Rust Never Sleeps

Spotted at the corner gas station on a recent walk:

Gas pump barrier - smashed
Gas pump barrier – smashed

Judging from the tire tracks and extrapolating from recent weather, a snowplow driver misjudged the truck’s right-side clearance while backing.

That big steel tube didn’t put up nearly as much resistance as the architect figured after consulting the relevant building codes:

Gas pump barrier - right base
Gas pump barrier – right base

The paint seems to have been the only thing holding the other side together:

Gas pump barrier - left base
Gas pump barrier – left base

Google Streetview suggests the barriers were new-ish in May 2009:

Gas pump barrier - newish 2009-05
Gas pump barrier – newish 2009-05

Steel is a great construction material, but it doesn’t fare well when installed at grade (or above) where it’s exposed to water and salt. On the other paw, they got over a decade out of it, so maybe it’s as good as it needs to be.

123 Block Links: Blackened!

While looking for something else, I came across my bottle of Aluminum Black, so I just had to do this:

123 Block Links - blackened
123 Block Links – blackened

Looks much snappier than the originals:

123 Block Links - trial assembly
123 Block Links – trial assembly

Those are plain old alloy steel cap screws with a black oxide finish.

The Aluminum Black package directions tell you to apply it with a swab, rinse, and repeat, which seemed like a lot of work for a handful of pins. Instead, I poured a little into a pill bottle, dumped the pins in, and gave it a good shake to coat the pins, whereupon the cap blew off as the contents proceeded to boil merrily. A quick cold-water rinse calmed things down, with no particular harm done, although I had to chase the threads with a tap to get the black powder out. A layer of oil prettied them up nicely.

Today I Learned: the reaction between selenium dioxide and bare aluminum is strongly exothermic.

123 Block Links: Cap Screw Head Pins

Contemplating a project using a small saw in the Sherline suggested that attaching the workpiece to the side of a 123 block would simplify the machining. My blocks have a centered quintet of 3/8-16 tapped holes through the 2×3 side, all the remaining holes are untapped, and it has no smaller holes. The hole spacing doesn’t match the Sherline tooling plate, but the T-nut slots in the underlying table would suffice.

Rather than run long 10-32 screws through the entire block, It Would Be Nice to use short screws from, say, the nearest holes:

123 Block Links - assembled
123 Block Links – assembled

I cannot possibly be the first person to have this idea, but the obvious keywords don’t produce any useful results on The Intertubes, other than a link to a different (and far more complex) block with counterbored holes of various sizes.

Update: Jason found a video about building those blocks and somebody else built some pins similar to mine. Nope, I’m definitely not the first person to have this idea!

Further doodling produced some useful dimensions:

123 Block Links - SHCS head pin doodle
123 Block Links – SHCS head pin doodle

The holes through the blocks probably came from a 5/16 inch drill, the 75% thread depth diameter for the 3/8-16 taps used on the threaded holes. They’re distorted, full of debris, and hardened enough to kill a file, so I eventually settled on 8.2 mm pins that pass through most of the holes.

The socket head screws seat at the pin axis, because the pin diameter is scary close to the counterbore diameter and I didn’t see much point in finesse. I started with a half-inch aluminum rod and peeled it to size, because it simplified the clamping and I have a bunch of them.

The pins are 3/4 inch long to leave a little space on either side of the 1 inch deep holes. I started with comfort marks along the length of the rod:

123 Block Links - laser alignment
123 Block Links – laser alignment

Center-drill so the clearance drill doesn’t skitter off the top:

123 Block Links - center drilling
123 Block Links – center drilling

The counterbore calls for a 0.204 inch = #6 drill, just slightly larger than the #7 clearance drill for a 10-32 screw:

123 Block Links - counterbore
123 Block Links – counterbore

I touched off the counterbore flutes on the sides of the hole, then drilled downward half the 12.8 mm actual rod diameter:

123 Block Links - 10-32 SHCS test fit
123 Block Links – 10-32 SHCS test fit

Lower the counterbore into the hole again, relax the vise enough to let the rod slide, jog the spindle to X = -25.4 mm, and tighten the vise again:

123 Block Links - index setup
123 Block Links – index setup

I figured I needed four pins, tops, so make half a dozen to be sure:

123 Block Links - all c-bored
123 Block Links – all c-bored

Stick the rod in the mini-lathe chuck, add some comfort marks, and prepare to peel it down to 8.2 mm:

123 Block Links - lathe setup
123 Block Links – lathe setup

Having done the lathe work during a Squidwrench remote meeting, I have no pictures of the process, but it goes a little something like this:

  • Peel off 0.5 mm at a time, stopping just beyond the mark on the left
  • Mark 3/8 inch on each side of the hole center
  • Face the end
  • Chamfer the rim with a file
  • Clean up the body hole and counterbore
  • Part the pin off a bit to the left of the mark
  • Remove the rod
  • Chuck the pin with the cut off end outward
  • Face to the mark
  • Chamfer
  • Repeat for all six pins
  • Done!

It’s tedious, but not particularly difficult.

Futher doodling suggested the need for threaded pins to join two blocks together.

Snow Flow

The recent snowfall arrived on a stiff north wind layering it atop the garage roof and sculpting the corner:

Snow - roof wave
Snow – roof wave

The retaining wall along the driveway accumulated a thick coat that gradually peeled off as the weather warmed:

Snow - wall wave A
Snow – wall wave A

The wave crashed to the driveway in slow motion:

Snow - wall wave B
Snow – wall wave B

It seems to rebound from the wall, even though we know it’s been there all along:

Snow - wall wave C
Snow – wall wave C

This winter has more snow in store for us, but so far it’s been more decorative than disastrous.

One difference between deep snow and strong hurricanes: not much looting after the snow stops falling…

Aerosol Can Corrosion

An odd smell in the Basement Laboratory Chemical Warehouse led to this discovery:

Leaking aerosol can
Leaking aerosol can

It’s a can of spray-on topical anesthetic That Came With The House™, so it’s almost certainly four decades old and, other than being moved to that shelf, hasn’t been touched in the last quarter century.

Surprisingly, the orange-brown goo wiped off the shelf almost completely. The similarly old box of stain remover on the left was a dead loss.

MOSFET Astable: NP-BX1 Rundown

After eight months from a full charge, an old NP-BX1 lithium battery has come to this:

Astable green - NP-BX1 - 2.31 V
Astable green – NP-BX1 – 2.31 V

The astable still ticks along at 1.4 seconds per blink, but the green LED barely lights up from a 2.1 V battery:

Astable green - NP-BX1 - 12 mV 100 ohm
Astable green – NP-BX1 – 12 mV 100 ohm

A pulse of 12 mV across the 100 Ω resistor puts the LED current at a mere 120 µA: no wonder the poor thing wasn’t visible in ordinary room light.

Another full charge restored its vigor for another couple of seasons.