Another Nice Doggy

We’re riding southbound on the recently opened section of the Empire State Trail, just south of Hopewell Junction, and are approaching a dog walker totally face-sucked by her phone in the middle of the path:

Empire State Trail - Dog Lunge - 2021-05-12 - 0
Empire State Trail – Dog Lunge – 2021-05-12 – 0

Mary has been dinging her bike bell for the last few seconds and finally manages to break through:

Empire State Trail - Dog Lunge - 2021-05-12 - 1
Empire State Trail – Dog Lunge – 2021-05-12 – 1

The dog walker leans against the fence while pulling on the leash as hard as she can, as if she knows the dog poses a threat:

Empire State Trail - Dog Lunge - 2021-05-12 - 2
Empire State Trail – Dog Lunge – 2021-05-12 – 2

Which it does:

Empire State Trail - Dog Lunge - 2021-05-12 - 3
Empire State Trail – Dog Lunge – 2021-05-12 – 3

The leash is too long for close-quarters work:

Empire State Trail - Dog Lunge - 2021-05-12 - 4
Empire State Trail – Dog Lunge – 2021-05-12 – 4

Nice teeth, doggie:

Empire State Trail - Dog Lunge - 2021-05-12 - 5
Empire State Trail – Dog Lunge – 2021-05-12 – 5

Surely, the dog just wants to lick me to death:

Empire State Trail - Dog Lunge - 2021-05-12 - 6
Empire State Trail – Dog Lunge – 2021-05-12 – 6

Tell me again how well-trained this dog is:

Empire State Trail - Dog Lunge - 2021-05-12 - 7
Empire State Trail – Dog Lunge – 2021-05-12 – 7

Seven seconds after the first picture:

Empire State Trail - Dog Lunge - 2021-05-12 - 8
Empire State Trail – Dog Lunge – 2021-05-12 – 8

The dog also lunged at the pair of bicyclists following us, so perhaps this is how she makes sure it get its exercise during the walk.

I hate dogs.

Bafang Brake Sensor Magnet Realignment

As mentioned earlier, the Bafang brake sensors on Mary’s Tour Easy require a magnet on the brake levers to activate the switches. They arrived with disk magnets that did not suit the levers, so I used neodymium “bar magnets”:

Tour Easy Bafang BBS02 - brake sensor - installed
Tour Easy Bafang BBS02 – brake sensor – installed

That worked for a few rides, but the alignment turned out to be entirely too critical, because the magnetization is through the bar’s thin dimension, rather than along its length, making the field weakest in the direction of the switch.

Magnetic field visualization film shows the field null along the thin edge of the bar:

Neodymium bar magnet - edge field
Neodymium bar magnet – edge field

That’s a slightly shorter magnet from a different toothbrush head, cemented edgewise into a holder conjured from the vasty digital deep:

Brake Magnet Mount - PrusaSlicer prevew
Brake Magnet Mount – PrusaSlicer prevew

The field is much more uniform on the flat side of the bar:

Neodymium bar magnet - side field
Neodymium bar magnet – side field

Some double-sided foam tape snuggles the sensor and the magnet together on the brake lever:

Bafang Brake Sensor - released detail
Bafang Brake Sensor – released detail

I coated the magnet with JB Plastic Bonder urethane adhesive in the hope of filling any gaps in its nickel coating caused while extricating it from the toothbrush head.

The rusty screw head in the upper right positions the lever at the proper distance from the grip to suit Mary’s hand. An earlier version of the holder shows the alignment:

Bafang Brake Sensor - released position
Bafang Brake Sensor – released position

The switch trips (opens) with the lever roughly parallel to the grip, again with the earlier holder:

Bafang Brake Sensor - activated position
Bafang Brake Sensor – activated position

A detailed view of the gap with the lever at the tripped position:

Bafang Brake Sensor - activated detail
Bafang Brake Sensor – activated detail

The levers have enough travel to prevent accidental trips due to light finger pressure, which turned out to be a problem with the original end-on alignment.

The brake pads don’t quite touch the rim when the switch trips, so the motor has plenty of time to shut off before the brakes take effect. It also stops when the pedals stop turning, so we should not see any disagreement between motor and brakes as to the bike’s momentum.

The wider base on the new mounts makes them much more stable on the levers, although I don’t like having them stick up so far. Mounting everything underneath the levers would look better, but any problems will be more obvious with everything in plain sight.

I may affix the magnets directly to the levers with Plastic Bonder if the foam tape doesn’t live up to its reputation. Removing them would be more challenging; a shot with a small chisel should suffice.

Tour Easy Front Fender Bracket Replacement

After nearly two and a half years, this happened:

Tour Easy front fender bracket - fracture
Tour Easy front fender bracket – fracture

Yup, it broke just where I expected!

The front fender on Mary’s bike suffers a bit more stress than you might expect, as she must wheel it through high grass to her Vassar Farms garden plot and the low-hanging spray flap can snag on the taller greenery.

Re-slicing the original model, printing the result, and installing it took about an hour:

Tour Easy front fender bracket - installed
Tour Easy front fender bracket – installed

Affixing the strut with duct tape and a cable tie looks déclassé, but continues to work better than anything else I’ve tried: simple, flexible, easily readjusted, totally nonfussy.

At least I now use black outdoor-rated double-stick foam tape, so life is increasingly good …

Tour Easy: Another Rear Fender Bracket

All the work on Mary’s bike reminded me of the rear fender bracket I meant to install on mine, with more clearance for the strut stabilizing the under-seat packs:

Tour Easy Rear Fender Bracket - long setback - solid model - show
Tour Easy Rear Fender Bracket – long setback – solid model – show

Rather than glue a PETG filament snippet into a screw, I turned a little Delrin plug:

Tour Easy Rear Fender Bracket - screw insert
Tour Easy Rear Fender Bracket – screw insert

It’s ready for installation when I’m willing to put the bike up on the rack and pull the rear wheel:

Tour Easy Rear Fender Bracket - screw detail
Tour Easy Rear Fender Bracket – screw detail

That’s actually the second iteration for the screw, as the first suffered a lethal encounter with the Greater Shopvac. I know exactly where it is, but I’m not going there …

Tour Easy: Bafang BBS02 Pedal Offset Fix

For unknown reasons, the Bafang BBS02 motor puts the left pedal 15.5 mm closer to the frame than the right pedal:

Bafang BBS02 dimensions
Bafang BBS02 dimensions

The diagram presents the motor assembly as seen from the bottom, lying on the ground looking upward with your feet forward around the front wheel.

That much offset may be acceptable for some (upright?) bikes and some riders, but this seemed better for Mary:

Tour Easy - Lekkie 160mm offset crank - installed
Tour Easy – Lekkie 160mm offset crank – installed

Lekkie Buzz Bars have a matching 15.5 mm offset in the left crank to center both pedals on the frame. She’s been pushing 165 mm cranks for long enough to know standard 170 mm cranks require too much leg travel, so that’s a 160 mm Lekkie crank.

With cranks installed in the BBS02, measured from the frame tube to the inside of the crank at the pedal axis:

  • Bafang 170 mm: L 42, R 62
  • Shimano 105 triple 170 mm: L 46, R 67
  • Lekkie 160 mm: both sides 60

For comparison, the Shimano 105 cranks on my Tour Easy measure 35 mm on both sides with an ordinary Shimano UM-BB72 bottom bracket cartridge, so the BBS02 + Lekkie cranks put each pedal 25-ish mm farther out. However,my pedals screw into 20 mm Kneesavers, putting them pretty close to the Lekkie spacing.

We hope the additional space won’t make much difference to Mary; it’s certainly better than sitting offset to the right to match the pedals, as she’s found herself doing with both the Bafang and Shimano cranks on the BBS02. Her right shoe just barely tapped the crank, so we moved the cleat a few millimeters inboard and it’s all good again.

The Cateye cadence sensor now has a rakish tilt to match the crank offset and looks scarily exposed. More riding is in order.

The Lekkie cranks have a hollow cross-section that’s concave on the frame side, so the magnet sits on a simple riser to get it out where the sensor can experience it:

Cateye Cadence Magnet mount - PS preview

It’s held in place with good foam tape; the cable tie makes me feel better.

The OpenSCAD code for the riser fits into the GitHub Gist:

module CateyeMagnet() {

OAL = 24.0;
D1 = 14.0;
D2 = 8.0;

    linear_extrude(height = 15.0)
        hull() {
            rotate(180/12)
                circle(d=D1,$fn=12);
            translate([OAL - D1/2 - D2/2,0])
                rotate(180/12)
                    circle(d=D2,$fn=12);
        }
}

… snippage …

    translate([0,-4*Block.x,0]) {
        rotate(-90)
            CateyeSensor();
        CateyeMagnet();
    }

The build plate is getting crowded:

Bafang Battery Mount - build view - cadence magnet
Bafang Battery Mount – build view – cadence magnet

In point of fact, that array pretty much fills the M2’s platform and would require over 11 hours of print time, which is just crazy talk. Have the slicer break it into separate parts, delete whatever you don’t want at the moment, print what’s left, and iterate until you have everything you need to finish the job.

Tour Easy: Bafang Mid-drive vs. Cateye Cadence Sensor

For inscrutable reasons, the Bafang 500C display includes all stopped time in its average trip speed. While that is, in fact, the average speed over the entire trip, the Cateye cyclocomputers we’ve been using forever stop averaging after a few seconds at 0 mph.

Bonus: Although the Bafang BBS02 motor knows the pedal cadence, it’s not part of the display.

The Bafang BBS02 bottom bracket shaft put its pedal cranks much farther from the Tour Easy’s frame than the Shimano cranks, to the extent that the existing Cateye cadence sensor position just wasn’t going to work, so I printed a simple clip to fit over the motor’s “fixing plate”:

Tour Easy Bafang BBS02 motor
Tour Easy Bafang BBS02 motor

It turns out putting a magnetic sensor immediately next to the winding end of a high-current three-phase motor isn’t the brightest idea I’ve ever had. The Cateye cadence display spent most of its time maxed out at 199 rpm, far faster than Mary can spin for, well, a single revolution.

A somewhat more complex mount put the sensor roughly where it used to be:

Cateye Cadence Sensor mount - installed
Cateye Cadence Sensor mount – installed

It looks precarious, but it spent nigh onto two decades there without incident, so we have precedent.

Those are the original 165 mm Shimano cranks, because the 170 mm Bafung cranks threatened to lock out her knees. More on this in a while, as it’s a more complex issue than it may appear.

The solid model looks about like you’d expect:

Cateye Cadence Sensor mount - solid model
Cateye Cadence Sensor mount – solid model

The OpenSCAD code replaces the simple clip in the original GitHub Gist:

// Cateye cadence sensor bracket

LockRingDia = [44.0,46.0];
LockRingLen = [4.0,6.5];
LockRingOAD = LockRingDia[1] + 2*WallThick;
LockRingOAL = LockRingLen[0] + LockRingLen[1];

Notches = 16;
SensorAngle = 3*360/Notches;
SensorBase = 10.0;

module Cateye() {

    difference() {
        union() {
            cylinder(d=LockRingOAD,h=LockRingOAL,$fn=Notches);
            translate([LockRingOAD/2 + LockRingOAL/2 - WallThick/2,0,LockRingOAL/2])
                cube([LockRingOAL + WallThick,2*WallThick + Kerf,LockRingOAL],center=true);
      rotate(SensorAngle)
                translate([LockRingOAD/2 + SensorBase - WallThick/2,0,LockRingOAL/2])
                    cube([2*SensorBase + WallThick,2*WallThick,LockRingOAL],center=true);
        }
        translate([0,0,LockRingLen[0]])
            PolyCyl(LockRingDia[1],LockRingOAL,Notches);
        translate([0,0,-Protrusion])
            PolyCyl(LockRingDia[0],2*LockRingOAL,Notches);

        translate([LockRingDia[0],0,0])
            cube([2*LockRingDia[0],Kerf,4*LockRingOAL],center=true);
        translate([LockRingOAD/2 + LockRingOAL/2,2*WallThick,LockRingOAL/2])
            rotate([90,0,0])
                PolyCyl(3.0,4*WallThick,6);

        rotate(SensorAngle)
            translate([LockRingOAD/2 + 2*SensorBase - SensorBase/2,2*WallThick,LockRingOAL/2])
                rotate([90,0,0])
                    PolyCyl(3.0,4*WallThick,6);
    }

}

Tour Easy: Asymmetric Handlebar Grips

Installing the Bafang BBS02 motor on Mary’s Tour Easy replaced the triple chainring, so I removed the front derailleur and SRAM grip shifter. This produced enough room for the thumb throttle and a full-length handgrip on the left side:

Tour Easy grips - left installed
Tour Easy grips – left installed

The round button is the PTT switch for the HT.

The right handlebar still has the rear shifter, so it requires a shorter grip:

Tour Easy grips - right installed
Tour Easy grips – right installed

Although it may be possible to buy such a grip and, thereby, get a backup pair of mismatched grips, it seemed easier straightforward to just shorten the grip to the correct length and be done with it.

Saw off a convenient length of aluminum rod:

Tour Easy grips - mandrel sawing
Tour Easy grips – mandrel sawing

Although I actually used a steady rest to produce this, it happened during a remote Squidwrench meeting and I have no proof:

Tour Easy grips - lathe mandrel
Tour Easy grips – lathe mandrel

The 22.2 mm = 7/8 inch end matches the more-or-less standard handlebar diameter, so the grip clamp can get a good hold:

Tour Easy grips - right peeled
Tour Easy grips – right peeled

A live center supports the right end of the grip.

The red coating seems to be gooey silicone rubber molded atop a PVC tube. Rather than (try to) use a lathe bit to cut through the silicone, I cut two slits with a utility knife and the spindle turning slowly in reverse, then peeled off the rubber between the slits.

With the silicone out of the way, an ordinary cutoff tool made short work of the PVC:

Tour Easy grips - right trimming
Tour Easy grips – right trimming

That was a cleanup pass with the utility knife, as the cutoff tool left a slight flange around part of the circumference. If I had the courage of my convictions, I could probably have cut the PVC with the knife.

Chamfer the end of the cut, slide it on the handlebar, tighten the clamp, and it’s all good.

The alert reader will note the clamp should go on first, but that would produce an inconvenient lump against the right shifter. Sliding them on backwards puts the clamp at the end of the handlebar and works out better in this admittedly unusual situation.