Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
I’ve always wondered what’s inside a metal-case vacuum tube:
Dual rectifier tube 5T4 – metal case opened
The cutter last saw action on the EMT used in the MPCNC, so it’s intended for use on steel tubes. I thought about parting the case off in the lathe, but a tubing cutter sufficed for a first attempt, even if it couldn’t cut quite as close to the flange as I wanted.
A 5T4 tube is a full-wave rectifier with two sections:
Dual rectifier tube 5T4 – upright
Unsurprisingly, the guts resemble those of glass-envelope rectifier tubes in my collection, like this 5U4GB:
5U4GB Full-wave vacuum rectifier – cyan red phase
The metal case would be far more rugged than a glass bottle and, perhaps, the flange locked the tube into its socket against vibration.
The filaments surely weren’t thoriated, so it’s all good …
In those 29 calendar months (maybe 20 riding months) I’ve ridden 4500-ish miles at perhaps 12 mph, so call it 375 hr = 22.5 k min. The camera fills a 4 GB file every 22.75 min, so it’s recorded 1000 files = 4 TB, which is 62× its capacity. This is better than the defunct Sandisk Extreme Pro card (3 TB & 50×) and much much better than the Sony cards (1 TB & 15×), although I have caught the camera in RCVR mode maybe twice, which means the card or camera occasionally coughs and reformats itself.
The SJCam M20 rear camera also uses a Sandisk 32 GB high-endurance card and has worked fine since early 2018. An external battery eliminated all the hassle of its feeble internal batteries, although the one that’s been in there has faded to the point of just barely keeping the clock ticking over during winter weeks without rides:
SJCAM M20 Mount – Tour Easy side view
All in all, paying the premium for video-rated MicroSD cards has been worthwhile!
The GCMCtypeset() function converts UTF-8 text into a vector list, with Hershey vector fonts sufficing for most CNC projects. The fonts date back to the late 1960s and lack niceties such as superscripts, so the Homage Tektronix Circuit Computer scale legends have a simpler powers-of-ten notation:
Tek CC – Pilot V5 – plain paper – red blue
Techies understand upward-pointing carets, but … ick.
After thinking it over, poking around in the GCMC source code, and sketching alternatives, I ruled out:
Adding superscript glyphs to the font tables
Writing a text parser with various formatting commands
Doing anything smart
Because I don’t need very many superscripts, a trivial approach seemed feasible. Start by defining the size & position of the superscript characters:
SuperScale = 0.75; // superscript text size ratio
SuperOffset = [0mm,0.75 * LegendTextSize.y]; // ... baseline offset
Half-size characters came out barely readable with 0.5 mm Pilot pens:
Tek CC – Superscript test – 0.5x
They’re legible and might be OK with a diamond drag point.
They work better at 3/4 scale:
Tek CC – Superscript test – 0.75x
Because superscripts only occur at the end of the scale legends, a truly nasty hack suffices:
function ArcLegendSuper(Text,Super,Radius,Angle,Orient) {
local tp = scale(typeset(Text,TextFont),LegendTextSize);
tp += scale(typeset(Super,TextFont),LegendTextSize * SuperScale) + SuperOffset + [tp[-1].x,0mm];
local tpa = ArcText(tp,[0mm,0mm],Radius,Angle,TEXT_CENTERED,Orient);
feedrate(TextSpeed);
engrave(tpa,TravelZ,EngraveZ);
}
The SuperScale constant shrinks the superscript vectorlist, SuperOffset shifts it upward, and adding [tp[-1].x,0mm] glues it to the end of the normal-size vectorlist.
Yup, that nasty.
Creating the legends goes about like you’d expect:
A new spool of retina-burn orange PETG snagged when the takeup guide let the filament fall off the inboard side and the extruder tightened the loops around the spool holder. I carefully unwound the loops without removing the spool to ensure I didn’t introduce a crossover, scraped the bird’s next off the platform, and restarted the print.
After undoing the second snag, I added a crude spool sidewall:
We spotted this near our usual parking spot during a recent grocery trip:
Adams crash – stone wall
The bush was pretty well uprooted, suggesting the vehicle stopped atop the bush after demolishing the wall.
Wondering how it got there, I looked across the parking lot:
Adams crash – reverse view
Yes, that’s a dead lamp post. The impact dislodged its concrete base by about four inches:
Adams crash – lamp pole detail
The greenery came from another eviscerated bush:
Adams crash – bush debris
I expected to see tire gouges in the grass, but … nope.
The bush got a haircut, although the right half seems undamaged:
Adams crash – bush detail
The boulder won its disagreement with the vehicle, although there’s surprisingly little shattered plastic and other debris along the trail:
Adams crash – boulder detail
The impact dislodged the boulder, which came to rest about four feet from its origin:
Adams crash – overview
The damage lies along a straight line from the middle of the Adams entrance intersection to the wall impact:
Adams crash – trajectory
There are no obvious skid marks, undercarriage scrapes, or gouges in the grass anywhere along the trajectory, suggesting the vehicle remained mostly airborne and ballistic during the whole event, and even the three (!) curbs involved have no marks.
The nice lady at the Adams Customer Service counter didn’t know what happened and, as usual, the Poughkeepsie Journal (newspaper) has nothing to say.
I did not check for a high-clearance pickup truck with tall tires and severe front-end damage in the body shop across the street, although one seems a likely suspect. Whatever the vehicle may have been, it was definitely traveling at the usual (tautological) “high rate of speed” …
As one might expect, the holiday season offers many suboptimal dietary choices and interferes with regular exercise:
Weight Chart – 2020-01 – Ed
I re-origined the skin-fold measurement series for the 2020 chart to move it further from the weight series. The 2 mm jump is close to the repeatability limit, particularly as I’m now eyeballing the measurement site based on a nearby freckle, rather than depending on a fading Sharpie dot.
The Smell of Molten Projects in the Morning 