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.

Author: Ed

Bafang vs. Tour Easy: Chain Guide

After adding the Bafang motor to my Tour Easy, the chain has fallen off the chainring a few times, prompting the gap filler between the motor and the chainring spider. That this has never happened to Mary’s essentially identical Tour Easy suggests I have a different shift technique, but adding a chain catcher seemed easier than re-learning shifting:

Chain Catcher - top view — Chain Catcher – top view

It’s more properly called a “chain guide” and is basically a shifter cage minus the mechanism:

Chain Catcher - side view — Chain Catcher – side view

Because the Tour Easy frame has a 25 mm tube where the guide’s clamp expects a minimum 31.8 mm tube, a 3D printed adapter fills the gap:

Chain Catcher adapter ring - solid model — Chain Catcher adapter ring – solid model

The hole is off-center because it seemed like a good idea, although it’s not strictly necessary. The flange helps align the pieces while tightening the clamp screw.

The guide cage clears the chain on all sides while up on the work stand, but there’s nothing like getting out on the road to find out why something doesn’t work as you expect.

The OpenSCAD source code as a GitHub Gist:

	// Chain catcher adapter ring
	// Ed Nisley – KE4ZNU – 2023-05

	/* [Hidden] */

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

	Protrusion = 0.1; // make holes end cleanly

	function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);

	ID = 0;
	OD = 1;
	LENGTH = 2;

	inch = 25.4;

	//———————-
	// Dimensions


	TubeOD = 26.0; // frame tube with silicone tape

	Clamp = [35.0,39.0,12.0]; // Chain catcher clamp ring

	Flange = [Clamp[ID],Clamp[OD],3*ThreadThick];

	Kerf = 1.0;

	Offset = (Clamp[ID] – TubeOD)/2 – 3*ThreadWidth;

	NumSides = 234;

	//———————–

	$fn=NumSides;

	difference() {
	union() {
	cylinder(d=Flange[OD],h=Flange[LENGTH]);
	cylinder(d=Clamp[ID],h=Clamp[LENGTH]+Flange[LENGTH]);
	}

	cube([2Flange[OD],Kerf,3Clamp[LENGTH]],center=true);

	translate([0,Offset,0])
	cylinder(d=TubeOD,h=3*Clamp[LENGTH],center=true);
	}

view raw Chain Catcher adapter ring.scad hosted with ❤ by GitHub

2023-05-05

Bafang Motor: Chain Gap Filler

When the chain falls off the top of the chainring toward the motor, the part remaining engaged with the chainring will inevitably drag the rest into the gap between the motor and the chainring spider, whereupon it will jam firmly in place and be almost impossible to extract. Preventing this means filling the gap, which required several iterations:

Bafang motor gap filler – prototypes

The Bafang motor has a cover held in place by seven M3 flat-head screws, shown here below a test filler using pan head screws:

Bafang motor gap filler – installed

Contrary to what you might think, the five screws that obviously sit on five points of a hexagon do not in fact sit 60° apart. How you find this out is by making the obvious layout, including the two screws bracketing the pinion gear in the lower right, then applying windage:

Bafang motor housing gap filler – hole adjustments

That’s one of the paper templates seen above, with laser-cut holes 60° apart and ugly holes punched at the actual screw locations. Then you scan and overlay that image with the LightBurn layout and twiddle the hole locations to make the answer come out right:

Bafang motor housing gap filler – hole adjustments – LB overlay

With that in hand, I cut a 1 mm acrylic shape to measure the clearance between the motor + filler and the chainring spider, with pan-head screws replacing the original flat-head screws:

Bafang motor gap filler – top view

That’s a single piece of 2.5 mm acrylic I used after discovering a pair of the 1 mm acrylic shapes fit with space to spare: hooray for rapid prototyping.

A test chain drop suggested it might suffice:

Bafang motor gap filler – test

If I were so inclined, 3 mm acrylic with countersunk holes and slightly longer flat-head screws would probably work, but I’ll use this until it fails to prevent a chain snag.

The careful observer will have noted the stress crack extending radially inward from the upper-right screw, which I am carefully avoiding doing anything about, pending the aforementioned failure.

The LightBurn layout as a GitHub Gist:

Loading
Sorry, something went wrong. Reload?

Sorry, we cannot display this file.

Sorry, this file is invalid so it cannot be displayed.
Viewer requires iframe.

view raw Bafang motor housing gap filler.svg hosted with ❤ by GitHub

2023-05-04
Zenni Optical Glasses: Nosepad Misalignment

Mary’s new glasses arrived from halfway around the planet with excruciatingly misaligned nosepads:

Zenni Optical glasses – misangled nosepads

Despite past experience, Zenni generally does better than this.

Fortunately, a few minutes with the same metal-forming pliers as before settled them in place.

Ya gotta have tools!

2023-05-03
Subaru Forest High Beam Bulbs: Thermal Damage

Although these passed the annual New York State safety inspection, I thought they needed replacing:

HB3 9005 Bulbs – bulged glass

A closer look:

HB3 9005 Bulbs – bulged glass – detail

The bulge was upward, of course.

The Forester’s manual says they’re HB3 bulbs, but the rest of the world knows them as 9005 bulbs. At full power they draw 60 W = 5 A each, although we rarely drive at night and then rarely have the opportunity for much high-beam use. I assume the blackening comes from nine years of running at half-ish power as the Forester’s daytime running lights.

The low beam headlights seem to be in fine shape.

These two went into the tray under the floor of the rear cargo area, because the crappy bulb you have is better than the one that just burned out on the road.

2023-05-02
Laser Cutter Z-Axis: Hitch in the Git-Along

My OMTech 60 W laser cutter has a stepper motor Z axis drive that has worked flawlessly since it arrived. However, it recently developed a periodic klonk during autofocusing and manual jogging, loud enough to shake the platform and rattle the cabinet’s bottom plate.

A few minutes of poking around revealed the klonk happened on each turn of the Z axis leadscrews, which quickly led to finding the cause:

Craft Stick – swarf in belt drive

It’s a rectangular wood chip, perfectly sized to jam into the Z axis motor pulley driving the belt: a belt tooth lifts up on the chip as the pulley turns, then klonks as it slips off the other side. The motor pulley and all four leadscrew pinons have the same number of teeth, so they’re all at the same point in their rotation when the belt slams down onto the pulley.

Where might such a thing come from? Well, I recently finished a batch of plant markers and hadn’t yet cleaned out the “chip tray” which is also just the bottom plate of the cabinet:

Craft Stick – swarf

I briefly considered building a guard for the motor pulley, but the belt most likely carried it from elsewhere. The leadscrews have an ample coating of grease that was also smeared elsewhere on the cabinet, making the belt sticky enough to catch such things.

The chip tray is once again pretty clean and the platform behaves normally again.

That was easy …

2023-05-01
Provide Drivers License Info

You know how we’re constantly reminded not to click on links in emails from “people we don’t know” and never provide personal information?

I’m certain this email came from a physician I’m about to see, but, with a concealed URL like that, somehow I just can’t bring myself to Get started like this:

Provide Drivers License

Remember, I’m in the US and *.co links are typically “foreign”, so they are going out of their way to look sketchy. I replaced several characters in the URL to make it invalid, but it closely resembles the original.

Of course, everything is outsourced these days, so the physician and her staff have nothing to do with the scheduling and patient information group, so they will have no idea what’s going on or be able to do anything about it.

2023-04-28
Craft Stick Plant Markers: Print-and-Cut Alignment

With the text laid out in the template, start LightBurn’s Print-and-Cut Wizard to align the template with the fixture on the laser platform.

Jog the laser to the upper-right target on the fixture, click the upper-right target in the template, and tell P-n-C that’s the First Target. Jog to the lower-left target, click the lower left target, and that’s the Second P-n-C Target:

Craft Stick Markers – fixture target detail

The colored circles indicate the targets on the template:

Craft Stick Markers – LB PnC layout

Select the Align No Scaling option, because the template and the fixture are exactly the same size.

Click-n-drag to select the entire template (because you should always use Cut Selected Graphics), then frame it Just To Be Sure. The red dot pointer (or whatever you use) should kiss the fixture’s perimeter all the way around.

Make sure the fill layer happens before the cut layer, then Release The Laser:

Craft Stick Markers – engraving

The cut layer trims around the engraved letters to leave them standing in the rectangle:

Craft Stick Markers – cutting

Some of the smaller bits won’t fall out as they’re cut, but a sharp thwack ejects them easily enough.

Producing a set of ten sticks takes maybe seven minutes:

Craft Stick Markers – fixture second fill

Because craft sticks aren’t intended for fine woodworking, don’t expect consistent engraving results:

Craft Stick Markers – wood engraving difference

Applying a finish would definitely improve their appearance, but most such chemicals don’t belong in an organic vegetable garden.

I poked the first few test sticks along the edge of the herb garden:

Craft Stick Markers – test sticks installed

The rest will be deployed as their eponymous plants go in, then we’ll see how long they survive out there in the real world.

They’re kinda cute and definitely improved my fixture / template skillz.

2023-04-27