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.

Author: Ed

Arch Linux: Downgrading Clipman
Come to find out that the new cut-n-paste handler in Inkscape 0.47 collides mightily with (among other things) Clipman 1.1.3, the xfce4 clipboard manager, as mentioned in bugs 487653 and 418242.

Seeing as how I depend on Clipman, the least-disruptive course of action seems to be downgrading it to 1.1.1, which required some fiddling with the Arch Build System.

I have a build tree set up in /var/abs/local, so…
```
cd /var/abs/local
cp -r /var/abs/extra/xfce4-clipman-plugin/ .
cd xfce4-clipman-plugin
```
The PKGBUILD file tells us that source tarballs are available at
```
source=(http://archive.xfce.org/src/panel-plugins/${pkgname}/1.1/${pkgname}-${pkgver}.tar.bz2)
md5sums=('2ba70c6bd710e2a18cba5add66d297dc')
```
Go there, get the md5 sum for the 1.1.1 package, then edit the PKGBUILD to suit:
```
pkgver=1.1.1
... snippage ...
md5sums=('0884207cabd3a3a94c86b919bbf1617b')
```
Remove the existing package, build & install the new / old one:
```
sudo packman -R xfce4-clipman-plugin
makepkg -s
sudo pacman -U xfce4-clipman-plugin-1.1.1-1-i686.pkg.tar.xz
```
Then edit /etc/pacman.conf to ensure Clipman remains obsolete:
```
IgnorePkg   = xfce4-clipman-plugin
```
Restart the panels:
```
xfce4-panel -r
```
And it seems to work just fine…

Doc for this is pretty good: building custom ABS packages and downgrading packages. The trick was finding the backlevel versions, which stumped me until I dug into the PKGBUILD file.

It’s worth nothing that this conflict isn’t unique to Arch Linux: the same problem is affecting other distros, too. What is unique to Arch is that it’ll distribute the fix earlier than anybody else, too, because as soon as the upstream versions change, they’re in the Arch repositories.

Memo to Self: remember to un-wedge Clipman when Inkscape gets its act together. Fortunately, pacman reports which packages it’s ignoring.
2010-05-23
Kmail: FAIL

In the unlikely event you’re keeping track of this, slashing the total volume of email made Kmail much more competent: it hadn’t trashed an index file in, oh, weeks…

Until it happened again.

I don’t know that 30 days of email is magic, but 64 MB worked much better than 3 GB. The offending folder has all of 6 MB and 280 files, which puts a pathetic upper bound on Kmail’s good behavior.

Anyhow, Kmail still screws up its indexes, but … it’s better than it was.

You’d think this would be an important thing to get right, but the KDE apparat has far more important things to worry about. Eye candy, as nearly as I can tell.

I use Kmail because it’s one of the few email readers that stores messages in maildir format. That’s important with large email collections, because mbox, the other choice, tucks all the messages into a single honkin’ big file (perhaps one file per folder). That doesn’t work well with a daily backup strategy, because each message changes the file and triggers a backup of the whole thing. Maildir format means backing up only the new messages, which makes far more sense.

But, if this blank email thing continues, it’s time to move on…

2010-05-22
Unit Pricing Obfuscation
The idea behind unit pricing was to simplify comparisons between packages with different quantities: each package would have a price-per-unit value.

Here are the two shelf labels for two sizes of the lah-dee-dah fluoridating remineralizing mouthwash that our young lady must use for the next few years. The unit price is in the orange block, with some fine print underneath giving the unit. Click for a bigger image; you’ll probably need it.

Unit Pricing Obfuscation

Need a bit more help? Here’s the one on the left:

Price Per Pound

And the one on the right:

Price Per Quart

For those of you in the rest of the world with volumes in liters and weights (uh, masses) in kilograms:
- 1 pint = 0.5 quart = 1 pound of water
What’s most interesting is that this only occurs when the package with the larger quantity has a higher per-unit price, as with these bottles.

This is a perfect example of something that’s technically legal, but definitely not in keeping with the spirit of the law.

Another interesting situation: if a shelf pricing sticker is missing for one of several similar items, you can be absolutely certain that package is more expensive. A missing shelf price sticker is technically illegal, but I doubt anybody ever gets prosecuted… it’s a simple mistake that could happen to anyone, right?

Because nothing in a Walmart store is left to happenstance, this is obviously planned and approved at the highest levels.

It happens elsewhere, too, but we just happened to be in Walmart this morning. Check it out where you shop…
2010-05-21
Power Outlet Expander Failure

Multi-Scorched Multi-Outlet Box

This story begins years ago, as mentioned there. I’d retrieved the offending outlet expander / extension cord from my mother’s apartment and tossed it in my big box of Extension Cords.

I recently plugged it in and was rewarded with a flash-bang inside the box. Taking it apart reveals two more blackened outlet compartments (in the lower right), but no more missing contact blades.

It turns out that the black (hot) wire got caught between a stiffening rib on the back plate and the edge of the box supporting the brass plate connecting the white (neutral) wire to the contacts. Here’s reconstructed view after I cut off the extension cord.

Crushed wire

Flipping the wire over shows the spot where the copper conductor eventually poked through the insulation.

Exposed conductor

It touched the sharp corner of the brass strip just to the left of the divider in this view. The notch in the divider channeled the jet of burning debris across the far wall of the right-hand compartment. The left-hand compartment is completely smudged.

Short-circuit point and debris jets

Looks like I get credit for this one… but even seeing how I did it, I’m not sure there’s any way to know none of the wires got crushed while reassembling the box.

It’s safely in the trash and the cord is in my big box of Random Power Cords.

Memo to Self: Make sure the box fits together smoothly?

2010-05-20
Rewiring Cheese Slicers

Cheese slicers

My ladies favor hard cheeses that are murder on cheese slicers. I just replaced the wires on a pair of favorite slicers, using 0.020 inch stainless wire. That’s thicker than the 14-mil wire they came with, so I’m hoping it’ll last longer.

Being thicker, it’s also harder to push through the cheese, so it’s subject to more force and might break sooner. Ah, tradeoffs…

What I really want are monomolecular wires that can cut through anything…

I’ve suggested using a knife on the Romano and Gruyere, reserving the slicers for Cheddar and other sissy cheeses…

Oh, the red stuff on the right-hand slicer is Liquid Electrical Tape. The handle is raw aluminum and leaves smudges all over the place. I’m assuming the layer doesn’t have much lead content, but who knows?

2010-05-19
Re-rebuilding a Recumbent Antenna Mount

Antenna Mount

Quite a while ago, I built this slab mount to hold an amateur radio antenna on our daughter’s Tour Easy. It worked fine until the bike blew over and whacked the antenna whip against something solid, at which point the mast cracked.

The antenna screws into an ordinary panel-mount UHF connector secured to the bottom of the slab, with a hole through the slab just large enough to accept the antenna mast. That put all the mechanical stress on the slab, not the connector.

Modified antenna mounting plate

Alas, the new antenna had a slightly different mast outside diameter, so I machined a new adapter to clamp the connector atop the slab. The antenna screws down into the adapter against a brass washer, again keeping the strain on the fitting.

I recently found the commercial mobile antenna cable that I’d been meaning to use on her bike, which required Yet Another Modification to that slab. It turns out that the UHF connector on the cable expects to be secured to sheet metal found in a car body, rather than a half-inch aluminum plate: the threads aren’t long enough!

So I machined circular recesses on the top and bottom to hold the mounting nut and washer, respectively, with 2 mm of aluminum remaining in the middle of the slab.

Milling top recess

The recesses are just fractionally larger than the nut & washer, so most of the stress gets transmitted directly to the slab. Even in the high-vibration bicycle environment, I think there’s enough meat in there to prevent fatigue fractures.

Milling bottom recess

I recycled a G-Code routine I’d written to chew out circular recesses. It does a bit of gratuitous (for this application, anyway) spiraling in toward the center, but got the job done without my having to think too much.

The bottom view shows the washer in action. The recess is deep enough that the cable just barely clears the slab.

Modified mounting plate – bottom

The top view shows the recessed mounting nut. The nut has an O-ring around the connector threads, but the water will probably drain out through the four through-holes left over from the old panel-mount connector.

Modified mounting plate

I turned the top nut down as far as I could with a wrench & (ugh) needle-nose pliers, then tightened the bottom nut about 1/3 turns with a wrench.

You’re not supposed to notice the crispy edges on the PVC bushing holding the reflector to the antenna mast. The high setting on that heat gun is a real toaster…

The G-Code is over there.

2010-05-18
Padded Spring Clamp Tips

Padded Spring Clamp Tips

The OEM padding on the ends of my spring clamps wore off long ago; it was some sort of entirely-too-soft dipped plastic.

Some large-diameter heatshrink tubing seems like it ought to be a good replacement… the tips are a bit floppy, but maybe that’s not entirely a Bad Thing.

We shall see…

2010-05-17