Micro-Mark Bandsaw: Acetal Blade Guide

The Micro-Mark bandsaw has a metal blade guide below the table that contributes to the awful noise it makes while running, even when it’s not cutting anything. Having recently touched the Delrin = acetal rod stash, a simple project came to mind.

A doodle with the original metal guide dimensions:

Micro-Mark Bandsaw - metal blade guide dimensions
Micro-Mark Bandsaw – metal blade guide dimensions

The 10 mm dimension is non-critical, so I started with a 1/2 inch acetal rod and turned the stub end to match.

A doodle suggested how to carve the slot with a 20.5 mil = 0.52 mm slitting saw, with the offset from a Z touchoff at the top:

Micro-Mark Bandsaw - acetal blade guide - slitting doodles
Micro-Mark Bandsaw – acetal blade guide – slitting doodles

The V block setup required swapping out the overly long OEM screw for a shorter 5 mm SHCS to clear the Sherline’s motor:

Micro-Mark Bandsaw - acetal guide slitting
Micro-Mark Bandsaw – acetal guide slitting

The end result looked pretty good:

Micro-Mark Bandsaw - acetal vs steel blade guides
Micro-Mark Bandsaw – acetal vs steel blade guides

And it looks like it pretty much belongs in the saw:

Micro-Mark Bandsaw - acetal blade guide installed
Micro-Mark Bandsaw – acetal blade guide installed

The 6 mm stud goes into a hole in the frame, where a setscrew holds it in place. You must remove the blade to extract / replace the guide, with the correct position having the end of the slot just touching the back of the blade.

The foam ring apparently keeps crud away from the stud on the backside; I doubt it’s mission-critical.

The saw became somewhat quieter; the ball bearing guides above the table now generate most of the racket. At some point I’ll try replacing them with a block, probably made from UHMW, with a simple slit to guide the blade.

Plastic guides may not last as long as the steel ones, but occasional replacements will be worth it if the saw runs quieter.

Tenergy 18650 Lithium Cells: Four Years of Running Lights

With the amber daytime running light connected to the Bafang’s headlight output and the Anker flashlight on the other side of the fairing getting fewer power-on hours, it’s a good time to see how those four Tenergy lithium 18650 cells are doing:

Tenergy 18650 Protected - 2021-09-09
Tenergy 18650 Protected – 2021-09-09

The overall capacity is down by 10%, with the voltage depressed by 120 mV over most of the curve.

Although I don’t keep daily records, the back of the envelope reveals 150 to 200 hour-long rides per year during the last four years, so call it 700 charging cycles:

Anker LC40 Flashlight - Anodizing fade
Anker LC40 Flashlight – Anodizing fade

High brightness draws 1.5 A and low is 50% duty cycle, so a typical ride requires 750 mA·h = 2.5 W·h. Each cell lives for three or four rides with the LED set to low brightness and the numbers work out close enough.

Depth Gauge Mounting Rods

A depth gauge arrived with a 3/8 inch = 9.5 mm mounting rod that fit one of my magnetic bases, but another base in my collection has a 5/16 inch = 7.9 mm clamp. Having recently rummaged through the aluminum rod stash, this happened:

Depth Gauge mounting rods
Depth Gauge mounting rods

The original rod at the top has an M6 thread, the drawer of random M6 screws provided suitable volunteers, and a bit of lathe work removed / shaped their heads accordingly.

The shorter rod has a blind hole, with a dab of epoxy holding the headless screw in place. Not that it matters, but the lathe held them in alignment for curing:

Depth Gauge mounting rod - epoxy alignment
Depth Gauge mounting rod – epoxy alignment

The longer rod got drilled all the way through, with more epoxy holding the screw, and, even with a relatively loose fit, no worries about alignment.

The longer rod gets the clamp away from the depth gauge’s base plate for better positioning:

Depth Gauge mounting rod - in use
Depth Gauge mounting rod – in use

They’ll surely come in handy along the way …

Tour Easy: Bafang BBS02 Lower Power

It turns out Mary rarely used assist level 6 and had no use for levels 7 and 8 of my derated BBS02 configuration:

LC=15
ALC0=0
ALC1=5
ALC2=7
ALC3=16
ALC4=25
ALC5=37
ALC6=51
ALC7=67
ALC8=85
ALC9=100

Level 9 must be 100% of the maximum motor current so the throttle can apply full power to get out of the way in a hurry.

The new and even more derated configuration allows small-step assist level selection for our usual riding, at the cost of an unused huge step to level 9 for the throttle:

[Basic]
LBP=42
LC=18
ALC0=0
ALC1=4
ALC2=6
ALC3=9
ALC4=15
ALC5=20
ALC6=25
ALC7=30
ALC8=40
ALC9=100
ALBP0=0
ALBP1=100
ALBP2=100
ALBP3=100
ALBP4=100
ALBP5=100
ALBP6=100
ALBP7=100
ALBP8=100
ALBP9=100
WD=12
SMM=0
SMS=1
[Pedal Assist]
PT=3
DA=0
SL=0
SSM=4
WM=0
SC=20
SDN=4
TS=15
CD=8
SD=5
KC=100
[Throttle Handle]
SV=11
EV=42
MODE=1
DA=10
SL=0
SC=5

The LC=18 line limits the maximum motor current to 18 A, rather than the rated 24 A, which may improve controller MOSFET longevity; reliable evidence is hard to come by. Controller failures seem to happen more often to riders who value jackrabbit acceleration on harsh terrain, so it may make little difference for road cyclists.

So level 5 now selects 75% × 20% = 15% of the motor’s nominal 750 W:

Tour Easy Bafang - display 26 mi
Tour Easy Bafang – display 26 mi

Call it 115 W: we’re both getting plenty of exercise!

Tour Easy 1 W Amber Running Light: Holder and First Light

Wrapping a left-side ball mount around the PVC case produced a holder:

Fairing 1 W LED Mount - Left side - show view
Fairing 1 W LED Mount – Left side – show view

Which looks like this in real life:

1 W Amber Running Light - installed front
1 W Amber Running Light – installed front

The support structure under the arch required a bit more cleanup than it got, so the clamp didn’t quite close around the ball on the first full test:

1 W Amber Running Light - installed side
1 W Amber Running Light – installed side

Both the phone camera and the eyeballometer report the 1 W amber LED isn’t quite as bright as the 400 lumen Anker flashlight on its low setting:

1 W Amber Running Light - First Light
1 W Amber Running Light – First Light

Stir the unusual (for a bike) amber color together with some blinkiness, though, and it’s definitely attention-getting.

The OpenSCAD source code as a GitHub Gist:

// Tour Easy Fairing Flashlight Mount
// Ed Nisley KE4ZNU - July 2017
// August 2017 -
// August 2020 - add reinforcing columns under mount cradle
// August 2021 - 1 W Amber LED
/* [Build Options] */
FlashName = "1WLED"; // [AnkerLC40,AnkerLC90,J5TactV2,InnovaX5,Sidemarker,Clearance,Laser,1WLED]
Component = "BallClamp"; // [Ball, BallClamp, Mount, Plates, Bracket, Complete]
Layout = "Build"; // [Build, Show]
Support = true;
MountSupport = true;
/* [Hidden] */
ThreadThick = 0.25; // [0.20, 0.25]
ThreadWidth = 0.40; // [0.40]
function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
Protrusion = 0.01; // [0.01, 0.1]
HoleWindage = 0.2;
/* [Fairing Mount] */
Side = "Right"; // [Right,Left]
ToeIn = -10; // inward from ahead
Tilt = 20; // upward from forward (M=20 E=10)
Roll = 0; // outward from top
//- Screws and inserts
/* [Hidden] */
ID = 0;
OD = 1;
LENGTH = 2;
/* [Hidden] */
ClampInsert = [3.0,4.2,8.0];
ClampScrew = [3.0,5.9,35.0]; // thread dia, head OD, screw length
ClampScrewWasher = [3.0,6.75,0.5];
ClampScrewNut = [3.0,6.1,4.0]; // nyloc nut
/* [Hidden] */
F_NAME = 0;
F_GRIPOD = 1;
F_GRIPLEN = 2;
LightBodies = [
["AnkerLC90",26.6,48.0],
["AnkerLC40",26.6,55.0],
["J5TactV2",25.0,30.0],
["InnovaX5",22.0,55.0],
["Sidemarker",15.0,20.0],
["Clearance",50.0,20.0],
["Laser",10.0,30.0],
["1WLED",25.4,40.0],
];
//- Fairing Bracket
// Magic numbers taken from the actual fairing mount
/* [Hidden] */
inch = 25.4;
BracketHoleOD = 0.25 * inch; // 1/4-20 bolt holes
BracketHoleOC = 1.0 * inch; // fairing hole spacing
// usually 1 inch, but 15/16 on one fairing
Bracket = [48.0,16.3,3.6 - 0.6]; // fairing bracket end plate overall size
BracketHoleOffset = (3/8) * inch; // end to hole center
BracketM = 3.0; // endcap arc height
BracketR = (pow(BracketM,2) + pow(Bracket[1],2)/4) / (2*BracketM); // ... radius
//- Base plate dimensions
Plate = [100.0,30.0,6*ThreadThick + Bracket[2]];
PlateRad = Plate[1]/4;
RoundEnds = true;
echo(str("Base plate thick: ",Plate[2]));
//- Select flashlight data from table
echo(str("Flashlight: ",FlashName));
FlashIndex = search([FlashName],LightBodies,1,0)[F_NAME];
//- Set ball dimensions
BallWall = 5.0; // max ball wall thickness
echo(str("Ball wall: ",BallWall));
BallOD = IntegerMultiple(LightBodies[FlashIndex][F_GRIPOD] + 2*BallWall,1.0);
echo(str(" OD: ",BallOD));
BallLength = IntegerMultiple(min(sqrt(pow(BallOD,2) - pow(LightBodies[FlashIndex][F_GRIPOD],2)) - 2*4*ThreadThick,
LightBodies[FlashIndex][F_GRIPLEN]),1.0);
echo(str(" length: ",BallLength));
BallSides = 8*4;
//- Set clamp ring dimensions
//ClampOD = 50;
ClampOD = BallOD + 2*5;
echo(str("Clamp OD: ",ClampOD));
ClampLength = min(20.0,0.75*BallLength);
echo(str(" length: ",ClampLength));
ClampScrewOC = IntegerMultiple((ClampOD + BallOD)/2,1);
echo(str(" screw OC: ",ClampScrewOC));
TiltMirror = (Side == "Right") ? [0,0,0] : [0,1,0];
//- Adjust hole diameter to make the size come out right
module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes
Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
FixDia = Dia / cos(180/Sides);
cylinder(r=(FixDia + HoleWindage)/2,h=Height,$fn=Sides);
}
//- Fairing Bracket
// This part of the fairing mount supports the whole flashlight mount
// Centered on screw hole
module Bracket() {
linear_extrude(height=Bracket[2],convexity=2)
difference() {
translate([(Bracket[0]/2 - BracketHoleOffset),0,0])
offset(delta=ThreadWidth)
intersection() {
square([Bracket[0],Bracket[1]],center=true);
union() {
for (i=[-1,0,1]) // middle circle fills gap
translate([i*(Bracket[0]/2 - BracketR),0])
circle(r=BracketR);
}
}
circle(d=BracketHoleOD/cos(180/8),$fn=8); // dead center at the origin
}
}
//- General plate shape
// Centered in the middle of the plate
module PlateBlank() {
difference() {
intersection() {
translate([0,0,Plate[2]/2]) // select upper half of spheres
cube(Plate,center=true);
hull()
if (RoundEnds)
for (i=[-1,1])
translate([i*(Plate[0]/2 - PlateRad),0,0])
resize([Plate[1]/2,Plate[1],2*Plate[2]])
sphere(r=PlateRad); // nice round ends!
else
for (i=[-1,1], j=[-1,1])
translate([i*(Plate[0]/2 - PlateRad),j*(Plate[1]/2 - PlateRad),0])
resize([2*PlateRad,2*PlateRad,2*Plate[2]])
sphere(r=PlateRad); // nice round corners!
}
translate([BracketHoleOC,0,-Protrusion]) // punch screw holes
PolyCyl(BracketHoleOD,2*Plate[2],8);
translate([-BracketHoleOC,0,-Protrusion])
PolyCyl(BracketHoleOD,2*Plate[2],8);
}
}
//- Inner plate
module InnerPlate() {
difference() {
PlateBlank();
translate([-BracketHoleOC,0,Plate[2] - Bracket[2] + Protrusion]) // punch fairing bracket
Bracket();
}
}
//- Outer plate
// With optional legend for orientation and parameters
module OuterPlate(Legend = true) {
TextRotate = (Side == "Left") ? 0 : 180;
difference() {
PlateBlank();
if (Legend)
mirror([0,1,0])
translate([0,0,-Protrusion])
linear_extrude(height=3*ThreadThick + Protrusion) {
translate([BracketHoleOC + 15,0,0])
text(text=">>>",size=5,spacing=1.20,font="Arial",halign="center",valign="center");
translate([-BracketHoleOC,8,0]) rotate(TextRotate)
text(text=str("Toe ",ToeIn),size=5,spacing=1.20,font="Arial",halign="center",valign="center");
translate([-BracketHoleOC,-8,0]) rotate(TextRotate)
text(text=str("Tilt ",Tilt),size=5,spacing=1.20,font="Arial",halign="center",valign="center");
translate([BracketHoleOC,-8,0]) rotate(TextRotate)
text(text=Side,size=5,spacing=1.20,font="Arial",halign="center",valign="center");
translate([BracketHoleOC,8,0]) rotate(TextRotate)
text(text=str("Roll ",Roll),size=5,spacing=1.20,font="Arial",halign="center",valign="center");
translate([0,0,0])
rotate(90)
text(text="KE4ZNU",size=4,spacing=1.20,font="Arial",halign="center",valign="center");
}
}
}
//- Slotted ball around flashlight
// Print with brim to ensure adhesion!
module SlotBall() {
NumSlots = 8*2; // must be even, half cut from each end
SlotWidth = 2*ThreadWidth;
SlotBaseThick = 10*ThreadThick; // enough to hold finger ends together
RibLength = (BallOD - LightBodies[FlashIndex][F_GRIPOD])/2;
translate([0,0,(Layout == "Build") ? BallLength/2 : 0])
rotate([0,(Layout == "Show") ? 90 : 0,0])
difference() {
intersection() {
sphere(d=BallOD,$fn=2*BallSides); // basic ball
cube([2*BallOD,2*BallOD,BallLength],center=true); // trim to length
}
translate([0,0,-LightBodies[FlashIndex][F_GRIPOD]])
rotate(180/BallSides)
PolyCyl(LightBodies[FlashIndex][F_GRIPOD],2*BallOD,BallSides); // remove flashlight body
for (i=[0:NumSlots/2 - 1]) { // cut slots
a=i*(2*360/NumSlots);
SlotCutterLength = LightBodies[FlashIndex][F_GRIPOD];
rotate(a)
translate([SlotCutterLength/2,0,SlotBaseThick])
cube([SlotCutterLength,SlotWidth,BallLength],center=true);
rotate(a + 360/NumSlots)
translate([SlotCutterLength/2,0,-SlotBaseThick])
cube([SlotCutterLength,SlotWidth,BallLength],center=true);
}
}
color("Yellow")
if (Support && (Layout == "Build")) {
for (i=[0:NumSlots-1]) {
a = i*360/NumSlots;
rotate(a + 180/NumSlots)
translate([(LightBodies[FlashIndex][F_GRIPOD] + RibLength)/2 + ThreadWidth,0,BallLength/(2*4)])
cube([RibLength,2*ThreadWidth,BallLength/4],center=true);
}
}
}
//- Clamp around flashlight ball
BossLength = ClampScrew[LENGTH] - 1*ClampScrewWasher[LENGTH];
BossOD = ClampInsert[OD] + 2*(6*ThreadWidth);
module BallClamp(Section="All") {
difference() {
union() {
intersection() {
sphere(d=ClampOD,$fn=BallSides); // exterior ball clamp
cube([ClampLength,2*ClampOD,2*ClampOD],center=true); // aiming allowance
}
hull()
for (j=[-1,1])
translate([0,j*ClampScrewOC/2,-BossLength/2])
cylinder(d=BossOD,h=BossLength,$fn=6);
}
sphere(d=(BallOD + 1*ThreadThick),$fn=BallSides); // interior ball with minimal clearance
for (j=[-1,1]) {
translate([0,j*ClampScrewOC/2,-ClampOD]) // screw clearance
PolyCyl(ClampScrew[ID],2*ClampOD,6);
translate([0,j*ClampScrewOC/2, // insert clearance
-0*(BossLength/2 - ClampInsert[LENGTH] - 3*ThreadThick) + Protrusion])
rotate([0,180,0])
PolyCyl(ClampInsert[OD],2*ClampOD,6);
translate([0,j*ClampScrewOC/2, // insert transition
-(BossLength/2 - ClampInsert[LENGTH] - 3*ThreadThick)])
cylinder(d1=ClampInsert[OD]/cos(180/6),d2=ClampScrew[ID],h=6*ThreadThick,$fn=6);
}
if (Section == "Top")
translate([0,0,-ClampOD/2])
cube([2*ClampOD,2*ClampOD,ClampOD],center=true);
else if (Section == "Bottom")
translate([0,0,ClampOD/2])
cube([2*ClampOD,2*ClampOD,ClampOD],center=true);
}
color("Yellow")
if (Support) { // ad-hoc supports
NumRibs = 6;
RibLength = 0.5 * BallOD;
RibWidth = 1.9*ThreadWidth;
SupportOC = ClampLength / NumRibs;
if (Section == "Top") // base plate for adhesion
translate([0,0,ThreadThick])
cube([ClampLength + 6*ThreadWidth,RibLength,2*ThreadThick],center=true);
else if (Section == "Bottom")
translate([0,0,-ThreadThick])
cube([ClampLength + 6*ThreadWidth,RibLength,2*ThreadThick],center=true);
render(convexity=2*NumRibs)
intersection() {
sphere(d=BallOD - 0*ThreadWidth); // cut at inner sphere OD
cube([ClampLength + 2*ThreadWidth,RibLength,BallOD],center=true);
if (Section == "Top") // select only desired section
translate([0,0,ClampOD/2])
cube([2*ClampOD,2*ClampOD,ClampOD],center=true);
else if (Section == "Bottom")
translate([0,0,-ClampOD/2])
cube([2*ClampOD,2*ClampOD,ClampOD],center=true);
union() { // ribs for E-Z build
for (j=[-1,0,1])
translate([0,j*SupportOC,0])
cube([ClampLength,RibWidth,1.0*BallOD],center=true);
for (i=[0:NumRibs]) // allow NumRibs + 1 to fill the far end
translate([i*SupportOC - ClampLength/2,0,0])
rotate([0,90,0])
cylinder(d=BallOD - 2*ThreadThick,
h=RibWidth,$fn=BallSides,center=true);
}
}
}
}
//- Mount between fairing plate and flashlight ball
// Build with support for bottom of clamp screws!
module Mount() {
MountShift = [ClampOD*sin(ToeIn/2),0,ClampOD/2];
OuterPlate();
mirror(TiltMirror) {
intersection() {
translate(MountShift)
rotate([-Roll,ToeIn,Tilt])
BallClamp("Bottom");
translate([0,0,Plate.x/2 + 3*ThreadThick])
cube(Plate.x,center=true);
}
if (MountSupport) // anchor outer corners at worst overhang
color("Yellow") {
RibWidth = 1.9*ThreadWidth;
SupportOC = 0.1 * ClampLength;
intersection() {
difference() {
rotate([0,0,Tilt])
translate([(ClampOD - BallOD)*sin(ToeIn/2),0,3*ThreadThick]) // Z = avoid legends
for (i=[-4.5,-2.5,0,2.0,4.5])
translate([i*SupportOC - 0.0,0,(5 + Plate[2])/2])
cube([RibWidth,0.7*ClampOD,(5 + Plate[2])],center=true);
translate(MountShift)
rotate([-Roll,ToeIn,Tilt])
sphere(d=ClampOD - 2*ThreadWidth,$fn=BallSides);
}
translate([0,0,ClampOD/2])
cube([Plate.x,Plate.y,ClampOD],center=true);
}
}
}
}
//- Build things
if (Component == "Bracket")
Bracket();
if (Component == "Ball")
SlotBall();
if (Component == "BallClamp")
if (Layout == "Show")
BallClamp("All");
else if (Layout == "Build")
BallClamp("Top");
if (Component == "Mount")
Mount();
if (Component == "Plates") {
translate([0,0.7*Plate[1],0])
InnerPlate();
translate([0,-0.7*Plate[1],0])
OuterPlate(Legend = false);
}
if (Component == "Complete") {
OuterPlate();
mirror(TiltMirror) {
translate([0,0,ClampOD/2 + BossOD*abs(sin(ToeIn))]) {
rotate([-Roll,ToeIn,Tilt])
SlotBall();
rotate([-Roll,ToeIn,Tilt])
BallClamp();
}
}
}

Running Light: 1 W LED Switched Parallel Resistors

Manually selecting the current through the 1 W amber LED with a switch actually intended for LED flashlights:

1 W LED Running Light - switched parallel R
1 W LED Running Light – switched parallel R

The resistors on the low side of the LED use the MP1584 regulator for current control, with the orange wire feeding the resistor voltage into the error amplifier.

The 15 Ω unswitched resistor sets the LED current at 53 mA = 0.8 V / 15 Ω, with the LED dissipating about 100 mW. The resistor dissipates 43 mW.

Closing the switch puts the two parallel 4.7 Ω resistors in parallel with the 15 Ω resistor to produce 2.0 Ω, which sets the LED current to 390 mA and runs it at 950 mW. Each of the 4.7 Ω resistors dissipates 140 mW.

That much power raises the aluminum body to 50 °C = 120 °F: definitely uncomfortable but probably survivable for the LED inside.

Eyeballometrically, a decimal order of magnitude difference in the LED current produces an obvious brightness difference. My first try ran the LED at 500 mW (a binary order of magnitude less than 1 W) and wasn’t visually different. Given that the LED will run from the Bafang’s headlight output, saving power isn’t all that important.

If this is the first time you’ve encountered parallel resistors, this is why your calculator has a reciprocal button: the total resistance is the reciprocal of the sum of the reciprocals of all the resistances:

1/R = 1/R₁ + 1/R₂ + …

A real engineering calculator does not have a shifted reciprocal function.

Running Light: 1 W LED Heatsink

The general idea: a cylindrical holder / heatsink for a 1 W LED on the end of a tube clamped in a Tour Easy fairing mount, much like a flashlight.

A pleasant evening at a virtual Squidwrench meeting produced the raw shape of the front end from a 1 inch aluminum rod:

1 W LED Running Light - heatsink raw
1 W LED Running Light – heatsink raw

Trace the outline of the LED’s PCB inside the cylinder just for comfort, align to the center, and drill two holes with a little bit of clearance:

1 W LED Running Light - heatsink drilling
1 W LED Running Light – heatsink drilling

For the 24 AWG silicone wire I used, a pair of 2 mm holes 8.75 mm out from the center suffice:

1 W LED Running Light - heatsink fit
1 W LED Running Light – heatsink fit

Gnaw some wire clearance in the lens holder:

1 W LED Running Light - wiring
1 W LED Running Light – wiring

Tap the central hole for an M3×0.5 screw, which may come in handy to pull the entire affair together.

Epoxy the PCB onto the heatsink with the lens holder keeping it aligned in the middle:

1 W LED Running Light - heatsink clamp
1 W LED Running Light – heatsink clamp

Then see how hot it gets dissipating 900 mW with 360 mA of current from a 2.2 Ω resistor:

1 W LED Running Light - heatsink test
1 W LED Running Light – heatsink test

As you might expect, it gets uncomfortably warm sitting on the bench, so it lacks surface area. The first pass will use a PVC cylinder for easy machining, but a full aluminum shell would eventually be a nice touch.

A doodle with some dimensions and aspirational features:

Running Light - 1 W LED case doodle
Running Light – 1 W LED case doodle

Even without a lens and blinkiness, it’s attention-getting!