Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
It’s been quite a while since BIOS boot sequences started with the floppy drive. Combined with a CMOS backup battery failure, I’d say this poor PC has been chugging along for two decades.
On another floor:
Kiosk – Windows Updates
Isolating a Windows kiosk from the Interwebs is an excellent design principle, but Windows Update really wants to phone home. The kiosk’s presentation ran Adobe Flash 10, so it’s been confined for maybe a decade.
Looks like it’s time for another fundraising drive to replace the PCs with Raspberry Pi controllers. The real expense, of course, goes into rebuilding the presentations using whatever tech stack is trendy these days.
Following a linkie I can no longer find led me to retrieve the Tektronix Circuit Computer in my Box o’ Slide Rules:
Tektronix Circuit Computer – front
I’m pretty sure it came from Mad Phil’s collection. One can line up the discolored parts of the decks under their cutout windows to restore it to its previous alignment; most likely it sat at the end of a row of books (remember books?) on his reference shelf.
The reverse side lists the equations it can solve, plus pictorial help for the puzzled:
Tektronix Circuit Computer – rear
Some searching reveals the original version had three aluminum disks, shaped and milled and photo-printed, with a honkin’ hex nut holding the cursor in place. The one I have seems like laser-printed card stock between plastic laminating film; they don’t make ’em like that any more, either.
TEK PN 003-023 (the paper edition) runs about thirty bucks (modulo the occasional outlier) on eBay, so we’re not dealing in priceless antiquity here. The manual is readily available as a PDF, with photos in the back.
Some doodling produced key measurements:
Tektronix Circuit Computer – angle layout
All the dimensions are hard inches, of course.
Each log decade spans 18°, with the Inductive Frequency scale at 36° for the square root required to calculate circuit resonance.
Generating the log scales requires handling all possible combinations of:
Scales increase clockwise
Scales increase counterclockwise
Ticks point outward
Ticks point inward
Text reads from center
Text reads from rim
I used the 1×100 tick on the outer scale of each deck as the 0° reference for the other scales on that deck. The 0° tick appears at the far right of plots & engravings & suchlike.
The L/R Time Constant (tau = τ) pointer on the top deck and the corresponding τL scale on the bottom deck has (what seems like) an arbitrary -150° offset from the 0° reference.
The Inductive Frequency scale has an offset of 2π, the log of which is 0.79818 = 14.37°.
The risetime calculations have a factor of 2.197, offsetting those pointers from their corresponding τ pointer by 0.342 = log(2.197) = 6.15°.
A fair bit of effort produced a GCMC program creating a full-size check plot of the bottom deck on the MPCNC:
By the conservation of perversity, the image is rotated 90° to put the 1 H tick straight up.
The 3018 can’t handle a 7.75 inch = 196 mm disk, but a CD-size (120 mm OD) engraving came out OK on white plastic filled with black crayon:
Tek CC bottom – ABS 160g 2400mm-min
The millimeter scale over on the right shows the letters stand a bit under 1 mm tall. And, yes, the middle scale should read upside-down.
Properly filling the engraved lines remains an ongoing experiment. More downforce on the diamond or more passes through the G-Code should produce deeper trenches, perhaps with correspondingly higher ridges along the sides. Sanding & polishing the plastic without removing the ink seems tedious.
The Great Dragorn of Kismet observes I have a gift for picking projects at the cutting edge of consumer demand.
More doodles while figuring the GCMC code produced a summary of the scale offsets:
It turned out easier to build vectors of tick mark values and their corresponding lengths, with another list of ticks to be labeled, than to figure out how to automate those values.
We rented a van to haul our bikes on a vacation trip, but the tire pressure warning alarm sounded when I turned into the driveway. Measuring the tire pressures showed the left rear tire was at 51 psi, far below the 72 psi shown on the doorframe sticker, and a quick check showed a possible problem:
Tire FOD – in place
The small circle in the tread to the left of that mark turned out to be a metal tube:
Tire FOD object
Their tire contractor determined the tire wasn’t leaking, the metal tube hadn’t punctured the carcass, and all was right with the world. After, of course, two hours when we expected to be loading the van.
The rental company was good about it, perhaps because I reported they sent the van out with the other rear tire grossly overinflated to 86 psi (!); obviously, their prep didn’t include checking the tires. Somewhat to my surprise, the space under the passenger seat for a jack was empty.
During the trip, the van laid an egg:
Transit Van with Egg
A good time was had by all, but our next bicycling vacation will definitely have much more bicycling and much less driving!
Voles apparently live only a few months, so this one may have run out of gas while crossing the driveway:
Vole – dead on driveway
Or it just caught a heart attack?
It definitely wasn’t playing possum; nobody can lie still with ants up their nose.
It had vanished when we returned from our afternoon ride, so somebody further up the food chain also noticed it. As my buddy dBm puts it, “In Nature, nothing goes to waste.”
Riding south on Rt 376 takes us across the Mighty Wappinger Creek on a four-lane concrete bridge built about 1995. This Dutchess County Aerial Access photo shows it in 2016:
Rt 376 – Wappinger Bridge – 2016 overhead
A pothole opened up on the south end of the span last year:
This year, we’ve been avoiding a new pothole opening on the north end:
Rt 376 – Wapp Bridge – 2019-09-11 – 0295
It’s difficult to ride between the right side of the hole and the weeds growing from the curb joint under the guide rail, so we take the lane whenever we can. The extensive vegetation growing in the bridge structure can’t possibly be a good thing.
The concrete seems to be failing by tension overload as the beams flex downward under traffic loading and pull the top surface apart. The surface has irregular transverse cracks across the deck width, not all of which look like control joints.
With potholes and surrounding cracks allowing brine into the deck, we expect much worse deterioration during the next few years.
My Professional Engineer license has long lapsed, not that I ever knew anything about bridge design, so this is mostly observational.
The Smell of Molten Projects in the Morning 