Posts Tagged Repairs
After all the height map tweaking, Slic3r duplicated the Tux and SqWr STL positive models, distributed them on the platform, and the small molds printed out easily enough:
The larger pin plate wasn’t quite as successful. Despite what this might look like, that’s the same black PLA as the smaller molds:
I used 10% infill density, which was structurally good enough for a very light slab, but it left large gaps near the side walls that the top fill didn’t quite cover. Part of the problem was that the walls, being cylindrical sections, kept overhanging toward the inside, leaving the top fill nothing to grab around the nearly tangential perimeter. I think printing the slab upside-down, with the top surface against the platform, would solve that problem and also produce a glass-smooth surface under the positive molds.
I took the easy way out by troweling JB KwikWeld epoxy into the holes, smoothing it, and sanding the surfaces more-or-less smooth. That should suffice to cast the negative mold in silicone over everything, but it sure ain’t pretty:
The molds are just sitting on their pegs and haven’t been taped in place; the lower-left Tux appears to be making a break for freedom.
The Mighty Thor will do the silicone negative mold… and the further I stay away from the chocolate tempering & pouring process, the better it’ll be for all parties concerned.
The speed control pedal on Mary’s sewing machine once again started racing away from a dead stop, which we now know means more disks inside the carbon pile rheostat have disintegrated. It looked pretty much the same as when I took it apart in 2009:
This time, it had one cracked wafer and several thin ones, reducing the length of the stacks so much that the pedal exerted very little force (thus, not starting the motor) before the shorting contacts caused a runaway.
Back then, I’d machined two brass disks to fill the empty space:
A rough measurement showed I’d have to double their thickness to about 7 mm each, but it seemed like replacing high-resistance carbon with low-resistance brass wasn’t a Good Idea, at least when taken to an extreme. Not knowing what would count as an extreme in this situation, I decided to replace the brass disks with graphite cylinders sized to fill up the empty space.
The Little Box o’ Machinable Graphite produced a small bar, from which I sliced a square with jeweler’s pull saw:
Cutting that in half, then one of the bars in half, produced a pair of cubes:
I tried sanding off the corners:
After it became painfully obvious that process would take just slightly less than forever, I deployed the Dremel sanding drum:
Much to my surprise, the shop vacuum didn’t quite inhale the cloth, I didn’t drop either of the cylinders into its gaping maw or sand away my fingertips, and the cylinders emerged more-or-less good looking. I sanded the faces reasonably smooth and parallel, removed a few high spots left by the Dremel, and the cylinders slid neatly into the holes in the ceramic rheostat.
I felt a definite kinship with those guys in the rackets (not squash, as I once knew) court under the stadium seats…
I put the cylinders at the end of the stacks, against the graphite buttons (shown in the top picture), and left the disks to settle themselves against the brass contacts. In retrospect, I should have put the cylinders against the brass, so that the inevitable erosion will chew on the (relatively) easily replaced bulk cylinders.
Each graphite cylinder displaced six disks, so now I have some spares for next time. I’m certain that the graphite has lower resistance than the equivalent length of disks, but it’s probably higher than the same length of brass. I was not going to slice those cylinders into disks.
After vigorous and repeated handwashing with gritty cleaner after leaving the Basement Laboratory Workshop, the pedal assembly went back together smoothly and, once again, operates the way it should: controllable smooth low speeds, crazy-fast high speeds, and a steady transition between the two. Mary has resumed quilting up a storm.
That shop vacuum may never forgive me, but it totally eliminated all the carbon dust from the work area. The filter started out coated with a generous layer of dust and crud, so I’m pretty sure it collected most of the very fine dust, too.
I briefly considered using the lathe, but came to my senses.
The cheap way to do AC motor speed control involves a triac chopping the sine wave, so as to produce all manner of hash above and beyond the usual motor commutation noise. It occurs to me that the sewing machine has a universal motor that would run just as happily on 120 V DC as it does on AC, so a cheap 120 V DC supply (around 2 A should suffice) from the usual eBay supplier and a high voltage MOSFET on a generous heatsink would work even better. One might even get by with just a full-wave rectifier bridge and pulsating DC.
The rheostat doesn’t dissipate more than a few watts, I think, so thermal management should not pose a serious problem.
The motor rating says it’s good for 1 A, which means the power should be less than a few tens of watts. Some resistance and current measurements are in order.
You can actually buy replacement pedals, but what’s the fun in that?
The fancy OXO can opener doesn’t work well on #10 cans, so we bought a not-bottom-dollar can opener with comfy handles to replace the one that convinced us to get the OXO. After maybe a year, tops, it gradually stopped working well, too, which prompted a trip to the Basement Shop Workbench.
- The handle wouldn’t move the cutter during maybe 1/4 of its revolution
- It pushed the handles apart during another quarter turn
Look carefully and you’ll see the teeth sticking out slightly more on the right side of the drive wheel:
When those protruding teeth line up with the gear behind the cutter wheel, the handles open and the drive wheel loses its grip. When the low side lines up with the cutter gear, the gears very nearly disengage.
Taking it apart shows that both “gears” (which is using the term loosely) have been pretty well chewed up:
Destroying those gears should require a lot more strength than either of us can deploy on a regular basis, which suggests they used mighty soft steel. It’s not obvious, but the drive gear hole is just slightly larger than the screw thread OD; it doesn’t ride on an unthreaded part of the screw shaft.
I’m not in the mood for gear cutting right now, so I filed down the wrecked teeth and buttoned them up with some attention to centering the gear. The can opener works, but sheesh this is getting tedious…
The pushbutton on the X10 wall switch controlling the fiercely incandescent lamp over the kitchen table has gotten erratic, so I dug into the Big Box o’ X10 Crap for a replacement. Turns out The Box has only 3-way switches, but the lamp needs a standard two-wire switch.
The instruction sheet shows this diagram:
The pushbutton on the CS277 “Companion” switch connects the red lead to the two blue leads. The blue leads are always connected together and carry the lamp current, so the red lead is just a signal from the remote button.
The WS477 “Master” switch will work as an ordinary switch if you cap the red lead with a wire nut and tuck it into the box.
Shortly after replacing the battery, the dreaded Malfunction Indicator Lamp popped on with a P0420 error code that, according to the Nice Man at Autozone, translates into “low catalytic converter efficiency”. A bit of diagnostic sleuthing reported that the most likely cause was an exhaust leak, followed by an out-of-calibration downstream oxygen sensor, followed by a bad converter. Internet lore has it that replacing the cat cracker is a dealer-only event (here in New York State, with a van sporting the California emissions package) that costs upwards of $2 k, which seems excessive for a 14-year-old van.
Actually, the most probable cause was replacing the battery: the brief power outage wipes out the stored performance data for the emissions control machinery. Because we make only short trips and it’s been bitterly cold, the algorithms may conclude the converter’s dead when it’s just a matter of measuring the variables under suboptimal conditions.
With all that in mind, after a peek under the van ruled out the exhaust leak, I decided to replace the oxygen sensor. All this happened during a week when the outdoor temperature hovered around 10 °F = -12 °C, but the forecast called for an atypical January day with a high of 55 °F = 13 °C; I might not get a second chance before the annual inspection came due in February.
The sensor is relatively cheap (about $70 at the local Autozone) and, entirely unlike Bank 1 Sensor 1, readily accessible on the tailpipe downstream of the cat cracker:
The OEM sensor cable runs in a sheath held to the chassis with a plastic clamp:
Jamming a small screwdriver into the clamp released the tongue and the sheath. The sheath vanishes into the van’s interior through a squishy rubber boot, with a crimped metal band joining the two:
Internet lore would have you believe you can replace the sensor without removing the front passenger seat, but it’s much easier if you remove the four bolts, disconnect the seat sensor, and lay the seat on its back:
More fiddly-diddly with the screwdriver under the van wrecked the band enough to separate sheath from boot, at which point deploying the BFW with the magic oxygen sensor socket showed that the anti-seize compound on the sensor’s thread worked as intended: after one oomph the sensor turned out by hand.
Then you just punch the boot through the floor and bring it all inside to splice new sensor onto OEM connector. Standardization is a wonderful thing; the sensor cable may use any one of eight color codes. The Toyota OEM sensor was a “Type B” that matches up with the Bosch replacement sensor thusly:
- Heater = two black leads ↔ two white leads
- Signal = blue lead ↔ black lead
- Ground = white lead ↔ gray lead
Although the splice block has water-resistant seals, I figured putting it inside the van couldn’t possibly be a Bad Idea, so there it is, nestled snugly into the recess in the floor:
Picked up a nice new Autel AL519 OBD Code Scanner from the usual Amazon vendor, reset the trouble code, drove to-and-from Squidwrench (across the river, just barely far enough to reset the performance data), and so far it’s All Good. The motivation for getting my very own scanner, rather than returning to Autozone, is that the AL519 can do real-time graphing and data capture from various sensors, so I can perform Science! should the spirit move me.
The AL519 has a USB connection that appears as a USB serial device but, alas, the relentlessly Windows-centric host program won’t run under Wine.
The strut supporting the two drawers in the bottom of the refrigerator came out in two pieces during a recent cleaning session. To judge from the condition of the joint, I’d done this once before in its history:
That tab inserts into a slot in the front of the elaborate frame that supports the drawers, where it’s captured by a metal bar. Should you lift the rear of the strut without first removing the bar, the tab snaps off at the base. I’ve annotated the top of the strut in the hopes of reminding me the next time around.
A pair of bumps at the front of the drawer guides should hold the drawers closed, but it’s pretty obvious that’s not working as intended:
I shaped strips of phosphor bronze spring stock around the bumps:
The bottom view shows they’re held in place by crimps and a generous dollop of faith:
That should serve until I know whether the plastic drawer rail will carve through the metal. The drawers slide out with much more enthusiasm now, so it’s a Good Thing until something else breaks.
Yes, this is the refrigerator with the Freezer Dog…
A circular polarizer screwed on the lens:
A sheet of linear polarizing film held in front of the lens:
For reference, none of the other instrument faceplates on the bench show anything other than uniform gray, with one exception that points directly to the plastic injection point.
I’d say this plate cracked due to unrelieved internal stresses and not anything I did or didn’t do.