The Smell of Molten Projects in the Morning
Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Taking & making images.
OK, I’m a sucker for sunlit solid water:
They’re hanging from the gutters over the patio. The house has six-foot soffits back there and nearly three feet elsewhere, plus the roofers installed rubber sheets along the walls, so we’re not worried about leaks…
Having repaired these once before, I wasn’t too surprised when this happened:
Evidently the “titanium” has fatigued, because the repair lasted barely nine months.
Rather than try to fix them again, I sent my new prescriptions halfway around the planet and, a bit under two weeks later, had three glasses: normal, computer, and sun. This time, I went with 38 mm tall lenses, a heavier nose bridge, and traditional aviator sunglasses.
For the record, the regular prescription was:
Tweaking that by +0.75 diopter on the sphere puts my far point focus on the monitors across the desk and backing -0.75 diopter from the adder keeps the same near-point reading correction:
They’re all no-line progressive bifocals made from 1.57 high-index plastic with anti-reflection coating, for a grand total of $135 delivered.
That being only slightly more than the estimated cost of fixing one broken Silhouette frame temple, Mary will try living in the future, too.
After the January snowstorm, everything above the water downstream of the Red Oaks Mill dam featured a snow cap rimmed with ice:
The jet emerging from a deep notch in the dam breast on the near side of the ice sheet chewed through the concrete-and-rubble structure:
Upstream, graceful curves in the ice highlight the flow streamlines:
Yes, that was on the same walk when we found the severed head…
Two snowstorms in a week converted our patio tables into gentle sculptures.
If you could flip the round table upside down, the mound might match the snow shadow underneath:
Snow falling through the 2 inch hole in the middle of the square table produces a large cone below:
Leaving a much larger caldera in the top:
Yes, I’m easily amused…
Nah, that can’t possibly be a …
Tell me it’s not a really bad wig …
Gently now …
Whew!
Found on Old Mill Road, just downstream of the Red Oaks Mill dam; the Mighty Wappingers Creek flows on the left.
That’s all I have to say…
Our Larval Engineer volunteered to convert the lens from a defunct magnifying desk lamp into a hand-held magnifier; there’s more to that story than is relevant here. I bulldozed her into making a solid model of the lens before starting on the hand-holdable design, thus providing a Thing to contemplate while working out the holder details.
That justified excavating a spherometer from the heap to determine the radius of curvature for the lens:
You must know either the average radius / diameter of the pins or the average pin-to-pin distance. We used a quick-and-dirty measurement for the radius, but after things settled down, I used a slightly more rigorous approach. Spotting the pins on carbon paper (!) produced these numbers:
The vertical scale has hard-metric divisions: 1 mm on the post and 0.01 on the dial. You’d therefore expect the pins to be a hard metric distance apart, but the 25.28 mm average radius suggests a crappy hard-inch layout. It was, of course, a long-ago surplus find without provenance.
The 43.91 mm average pin-to-pin distance works out to a 50.7 mm bolt circle diameter = 25.35 mm radius, which is kinda-sorta close to the 25.28 mm average radius. I suppose averaging the averages would slightly improve things, but …
The vertical distance for the lens in question was 0.90 mm, at least for our purposes. That’s the sagitta, which sounds cool enough to justify this whole exercise right there. It’s 100 mm in diameter and the ground edge is 2.8 mm thick, although the latter is subject to some debate.
Using the BCD, the chord equation applies:
Using the pin-to-pin distance, the spherometer equation applies:
Close enough, methinks.
Solving the chord equation for the total height of each convex side above the edge:
So the whole lens should be 2 · 3.5 + 2.8 = 9.8 mm thick. It’s actually 10.15 mm, which says they were probably trying for 10.0 mm and I’m measuring the edge thickness wrong.
She submitted to all this nonsense with good grace and cooked up an OpenSCAD model that prints the “lens” in two halves:
Alas, those thin flanges have too little area on the platform to resist the contraction of the plastic above, so they didn’t fit together very well at all:
We figured a large brim would solve that problem, but then it was time for her to return to the hot, fast core of college life…
So we took an out-and-back walk across the Walkway Over the Hudson, after which I spotted this amusing sight:
The horrible color balance comes from using a preset tuned for the M2’s new LED lights, rather than letting the camera figure things out on its own, then fighting it down after cropping.
Anyhow, we did a bit over two miles of walking with outdoor temperature just over freezing. The camera lives in the left cargo pocket of my pants and the spare NB-5L battery in the camera case faces outward. Neither battery would power the camera at ambient temperature; evidently, being that cold reduced their output voltage below the level that the camera would accept.
With a cold battery, the camera grunted, displayed a message about replacing the battery, and promptly shut itself off. Warming one of the batteries boosted its terminal voltage enough to take the picture, which accounts for not getting the proper color balance: I was fully occupied just getting the camera working.
Back home and warmed up, the camera said both batteries were fully charged. They came from the BNF27 lot that produced low terminal voltages, so I’ll reserve them for warmer weather and use the BNI13 lot during the next few months.
The Smell of Molten Projects in the Morning 