Author: Ed

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?

2021-06-24

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.

2021-06-23

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
A Spider at Breakfast

The underside of a spinach leaf makes a fine place for a spider to guard her egg sac, right up until the leaf arrives on the kitchen cutting board just before breakfast:

Spider guarding egg sac

We deported her (and her incipient family) to the flower garden just outside, wished her well, and continued with breakfast.

2021-06-19
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