Archive for October, 2010

Monthly Aphorism: Fundamental Principles of Rope

Two fundamental Principles of Rope:

  1. You cannot push a rope.
  2. If a tangle of rope has one end, it must have at least one other.

The First Principle should be obvious, but all too often I find myself trying to thread a wire through a structure… and eventually realize I’m attempting something that’s isomorphic to pushing a rope. Doesn’t work, never has, never will.

The Second Principle comes in handy with hoses and cables. If you separate the tangle into two parts, any part without an end is topologically either a knot or a loop, but won’t contribute much to the untangling. Conversely, any part with an end can be reduced to a straight section (possibly leading to a tangle in the other part) by fiddling around for a while.

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Dehumidifier Performance

Having ever so many books & papers in the Basement Shop & Office, I must run a dehumidifier to fight the mildew to a standstill. It’s actually under 55% most of the time, but humid summer days are killers.

Being the sort of bear who owns a Kill-A-Watt meter, I jotted down dates, runtime hours, and kWh when I filled each 5-gallon bucket. Eventually, we acquired a cheap scale that found its way under the buckets to weigh the outgoing water.

My data collection foundered on errors of omission, power failures, and general forgetfulness, but, nonetheless, a few interesting numbers emerged.

Outside weather:

  • Dry weather = 0.14 kWh/elapsed hour
  • Wet weather = 0.37 kWh/elapsed hour

It draws about 485 W, so the duty cycle works out to

  • 0.14 kWh/hour -> 140 W -> 29%
  • 0.37 kWh/elapsed hour -> 370 W -> 76%

If I were more industrious, I’d grab a plot of daily humidity from the NWS and rub those numbers against it, but … maybe next year.

The thing requires somewhere between 2.0 and 3.5 kWh to extract each pound of water. It’s rated at 1.6 liter / kWh = 3.5 lb / kWh, undoubtedly under standard conditions, so the actual efficiency is in the right ballpark.

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Microsoft Comfort Curve Keyboard Cleanout

Pin punch in keycap stem

Pin punch in keycap stem

Comes a time in the life of every keyboard when you must simply tear it apart to clean out the crud. I’ve been using a Microsoft Comfort Curve keyboard for several years and it’s worked well, but the grunge finally exceeded even my lax standards.

A handful of screws secures the bottom cover; the shortest screws run down the middle. Surprisingly, the giant HEALTH WARNING label doesn’t cover any screws. A row of gentle snap latches along the edges holds the covers together; ease them apart with a small screwdriver or your fingernails.

The lower cover holds the crosspoint matrix under a giant silicone rubber spring mat, with the USB interface board to the upper left. I left those in place, as the top cover captured nearly all the crud.

The keycaps have stems that slide in guide tubes molded into the top cover, with triangular latches that both secure the stem and prevent it from rotating. I used a small pin punch to push the keycaps out, as shown in the top picture; the punch much be small enough to allow the latches to bend inward as they clear the notches.

Keycap retaining latches

Keycap retaining latches

The larger keys have equalizing wire bails that latch under guides molded into the top cover. They’ll slide right out, but don’t shove the pin punch too far too fast.

Keycaps with equalizing wires

Keycaps with equalizing wires

Many of the keycap stems have ridges along their length to ensure each one fits only in its proper position; the triangular latches also have different orientations. This view shows the numeric pad (from the “screen” side of the keyboard) with a variety of coded guide tubes, wire bail guides, and the surprisingly deep tub underneath the keycaps that may capture much of the inevitable liquid spill and route it out the drain hole near the far edge.

Keyboard top panel

Keyboard top panel

I tossed the keycaps and top cover in the dishwasher, which did a wonderful job of cleaning them out. A dab of silicone grease on the wire bail contact points should keep them sliding freely.

Reassembly is in reverse order, although I defy you to put all the keycaps back in their proper places without referring to another keyboard…

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Ending an Antenna Rattle

This Comet HT-224 antenna fits on my Kenwood TH-F6A radio, but the connector fitting is just slightly too long / short / something: it moves just a little bit, even with the nut firmly tightened.

This isn’t a real fix, but it pretty much eliminates the rattle: a rubber O-ring between the nut and the antenna…

Antenna connector and O-ring

Antenna connector and O-ring

The ring lasts for a few years, then cracks and falls off. My O-ring stash has what could possibly be a lifetime supply.

Antenna with O-ring in place

Antenna with O-ring in place

There’s a wrap of tape around the label, just for neatness.

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Cusinart Santoku Knife

The killer discount coupon that brought a new cutting board into the house also produced a new santoku knife from Cusinart (not that that makes much difference), seen here with my favorite knife:

Santoku knives

Santoku knives

Pursuant to that discussion, I’ve been looking for a Teflon-coated Santoku blade, but nobody in the area seems to have one.

This one claims that the row of dimples on each side make cheese slices slide right off, but that’s not what happens. Maybe it’s not quite so sticky as my knives, but I’d call it a tie.

Likes:

  • It’s scary sharp, but so are my knives. In fact, I think mine are even more keen, because the blade is thinner.
  • The metal handle feels better than I expected. Dishwasher safe, not that we run ‘em through there very often.
  • Thin blade with good keen edge.
  • Surprisingly light, despite the handle.

Dislikes:

  • Weird balance point, maybe 20 mm back from the heel. It wants to fall out of the dish drainer.
  • The heel is an obtuse angle; I like an acute heel to punch into things like orange peels and milk jugs (to convert them into worm compost bins). Nothing I can’t fix with a grinding wheel, but I’m letting it slide for now.
  • The blade is curved, which means I can’t just whack my way along the veggies.
  • The handle is marginally too close to the cutting board for my fingers: I tend to knock my knuckles on the board when rocking through the cut.

On the other paw, maybe you can see how the blade near the heel on the old knife is getting ever so slightly hollowed out from my use of the steel. The new flat cutting board makes that embarrassingly obvious; it’s getting to be time for a trip to the slow stone.

All in all, pretty good. I use it, but not as much as the Good Old Knives.

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Floor Lamp Base: Poor Planning

Floor lamp base - cord exit

Floor lamp base - cord exit

We have an old floor lamp that’s always been a bit tippy and I finally got around to wondering what’s going on.

The cord exits through the center of the base, where it passes through a plastic nut that keeps it off the raw metal edge of the central rod holding the lamp together.

The ruler has 1/16 inch divisions, so the cord requires a bit over half an inch of clearance.

Floor lamp foot with bumper

Floor lamp foot with bumper

Here’s what one of the five molded-in feet look like, with a white rubber bumper that I just added to improve the ground clearance…

Notice that the foot is barely 1/4 inch tall, so the lamp has always been resting on the cord and two other randomly chosen feet. No wonder the thing was tippy.

The new rubber feet make it a lot less tippy, but there’s not a lot of clearance under there. When one of those things falls off, I’ll think of something better.

The lamp was nominally UL approved, of course…

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Foxconn R20-D2 Case vs. Optical Drive: Button Padding

Extended optical drive button

Extended optical drive button

So I stuck a CD-RW drive into the Foxconn Atom box and discovered that the pushbutton on the front panel doesn’t move quite far enough to actually hit the corresponding button on the drive.

Popped another drive off the heap and tried it out, just for grins, with the same result. Evidently the cute little ribbed back on the silvered panel button (near the bottom of the picture) isn’t quite long enough.

Solution: a bit of rubberized high-traction tape stuck to the drive button (near the top of the picture).

This is a black-on-black situation, so I pushed the contrast enough that you can actually see it.

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