Archive for category Oddities
HP 7475A Plotter: Ceramic-Tip Pen EOL
Posted by Ed in Machine Shop, Oddities on 2019-07-25
Ceramic-tip plotter pens draw wonderfully crisp lines:
Eventually, though, the fiber tip wears flush with the ceramic shell, becomes slightly indented, and ceases to make its mark in the world:
As the lady says, “Starting from zero, got nothing to lose”, so I applied a fine diamond file around the tip:
Well, all I can say is it seemed like a good idea at the time.
Alas, even the newly exposed fiber didn’t make much of a mark on the paper and, as you’d expect, the ragged ceramic tip dragged painfully across the paper. I assume the fiber had filled with fossilized dry ink.
A New Old Stock bag of fiber-tip pens emerged from the Big Box o’ Pens while I was flailing around:
I think the “812” in the lower right corner is a date code, most likely early in 1988, so the pens started their lifetime countdown at least three decades ago. They still work, though:
The plotter appeared at HV Open’s Mad Science Fair, because everybody loves a plotter!
Mower FOD
Posted by Ed in Home Ec, Machine Shop, Oddities on 2019-07-21
For reasons not relevant here, the lawn mower suffered some Foreign Object Damage:
I’m sure the hard stop loosened the tolerances along the shaft, but the mower fired right up (with that new blade!) and has no more vibration than usual, despite the seriously bent blade mount.
I no longer have a deep emotional attachment to lawn mowers, which is apparently common, as the label advises me there’s no need to change the oil:
Drive it ’til it drops …
Houses Are Trouble: Electrical Service Division
The ancient utility pole on the north side of our property fell over a few hours after a thunderstorm rolled through:
Fortunately, the wire clamps were upward and it just lay there without sparks or excitement. It feeds the vacant house out back, so restoring power wasn’t urgent.
Unfortunately, the lines neatly bisected Mary’s garden:
The utility crew arrived a few hours later, disconnected the triplex at the fallen pole, rolled it up, secured it to the source pole out front, and promised a different crew would replace the pole in a while:
We agreed restoring service to other folks who needed it should take priority.
Mary’s been ducking the various cable TV / phone / FiOS cables ever since.
The pole has been God’s own toothpick for quite some time, as shown by this picture from 2001:
Fortunately for us, its pole tag hadn’t fallen off in all those years:
That little tag may save us ten large during this exquisite little inconvenience …
MPCNC: Calculating Spring Rates
Posted by Ed in Machine Shop, Oddities, Software on 2019-07-18
Calculate the spring rates for the drag knife, diamond engraver, and collet pen holders by measuring the downforce every 0.5 mm (or so):
Then plotting the data points and eyeballing a straight-line curve fit:
Doing it on hard mode definitely has a certain old-school charm. The graph highlights mis-measured data and similar problems, because, if you don’t see a pretty nearly straight line, something’s gone awry.
But we live in the future, so there’s an easier way:
Well, OK, it’s the future as of the early 1990s, when HP introduced its HP 48 calculators. I’m using the Droid48 emulator on my ancient Google Pixel: living in the past, right here in the future.
Start by firing up the STAT library (cyan arrow, then the 5 key), selecting Fit Data … from the dropdown list, then selecting the Linear Fit model:
Then tap EDIT and enter the data in a tiny spreadsheet:
My default “engineering mode” numeric display format doesn’t show well on the tiny screen. Tapping the WID→ key helps a bit, but shorter numbers would be better.
With the data entered, set an X value and tap the PRED key to get the corresponding Y value:
Tapping the OK button puts the line’s coefficients on the stack, as shown in the first picture. Write ’em on a strip of tape, stick to the top of the holder, and it’s all good:
Works for me, anyhow.
HP still has the HP 48g manuals online. The (unofficial) HP Museum has a page on the HP 48S. More than you want to know about the 48 series.
Monthly Image: And Then There Were Two
Posted by Ed in Oddities, Photography & Images, Science on 2019-07-15
The turkey hen who once had nine chicks, then seven, now has only two:
We haven’t seen the fox since it nailed the previous chick, but it may be responsible for taking a chick a day, every day, for a week.
We wonder if she misses the rest of her brood as much as we do …
Taken through two layers of 1950s window glass, zoomed all the way in, with a phone camera.
Chipmunk Shelter
This chipmunk has been hanging out near the collection of yard & garden tools on the patio:
When threats appear, the critter vanishes into the clutter and waits until we go elsewhere. It’s almost as good as the roof gutter pipe!
Those stripes remain surprisingly visible in the shadows between stacks of clay pots, though, if you know where to look.
Arlington Fire Department Practice Session
Posted by Ed in Oddities, Recumbent Bicycling on 2019-07-07
The normal Vassar Farm exit was blocked by Arlington Fire District equipment, but the scene was calm and nobody objected when I asked to ride through:
They were practicing hose deployment and structure entry in a soon-to-be-demolished building:
That’s theatrical smoke, not a real fire; the folks off the right of the picture told me it’s impossible to burn down old structures for practice nowadays, what with all the environmental regulations.
The Tower Truck obviously has more reach than they’ll need for the second floor:
A few days later, we spotted Fairview Fire District folks scoping out the house.
We think this might be Vassar’s way of contributing back to the various emergency departments, as the College is mostly tax-exempt.
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