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

One-Watt LED Autopsy: No Trouble Found

Over the last several weeks the taillight on Mary’s Tour Easy became dim. I verified the LED had failed by soldering the taillight driver to a different 1 W LED stuck on a separate heatsink, whereupon the LED lit up as it should.

Testing the failed LED with a bench power supply clipped to its wires showed it passed only 15 mA, even with 6 V applied directly to the wires. Those 1 W LEDs normally drop 2 V at 400 mA, so something was definitely wrong in there.

Which meant I had to build another taillight, as described yesterday, and reuse the original electronics and PVC tube. After mounting the new taillight on Mary’s bike, I could autopsy the failed LED.

Because everything is glued into the heatsink, the first step is cutting it apart to free the LED:

1W red LED Autopsy – heatsink parting

I stopped the first cut when it just kissed the two wire holes, moved over a little more than the width of the cutoff tool, and tried again. Second time was the charm and I now have a clean aluminum tube that ought to come in handy for something, sometime.

Concerted prying under the edge of the LED PCB popped it off the heatsink:

1W red LED Autopsy – heatsink epoxy bond

The red wire sticking out on the right shows a little damage from the cutoff tool, which also chipped the epoxy while bending the aluminum LED base. The bare spot in the middle matches the screw hole in the heatsink, with the rest remaining firmly bonded, so the epoxy was doing its job.

Prying the LED off the lens holder:

1W red LED Autopsy – lens holder detached

If I didn’t know better, I’d say the red silicone insulation was sun-faded, but for sure no sun gets inside the lens holder.

An ohmmeter showed both wires had good continuity to their LED pads, which were firmly soldered to the PCB pads; the pads don’t carry any current in this setup. I then hitched up the bench supply to the wires again:

1W red LED Autopsy – no trouble found

Whereupon the LED glowed brightly and some quick testing (because it’s not on a heatsink) with the bench supply in constant-current mode showed it once again drew about 400 mA with 2 V applied and glowed brilliantly as it should.

I had previously removed the reflowed solder from the PCB thermal pad and added thermal paste before resoldering the LED:

1W LED – thermal grease

So I have no idea what caused the original failure, how the LED could survive with 6 V applied to its terminals, or what would have caused it to recover. It now has a “?” scrawled on the PCB for future reference.

The world is full of mysteries …

2026-10-23
Tour Easy Running Light: Machining & Assembly
The 1 W red LED in the taillight on Mary’s Tour Easy failed and, because the LED is epoxied into the heatsink forming the business end of the light, I had to machine a replacement. This proceeds much as before, with some improvements & simplifications.

A revised sketch of the key dimensions shows a clearance hole for the 3 mm screw (to eliminate tapping the heatsink) and a reminder about how to locate the wire holes:

Tour Easy running light – housing dimensions – M3 clear – detail

Bore a 19 mm ID recess 10 mm deep in the (1 inch OD × ¾ inch ID) aluminum tube and score the ID for improved epoxy griptivity:

Tour Easy Running Light – heatsink scoring

Knurl the ¾ inch rod to bring the OD to a slip fit in the shell:

Tour Easy Running Light – heatsink plug knurling

Take them ouside, hose down with brake cleaner to get rid of the cutting fluid, butter ’em up with epoxy, align in the lathe, and let ’em cure overnight:

Tour Easy Running Light – heatsink epoxy fixture

This time I managed to not cut off the rod, which dramatically simplifies boring the shell and facing the front end of the rod flush with the inside of the shell so the LED PCB sits flat in there:

Tour Easy Running Light – heatsink front ID

Clean up the shell OD and turn the back to 23 mm OD to fit the PVC tube from the failed taillight:

Tour Easy Running Light – heatsink shell OD

Crisp up the edge for a tidy fit:

Tour Easy Running Light – heatsink shell corner

Break / file all the corners, then bandsaw the rod and face the back end:

Tour Easy Running Light – heatsink rear facing

Set it up on the Sherline mill, find the center, and use manual jogging to poke the holes at the proper coordinates:

Tour Easy Running Light – heatsink Sherline setup

Take the finished heatsink outside again for more brake cleaner action.

The 3D printed circuit plate now sports two inserts:

Running Light Circuit Plate – two inserts – solid model

Epoxy the inserts in place, prepare two 1.6 mm = 1/16 inch steel wires, and chop the head off an M3 screw:

Tour Easy Running Light – heatsink with circuit plate

Stipulated: my center-finding hand is weak.

Aligning the LED heatsink with those wire holes is a pain:
- Clean up the 1 W LED PCB
- Solder the LED in place atop some heatsink compound
- Push the lens holder (without the lens!) over the LED
- Insert holder + LED into the heatsink
- Rotate to put one LED terminal between the wire holes in the heatsink
- Rotate to align the recesses in the PCB with the wire holes in the heatsink
- Match-mark the holes on the lens holder with a transfer punch
- Grab the holder in the Sherline vise
- Align & drill wire holes in the holder
- Solder wires to the LED PCB, aimed inward atop the LED leads
With the LED & lens holder prepared & set aside, butter the circuit plate parts with JB PlasticBonder, align the plate perpendicular to the heatsink using V-blocks / 123 blocks / whatever, and let it cure overnight.

The lens allows plenty of room to run the wires from the PCB around the LED inside the holder to the holes:

Tour Easy Running Light – 1W LED lens fit

So do that:
- Dab PlasticBonder on the bottom of the lens holder
- Stick the LED to the holder (still with no lens!)
- Thread the LED wires through the holes in the holder, the LED PCB, and into the heatsink
- Dab PlasticBonder on the bottom of the PCB
- Ease the holder + LED into the heatsink while pulling the wires through the holes
- Finally install the lens in the holder
- Clamp the whole mess lenthwise with padding atop the lens to prevent scratches
I transferred the circuitry from the failed taillight to the new one, atop refreshed double-sided foam tape:

Tour Easy Running Light – Arduino side

With hot-melt glue securing the 2 Ω current-sense resistor to the circuit plate:

Tour Easy Running Light – regulator side

Slide the PVC case over the circuit plate, secure the end cap with a 25 mm screw, and reinstall on the bike:

Tour Easy Running Light – taillight installed

It’s angled 1° up from horizontal:

Tour Easy Running Light – taillight in use

Wow, is that thing bright!
2026-10-22
One-watt LED Thermal Pad Reflow: Nope

While building up another taillight for Mary’s Tour Easy (about which, more later) and based on previous experience, I wondered if the 1 W red LED’s thermal pad was soldered to the circuit board as it should be.

Lo and behold, the solder paste was reflowed, likely while tinning the six solder pads:

Tour Easy Running Light – 1W LED PCB solder

But not with the LED in place:

Tour Easy Running Light – 1W LED base glue

What looks like melted solder is really an adhesive layer, much like the craft adhesive sheet I use to stick things together. Presumably, they just glue the LEDs to the PCB / heatsink, solder its two leads by hand, and call it done.

Checking an LED marked “Dead” on the backside of its heatsink shows the amount of solder paste varies, but the LED wasn’t there when it melted:

1W LED – base glue and PCB solder

This not being the first time, I cleaned the adhesive off the center pad and the LED, removed the solder, applied a dab of heatsink grease, and soldered the LED in place.

Which looked like this on the previous taillight:

1W LED – thermal grease

Might be a bit too much grease, but it’s certainly a better heat conductor than adhesive.

2026-10-21
Bike Rack Tray Holder: Small Version

Mary wanted to haul seedlings started in half-gallon milk bottles to their destination and I figured they shouldn’t slide around while being transported:

Milk bottle seedling starter carrier

That’s a half-width drawer from the same salvaged collection that produced the Bike Rack Tray Holder and a few minutes with LightBurn adapted the wider cardboard bike rack mount to fit the narrower drawer:

Bike Rack Tray Holder – small – LightBurn layout

Basically, use Node Edit to delete the horizontal lines, move the sides inward by half the difference of the drawer widths, then draw a few short lines to close the gaps.

Hot-melt gluing four layers of cardboard with crossed corrugations, plus three flat bottom layers, got it done:

Bike Rack Tray Holder – small drawer – installed

Those are the same stretchy TPU straps, with an additional link on each rear chain to compensate for the slightly higher block mount and a slightly narrower front block to fit in the slightly narrower drawer handle:

Bike Rack Tray Holder – half-width drawer straps

Of course, the only way to know what didn’t fit was to make a pair of the original ones, try them on for size, then adapt the OpenSCAD code accordingly.

That was surprisingly easy …

2026-09-09
Bike Helmet Mirror: Always Have A Spare

As fate would have it, the telescoping stalk on Mary’s helmet mirror broke off at the ball mount a few days after I assembled another spare mirror:

Helmet Mirror Ball Mount – broken shaft

That’s the point where all the stress concentrates, but the stalk lasted almost exactly six years and didn’t owe me anything.

So I clamped the mirror+shaft+ball from a spare into the mount on her helmet, and she rode off as planned.

Once again being down to a single spare, I drilled a few more 10 mm balls:

Helmet Mirror Ball Mount – ball drilling

Cleaning up the end of the broken shaft let me shove it into a drilled ball:

Helmet Mirror Ball Mount – repaired – drilled balls

The insert and random screw came from the stub end of the broken shaft: ramming it into the cleaned-up end makes the job look Good Enough™.

Clamp the repaired stalk into the spare mount, drop the drilled balls & lathe fixture back in their bag, and maybe it’ll be another six years before they’re needed.

Life is good!

2026-08-25
Bike Helmet Mirror: Another Spare

One of Mary’s garden neighbors recently started biking, she recommended he needed a helmet mirror, and I handed her a spare from the Bag o’ Mirrors:

Helmet Mirror Ball Mount – on helmet

So I built another one:

Helmet Mirror Ball Mount – epoxy clamping

Fortunately, the Bag also had that (slightly rusted) mirror with a drilled ball, so all I needed was a new printed mount with two brass inserts and screws.

Now we have two spares against future need:

Helmet Mirror Ball Mount – ready spares

They’re much better than the old yellow Az-El mount, but I couldn’t have made the ball mounts without that experience.

Both versions outlasted all the commercial versions we’ve had over the decades, so that’s a 3D printing success story right there.

2026-08-21
Tour Easy: E-Bike Brake Sensor Installation
Having verified the brake sensors work and with some idea of their actuation distances, installing them on Mary’s Tour Easy involved no more than:
- Remove the fairing
- Unwrap three spiral looms from All The Cables
- Wrestle the Julet connectors apart
- Plug in the new sensors
- Stick the sensors in the proper locations
- Verify proper brake operation
- Rewrap the looms
- Install the fairing
The “proper location” put the actuation point about halfway between the brake lever’s released and pulled positions. Given that the previous sensors lacked indicators, I don’t know where their actuation point might have been, other than likely too close to their released position.

A slideshow of the front brake lever positions:
Tour Easy LED brake sensor – front released
Tour Easy LED brake sensor – front activated
Tour Easy LED brake sensor – front pulled
Similarly for the rear brake lever positions:
Tour Easy LED brake sensor – rear released
Tour Easy LED brake sensor – rear activated
Tour Easy LED brake sensor – rear pulled
Obviously, the rear brake lever sensor has the “dim” LEDs.

There’s not much to go wrong and the first ride was uneventful, so we’ll declare victory until the sensors or magnets shift their position, despite the wraps holding their wires to the brake cables.

The magnets come from power toothbrush heads, encased in urethane adhesive in 3D printed mounts.

Stipulated: I sometimes over-do things.

However, I am absolutely not going to back down from saying the lashup shown in this screen grab from the sensor installation video is utterly and completely wrong:

E-bike Brake Sensor – suggested installation

Do not get me started, you know how I am. OK?
2026-08-17