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.
Mechanical widgetry
The braided cord on the NSA pull tab dangling from my belt pack has a monofilament core:
The Basement Laboratory Warehouse Wing doesn’t have an exact replacement, but braided nylon fishing line should come close:
If I keep a closer watch on the situation, maybe I can replace the cord before the tab goes missing…
There never seems to be a good time to drain your water heater and check the anode rod, but I finally found a Round Tuit…
Pursuant to that comment, I drained a few gallons before applying the six-point 1-1/16 inch socket and loosening the anode rod without fuss or bother. I couldn’t get a good finger grip on the bolt head inside the enlarged hole, but a long-nose Vise-Grip pliers did the trick:
The first look showed a solid bar of corrosion:
You can see the 3/4 inch socket wrench in the background: I didn’t need the breaker bar this time!
The magnesium anode rod corroded down to the steel core wire just under the bolt head:
The entire rod was about half a foot shorter than the new one, but I cannot tell whether that much corroded away or rods have gotten longer (they’ve certainly gotten more expensive):
I sawed the rod to get it out of the heater, because I also wanted to see how much magnesium remained inside the corrosion. Quite a lot, as it turned out, so I suppose I could have reinstalled the rod and left it for another few years:
I don’t know where all the corrosion products went, because the water heater drained uneventfully, without clogging the valve or depositing a pile of crud at the end of the hose. There were a few particles, but nothing like the residue from the aluminum rod.
Then I cleaned off a new magnesium rod, tilted the water heater to get enough clearance, installed the rod with a wrap of PTFE tape, and reinstalled the water supply lines. I suspect the next owners of the place will be looking at it a decade down the calendar…
If I had more guts and less sense, I’d chuck the bar stubs in the lathe and turn off the corrosion to get some nice steel-core magnesium rods. The prospect of extinguishing a magnesium fire in the basement doesn’t entice me in the least.
After 30 years, IBM gave Mary a commemorative clock, after which she promptly retired. Back in the day, they used to hand out Atmos clocks (admittedly, on more momentous occasions), but this isn’t one of those. In fact, although it appears to have a torsion pendulum, that’s a separate motor-driven foo-foo which we immediately turned off:
It normally sits on the living room coffee table (which actually holds a myriad plants next to the front window) where, after we scrapped all the upholstered furniture, the two of us can’t both see the clock face from our chairs. Having a spare clock insert from that repair, we had the same bright idea at the same time: we need a clock with two faces! We came up with Janus independently…
Despite its fancy appearance, the IBM clock consists mostly of brass and plastic, so I had no qualms about having my way with it in the shop. The new clock insert spanned the clock’s gilt plastic back cover, needing only a #1 drill hole for the adjustment stem, and exactly filled the available space between the back cover and the case. Both movements had enough interior clearance for 3-48 brass screw heads and nuts, so I eyeballed the right spots on the new cover, centered the Sherline spindle on the plate, and drilled two clearance holes 6 mm in from the edges on the vertical diameter:
That put them 61.3 mm apart across the diameter, which would be awkward to duplicate by hand. Manual CNC makes it trivially easy to match-drill holes; I clamped down the gilt back cover from the IBM clock, aligned it to the table, located the center, and drilled two 3-48 clearance holes:
The glow from that polycarbonate packing block isn’t quite so nuclear in real life. The clamping force goes down the side panels of the cover, which had enough of a curve to be perfectly stable. Yes, I’m drilling into air, but came down real slow using the Joggy Thing and it was all good.
Assemble the two back covers (the holes matched perfectly), mark the adjustment stem hole, disassemble, hand-drill, reassemble, tighten nuts, and install:
It does look a bit lumpy from the side, but that’s just because I don’t have any gilding for the black tape wrap:
There, now, that was easy.
Long ago, in a universe far away, IBM gave Mary a desk clock as part of that Technical Excellence Award:
The double-stick foam tape holding the plate on the front aged out a few years later, at which point I cleaned off the solidified goo, drilled 2-56 clearance holes in the plate and tapping holes in the clock base, installed four pan head stainless screws, and neatly aligned the slots. That’s what it should have looked like from the beginning; this was, after all, a Technical award…
The clock movement failed recently and I got a drop-in clock insert from Klockit to put it back in operation. The fit wasn’t quite solid, but two wraps of silicone tape around the case under the ribbed friction-fit band solved that problem.
One new movement cost just about as much as the shipping, so I bought a pair with black and white faces. Mary picked the white face for this clock, which left the black movement as a spare.
Tomorrow: what to do with a spare clock insert.
It’s leaf-shredding season again and our MTD Chipper-Shredder began shredding not nearly as well as it had in years gone by. Last season I laid in a stock of replacement parts, so I swapped in a new Shredder Screen (781-0457):
The flail blades (719-0329) on the massive rotating impeller assembly protrude through the parallel openings in the screen, which is where most of the shredding action happens. The old red screen bent outward enough so that the blades pushed the leaves against the screen, rather than through it, producing frequent clogs.
Now it works fine again… although I’ve had just about as much fun shredding leaves as any one person should experience in one month.
The Vassar Farm Garden requires fairly heavy watering, because it’s in full sun all day long, so we lay in a set of drip lines connected through Y valves to a main feeder line running down one end of the plot. Plastic valves tend to be overly fragile, so this year I tried a few much larger full-flow ball valves with a metallic housing:
This valve lay on the ground (as they all do) just inside the gate and served as an occasional supply for a short hose with the hand sprinkler head. I don’t know what’s driving this corrosion, but it’s eating the external threads as well as the valve bore.
Overall, I’m unimpressed…
The alert reader will have noticed two slip faults in the jellyfish cookie cutter:
Look closely…
Those failures came from two separate cable snags that stalled the X and Y stepper motors for about 1 mm of travel. Fortunately, I wasn’t paying attention and, by the time I figured this out, the thing was nearly built, so I let it run to completion. The thick base plate accounts for most of the plastic, anyway.
First, the cable bundle on the right snagged on the socket-head cap screw just in front of the X axis limit switch (hidden behind the bundle here). This picture, taken after the +12 V pin in the HBP connector burned through, shows the typical snarl of wires inside a Thing-O-Matic:
The rewired thermistor cable snagged on the bulldog clip holding the top aluminum plate. This picture, taken after the thermistor pads fell off the HBP, shows the filler plate I put in place to prevent the cable (entering from the top and passing below the white cable on the HBP) from jamming in the gap between the Y axis stage and the case, but you can see how the bulldog clip handle could snag it when the platform moves rearward from the front left corner (+X +Y):
The fat gray cable flat against the case in that picture carries the X axis stepper drive signals up-and-over the Y axis. The thinner gray thermistor cable emerges from the electronics bay inside the case corner, then arches in from thetop.
My buddy Aitch recently gave me a few meters of corrugated wire loom, so I moved the bulldog clip rearward and bundled all those loose HBP wires in one tidy snood:
I’m sure something else will go wrong, but the machinery looks marginally less haphazard and the cables don’t snag while I’m watching…
The Smell of Molten Projects in the Morning 