The Butterfly Bush is attracting all manner of insects, including these bumblebees. It looks like one is gathering propolis, as the stuff on her back leg looks sticky rather than grainy.
I’d never noticed their three ocelli before!
Author: Ed
-
Resistance Welding: AA Cell Positive Terminal Gadetry
AA Cell Clamping Pliers I’m trying to find out if I can use my hulking resistance soldering setup to weld nickel strips on AA cells, with the intent of making some decent 8-cell packs that don’t have crappy stainless-steel springs. Having slit the copper sheet for the jaws, I just now kludged together some electrodes…
The positive terminal on an AA cell is almost exactly 3/16 inch in diameter, call it 0.188 inches. That’s the hole in the middle of the copper sheet, which is neatly split so it clamps the terminal button from all sides with nearly equal griptitude.
The pliers are snap-ring pliers, with the original weird metric screws (neither 3 nor 4 mm, which is all I have) replaced with stainless steel 8-32 screws. Drill-and-tap the pliers jaws, clearance drill the not-quite-rectangular clamping plates, bend the jaws so the copper sheet aligns properly. It’s all good.
I plan to add a jumper connecting the two copper sheets; obviously, you don’t get good current transfer without a solid connection. The darker gold-copper color in the center section is Kapton tape insulating the top of the jaw sheets.
The cable goes off to one terminal of the resistance soldering transformer, which is a rewound kilowatt-class microwave oven transformer. The basics are 5 V RMS at about 200 A, with a foot switch into a microcontroller that drives a triac on the transformer primary. I can set the timing in multiples of 100 ms (6 AC line cycles) and the duty cycle from 1 to 6 of the cycles in each 100 ms. More on that later; the triac triggering is nightmarishly complex because I was doing a Circuit Cellar column and wanted to show how a triac gets all confused driving an inductive load. It really needn’t be that fancy in real life.
Anyhow, 200 A is at least an order of magnitude less than the current from a capacitive-discharge welding setup, but I’m hoping that with some tweaking I can get enough heat to make it all work out. If not, it’ll still be a king-hell resistance soldering setup.
AA Cell Center Contact Electrode The center electrode started life as an oil-burner ignition electrode. It’s a steel shaft joined to a (most likely) tungsten probe within the ceramic insulating tube. The cable goes off to the other transformer terminal.
Center Electrode – Side Detail Tungsten is a fairly crappy conductor, so I forged a copper clamp around the end of the electrode. It started as a section of the same copper pipe that went into the pliers, hammered around the wire. That took many annealing cycles, which basically consists of heating the copper red-hot with a propane torch and letting it cool for a bit.
The two smaller screws apply clamping pressure to the copper around the electrode, which ought to improve the contact area. I plan to anneal the clamping area one more time, scrubulate the inside of the clamp, then screw everything together nice & tight with maybe a bit of anti-oxidation compound in there for good measure.
Center Electrode – Front Detail The general idea is to apply the current as close to the AA cell’s terminal as I can. I think I must file / grind down the end of the probe so that it’s applying the juice exactly to the center of the nickel strip at the middle of the terminal.
The first test was 500 ms at 100% duty cycle, which produced a nice spatter of sparks from underneath the strip, the tungsten glowed orange, but the 8 mil nickel strip didn’t weld itself to the cell top. No weld nugget. Bupkis.
I think it’s got potential, though.
-
Tucking Other Files into an OpenDocument Document
WordPress doesn’t allow ZIP files, but very often I want to upload a collection of files that all relate to a common topic. For example, the three Tek 492 EPROM HEX files ought to come with a bit of documentation about how to use them.
Fortunately, OpenDocument documents (sounds like something put out by the Department of Redundancy Department) are actually ordinary ZIP files with a different extension. There’s no good reason you can’t tuck some additional files into that container. Nay, verily, if you use a word processor file, then you can have documentation accompany your files!
Note that the additional files don’t have any effect on the word processor document: OpenOffice simply uses the files it knows about and ignores the additional ones. You won’t see them in the word processor document; you won’t even know they’re present.
However, because OpenOffice doesn’t know about them, it won’t transfer them to the new document when you save the file. You must add the files as the last step, after editing and saving the word processor document for the last time.
I suppose there are pathological cases where this will cause trouble and I certainly hope that OpenDocument validators will complain vehemently about the presence of additional files. Use this knowledge wisely, OK?
So, for example…
Create a document and save it as the default ODT format using OpenOffice; let’s call it Tek 492 ROM Images.odt, just so you can see one in action.
Now, to add those HEX files to it, you’d use the ordinary ZIP utility:
zip "Tek 492 ROM Images.odt" *hex
The quotes protect the blanks in the file name and you must type the entire file name out with the extension, because ZIP doesn’t expect to work with ODT files.
You can list the file’s contents, which will show you all the other files that go into making an OpenDocument document work:
unzip -l "Tek 492 ROM Images.odt" Archive: Tek 492 ROM Images.odt Length Date Time Name -------- ---- ---- ---- 39 07-30-09 18:09 mimetype 0 07-30-09 18:09 Configurations2/statusbar/ 0 07-30-09 18:09 Configurations2/accelerator/current.xml 0 07-30-09 18:09 Configurations2/floater/ 0 07-30-09 18:09 Configurations2/popupmenu/ 0 07-30-09 18:09 Configurations2/progressbar/ 0 07-30-09 18:09 Configurations2/menubar/ 0 07-30-09 18:09 Configurations2/toolbar/ 0 07-30-09 18:09 Configurations2/images/Bitmaps/ 23156 07-30-09 18:09 content.xml 18259 07-30-09 18:09 styles.xml 1240 07-30-09 18:09 meta.xml 4943 07-30-09 18:09 Thumbnails/thumbnail.png 8742 07-30-09 18:09 settings.xml 1889 07-30-09 18:09 META-INF/manifest.xml 4876 07-30-09 11:56 U1012 - 160-0886-04.hex 19468 07-30-09 11:56 U2023 - 160-0838-00.hex 19468 07-30-09 11:56 U2028 - 160-0839-00.hex -------- ------- 102080 18 files
For obvious reasons, if you’re stuffing a bunch of files into an ODT file, you should probably ZIP them into a single ZIP file of their own, then add that single file to the ODT file. That means your victims users must also apply UNZIP twice, which may be expecting too much.
When you want to use the HEX files, extract them:
unzip "Tek 492 ROM Images.odt" *hex
And there they are again:
ls -l -rw-r--r-- 1 ed ed 15447 2009-08-11 20:51 Tek 492 ROM Images.odt -rw-r--r-- 1 ed ed 4876 2009-07-30 11:56 U1012 - 160-0886-04.hex -rw-r--r-- 1 ed ed 19468 2009-07-30 11:56 U2023 - 160-0838-00.hex -rw-r--r-- 1 ed ed 19468 2009-07-30 11:56 U2028 - 160-0839-00.hex
That’s all there is to it…
For what it’s worth, Microsoft DOCX files (and their ilk) are also ZIP files in disguise, so this same hack should work there, too. However, many folks (myself included) treat MS DOC files with the same casual nonchalonce as they do any other hunk of high-level radioactive waste, so stashing an additional payload in those files might not have a happy ending.
This trick will certainly come in handy again, so I better write it down…
-
Slitting Copper Sheet
Slitting Copper Jaws I’m kludging up a clamp to grab AA cells around their positive terminal so that I can resistance-weld nickel strips to that button. The general idea is that the current passes through the strip, through the button, and out the side to the clamp, rather than trying to heat the button through the strip from the top.
Trial Fitting the Jaws A snap-ring pliers has pretty nearly all the right attributes, so I’m making up a set of copper jaws with a hole in the middle to grab the terminal. Basically, I whacked off a ring from a copper pipe, hacksawed it lengthwise, hammered it flat (work-hardening it in the process), and drilled some holes.
Then I grabbed it in the Sherline vise and set up a teeny 4-mil slitting saw. A bit of manual CNC ran the saw past the copper and, after a while, the top half just fell over dead with a perfectly shiny cut right down the middle!
Slitting Success Useful things to remember for the next time around:
- Cut only 0.2 mm into the copper per pass
- 100 mm/min feed is fine
- 4000 rpm is fast enough
- A drop of cutting lube is a bunch on this scale
This worked out a whole lot better than I expected…
-
Tour Easy: Easy Reacher Underseat Rack Modifications
Easy Reacher Underseat Rack Improvements As mentioned there, I have a pair of ERRC’s Easy Reacher underseat packs. They’re supported by an Easy Reacher rack that’s specifically designed for Tour Easy bikes.
Perhaps because I carry dense stuff in the packs, they tend to flop side-to-side. I added a rear strut across the bike frame and a pair of lengthwise plastic (acrylic?) struts to stabilize the packs.
A pair of padded clamps holds the crosswise strut to the bike frame and a washer captures the rear fender’s mounting bracket.
Looks hideous, works fine.
The black tit hanging down from the strut clamp is a bit of heatshrink tubing that cushions the kickstand when it’s up; otherwise, it rattles against the stub end of the aluminum rod.
Yeah, the bike’s pretty grubby. I’d rather ride it than wash it… and, anyway, I follow my father’s advice: “If you have to move it to clean behind it, don’t move it!“
-
Tour Easy: ERRC Easy Reacher Pack Repairs
Grocery Hauling Setup I have a pair of underseat packs on my Tour Easy that have sagged rather badly over the years. That might have something to do with the fact that my toolkit and other odds & ends weighs more than some bike frames; while I don’t need that stuff very often, it’s good to have around.
Tools & suchlike live in the left-side pack, the near one in the photo, and you can see the problem. The right-side pack holds HT batteries, my belt pack, and other relatively lightweight stuff; I’ll fix that one when I see whether this works. The panniers at the rear wheel are for groceries and other bulky items. The trailer, well, that’s how we do groceries…
Broken Pack Backplate Anyway, the underseat packs have a black plastic (styrene?) backing that cracked under the stress of the stuff inside, allowing the top corners to cave in and the bottom to droop.
The hooks holding the pack to the underseat rack were riveted through the backing sheet and the hardware, but a couple of good shots with a punch broke them free.
Some rummaging in the Parts Heap turned up a big acrylic sheet (“100 times stronger than glass!”) that’s absolutely the wrong material for the job: it’s too brittle. However, I’d like to see whether a stiff backplate will solve the problem or if I’m going to have to get ambitious and build an internal pack frame.
Acrylic Plate and Aluminum Stiffener It’s essentially impossible to get a picture of a project built largely from acrylic sheet, but here goes.
I traced the outline of the old backplate onto the new sheet’s protective paper, introduced it to Mr Belt Sander to get those nice round corners, then drilled the holes. It turns out to not be quite symmetric, so there’s a right way and a wrong way to insert it into the pack.
All the hardware is stainless steel. They used aluminum rivets, which is the only reason I could punch them out without too much difficulty, that I’m replacing with SS 10-32 machine screws & nuts.
The aluminum stiffener is a random chunk of ribbed extrusion from the Heap; the original was almost exactly twice as long as one backplate, so the two halves (one for the other pack) are precisely right. I milled out the center rib around the nuts to get enough clearance for a nut driver.
Stiffener Hardware Detail Herewith, a closeup of the hardware. There’s an acrylic sheet in there, honest, it’s under the aluminum extrusion and fender washer. Really!
I put an automobile license plate in the bottom of each underseat pack to act as a floor for all the crap inside; it’s an almost perfect fit and should give you an idea of the pack’s size. It also maintains the bottom’s rectangular shape and keeps heavy stuff from sagging; there’s a hole scuffed in the bottom from the intersection of a high curb and just such an oversight.
Tour Easy Underseat Pack Detail Having washed the pack while it was apart (there’s a first time for everything), it looks a lot better than it did before. The yellow block in the front pocket is the kickstand plate mentioned there. It used to have a mesh pocket along the side, too, but that snagged on something and got pretty well ripped, so Mary trimmed it off when she sewed a patch over the aforementioned hole.
It’s still saggy, but the top corners of the plate are holding it up a lot better now. If they crack again, I might just have to go with some aluminum sheet.
These packs seem to be obsolete. The ERRC Lloonngg panniers (search for them) seem to be, well, too long for most purposes; they look as though they would interfere with ordinary rack packs. If I were doing it over, I’d look into hacking a pair of smallish duffel bags.
-
NiMH AA Pack Discharge Test: Tenergy RTU 2.3 Ah
Here’s a quartet of discharge tests for a new set of Tenergy Ready-to-Use cells. It’s the same one that produced the green and red traces in that post. It looks as though it still has a weak cell, but it’s not too far off of the others.
Tenergy RTU Pack A Tests – Aug 2009 The lower black trace is after sitting around for a few days, the others are hot off a 4C charger. I think the black trace is more representative of the long-term voltage.
The two middle traces are essentially identical: same charging method, same discharging method.
The blue trace is at 100 mA (C/23); the others are at 500 mA (C/4.6). The cells don’t produce much more energy at the lower rate and, at 1.8 Ah, are still well below their 2.3 Ah rating.
The difference in voltages between the green and blue traces most likely has more to do with the relatively skinny wires and crappy spring-loaded stainless-steel battery connections. The current varies by 400 mA and a mere 0.5 Ω between the battery and the voltage measurement would account for the entire difference.
The Smell of Molten Projects in the Morning 