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: Repairs

If it used to work, it can work again

  • Another Bike Flat: Michelin Hair

    Rode around the big block on some errands, stopped at the Vassar Farm garden to haul some squash home, rode off… and the bike handled poorly. Well, with a few dozen pounds of produce in the panniers that’s not unusual, but this was worse. Yup, another flat.

    This time, however, our daughter was home and could rescue me in the van. Back in the shop, I found this obvious suspect:

     

    Embedded glass fragment
    Embedded glass fragment

     

    Once again, however, this wasn’t the problem, as the tire liner was barely scuffed. Those are glass fragments inside the gash, which might actually be the same one as before.

    There weren’t any other pointy objects embedded in the tire, but the tube wouldn’t stay inflated long enough to find the leak. I took the tube upstairs, submerged it in a pan of water, and found a rash of holes. Not pinholes, not a failed tube, but a series of punctures.

     

    Steel wire fragment
    Steel wire fragment

     

    Examining the tire liner revealed the cause: a strand of what my buddy DBM calls Michelin Hair poking through the tire liner. It’s a fragment of the steel belt from a car or truck tire, most likely shed from a disintegrating semitrailer recapped tire.

    There is absolutely no defense against these things, because they have razor-sharp points on both ends where the wire fractured. When the tire picks one up, every rotation drives it through the rubber, the Kevlar belt, the tire liner, and the tube. The usual symptom is a slow leak, eventually followed by a row of holes in the tube as it shifts position under low pressure.

    In fact, the tube had a slow leak since I installed it a few weeks ago after a tube failure. I wondered if I’d inadvertently installed a fold, but now I think I ran over this wire during the first few rides and it’s been getting worse ever since.

    That tube is a goner! I installed another Schwalbe tube and we’ll see what happens; one has been working fine on Mary’s bike for the last three months.

    Here’s a look at the steel wire from the side:

     

    Steel wire fragment through tire liner
    Steel wire fragment through tire liner

     

    It was completely through the liner, with only a stub sticking out on the tire side. There’s certainly a matching hole somewhere on the tire, but it’ll be indistinguishable from all the other nicks and gashes.

  • LED Flashlight Disassembly

    Of late I’ve been toting an LED flashlight / laser pointer around in my pocket for peering into dark corners and highlighting interesting objects. It started flickering and I discovered the joint just aft of the switch had become slightly loose.

    Disassembled LED Flashlight
    Disassembled LED Flashlight

    Well, I always wondered how the thing came apart and now I know!

    The threadlocking compound seems to have turned into dusty white powder, although my pocket doesn’t seem all that hostile an environment.

    Flashlight innards
    Flashlight innards

    The switch assembly pulls out, revealing the LED circuit board with the laser module in the middle. The two wires correspond to the two ON states: flashlight and laser.

    For what it’s worth, the 8 LEDs draw 130 mA (16 mA each), far more than the 3 mA each in that pathetic work light.

    The laser draws 20 mA.

    Screwed everything back together and it works fine again…

  • X Server 1.18 vs Wacom: Back to the Mainline

    As mentioned there, I had to use the Arch Linux linuxwacom-bamboo-cth-ctl package because X Server 1.8 discarded all the carefully tweaked HAL baggage and the existing xf86-input-wacom package wasn’t yet compatible with the new server.

    That worked fine, until the most recent X Server tweak killed the Bamboo driver (which I hadn’t manually updated). As I expected, though, the new xf86-input-wacom package works just fine, so I can discard my manual workaround.

    Having recently tweaked the tablet coordinates to keep the pointer out of the gutter, I first thought I’d killed something… but that would happen instantly, not after a while. The key was looking in /var/log/Xorg.0.log to find this gem:

    [  3447.599] (II) LoadModule: "wacom"
[  3447.638] (II) Loading /usr/lib/xorg/modules/input/wacom_drv.so
[  3447.651] dlopen: /usr/lib/xorg/modules/input/wacom_drv.so: undefined symbol: dixScreenOrigins
[  3447.652] (EE) Failed to load /usr/lib/xorg/modules/input/wacom_drv.so
[  3447.652] (II) UnloadModule: "wacom"
[  3447.652] (EE) Failed to load module "wacom" (loader failed, 7)

    Removing the bamboo package seems to have wiped out the udev rule that creates the /dev/input/wacom symlink. Adding that back in, as described there, solves that problem. Again.

    The evidence in /var/log/Xorg.0.log looked like this:

    [ 52121.754] (**) Option "Device" "/dev/input/wacom"
[ 52121.754] (EE) xf86OpenSerial: Cannot open device /dev/input/wacom
        No such file or directory.
[ 52121.754] (EE) Wacom - stylus: Error opening /dev/input/wacom (No such file or directory)
[ 52121.754] (II) UnloadModule: "wacom"
[ 52121.754] (EE) PreInit returned NULL for "Wacom - stylus"
[ 52121.754] (**) Option "Device" "/dev/input/wacom"
[ 52121.754] (EE) xf86OpenSerial: Cannot open device /dev/input/wacom
        No such file or directory.
[ 52121.754] (EE) Wacom - eraser: Error opening /dev/input/wacom (No such file or directory)
[ 52121.754] (II) UnloadModule: "wacom"
[ 52121.754] (EE) PreInit returned NULL for "Wacom - eraser"

    Everything is logged somewhere: the evidence is out there!

  • Biting Through the Bite Valve

    I carry a water pack behind the seat on my Tour Easy, with the hose over my left shoulder and the valve captured by a magnetic thingie pinned to my shirt. On a recent ride I hit a substantial pothole while drinking from the tube and managed to bite completely through the miracle plastic “Bite Me” valve, mostly due to clenching my teeth in concentration rather than from the impact.

    Bitten bite valve
    Bitten bite valve

    A few days later my dim consciousness finally took note that the water kept draining down into the pack between sips: every sip came with a mouthful of air.

    A year or so ago, the original valve developed a nasty case of embedded gunk and I picked up a quartet of Genuine Nalgen valves (or a credible imitation thereof) from the usual eBay supplier. I wonder if the reservoir and tubing will outlast the remaining two valves?

  • Plastic Screw-top Flashlight Fix

    As part of my clear-off-the-workbench effort, this flashlight emerged from the dark depths. It’s a few decades old and wasn’t a good design: the “switch” is a simple contact between the end of the cell casing and the reflector rim, activated by screwing the reflector tighter on the case.

    Broken flashlight case
    Broken flashlight case

    The failure is simple: the case cracks through at the stress raiser formed where the “switch” contacts rest on a sharp inside corner. That stiff little spring maintains pressure on the cells, so the case is always under tension and eventually fractures.

    Flashlight clamped in mill
    Flashlight clamped in mill

    I grabbed the broken pieces in the lathe, turned off the fractured plastic, and wound up with a pair of nicely mating surfaces (and a somewhat shorter flashlight, but it’s still long enough). Apply enough Plastruct solvent glue to soften the new faces, then clamp them together. The big manual mill knows how to apply a strong, steady vertical force to a project like this.

    It’s once again hanging by the basement door, where it gets used roughly once every other blue moon (yeah, it’s color-coordinated). This isn’t the first time this flashlight has failed that way, but it’ll be the last: next time, it’s in the trash.

    Honest, I swear it!

  • Screwdriver Bit Ball Repair: Rubberdraulics!

    Went to use a small multi-bit screwdriver and the bit fell right out: evidently, the ball wasn’t swaged tightly enough; it and the spring went walkabout. Given that I don’t know when or where that might have happened, there’s no chance I’ll ever see those parts again.

    Screwdriver bit with missing ball
    Screwdriver bit with missing ball

    But I do have some 2 mm steel bearings that aren’t grossly oversized, so all hope is not lost. Alas, I have no idea what sort of spring to put in there, other than that I don’t have one of those.

    Drilled hole with ball
    Drilled hole with ball

    This looks like an application for rubberdraulics: use compliant silicone snot rubber as a spring. Lautard described a use with a lock ring and an external screw to apply pressure, but here it’ll work fine to allow a small motion for a tiny ball.

    Drill out the recess barely larger than the ball: the slight clearance allows the cured rubber to squish out around the ball. I clamped it in the Sherline vise and jogged into position by eyeball, then poked a hole with G83 down 1.5 mm. The original recess was a bit over 2 mm deep, so there’s plenty of room for the silicone in the bottom.

    Then mush some silicone into the hole, install the ball, push it down until it stands barely proud of the surface, scrape off the excess rubber, and let it cure overnight.

    New ball in place
    New ball in place

    There, now, that wasn’t so bad, was it?

  • AA Cell Holder: Fragile Contacts

    Broken cell holder contact
    Broken cell holder contact

    It seems I applied a bit too much pressure to one of the contacts on a metal AA cell holder: the outer rim of the rivet holding the solder tab in place departed for the distant reaches of the Basement Laboratory.

    No big deal, I thought: pop another rivet in place and get back in operation…

    You really want the rivet to go in with the flat head inside the cell holder where the original flat head was. Unfortunately, the rivet yanker’s head won’t fit into the holder; I’m pretty sure the manufacturer has a Special Machine to make that happen.

    So I put the reinforcing washer and lumpy end inside. That meant switching the insulating washers to keep the overall distance from the negative cell contact about the same.

    Cell holder rivet - inside
    Cell holder rivet – inside

    The outside looks much better…

    Cell holder rivet - outside
    Cell holder rivet – outside

    For what it’s worth, these pix came from the Sony DSC-H5 with the flash turned down 1 EV. Much better results than the Casio EX-Z850, even with its flash set to Soft (whatever that is). The H5 has much better macro capability… and with the new Eneloop cells, it lasts long enough to make it usable in the shop.