Sofa Handle Repair

2021-05-30 15:33 - General

About ten years ago I bought a recliner sofa. Early on, I tried to vary where I sat, to not wear out one part more than another. That didn't last, though. I'm a creature of habit. These days I'm always sitting in the left position, with a side table in reach. This afternoon I reached down to pull the handle that releases the recliner and snap it came off in my hand.

The (maybe) repaired recliner handle.

The first thing I did was swap the handles, they're symmetrical. Then I did my best to repair the broken one. Some CA glue held it together at first, but I've seen plenty of weaker-than-new CA glue repairs, so then I tried sinking some staple-gun staples through the plastic across the break, ideally stronger than the glue. (By heating the staple with a soldering iron, melting the plastic to make a hole.) I re-installed it in the less-used side. My first check quickly revealed some scary cracking noises, so I've left it for now.

Battery Holder

2021-05-05 20:15 - Making

A 3D printed battery holder I designed and made.

I love rechargeable batteries. Much cheaper over time, and more convenient: it's pretty easy to keep a few charged and ready, and thus never need to worry about running out or getting more. For a while I had two little plastic buckets (old takeout containers!) to hold charged and used batteries each. But that's still a bit messy, and doesn't allow for even rotation.

It's pretty easy to buy battery holders, but the ones I could find are bulky (almost all including lots of C and D cell slots I don't need) and surprisingly expensive for a little chunk of plastic. So I made my own chunk of plastic! It's just a little box with some circular holes, of the right size to fit AAA and AA cells. I can put them + side up to signal that they're charged, and build a left-to-right kind of plan to make sure I'm always picking up the oldest one to use next, and putting the used ones back in at the "end of the line".

Lights for 3D Printer

2021-04-14 21:44 - Making

I've wanted extra lighting on my 3D printer for a while, but only a little. A while back I replaced the broken extruder(s). The old ones had fans built in, but they always seemed pointless: they were mounted on the outside of the extruder, so they couldn't even cool the stepper effectively. And they were incompatible with the new extruders so they came off.

LED light strips installed on the bottom of the top layer of my 3D printer.

This left extra unused power connectors exactly where I planned on installing lights. Today I finally took the time to put some LEDs from the strip I already had in place, using that connector. They provide decent illumination, but reveal how unreliable the 12v rail is: I can now see as the heaters kick in, because they cause an immediate dip in the brightness of these LEDs. I'll need to try adding capacitor(s), at least.

Mini Tesla Coil Kit

2021-02-10 21:12 - Making

The kit as it arrived.

Stuck at home so much, my habits have shifted a bit. I haven't made much of anything in quite a while. I dropped a whole three dollars (shipped!) on a little mini tesla coil kit just to shake things up a bit. Here's how it arrived, no instructions at all, which worried me at first. But there's very few parts, and it's actually almost impossible to get them wrong. Turns out they're tiny, but the markings right on the board disambiguate everything.

Weird parts: it came with two resistors and two LEDs — and the description called this out specifically — but there's only one place to put each, same for the little capacitors: comes with two but only one spot to put one in. It came with four little feet, but there's only three spots to put them. The component nearest the middle of this shot is a neon lamp, which doesn't connect to anything at all!

The assembled mini tesla coil.

It only took a little while to assemble. Here it is in operation, hooked up to my bench power supply so I could vary, limit, and monitor the power it consumed. It claimed to need 9 to 12 volts, and it works across that range and below. It doesn't actually do very much, but it does cause quite an electric field to be established. As a result, the little neon lamp it comes with will illuminate when it's nearby and the coil is powered on. But not connected at all! Spooky!

To rather dimly illuminate this small bulb, it consumes around six watts. And the little heat sink gets quite hot!

"Fixing" my 3D Printer's Extruders

2021-02-07 15:22 - Making

I got a 3D printer a few years ago when I came into a lucky collection of free filament. Long story short, things were okay, but I had trouble with the (free) ABS filament, it's extra hard to work with. I got some PLA recently, which slightly but not totally improved things.

Broken extruder arm.

I eventually figured out that the cause was a cracked part. The "extruder" of a 3D printer is responsible for pushing the plastic filament down into the "hot end" which melts it, so that it can be laid down into the design in question. This particular part pinches the filament onto the drive gear, so that it can be pushed. And the crack means it wasn't pinching as strongly as it should, so it would slip and not move correctly.

New metal extruder parts, in place.

My 3D printer is "dual extruder", so it's capable of using two different filaments at the same time. I almost never use that, so I simply switched over to the other non-broken extruder for a while, but that wasn't a real fix. I ordered some replacement parts, made of metal instead of plastic, and here they are installed. You can see the (brass) gear in the middle, of the metal extruders in red. The spring pushes the top arm up, which pivots on the top left screw, pinching the silverish roller into the brass gear. The plastic filament goes between them, and down from here.

This much is a nice improvement. No longer does the drive gear turn but just slip past the filament, not pushed strongly into it. Now I've got a new problem to solve: for some reason somewhere around the second layer it stops trying to drive the filament at all!

Working around broken traceroute on FiOS

2021-01-12 17:42 - Tech

After a long and slow process, I've decided to "cut the cord". I haven't been using my cable subscription much lately, and I've done very well filling in the gap with over-the-air and online services. Today I took the first big step in making that happen. I had a TV and internet bundle from Spectrum cable. I got today a faster internet-only plan from Verizon FiOS, for about half the cost. It's mostly fine. But one of the first things I discovered is that mtr was misbehaving. Every host appeared two hops away, and only a few milliseconds away. I know this is not true.

$ mtr -4 --report -n
Start: 2021-01-12T16:57:18-0500
HOST: laptop                      Loss%   Snt   Last   Avg  Best  Wrst StDev
  1.|--                0.0%    10    0.8   1.3   0.8   2.7   0.6
  2.|--              0.0%    10    4.0   9.5   3.5  23.8   7.5
$ mtr -4 --report -n
Start: 2021-01-12T16:58:15-0500
HOST: laptop                      Loss%   Snt   Last   Avg  Best  Wrst StDev
  1.|--                0.0%    10    2.5   1.8   0.8   3.1   0.9
  2.|--              0.0%    10    4.7   4.9   1.9   9.8   2.5

Traceroute usually/sometimes works by sending ICMP echoes with a low TTL. Too low, so the connection fails, and the hop at that distance replies that it fails. Up the TTL by one until a successful reply, and we've found the target. Verizon is forging successful answers when only one TTL (my router, plus one) remains. I discovered this by searching around for an explanation of what was going wrong exactly, and found a forum post (on a thread from 2018, so not a very temporary issue) with an acceptable workaround. Have the router never send a packet with TTL=1, bump it up to 2 instead. This doubles the next hop, but that's the best we can get if Verizon is going to lie. Problem is, the solution was given in a proprietary (?) configuration format.

I use OpenWRT, which is "just" standard Linux. So it uses iptables. I came up with:

# iptables -t mangle -I POSTROUTING -o eth1.2 -m ttl --ttl-eq 1 -j TTL --ttl-inc 1

Phew. That's: -t mangle use the "mangle" table (manpage: "This table is used for specialized packet alteration."), -I POSTROUTING use the "POSTROUTING" chain ("for altering packets as they are about to go out"), -o eth1.2 for packets going out on the eth1.2 interface (my WAN interface), -m ttl use the "ttl" match extension module, --ttl_eq 1 the TTL value equals one, -j TTL jump to the (custom) "TTL" chain, and -ttl-inc 1 increase that TTL value by one (from one, to two).

Now Verizon never sees a TTL=1 ICMP packet coming from me, and never forges the answer, and mtr just works (except that the first hop past the router is a duplicated copy of the next hop):

$ mtr -4 --report -n
Start: 2021-01-12T17:32:33-0500
HOST: laptop                      Loss%   Snt   Last   Avg  Best  Wrst StDev
  1.|--                0.0%    10    1.2   1.0   0.8   1.2   0.1
  2.|--             0.0%    10    5.0   7.4   5.0   9.2   1.4
  3.|--             0.0%    10    5.7   8.5   4.8  15.5   3.0
  4.|-- ???                       100.0    10    0.0   0.0   0.0   0.0   0.0
  5.|--             0.0%    10    7.7   7.1   4.8   9.3   1.4
  6.|--               0.0%    10    7.3   7.4   5.4   9.4   1.1
  7.|--              0.0%    10    8.9   8.7   7.0  10.0   0.9
  8.|--              0.0%    10    9.3   7.4   5.2   9.3   1.3
  9.|--              0.0%    10    4.9   6.9   4.8  13.2   2.6

All I need to do is put this in OpenWRT's /etc/firewall.user file. Google is actually only a few milliseconds away, but they're also 9 hops away, not two.

Another Home Repair: Kitchen Sink

2020-11-14 22:06 - General

For years I've had an extremely minor leak in my kitchen sink drain. For a long time I had a try under there to catch drips, and though it clearly displayed signs of having been wet, whenever I'd check, it would also be dried out. At one point I felt like things got better and removed they tray after not seeing new signs of drips for long enough. Then things got worse. More recently I re-added a tray to catch drips, and regularly found it full of standing water. And started checking more often, and needing to empty it more and more often. Can't ignore it anymore. The drips are coming from the top joint right between the sink and the drain. So today I finally did something about it.

What I found with the drain removed.

I also feel like I've always been just a bit unhappy that the drain was off-center with regards to the opening in the sink. And when I got it out, the discharge pipe certainly does not line up with the center of the opening either. Here is where mild hijinks ensue. It took craziness to get this far: wood blocks and clamps and lots of inappropriate hammering on the lock nut to remove the drain. Now I'm stuck, if I want to fix this. I really can't see how to line the pipe up with the drain correctly, plus I'd really like to end up with a nice on-center look. So, an extra trip to Home Depot to grab a big pipe wrench, and I've got things further disassembled. I made another extra trip to grab a replacement part: Under my sink('s drain) are two 90 degree elbows, a short pipe for the dishwasher to connect to, and a huge solid brass P trap. I tried getting a different 90 degree elbow, smaller, which would move things closer in enough to (I thought) line up.

Turns out, wrong thing. Not only would it mean going from metal to plastic pieces, it didn't have the right style of connectors on both ends (threaded, both sides while I needed threaded on just one). In figuring this out I did further disassembly, and found that the existing elbows were adjustable enough to be installed so they line up correctly!

A bead of plumber

So I laid a healthy bead of plumber's putty in the sink, and (with the discharge pipe out of the way) started installing just the drain, which went pretty well. Then, re-assembled the various parts to connect to it, which also went well. It seemed. I filled up a 2-quart bucket and dumped it down to find ... worse leaks than when I started.

Thankfully all it took was re-dis-assembly to add some teflon tape (in spots where it wasn't, before I started). Tried again: no leaks, no drips at all!


There we go. Almost perfect, except tightening the last connection turned that slot a bit and it's no longer nicely lined up...

Minor home repair: window shades

2020-09-26 16:20 - General

The freshly repaired blinds in my windows.

I mostly leave my window blinds in the same spot all the time. I know the spot I like. But it's autumn and so I'm opening and closing the window, and sometimes the blinds too, to let fresh air in while it's nice outside. Recently one set of blinds started to sag on one side. I got up on a stool to check, and the hanger was loose on that side. It's been a few weeks, but I've finally repaired that, today.

I first investigated the hangers and found a typical arrangement: A little springy piece of metal in back, released by levering with a screwdriver, holds the back edge of the blinds while the front edge of the hanger clips into a slot on the front. The blinds were a little tricky to move about by myself while standing on a stool, but I got them safely out of the way and looked at the hanger. It was screwed straight into drywall, no anchors. I'm surprised it lasted as long as it did. I got some anchors and installed them: voila, back in place where it belongs.

Finished "Upstairs" Dividers

2020-09-26 16:12 - Making

I live on the back (away from the street) side of my apartment building. So things tend to be pretty quiet, and there's no street lights outside my window. But there is another building, with a hallway with windows and bright fluorescent lights that never turn off. It's not much, but it's enough to be annoying at night.

The partial screening curtain for my sleeping loft.

So a while back, I got some black curtains and a rod to hang them from (which friction fits between the support beams). This basically solves the problem. They're thin but good enough to block most of the light from outside in the "upstairs" sleeping loft where my bed is. But it does leave a section open. I always wanted to fix that. When I first set this up, I considered continuing the curtains straight across to the wall. that would have divided the hallway a bit too much though.

Making the curtain rod clips. The completed curtain rod clips.

After quite a long time I finally came up with an idea I like. I've got a standard curtain rod, intended to bridge across the top of a window. But this spot is a concrete support beam: not easy to screw into for mounting. The solution was some tiny brackets, with enough surface area to simply hot glue to the wall. One of them ripped the paint/plaster off after a day or so, but that was a week ago and they've held fast since, after being re-glued to the bare surface beneath.

My completed screening curtain, including a dip under the suport beam and a turn around the corner.

First I had to do some sewing, to fit the curtain around the support beam. Then it turns the corner and covers the remaining open area on this side. It's a minor change but a great improvement in feel.