The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Category: Recumbent Bicycling

Cruisin’ the streets

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

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

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

It’s unobtrusive with the handle released:

Terry Bafang brake sensor – released

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

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);
    }

}
```
2021-06-22
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

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

The sawed-off mount is visible from below:

Bafang BBS02 Speed Sensor – reversed bracket – bottom

It looks fine from the outside:

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.

2021-06-21
NY Bike Route 9 Signage Overgrowth

The North Residency of NYS DOT Region 8 normally does a pretty good job of clearing roadside brush, but they’re apparently daunted by the prospect of trimming shrubbery and hedges encroaching on the right of way:

Rt 376 at Red Oaks Mill – Bike Route vs ped facilitie

Truck traffic crops the overhanging branches, but the lower greenery forces pedestrians (who have nowhere else to walk) into the middle of the lane. A DOT staffer once said they didn’t design sidewalks into a project unless a clear path showed in the grass along a road.

The Red Oaks Mill intersection has no pedestrian facilities at all, although nowadays we see more walkers than ever before, and bicyclists no longer expect anything other than Bike Route markers.

This is well beyond the capability of my puny pruner …

2021-06-20
Bafang BBS02: Drop-bar Throttle Adapter

The Bafang BBS02 package includes a thumb-activated throttle which, like the display, should clamp onto a 22.2 mm handlebar. The one on Mary’s bike fit neatly at the end of the left handgrip:

Tour Easy grips – left installed

There’s no similar location on a drop-bar bike that doesn’t get in the way, particularly on my friend Gee’s bike with narrow bars.

With a display handlebar adapter in hand, this seemed less awful than anything else I had in mind:

Bafang Throttle adapter – front view

That’s the front view, so it’s on the right side in front of the handlebar. I think it’s usable with either a thumb or fingertips from a hand on the top of the bar. The handlebar lacks tape, as mounting the brake sensors poses a challenge.

The view from the rear isn’t too revealing:

Bafang Throttle adapter – rear view

Not too unsightly, but definitely not a standard setup!

2021-06-18

Bafang BBS02: Drop-bar Display Adapter

All of the Bafang BBS02 displays have a compression clamp intended for more-or-less standard 22.2 mm handlebars, as found on typical upright BMX-ish bikes suitable for conversion to e-bikes and, oddly, our Tour Easy recumbents. My friend’s bike has drop-bar handlebars with a 25.4 mm (yes, exactly 1 inch) center section that just isn’t going to fit through that hole.

The least awful solution involved summoning an adapter from the vasty digital deep:

Display adapter mount - solid model — Display adapter mount – solid model

The hole clamps around the handlebar with an M3 SHCS pulling it snug and the display clamps around the peg to hold everything together:

Bafang Display adapter - front view — Bafang Display adapter – front view

There’s not much to see from the side:

Bafang Display adapter - left view — Bafang Display adapter – left view

Those scuffs arrived on the protective plastic film!

The OpenSCAD source code includes some cruft from an idea that didn’t work out quite right:

HandlebarMax = 1*inch;                      // middle handlebar diameter
HandlebarMin = 24.0;                        //  .. tape section

BafangClampID = 22.3;                       // new handlebar diameter


… snippage …

// 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);

    }

    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");

}

It’s rock-solid stable: pushing the buttons doesn’t budge it in the least.

2021-06-17

Bafang BBS02 Programming Adapter: CP2102 Version

The last view before sticking the lid in place with hot melt glue:

Bafang BBS02 - CP2102 Programming Adapter — Bafang BBS02 – CP2102 Programming Adapter

The cable on the right goes to the motor controller through the display pigtail cable, sporting colors from a parallel universe.

A (possibly not counterfeit) CP2102 USB-to-serial adapter allows a slightly smaller case than one with the known-fake FTDI adapter and added some identification:

Bafang BBS02 - CP2102 Programming Adapter - case solid model — Bafang BBS02 – CP2102 Programming Adapter – case solid model

It splits along the midline for printing, of course.

The OpenSCAD source code replaces the previous version:

// 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();
    }
}

// .. snippage ..

        translate([0,2*Block.x/2 * gap,0]) {

            translate([gap*ProgBlock.x/2,0,ProgBlock.z/2])
                rotate([180,0,0])
                    HalfCase("Upper");
            translate([-gap*ProgBlock.x/2,0,0])
                HalfCase("Lower");
        }

My friend rides about the same way we do, except from a much higher perch, so I’ll start her off with a configuration similar to the one we settled on for Mary’s Tour Easy.

2021-06-15

Bafang BBS02: Speed Sensor Nut Reshaping
A Bafang BBS02 (for a friend’s upright bike) arrived with a deformed speed sensor nut:

Bafang BBS02 – Deformed speed sensor nut – end view

It traveled halfway around the planet while trapped underneath the motor and, if it rode in the top layer or two of containers, the combination of pressure and heat would be irresistible.

The plastic was stiff and I couldn’t force the nut over the connector using as much force as seemed reasonable:

Bafang BBS02 – Deformed speed sensor nut – test assembly

On the upside, the nut just compresses the silicone washer between the connector and the sensor to make a waterproof joint, so it need not have perfect threads or a uniform shape. Once the nut is in place, it will likely never be removed and should never bother anyone else.

Being unwilling to apply a hot-air gun near the cable, I decided to try slowly cold-forming the nut inside a mold:

Sensor Nut mold – solid model

The gap isn’t a kerf: the two halves meet to form a cylindrical pocket. The smaller holes fit a pair of brass tubes keeping the halves lined up while I arrange things:

Bafang BBS02 – Deformed speed sensor nut – clamp detail

A pair of swivel-pad clamps apply the pressure:

Bafang BBS02 – Deformed speed sensor nut – compression clamp

A few days of squashing made it round-er, whereupon I applied the clamp directly against the remaining high point with the other side cradled in the mold. It still doesn’t slide over the connector body, but I’m not in a rush.

Bafang tech support generously sent a speed sensor extension cable from which I can extract a good nut, which will require cutting and splicing the cable from the motor.

I’m still hoping gentle suasion will prevail.

The OpenSCAD source code tucks into the overall file producing various useful bits:
```
// 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();
            }
}

… snippage …

if (Layout == "NutMold")
    NutMold();
```
I haven’t worked on a safet y bike in years!
2021-06-10