End of the Thing-O-Matic

After nine years, it’s come to this:

End of the Thing-O-Matic
End of the Thing-O-Matic

The Thing-O-Matic got me started in 3D printing (and blogging!), provided an education in many useful subjects, and has long since outlived its usefulness.

A view from happier times:

Thing-O-Matic Overview
Thing-O-Matic Overview

Its components will live on in other projects.

One of those bittersweet moments, fer shure …

Nut Socket Wrench Improvement

The recesses in cheap 1/4-inch shank nut drivers aren’t much deeper than the nuts, which means a screw sticking out of the nut by more than a few threads defeats the entire purpose.

Well, I can fix that:

Drilling 5.5 mm socket
Drilling 5.5 mm socket

That’s a 5.5 mm socket for M3×0.5 machine screw nuts, getting a screw clearance hole drilled into it with a #28 drill (0.1405 inch = 3.5 mm). The sockets are allegedly “forged and hardened”, but an ordinary HSS drill bit cuts like they’re butter, so I’m thinking somebody skipped the hardening step.

Turns out I had a lot of nuts to remove from black oxide M3 socket head cap screws, making a brief pause in the action totally worthwhile.

Bike Helmet Mirror Mount Tightening

Almost exactly three years later, it’s time to tighten the helmet mirror mount screws:

Helmet mirror mount - bottom view - setscrew
Helmet mirror mount – bottom view – setscrew

That’s a 0.035 inch = 35 mil hex wrench, of which Eks reminds me “Any time your design requires a tiny [obscene gerund] wrench, you’re doing it wrong”.

The sequence goes like this:

  • Loosen that tiny setscrew
  • Unscrew & remove the mirror boom
  • Remove brass screw & azimuth pivot
  • Tighten screw in elevation pivot
  • Tighten tiny setscrew on elevation arc
  • Reinstall & tighten azimuth pivot
  • Reinstall mirror boom
  • Tighten tiny setscrew

Going strong after seven years!

Herringbone Pinion Gears

These herringbone gears were part of updating my old Thing-O-Matic:

Herringbone gears with nut inserts
Herringbone gears with nut inserts

But, as the saying goes, that’s not a herringbone gear. This is a herringbone gear:

Bethlehem Steel - 48 inch rolling mill gears
Bethlehem Steel – 48 inch rolling mill gears

We always read the signage:

Bethlehem Steel - 48 inch rolling mill gears - description
Bethlehem Steel – 48 inch rolling mill gears – description

They’re parked in front of the National Museum of Industrial History in Bethlehem, PA.

Squidwrench Electronics Workshop: Session 3

Ex post facto notes from the third Squidwrench Electronics Workshop.

Exhibit various 50 Ω resistors, including my all-time favorite, a 600 W 3 GHz dummy load:

600 W Dummy Load Resistor
600 W Dummy Load Resistor

… down to a 1/8 Ω metal film resistor.

The dummy load’s N connector triggered a regrettable digression into RF, belatedly squelched because I wasn’t prepared to extemporize on AC concepts like reactance which we haven’t covered yet.

Discussion of resistor applications, power handling, power derating with temperature, etc:

Whiteboard - Session 3 - Resistor power derating
Whiteboard – Session 3 – Resistor power derating

Why you generally won’t find 50 Ω load resistors in Raspberry Pi circuits. Cartridge heaters for 3D printers, not aluminum power resistors, although everyone agrees they look great:

Power resistors on heat spreader
Power resistors on heat spreader

Discussion of voltage vs. current sources, why voltage sources want low internal resistances and current sources want high resistances. Bungled discussion of current sources by putting diodes in parallel; they should go in series to show how added voltage doesn’t change current (much!) in sources driven from higher voltages through higher resistances:

Whiteboard - Session 3 - Voltage vs Current Sources
Whiteboard – Session 3 – Voltage vs Current Sources

Use Siglent SDM3045X DMM in diode test mode to measure forward drop of power / signal / colored LEDs, discuss voltage variation with color / photon energy. Measure 1.000 mA test current for all forward voltages.

Compute series resistor (500 Ω) to convert adjustable power supply (the digital tattoo box, a lesson in itself) into reasonable current source; roughly 10 V → 20 mA. Find suitable resistor (560 Ω) in SqWr junk box parts assortment, digression into color band reading.

Wire circuit with meters to measure diode current (series!) and voltage (parallel!), measure same hulking power diode (after discovering insulating washers now in full effect) as before in 1 mA steps to 10 mA, then 15 and 20 mA, tabulate & plot results:

Whiteboard - Session 3 - Diode current vs forward drop
Whiteboard – Session 3 – Diode current vs forward drop

Discover warm resistor, compute power at 20 mA, introduce cautionary tales.

Lesson learned about never returning parts to inventory, with 560 Ω resistor appearing in diode drawer. Cautionary tales about having benchtop can of used parts as front-end cache for inventory backing store.

Another intense day of bench work!

Tour Easy: White ABS vs. Six Years of Sunlight

These white ABS fairing plates held the Zzipper fairing on my Tour Easy ‘bent since 2011:

ABS Fairing Plates - 6 years
ABS Fairing Plates – 6 years

Over the course of those six years I’ve ridden about 6 × 2500 = 15000 miles, maybe more, maybe less. I can ride at 15 mph for a while, but 12 mph seems a more reasonable overall estimate, making for a bit over 1000 hours. Figure the bike spends that much time sitting outdoors at the far end of the ride and you’re looking at what 2000+ hours of sunlight does to ABS.

In addition to discoloration, the plates have become brittle, as shown in the chips in third one down, and permanently deformed due to the pressure of the nylon bolts compressing the black foam against the fairing.

A closer look at the top plate:

ABS Fairing Plates - 6 years - detail
ABS Fairing Plates – 6 years – detail

My 3D print quality has improved a lot since then.

New plates of a different design are, as NASA puts it, “in work”.

The pix come from the new LiDE 120 scanner. It does a good job with the color, but has (for good reason) an essentially zero depth of field: if it’s not on the glass, it’s out of focus.

Zire 71 Protector: Some Things Last

This ABS slab emerged from the Thing-O-Matic in early 2012:

Zire 71 protector in place
Zire 71 protector in place

The Zire would power on whenever the switches clicked or that little joystick moved, which happened regularly enough to be annoying.

Mary made a small case that matched the other pouches I carry around:

Belt pack - camera case - PDA case
Belt pack – camera case – PDA case

She made the case to fit an HP48 calculator, but it was close enough for the Zire.

Time passed, the Zire died, I started carrying a Kindle Fire in another pocket, but the ABS slab provided a convenient stiffener between some Geek Scratch Paper and the various pencils / pens / markers / screwdrivers / flashlight filling the available space.

Unfortunately, minus the backup of an electronic slab, the protector finally failed along an obvious stress riser:

Zire 71 protector - cracked
Zire 71 protector – cracked

I cut a similar rectangle from a sheet of unknown flexy plastic, rounded the corners, clipped the pencils & whatnot to it, and maybe it’ll survive for a while.