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Archive for category Machine Shop

Desk Lamp Conversion: Photo Light Cold Shoe

Having recently acquired a pair of photo lights and desirous of eliminating some desktop clutter, I decided this ancient incandescent (!) magnifying desk lamp had outlived its usefulness:

Desk Lamp - original magnifiying head
Desk Lamp – original magnifiying head

The styrene plastic shell isn’t quite so yellowed in real life, but it’s close.

Stripping off the frippery reveals the tilt stem on the arm:

Desk Lamp - OEM mount arm
Desk Lamp – OEM mount arm

The photo lights have a tilt-pan mount intended for a camera’s cold (or hot) shoe, so I conjured an adapter from the vasty digital deep:

Photo Light Bracket for Desk Lamp Arm - solid model
Photo Light Bracket for Desk Lamp Arm – solid model

Printing with a brim improved platform griptivity:

Photo Light Bracket for Desk Lamp Arm - Slic3r preview
Photo Light Bracket for Desk Lamp Arm – Slic3r preview

Fortunately, the photo lights aren’t very heavy and shouldn’t apply too much stress to the layers across the joint between the stem and the cold shoe. Enlarging the stem perpendicular to the shoe probably didn’t make much difference, but it was easy enough.

Of course, you (well, I) always forget a detail in the first solid model, so I had to mill recesses around the screw hole to clear the centering bosses in the metal arm plates:

Photo Lamp - bracket recess milling
Photo Lamp – bracket recess milling

Which let it fit perfectly into the arm:

Desk Lamp - photo lamp mount installed
Desk Lamp – photo lamp mount installed

The grody threads on the upper surface around the end of the slot came from poor bridging across a hexagon, so the new version has a simple and tity flat end. The slot is mostly invisible with the tilt-pan adapter in place, anyway.

There being no need for a quick-disconnect fitting, a 1/4-20 button head screw locks the adapter in place:

Photo Lamp - screw detail
Photo Lamp – screw detail

I stripped the line cord from inside the arm struts and zip-tied the photo lamp’s wall wart cable to the outside:

Photo Lamp - installed
Photo Lamp – installed

And then It Just Works™:

Photo Lamp - test image
Photo Lamp – test image

The lens and its retaining clips now live in the Big Box o’ Optical parts, where it may come in handy some day.

The OpenSCAD source code as a GitHub Gist:

The original dimension doodles, made before I removed the stem and discovered the recesses around the screw hole:

Photo Light - Desk Lamp Arm Dimensions
Photo Light – Desk Lamp Arm Dimensions
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Vacuum Tube Lights: Triode

With the wrecked 5U4GB safely in the trash, I popped a smaller, somewhat less stately triode from the Big Box o’ Hollow-State Electronics and wired it up with a pair of SK6812 RGBW LEDs:

Triode - Purple-green phase
Triode – Purple-green phase

The tube’s markings have long since vanished, but, at this late date, all that matters is an intact glass envelope!

After two years, the ordinary white foam tape holding the knockoff Arduino Nano lost most of its sticktivity and easily popped off the 3D printed base:

Triode - Nano PCB - white strips
Triode – Nano PCB – white strips

Two layers of 3M outdoor-rated foam tape clear the bottom-side components and, based on current evidence, its stickiness should stick forever more:

Triode - Nano PCB - 3M strips
Triode – Nano PCB – 3M strips

The alert reader will notice the mis-soldered 1 kΩ SMT resistor above-and-right of the CH340 USB interface chip. I think those two resistors are the isolators between the 328P microcontroller and the CH340, letting you use the TX and RX lines as ordinary I/O without killing either chip.

Despite the mis-soldering, it evidently passed their QC and works fine. Seeing as how I didn’t notice it until just now, it’ll remain in place until I must open the lamp base for some other reason, which may never happen.

The data output is now on pin A5, to match the rest of the glowing widgetry:

Triode - Nano installed
Triode – Nano installed

Blobs of hot melt glue affix the SK6812 and wiring to the socket:

Triode - socket wiring
Triode – socket wiring

The original “plate cap” wiring ran directly through a hole in the hard drive platter, which I embiggened for a 3.5 mm panel-mount headphone jack. The knurled metal plug looms next to this smaller tube, but it looks better (in a techie sense) than the raw hole:

Triode - plate cap plug
Triode – plate cap plug

Octal tubes have an opaque Bakelite base, so I devoted some Quality Shop Time™ to the post:

Triode - base tip exposed
Triode – base tip exposed

Although I’d made a shell drill for 5U4’s base, this base was so crumbly I simply joysticked the spinning cutter around to knock off the rest of the post:

Triode - finished base
Triode – finished base

The shell drill would open the bottom to admit a bit more light. I may do that to see if it makes any visible difference.

I didn’t expect the serrations in the top mica plate to cast interesting patterns around the platter:

Triode - cyan-purple phase
Triode – cyan-purple phase

Memo to Self: use the shell drill to avoid nicking the evacuation tip!

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3D Printed Chain Mail Armor: Failure Analysis

While dropping some recent 3D printed odds-n-ends into the show-n-tell box, I discovered the large sheet of square chain mail armor had a missing link:

Chain Mail Armor - the missing link
Chain Mail Armor – the missing link

Fortunately, the link fell off in the box and I recovered all the pieces for a failure analysis:

Chain Mail Armor - failed link - glue spots
Chain Mail Armor – failed link – glue spots

I’d glued the PLA together with IPS #4, a hellish mixture of plastic solvents including methylene chloride, one of the few chemicals able to chew into PLA, but there’s not much penetration or bonding going on.

Let’s try that again with a bit more solvent.

First, slide the bars into place:

Chain Mail Armor - failed link - bars in place
Chain Mail Armor – failed link – bars in place

I applied four solvent drops in two passes to give it time to work its way in, put four matching drops on the armor cap, squished the cap in place, tweaked the bar alignment, then applied pressure while contemplating the whichness of the why for half a minute while the solvent worked its magic.

Things look pretty good once more:

Chain Mail Armor - missing link - repaired
Chain Mail Armor – missing link – repaired

There’s no way to determine the repair’s goodness, other than by deliberately trying to snap off a bar, so I’ll just put it back in the box and hope for the best.

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Injured Arm Support Table: Wide Version

This table must sit across the threshold of a walk-in / sit-down shower, with the shower curtain draped across the table to keep the water inside.

Starting with another patio side table, as before, I installed a quartet of 5 mm stainless screws to lock the top panels in place and convert the table into a rigid assembly:

Arm Supports - wide table - overview
Arm Supports – wide table – overview

Because the shower floor is slightly higher than the bathroom floor, I conjured a set of foot pads to raise the outside legs:

Patio Side Table Feet - OpenSCAD model
Patio Side Table Feet – OpenSCAD model

The sloping top surface on the pads compensates for the angle on the end of the table legs:

Arm Supports - leg end angle
Arm Supports – leg end angle

I think the leg mold produces legs for several different tables, with the end angle being Close Enough™ for most purposes. Most likely, it’d wear flat in a matter of days on an actual patio.

Using good 3M outdoor-rated foam tape should eliminate the need for fiddly screw holes and more hardware:

Arm Supports - leg pads
Arm Supports – leg pads

The feet fit reasonably well:

Arm Supports - leg pad in place
Arm Supports – leg pad in place

They may need nonskid tape on those flat bottoms, but that’s in the nature of fine tuning.

And, as with the narrow table, it may need foam blocks to raise the top surface to arm level. Perhaps a pair of Yoga Blocks will come in handy for large adjustments.

The OpenSCAD source code as a GitHub Gist:

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Injured Arm Support Table: Narrow Version

For reasons not relevant here, I recently conjured a pair of tables to support an injured arm (ours are OK!) in the bathroom: one table fitting in the narrow space adjacent to a toilet and the other across the threshold of a walk-in / sit-down shower.

The raw material came from a plastic side table intended for outdoor use:

Arm Supports - OEM Patio table
Arm Supports – OEM Patio table

That’s the Patriotic Blue version, which seemed the least offensive of the colors on offer at the local store.

The plastic pieces unsnap easily enough:

Arm Supports - top panel disassembly
Arm Supports – top panel disassembly

The legs also come apart by pulling outward at the crossover points. You may need to clean the flashing from all the joints, as they’re only as finished as absolutely necessary.

A table about half the width seemed about right, so I sawed the two top plates off their struts, then angled the strut ends to match the new leg angle:

Arm Supports - trimming table struts
Arm Supports – trimming table struts

Because it’s now completely floppy, I drilled holes for 5 mm screws through the struts:

Arm Supports - cross-drilling struts
Arm Supports – cross-drilling struts

In the process, I discovered stainless steel nyloc nuts tend to gall on stainless steel screws:

Galled stainless steel cap screw and nyloc nut
Galled stainless steel cap screw and nyloc nut

I lost a pair of screws + nuts before I got a clue and began adding a drop of machine oil to each screw before tightening the nuts. Haven’t had that problem with the 3 mm SS screws, so there’s always something new to learn.

With all the screws in place, the half-table becomes a rigid contraption:

Arm Supports - narrow table - bottom view
Arm Supports – narrow table – bottom view

The top looks like it’s suffering from severe barrel distortion, but it really started out looking that way:

Arm Supports - narrow table - overview
Arm Supports – narrow table – overview

The slat sides are all curved, except the far edge that was once in the middle of the table and now fits against the wall.

It may be slightly too short, but we can stack foam slabs on the top, probably held in place with cable ties.

Memo to Self: lube all the stainless steel screws!

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Another WS2812 Failure: Broken Glass

The WS2812 under the 5U4GB full-wave rectifier tube went into pinball panic mode:

Failed WS2812 - 5U4GB Rectifier
Failed WS2812 – 5U4GB Rectifier

It’s been running more-or-less continuously since late 2016, so call it

Because I’d be crazy to replace it with another likely-to-fail WS2812, I had to remove both of them before installing SK6812 RGBW LEDs and updating the Arduino Nano.

Unfortunately, I did a really good job of bonding the side light to the tube with epoxy:

Failed WS2812 - 5U4GB broken glass
Failed WS2812 – 5U4GB broken glass

The last tube manufacturing step involved flashing the getter onto the tube envelope, so as to remove the last vestige of air. Admitting air oxidizes the getter:

Failed WS2812 - 5U4GB getter oxidation
Failed WS2812 – 5U4GB getter oxidation

It was such a pretty tube, too …

5U4GB Full-wave vacuum rectifier - cyan red phase
5U4GB Full-wave vacuum rectifier – cyan red phase

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Improved Shoelace Ferrule Aglets

After considerable evaluation, the Customer decided the shoelaces were still too long and said the hex-crimped ferrules were entirely too rough and tended to snag on things. This time, I prepared the ferrules by chucking them in the lathe:

Ferrule - original flange
Ferrule – original flange

The steel rod inside the ferrule encourages it to remain round and not collapse while I’m filing off the flange that normally holds the plastic strain-relief doodad:

Ferrule - reshaped flange
Ferrule – reshaped flange

I snipped another half inch off each end of the laces and crimped on the prepared ferrules:

Shoelace ferrule aglets
Shoelace ferrule aglets

Which were definitely too jaggy, so they now sport an epoxy coat:

Ferrule aglets - epoxy coat
Ferrule aglets – epoxy coat

Alas, JB Kwik epoxy has a pot life measured in minutes, so the last ferrule looks a bit lumpy. They seem to work fine and the Customer is happy with the results.

Memo to Self: Next time, dunk the ferrules in a pot of slow-curing JB Weld and let them drain overnight.

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