Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Tucking seasonal decorations into the lamps bracketing the garage door would be much easier if the rubber buttons retaining the glass panes were squishy cylinders, rather than fossilized pebbles:
Outdoor Lamp Glass Retainers – old vs new
The five tidy buttons on the right are black TPU, hot off the MK4’s printbed:
The flange allows for some, shall we say, dimensional variation in the installation:
Outdoor Lamp Glass Retainers – old vs new – installed
They’re just a tube atop a cylinder:
nx = ceil(sqrt(NumButtons));
ny = nx;
union()
for (nx = [0:nx-1], ny = [0:ny-1])
right(nx*(FlangeOD + Gap))
back(ny*(FlangeOD + Gap))
render()
union() {
cyl(FlangeHeight,d=FlangeOD,circum=true,anchor=BOTTOM);
tube(ButtonOA.z,od=ButtonOA[OD],id=ScrewOD,circum=true,anchor=BOTTOM);
}
Feel free to set up your own dimensions, in the unlikely event you have lamps in need of similar buttons.
Each of the three lamps has sixteen buttons and, although PrusaSlicer allows you to set the number of instances, its Arrange tool doesn’t make a tidy / compact layout. Doing the layout in OpenSCAD saves a bunch of hassle, with the overall union() turning the array into a single object.
It might not be the best decoration, but it should suffice:
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.
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.
The Shopvac Model 500A (1.25 HP!) inhaling dust from Tiny Bandsaw didn’t start up when I flipped the switch. It had been making horrible noises, but Shopvacs typically sound like they’re on the ragged edge of death, I wear 30 dB earmuffs when it’s running, and that wasn’t the problem anyway.
It turned out the hot (black) wire lead to the motor burned up:
Shopvac motor – charred wire
The neutral (white) wire over on the left side looked just fine:
Shopvac motor – good wire connector
But the hot wire connector was toasted:
Shopvac motor – charred connector
As the connector failed its resistance went up and so did the wire temperature, as shown by the plastic case:
Shopvac motor – melted cover
With barely an inch between the motor armature and the failed connector, this became a zero-Mulligan repair:
Shopvac motor – remaining armature wire
I clipped the failed connector off the wire, very carefully sanded off the burned insulation, then gingerly crimped the business end of a ferrule around the wire + a doubled length of 22 AWG hookup wire:
Shopvac motor – lengthened wire
Doubling the wire brought it up to 19 AWG, a bit larger than the 20 AWG armature wire, and maybe improved its durability. The ferrule surely isn’t rated for this sort of abuse, so I eased some solder into its end in the belief that any amount of solder is a better conductor than a similar amount of air.
Crimp the other end of the hookup wire into the business end of a solderless ring terminal along with the hot wire, anchor the ferrule to (and insulate it from) the armature with a wrap of silicone tape, do the same around the ring terminal, then squirt hot melt glue into the ruined connector housing to keep the wire from flopping around:
Shopvac motor – repaired wire
If it gets hot enough to melt the hot melt glue, there are other problems about to happen.
Reassemble in reverse order and the Shopvac once again makes its on-the-eve-of-destruction whine while inhaling chips.
A slip of tape marked “$5” fell off during this process, reminding me it was a garage sale find from quite a few years ago: saving it from an early grave may be an overall Good Deed.
One of the living room window latches stopped working and, although the correct response would be to simply replace it, the window sash already had six holes surrounded by paint scars suggesting this wasn’t the first failure.
The latch as built:
Window latch cam – as built
The stamped steel spring holder was loose on the handle arm’s square pot-metal post, due to obviously poor factory swaging during assembly. Unseen below the plate is a cam molded into the handle intended to slide the white latch plate with the stamped post (over on the left) guiding the plate around the curved track and into the recess.
I don’t have a “before” picture of the cam, but it had completely worn away against the various steel parts. The task boiled down to replacing it with something more durable, which turned out to be a reshaped M3 brass screw:
Window latch cam – test fit
The Sherline setup to remove the worn cam, with the screw in place for a test fit:
Window latch cam – Sherline setup
The vise loosely clamps the handle, mostly for alignment, with the step block clamp holding it firmly in place.
The lever arm looked like this after poking the endmill into it a few times to clear the rubble, then using a smaller endmill as a drill to get a flat-bottomed recess:
Window latch cam – milled hole
Obviously, that was accomplished with eyeballometric alignment and manual jogging.
Reshaping and trimming the screw with Tiny Lathe produced a suitable cam-like object:
Window latch cam – screw installed
I planned to epoxy it in place, but AFAICT there is no way for it to go anywhere, so I just reassembled everything in reverse order:
Window latch cam – reassembled
I brutally swaged the square post with an automatic center punch cranked to maximum throttle while forcing the spring holder firmly atop the stack. The latch now moves smoothly and everything stays properly aligned.
While that was going on, the window sash had wood pins pounded into the errant screw holes with wood epoxy filling the gaps. Aligning the latch, drilling holes in the proper spots, and screwing the latch in place proceeded as expected.
That wasn’t easy, but now I can install plastic film over those windows for the winter.
The vertical bar between the doors of the Samsung French Door refrigerator that Came With The House™ is called a “mullion” and the curvy doodad on top that moves it out of the way when you open the door is called a “mullion flipper”, which I learned while attempting to repair it:
Samsung Refrigerator Mullion Flipper – regluing
The entire top of the mullion broke off and, while a solvent bond can (ideally) be as strong as the original plastic, if the part broke once it will probably break again. Which happened in short order, despite all the clamping.
Samsung Refrigerator Mullion Flipper – 3D print top view
It’s printed in clear PETG, which seemed a better match than white, and is held in place with a wrap of double-sided tape around the top, which may not be strictly necessary.
It flips the mullion just like the original:
Samsung Refrigerator Mullion Flipper – 3D print outside view
The yellow strip is 2 mil Kapton tape applied to both sides of the torn flexible seal running the length of the door, which we agreed was less awful than attempting to replace the entire seal on both doors. It must be trimmed slightly narrower than shown to avoid jamming on the other door.
For reasons not relevant here, a friend must fill several pre-drilled countersunk flat-head screw holes with brass plugs suitable for M5 screws. These proof-of-concept samples give the general idea, with the red blotch on the left marking the first attempt:
Shelf flush screw fillers – samples
He gets to make as many as needed …
The flat-head screws have an 82° included angle, so the lathe compound angle must be 41°. Tiny Lathe lacks sufficient reach to accomplish that on the front side, but cutting the back of the brass rod with the spindle running in reverse will work:
Shelf flush screw fillers – lathe setup
The quick-change tool post is aligned parallel with the lathe bed to put the tools at the proper angle.
It turns out 41° is about as far as the compound will go:
This, readers of long memory may recall, is the mini-lathe with the cross-slide DRO interfering with the compound enough to prevent it from cutting ordinary 60° screw threads, which is why the angle tops out at 42° instead of 60° in both directions.
The filler needs a 5.1 mm hole for EZ clearance, which is straightforward:
Shelf flush screw fillers – drilling
That was the first attempt after I got the compound angle worked out, which is why it eventually got the red mark. You want to drill on a flat end after countersinking with a center drill. It’s also good practice to drill only a few diameters deep, rather than trying to gun-drill sufficient hole for half a dozen fillers with one poke.
Run the spindle in reverse to cut the 41° angle on the back side:
Run the spindle forward to separate the finished filler with a cutoff tool:
Shelf flush screw fillers – parting off
The length isn’t critical, so holding a millimeter scale against the right side of the tool and eyeballing the distance from the end of the taper should suffice.
Filing to polish, deburring to finger-frendliness, and similar activities are in the nature of fine tuning.
