign="center");
}
// Half case sections for printing
module HalfCase(Section = "Upper") {
intersection() {
translate([0,0,ProgBlock.z/4])
cube([2*ProgBlock.x,2*ProgBlock.y,ProgBlock.z/2],center=true);
if (Section == "Upper")
ProgrammerCase();
else
translate([0,0,ProgBlock.z/2])
ProgrammerCase();
}
}
//----------
// Build them
if (Layout == "Frame")
Frame();
if (Layout == "DispMount")
DispMount();
if (Layout == "BrakeMagnet")
BrakeMagnet();
if (Layout == "ShiftCap")
ShiftCap();
if (Layout == "HeadClip")
HeadClip();
if (Layout == "BuildClip")
rotate([-90,0,0])
HeadClip();
if (Layout == "BuildShiftCap")
translate([0,0,CapBlock.z])
rotate([180,0,0])
ShiftCap();
if (Layout == "Case")
ProgrammerCase();
if (Layout == "NutMold")
NutMold();
if (Layout == "Upper" || Layout == "Lower")
HalfClamp(Station,Layout);
if (Layout == "Block") {
ClampBlock(Station);
if (false)
color("Red", 0.3)
Frame();
}
if (Layout == "AllBlocks") {
gap = 3*Block.x;
for (i=[0:4])
translate([i*gap - 2*gap,0,0])
Clamp(i);
if (true)
color("Red", 0.3)
Frame();
}
if (Layout == "BuildBlock") {
gap = 5.0;
translate([gap,0,Block.x/2])
rotate([0,90,0])
HalfClamp(Station,"Upper");
translate([-gap - Block.z/2,0,Block.x/2])
rotate([0,90,0])
HalfClamp(Station,"Lower");
}

Bafang BBS02: Terry Head Tube Clip

The Bafang BBS02 runs a fat “harness cable” from the motor to the four handlebar components (two brake sensors, throttle, and display), with a lump covering the junction where the four smaller cables emerge. Securing the lump to the head tube seemed like a good way to keep the motion in the (presumably) more flexible smaller cables:

Terry Bafang - headset cable clip - front
Terry Bafang – headset cable clip – front

From the rear:

Terry Bafang - headset cable clip - rear
Terry Bafang – headset cable clip – rear

I later bound the four connectors into a cluster using cable ties to further reduce the clutter and keep them from tapping the top tube.

The clip captures the cable tie in those indents:

Terry - Bafang head tube clip - solid model
Terry – Bafang head tube clip – solid model

The overhangs require easy cleanup with a square file to get rid of a few droopy threads. Avoid the temptation to print it standing up as an arch, because you want the perimeter threads to go around the whole thing, not across the thinnest sections. Trust me on this.

The OpenSCAD source code:

module HeadClip() {

CableOD = Harness[OD];

    difference() {
        linear_extrude(height=HeadTube[LENGTH],convexity=10)
            difference() {
                hull() {
                    circle(d=HeadTube[ID] + 2*WallThick,$fn=FrameSides);
                    translate([0,-(HeadTube[ID] + CableOD)/2])
                        rotate(180/(FrameSides/2))
                            circle(d=CableOD + 2*WallThick,$fn=FrameSides/2);
                }
                circle(d=HeadTube[ID] + HoleWindage,$fn=FrameSides);
                translate([0,-(HeadTube[ID] + CableOD)/2])
                    rotate(180/(FrameSides/2))
                        circle(d=CableOD + HoleWindage,$fn=FrameSides/2);
                translate([0,-HeadTube[ID]/2])
                    square(0.75*CableOD,center=true);
                translate([0,HeadTube[ID]])
                    square(2*HeadTube[ID],center=true);
            }
        translate([0,-(HeadTube[ID]/2 + CableOD + WallThick - CableTie.z/2),HeadTube[LENGTH]/2])
            cube([HeadTube[ID],CableTie.z,CableTie.y],center=true);

       for (i=[-1,1])
            translate([i*(HeadTube[ID]/2 + WallThick - CableTie.z/2),0,HeadTube[LENGTH]/2])
                cube([CableTie.z,HeadTube[ID],CableTie.y],center=true);
    }
}

I briefly thought of holding two pieces together around the head tube with M3 screws, but came to my senses: a cable tie is exactly what you want when holding a cable in place. Right?

Bafang BBS02: Terry Cable Stop Cap

The Terry Symmetry had shift cables running along the down tube, with cable housing stop bushings at the top:

Terry Bafang - OEM shift stop
Terry Bafang – OEM shift stop

Without the front derailleur and with the wiring harness cable on the left side, a tidy cap seemed in order:

Terry Bafang - shift stop cap
Terry Bafang – shift stop cap

The oversize passage give the cable a little flex room, although that’s probably unnecessary. I reused the original M5 screw, with a washer to spread the load.

The solid model is basically a hull around some cylinders:

Terry - Bafang shift cap - solid model
Terry – Bafang shift cap – solid model

The interior matches the stud brazed onto the downtube:

Terry - Bafang shift cap - interior - solid model
Terry – Bafang shift cap – interior – solid model

The only practical way to build the thing required a brim stabilizing it on the platform:

Terry - Bafang shift cap - slice preview
Terry – Bafang shift cap – slice preview

My usual 0.25 mm layers came out a bit crude on the vast overhang, but 0.15 mm layers worked fine.

The OpenSCAD source code snippet:

CapBlock = [18,18,16.5];

module ShiftCap() {

Rounding = 3.5;
CapM = 3.0;
StudBase = [12.5,12.5,4.5];
Stud = [5.0,9.3,15.5];

    difference() {
        hull() {
            translate([0,0,CapBlock.z - 0.5])
                PolyCyl(Washer5[OD],0.5,12);
            for (i=[-1,1], j=[-1,1])
                translate([i*(CapBlock.x/2 - Rounding),j*(CapBlock.y/2 - Rounding),0])
                    sphere(r=Rounding,$fn=12);
            translate([-CapBlock.x/2,-Harness[ID]/2 - StudBase.y/2,StudBase.z/2])
                rotate([0,90,0])
                    cylinder(d=Harness[ID] + 2*WallThick,h=CapBlock.x,$fn=12);
        }

        translate([0,0,-(FrameTube.z/2 - CapM)])
            Frame();

        PolyCyl(Screw5[ID],2*CapBlock.z,6);

        PolyCyl(Stud[OD],Stud[LENGTH],12);

        translate([0,0,StudBase.z/2])
            cube(StudBase,center=true);

        translate([0,-StudBase.y/2,StudBase.z/2])
            cube(StudBase + [0,-StudBase.y/2,0],center=true);

       translate([-CapBlock.x,-Harness[ID]/2 - StudBase.y/2,StudBase.z/2])
            rotate([0,90,0])
                cylinder(d=1.5*Harness[ID],h=2*CapBlock.x,$fn=12);

    }
}

Of course, I needed three tries to get the correct dimensions, but that’s what rapid prototyping is all about.

Bafang BBS02: Terry Brake Sensor

The old-school “aero” brake levers on Gee’s Terry Symmetry bike have rubberoid cushion covers, so I slid the Bafang brake sensors inside:

Terry Bafang brake sensor - front
Terry Bafang brake sensor – front

They make the grips somewhat wider, but I can’t figure out a less destructive way of installing the things.

I glued the magnet inside a holder contoured to fit the space available:

Terry - Bafang brake sensor - solid model
Terry – Bafang brake sensor – solid model

Knocking the corners off makes it much more finger-friendly.

It’s unobtrusive with the handle released:

Terry Bafang brake sensor - released
Terry Bafang brake sensor – released

When you squeeze the lever, your fingers are nowhere near the magnet:

Terry Bafang brake sensor - pulled
Terry Bafang brake sensor – pulled

The lower edge actually slides along the brake lever housing without touching, but it’s a near thing.

Those are the same magnets I used for the Bafang brake sensors on Mary’s Tour Easy, once again aligned to aim the strongest volume of the magnetic field toward the sensor. The brake sensors activate just before the pads touch the rims and release with the magnets a few millimeters away from the sensors.

A complete coat of JB Plastic Bonder urethane adhesive covers each magnet to both isolate it from the weather and conceal the fact that they’re recycled from a power toothbrush.

Now that I know they work in this position, I must ease adhesive underneath the sensors so they don’t move around under normal hand pressure.

The OpenSCAD source code snippet:

module BrakeMagnet() {

    Magnet = [10.5,3.0,5.5];
    Plate = 2*ThreadThick;
    BrakeRad = 10.0;            // brake handle curve Radius
    Holder = [2*BrakeRad,7.0,Magnet.z + Plate];


    difference() {
        intersection() {
            translate([0,-BrakeRad,0])
                rotate(180/24)
                    cylinder(r=BrakeRad,h=Holder.z,$fn=24);
            translate([0,BrakeRad - Holder.y,Holder.z/2])
                cube([2*BrakeRad,2*BrakeRad,Holder.z],center=true);
            translate([0,0,-2*BrakeRad/sqrt(2) + Holder.z - 3.0 + BrakeRad])
                rotate([0,45,0])
                    cube(2*[BrakeRad,2*BrakeRad,BrakeRad],center=true);
        }
        translate([0,Magnet.y/2 - Holder.y - Protrusion/2,Magnet.z/2 + Plate + Protrusion/2])
            cube(Magnet + [0,Protrusion,Protrusion],center=true);
    }

}

Bafang BBS02: Speed Sensor Alignment

My friend Gee’s bike is a Terry Symmetry, designed for (small) women, which poses challenges when mounting “normal size” components. The Bafang BBS02 speed sensor mount (with a reshaped nut) requires far more clearance between the chainstay and the wheel spokes than the Symmetry has:

Bafang BBS02 Speed Sensor - OEM bracket
Bafang BBS02 Speed Sensor – OEM bracket

The chainstay is nearly parallel to the spokes, so the sensor fits equally poorly anywhere its cable will allow.

The obvious solution is to reverse the mount and stick it to the outside of the chainstay, but it’s not mmmm symmetric: the other end is closed. Use a pull saw to cut off the closed end, stick the sensor post in the other way, and then it fits fine:

Bafang BBS02 Speed Sensor - reversed bracket - top
Bafang BBS02 Speed Sensor – reversed bracket – top

The sawed-off mount is visible from below:

Bafang BBS02 Speed Sensor - reversed bracket - bottom
Bafang BBS02 Speed Sensor – reversed bracket – bottom

It looks fine from the outside:

Bafang BBS02 Speed Sensor - reversed bracket - left side
PXL_20210620_160950653 – Bafang BBS02 Speed Sensor – reversed bracket – left side

Mad props to Bafang for the LED showing when the magnet is properly positioned.