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.

Tag: Improvements

Making the world a better place, one piece at a time

Dual Displays vs Wacom Tablet vs xorg.conf
So, as I wondered there, it turns out that the tablet cursor can fall into the crack between my landscape left monitor and portrait right monitor, with the distressing result that the X server jams with the pointer jittering between the two displays. Worse, the keyboard isn’t active, so I can’t switch to a console screen and shoot X in the head.

I’m guessing this is a picket-fence error, where Something Bad Happens when the cursor hits the maximum possible value: X=16704, in this case.

The solution seems to be telling the Wacom driver that the tablet is just slightly wider than it really is, so that the X value can’t ever reach the maximum. Having done this before, the line is already in my xorg.conf, just waiting to be un-commented:
```
Section "InputDevice"
    Identifier      "Wacom - stylus"
    Driver          "wacom"
    Option          "Device" "/dev/input/wacom"
    Option          "USB" "on"
    Option          "Type" "stylus"
    Option          "Button2" "3"
    Option          "Button3" "2"
    Option          "MMonitor" "off"
    Option          "ScreenNo" "0"
    Option          "BottomX" "16710"
#    Option          "BottomY" "11893"
EndSection

Section "InputDevice"
    Identifier      "Wacom - eraser"
    Option          "Device" "/dev/input/wacom"
    Driver          "wacom"
    Option          "USB" "on"
    Option          "Type" "eraser"
    Option          "MMonitor" "off"
    Option          "ScreenNo" "0"
    Option          "BottomX" "16710"
#    Option          "BottomY" "11893"
EndSection
```
That seems to work, but the failure was intermittent. We shall see…
2010-10-01
CPU Heatsink: Flattening Thereof

I suppose I should have known better: the bottom of that heatsink wasn’t anywhere near flat. I think it mated directly with the top of the CPU through thermal grease, not a compliant pad.

Curved copper heatsink surface

The obvious solution is to flycut the thing, which is where the Sherline’s limited Y-axis travel and teeny table put a cramp on your style. Normally, you’d put the length of the heatsink parallel to the X axis so the flycutter would clear on both ends, but there’s no obvious (read: quick and easy) way to clamp the thing that way.

So I mounted it parallel to the Y axis, which meant I couldn’t get the flycutter completely off the near end. The first pass at Z=-0.1 mm, however, showed that not only was the surface curved, but it wasn’t parallel to the top of the fins (which were flat on the tooling plate). I suppose I should have expected that.

This cut is has Z=-0.1 mm referred to the front end. It completely missed the other end:

First flycut pass

I flipped the heatsink around, measured the front-to-back tilt (about 0.16 mm), stuck a couple of brass shims under the front, and the second pass at Z=-0.05 mm from the new low point did the trick. Copper is nasty stuff and I did these cuts dry: the chips visible near the front are stuck firmly to the surface.

Final flycut pass

I scrubbed both the heatsink and the spreader plate on some fine sandpaper atop the sacrificial side of my surface plate until they were all good. I can see the remaining flycutter marks, but I can’t feel them, and the plates slap solidly together with a pffff of escaping air:

Flattened heatsink and spreader

A dab of heatsink compound should work wonders; the maximum dissipation will be under 20 W, roughly comparable to that old K6 CPU, but now the heatsink will be contacting the entire hot surface.

2010-09-22
New Theme?

There’s no way to tell if a theme will actually look right without enabling it and investing an hour fiddling with the options.

That’s why it looks different with each refresh…

2010-09-21
Comfy Office Desk Chair
Chair from auto seat

Most office desk chairs are crap. Spend a couple of hours in a typical office chair and you wonder if it had been designed by aliens who, perhaps, read the specs for human beings, but never actually met a person in the flesh.

Conversely, you can drive for a couple of hours and get out of the car feeling at least OK. (Well, if you buy a decent car, that is. Last rental car I drove had terrible seats.)

Anyway, you can buy an office chair made from a car seat, but they seem staggeringly expensive for what you get.

So, a couple of decades ago, I went to a junkyard and picked up a nice seat from a fancy wreck for about $50, built a plywood base with six casters from Home Depot, put a 1-foot-diameter Lazy Susan bearing between the two, and bolted everything together. The seat even had power adjustments, so (just for fun) I tucked a battery underneath.

After a while, I stripped off the seat belt doodads… and, of course, you really don’t need power adjustments after the first week.

Worked like a champ for about a decade, but even a high-end seat cushion eventually goes flat. So I swapped in a front seat salvaged from one of our cars (a Toyota Camry wagon, from back before minivans ruled the road) and that lasted another decade. It finally went flat and I swapped in the other front seat.

The 2×6-inch upright boards have slopes and cutouts that match the peculiar shape of the seat frame, with holes drilled in the wood for the metric machine bolts, and that’s a good enough anchorage for an office environment.

Chair base

The Lazy Susan bearing is between the top plywood layer and the square corner sticking out to the front. That layer bolts to the bottom sheet, providing enough clearance for the various heads and whatnot.

You really need six casters on a fairly large base, because the chair is immensely heavy (it was, after all, designed to not fall apart during a full-on collision) and rather top-and-back-heavy without you in place.

Considerations:
- Get the seat close to the right height, as the adjustment range isn’t all that wide
- Put your center of gravity in the middle of the base. Fortunately, the seat has plenty of forward-aft adjustment
- Get the seat base pretty much horizontal
A closer look at the front:

Front detail

The back isn’t a lot different:

Back detail

Maybe I just have a weird butt or don’t spend enough money on office chairs.
2010-09-21
Continuous Ink Reservoirs: Elevation Thereof

Do Not Raise External Ink Reservoir

The continuous ink system I have on the Epson R380 occasionally stops the yellow ink flow. I think it’s related to back pressure: the lines drain down quickly after the printer stops and the yellow line is on top.

The label on the front of the continuous ink supply reservoir minces no words:

Do not raise the external ink reservoir higher because of curiosity or insufficient ink-supply …

Well, maybe a little bit won’t hurt?

As it turns out, the original ink tanks inside the printer are pretty high up, with the bottom of the print heads maybe 60 mm off the table. That chunk of foam packing material is 40 mm tall: the bottom of the ink supply remains well below the heads.

The ink supply tubes drain back a few cm when the printer has been idle, which means the elevated reservoir isn’t applying positive pressure to the heads. And, after a few weeks of this treatment, the yellow ink flow hasn’t stopped!

I’ll call it a win.

Here’s the overall view, with a few ink splotches visible from previous blunders. If the table wasn’t a raw slab of half-inch plywood bolted to a surplus printer (?) stand in the basement, I’d care a lot more…

Elevated continuous ink reservoir

The amount of ink in the waste ink tank beside the printer is breathtaking: about 50% more than noted there.

2010-09-20
Third Eye Hardshell Mirror Repair

Alas, the mirror I installed this spring didn’t survive our bicycling vacation; it succumbed to the second of three stuff-all-the-bikes-in-a-truck schleps arranged by the tour organizers. Being that sort of bear, I had a spare mirror, duct-taped it in place, lashed it down with some cable ties, and we completed the mission.

So.

Back to the Basement Laboratory Plastic Repair Wing.

The strut broke just behind the ball at the mirror, which implies the mirror plate got stuffed against something, rather bending the strut. The ball joint still worked, so I maneuvered the stub perpendicular to the mirror.

Drilling the strut

Normally I’d try to re-glue the joint as-is to get the best fit, but past experience shows that if it breaks once, it’ll break there again. I wanted to put some reinforcement into the strut, not just depend on a solvent glue joint. Some rummaging in the brass tubing stock produced a 1/16-inch diameter aluminum (!) tube about 18 mm long: just what’s needed.

So I filed the deformed plastic flat & perpendicular to the stubs, mounted the strut in the 3-jaw chuck on the Sherline’s table, lined the spindle up with the axis, and poked a 1/16-inch hole into the strut. The alignment looks decidedly off in the picture, but it’s actually spot on: what you’re seeing is some swarf clinging to the far edge. Honest!

Then I grabbed the mirror plate in the 3-jaw, lined up on the stub, and drilled maybe 4 mm down, which was roughly to the middle of the ball. The tubing was a firm push-fit in the hole and I hope it won’t over-stress the plastic into cracking.

Gluing the mirror strut

Run the spindle up, remove the drill, grab the strut in the chuck (actually, I had to swap in the larger chuck first), dab some Plastruct solvent glue on both ends, align the strut with the stub (they’re actually square in that section), run the spindle down to ram the tubing into the strut, then a bit more to apply pressure to the joint. I made the total hole depth about 2 mm longer than the tubing, so as to avoid the embarrassment of having the ends not quite meet in the middle.

No CNC; pure manual Joggy Thing action.

Let it cure overnight.

It’s now back on Mary’s helmet, with a pair of black cable ties ensuring that it won’t pop off, and seems to be working fine. I’m sure the ball joint will fail later this year, although that won’t be due to this repair.

Mirror on helmet again

2010-09-04
Improved Tour Easy Chain Tensioner

A discussion on that post reminded me of this old project: replacing the chain pulleys in the midships chain tensioner on my Tour Easy recumbent.

The problem is that the original pulleys used steel bearings in a plastic race, for reasons that I cannot fathom. They last for a few thousand miles, then get very wobbly and noisy. The solution, as nearly as I can tell, is to replace them with pulleys using cartridge bearings.

This is what one looks like after four years slung below my bike. Surprisingly, the bearings still feel just fine, even though they’re not really sealed against the weather.

Tour Easy – Cartridge Bearing Chain Tensioner

Gotcha: the OEM pulleys are not the same OD / number of teeth as pulleys found in rear derailleurs.

Soooo, after a bit of Quality Shop Time, I had these…

Tour Easy Replacement Idler Pulley

This is where you really want an additive machining process, as I turned most of a big slab of aluminum into swarf while extracting each pulley.

The first step is to drill holes around the perimeter where the chain rollers will fit, plus drill out as much of the center bore as possible. Then mill down to the finished thickness across the roller holes and helix-mill the bore to size.

Side 1

Flip it over and mill the other side to the proper thickness.

Run it through the bandsaw to chop off all the material beyond the outer diameter.

Grab what’s left in the three-jaw chuck and mill around the perimeter to get a nice clean edge.

Side 2

And then it Just Works. I made another for Mary’s bike, but she said it was too noisy (which is why they used plastic rather than aluminum) and I swapped it for a Terracycle idler.

This is from back in the Bad Old Days before EMC2’s version of G-Code supported loops. You don’t need to see that code, trust me on this.

2010-09-01