Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Mary dropped a pair of her sunglasses that disintegrated on impact: both earpieces broke off. She has trouble finding sunglasses that fit, so this is not to be taken lightly…
The sunglasses had interchangeable lenses, a feature which she’d never used, and the lower of the two tabs that snapped into the earpieces had broken off — on both sides, simultaneously. These weren’t high-snoot items, but they were name-brand: Rudy Project from, IIRC, nashbar.com.
Peering through the microscope, it turns out that the lens material may have been pretty good optically, but wasn’t up to the mechanical task: the two remaining tabs had deep stress cracks. The right-side picture shows the lens upside-down, as that was the easiest way to set up the shot.
Notice the many, many cracks that penetrate nearly all the way through the tabs. The tabs didn’t break because she dropped the glasses on the floor, they broke because there was barely anything left holding the tabs in place.
Mind you, she’d never removed the lenses from the earpieces, so this isn’t a case of failure-from-overuse, either. They’re about a year old, more or less, and have been used in stressful tasks like gardening and the occasional bike ride.
Urethane adhesive foam-in-place
I slobbered urethane glue into the ends of the earpieces to mechanically lock the remaining tabs in place and fill all the voids. It looks rather ugly here, but the excess adhesive simply snaps off because it doesn’t chemically bond with either of the other two plastics.
Rudy sunglasses stress cracking – center
After screwing everything back together again, I noticed that there’s another stress crack growing in the middle of the lens, just over the nosepiece. These sunglasses are not long for this world: that failure will be an end-of-life event.
The frames claim “Designed in Italy” which doesn’t win any points with me; the design is fundamentally flawed.
Yo, Rudy, how about designing some sunglasses with a high-tech feature like durability… rather than style?
Oh, yeah, I suppose this repair voids the Warranty. Perhaps buying from Nashbar on sale triggers this clause: “Buying Rudy Project sunglasses, goggles or helmets from an online retailer at a price below the suggested retail price (MSRP) voids your warranty.” The expense of sending them in negates any possible benefit, which I’m sure they realize, too.
EXT. UPSTATE NY APARTMENT COMPLEX — EARLY AFTERNOON
Clouds
A STRANGER emerges from an apartment and walks through the adjacent parking lot to the complex’s central roadway. A late-middle-age white male, he is dressed casually in black trousers, red t-shirt with STAFF in large white letters on the back, well-worn blue-and-white pinstriped locomotive driver (“engineer”) cap, and dark sunglasses. His graying beard is trimmed short, but he is obviously overdue for his quarterly haircut. He carries a bulky black prosumer digital camera.
The bright blue sky is filled with large clouds from an approaching storm front and, opposite the sun, a cumulonimbus bank looms over the far horizon above a row of apartment buildings.
The Stranger studies the clouds, moves to various vantage points, examines the rest of the sky. He braces the camera against a road sign pole and fiddles extensively with the knobs & buttons while taking several pictures.
WOMAN #1 emerges from a building, enters a car, and drives along the central roadway. She slows, stops next to the Stranger, and rolls down her window.
WOMAN #1
What are you taking pictures of?
STRANGER
Those great clouds over there! Looks like we’re in for a real storm later today!
WOMAN #1
Oh. Have a nice day. (She rolls up the window and drives off)
The Stranger is joined an elderly COUPLE, WOMAN #2 who is probably his wife, and a teenage GIRL who vaguely resembles all of them. The Girl is wrapped in a large towel. They walk slowly through the apartment complex to the pool, appear baffled by the childproof latch on the gate, and are finally admitted by WOMAN #3 who shows them how to operate it.
INT. IN-GROUND POOL PATIO
They sit around a table in the corner, jockeying the uncomfortable plastic chairs for position in the shade cast by the table’s umbrella, while the Girl removes a towel to reveal a red swimsuit, enters the pool, and begins swimming laps.
Coming up for air
Various other PEOPLE occupy the area near the pool, including older couples, males of various ages, several curvaceous mid-twenty-ish females clad in revealing swim / sunbathing attire, and a group of middle-age couples.
The Stranger takes several pictures of the Girl in the pool.
Time passes.
The Stranger, realizing that he’s about to spend the next three hours sitting on his well-flattened butt in the van while driving home, stands up, stretches, and walks to the gate. He intently studies the labels on the childproof latch, which is misinterpreted as being baffled, and leaves the pool area.
EXT. APARTMENT COMPLEX ROADS
Manhole cover
The Stranger strolls around the apartment complex to the side entrance road, and returns along a different route. He seems to take a particular interest in drain grates, manhole covers, garage doors, and infrastructure in general. He scuffs the dirt from one manhole cover and takes a picture of it. He continues walking around the complex and returns to the pool.
His companions gather themselves together and emerge from the pool gate.
EXT. POOL AREA
A New York State Police car drives slowly into the complex through the side entrance. The TROOPER scans the area, spots the Stranger, and pulls up beside him.
TROOPER
Good day. How are you doing?
STRANGER
(Smiling) So far, so good.
TROOPER
What brings you here today?
STRANGER
We’re visiting my wife’s parents. (Gestures to indicate the Couple among his companions)
TROOPER
(Eyes the group) We’ve had a report of someone in the area taking pictures of buildings and possibly people.
STRANGER
Well, I’ve been taking pictures of clouds, a manhole cover, and my daughter. (Smiles) I think it’s still permitted for me to take her picture.
TROOPER
(Getting down to business) Your name?
STRANGER
(gives name, helpfully spells last name)
TROOPER
What’s your birth date?
STRANGER
(Gives a date long in the past)
TROOPER
(Typing on laptop PC) And your address?
STRANGER
(Gives city and state)
TROOPER
(With emphasis) Your street address.
STRANGER
(Gives street address)
TROOPER
Phone number?
STRANGER
(Gives phone number, repeats when trooper misses last four digits)
TROOPER
(Types, pauses, types, reads screen) Enjoy your stay.
Trooper drives off, leaving apartment complex through main entrance.
STRANGER
(To his companions) Well, I now have a police record tagged “suspicious behavior”.
The group walks back to the apartment while discussing recent events and their plans for the remainder of the Independence Day weekend.
EXT. APARTMENT COMPLEX
P.O.V. pulls back and ascends in Google-Earth fashion to show entire Adirondacks region. The Stranger assumes the role of voice-over INTERLOCUTOR. Fade to black during narration.
INTERLOCUTOR
Despite my pique, the Trooper performed his job properly and with decorum. While the opinions of my companions differ, I contend that once a 911 call has been received, the police must follow established procedures to resolve the complaint. The response depends on the initial report and what the Trooper finds during his approach.
The fault, if any is to be found, thus resides with people who have been recently trained to suspect once-normal behavior: anything they wouldn’t do is considered threatening, if not hostile, when done by someone they don’t recognize.
Photography, in particular, is now treated as reconnaissance for an assault. Unless it’s done by surveillance cameras, in which case it’s perfectly benign.
–THE END–
Perhaps you can tell a similar story.
Extra Credit
Explore these 27 parametric variations on the theme of Stranger:
Double Bonus
Consider the behaviour variation where a [white + casual + friendly] Stranger politely but firmly refuses to cooperate with the Trooper’s inquiries. Explore the range of perfectly legal and extremely unpleasant outcomes. Possible working title: “How to ruin the rest of your holiday weekend in five minutes flat”.
Update: Many internal links on Schneier’s blog are broken. As nearly as I can tell, all inter-word hyphens should now be underscores: the-war-on-the.html becomes the_war_on_the.html. Perhaps they switched the back-end database?
Our daughter has been helping a friend learn to ride a bike (at age 15: it’s never too late!) and we’ve been rehabilitating a new-to-her bike in the process. It’s an inexpensive Ross bike, perfect for the task at hand, and is providing a good introduction to machine-shop work.
The fact that it’s much older than she is makes not a whit of difference. Nay, verily, I rode a bike pretty much like this one for hundreds & hundreds of miles back in the day. I got better ones when I could afford them and she will, too; maybe we’ll tempt her into a recumbent bike some day…
Anyhow, the seat tended to spin around even with the clamp cranked dangerously tight. Taking a look down the tube showed that they used welded-seam tubing (it really was an inexpensive bike) and didn’t bother to clean up the internal seam. As a result, the chromed steel seat post rested on maybe three small patches of metal that didn’t provide much friction at all.
I wrapped a neodymium magnet in a rag and stuffed it down the tube to catch the filings, then applied a coarse cylindrical file (a rat-tail would work as well) to the seam. When it was nearly flush, I switched to a finer file to smooth it and the other high spots. The picture shows the improved seam, ready for the seat post. Ugly, but rough is actually a Good Thing in this situation.
Seat Clamp Swaging
The seat tube has a nominal 1-inch OD, so I clamped a random round from the heap in the vise, tapped the clamp around it, and massaged it lightly with a hammer to persuade it into a more cylindrical shape. It’s still not perfect, but at least the bolt lugs engage the seat tube around the slit somewhat better.
With all that in hand, the seat post is now perfectly secure.
On her first “I can ride!” parking-lot outing, she experimentally determined that a bicycle wheel’s lowest-energy state resembles the edge of a potato chip. Fortunately, it was the front wheel and, after a bit more shop derring-do than one might wish, we swapped in another wheel that’s been hanging on the garage wall for a decade, ready for just such an occasion.
Remember how independent your first bike made you feel? It’s working that way for those two, just like it did for us. Life is full of bumps and they’ll get hurt every now and then, but there’s no other way to get through it; they’re just about ready to ride over the horizon.
Happy Independence Day for those of us in the USA!
A friend brought over a broken toy (well, an Argent GPS tracker) with a peculiar problem: everything worked, but after a few minutes the front-panel LEDs would get intermittent. The LEDs are hand-soldered to the board with leads that extend maybe 7 mm from the surface.
After a bit of poking around, I stuck the gadget under the microscope, at which point the problems became obvious.
See that distinct line where the solder meniscus ends at the lead? Yup, that’s the teltale sign of a cold solder joint. The lead never got hot enough to bond properly with the solder, so the failure extends all the way down through the board. The only electrical contact is at a random point where the flux layer is thin enough to pass current; as the joint heats up, that point Goes Away.
Worse, do you see (click on the pix for bigger images) the small discontinuity about 1/3 of the way down the solder cone? My buddy Eks alerted me to that failure: that’s where the solder joint fractures from repeated heat stress.
Solder Thermal Stress
Here’s the quick sketch he drew on the canonical back-of-the-envelope. I added the red oval as a replacement for his emphatic gestures; with any luck, you’ll never forget it, either.
In this case the LED is anchored in a front-panel hole and the lead is mechanically locked to the board. As the lead heats & cools, it expands & contracts (duh) at a slightly different rate than the solder. After a while, the solder cracks; it’s much less ductile than copper.
Joint 2 – clear fracture
I’m not convinced that’s what happened here, as the LED leads have a bend in the middle that should relieve the stress, but it’s at exactly the spot where he sketched the failure he’s found in many, many gadgets. Power transistors standing above boards with their backs screwed to heatsinks seem particularly prone to this failure, as they have short leads stressed by the differential expansion between copper and aluminum.
Here’s another LED lead from the same gadget. A random out-of-focus fiber enters from the right and exits around to the left rear, but you can clearly see the bad joint at the top of the solder cone and the fracture line just below the fiber.
A touch of the soldering iron generally solves the problem, although you might want to suck the old solder out so the new solder can re-flux the joint.
Arduino Pro USB (cold) Solder Pads
This doesn’t happen only to hand-soldered joints. The USB header fell right off an Arduino Pro board while I was debugging something else. I had to re-heat the joints and the header separately, add flux, and then solder ’em together. Notice the bubbles in the solder layer? That header just never got up to the proper temperature. The current version of that board uses a through-hole header, which is more rugged than this surface-mount equivalent.
TinyTrak3 cold-solder joints
And a TinyTrak3+ board had few cold joints, too, where the leads just didn’t bond at all.
In both of those cases, the vendors did a quick check and didn’t find similar problems with their stock, so the boards I got seem like random failures on the soldering line.
Now, if I’d never made a cold solder joint in my life, I’d be in a position to get all snooty. That’s just not the case: it happens to everybody, once in a while, and you just learn to live with it.
Just got a letter from Canada, allegedly from the Readers Digest Sweepstakes, but with a letterhead address of 1125 Cornell Ave, Atlanta GA 33412. The phone/fax number is 912-480-0353, oddly not a toll-free business number. The letter has medium production values, pixellated Readers Digest logos, surprisingly few typos, and a painfully ersatz signature.
I’m to believe I’ve won $255,069.00 in a contest I’ve never entered (the way I see constests, while you’ve got to play to win, entering doesn’t improve your chances of winning). The “69” is a nice touch, I’d say.
Enclosed is an exceedingly valid-looking check for $3892.91 “to help you cover any charges that may be required before you receive your funds.” Check number 1100912681, if you can believe that. It has excellent production values, a genuine artificial watermark on the back, and is nominally drawn on an actual Canadian bank.
Bogus check
Obviously, a fraud. International and postal, no less.
I’m impressed at the level of effort they went to, but it seems that with an actual telephone number (the address is surely faked), some branch of law enforcement should be able to fly right into their ears. No, I am not going to call that number…
I gave the FBI a tip, but I’m reasonably sure nothing will come of it.
[Update: Well, maybe the FBI didn’t do anything, but there’s an absolutely wonderful riff based on this letter. I’ll only quibble about the 57 Chevy… it was really a Studebaker.]
I managed to jam the 3-jaw chuck on my lathe by turning the lathe on without the formality of snugging the chuck against the spindle first; IIRC, there was maybe 1/8″ clearance. The resounding thunk when the irresistible force hit the immovable object was the prelude to about a year of increasingly desperate attempts to remove the chuck, punctuated by long periods of despair.
The absurd derring-do with clamping the 4-jaw Sherline chuck in the 3-jaw lathe chuck described there finally prompted me to ask my buddy Eks for advice, which is what I should have done in the first place. He suggested removing the chuck body from its backplate, building a lever that bolted to the backplate with the same six bolts as the chuck, blocking the spindle with wedges under the belt pulley, and wailing on the lever with a lead hammer.
We wondered if a hard hammer would be better than the lead hammer, perhaps because the impact would be less squishy, but that was in the nature of fine tuning.
The key idea is that removing the chuck body also removes a tremendous amount of rotational inertia, so that wailing on the lever arm actually transfers force / impact directly to the backplate, rather than trying to spin the body. The somewhat risky part is that there’s a pin connecting the spindle with the drive pulley (it’s disengaged when using the back gears), so that it’s entirely possible to break the pin rather than unstick the chuck. But it was still a better idea than any I’d had so far.
Stuck backplate
Making note of the witness marks on the backplate and chuck body, I removed the body. Fortunately, there was just enough clearance between the front bearing journal and the backplate that I could get the bolts out without dismantling anything else.
That left me with the rather grody and still firmly stuck backplate. The bolt disk was brazed onto the threaded cylinder with a keyway. Although the chuck body had a key slot, it looks like the matching key had been machined off of the cylinder, so the bolts were taking all the cutting torque. Worked OK for both the previous owner and for me, so I suspect it’ll continue to work just fine for the next owner, too.
Bicycle handlebar stem in spindle
Peering through the spindle reminded me of some recent bike repairs and it occurred to me that maybe, just maybe, a old-skool split-wedge handlebar stem would get enough traction inside the spindle to hold it in place. Some rummaging in the Bike Junk box produced just such a stem and it fit exactly into the spindle bore. Now the spindle is fixed in place by its ID and there’s no risk of breaking the locking pin or (shudder) the back gear.
Even better, the lumber pile emitted a chunk of 1×4 (actual dimensions!) wood that was precisely the correct length to reach from the floor to the stem. I like it when projects work like that; finding exactly the right stuff in the pile is sort of an omen that things are going well.
Fundamental rule: always start with a hunk of something that looks a lot like what you want to end up with.
Corollary: ya gotta have stuff!
Coordinate-drilling the lever arm
Some rummaging in the parts heap turned up several feet of nice “angle iron”, so I bandsawed off a hunk. I should have realized something was wrong when a foot of teeth stripped right off the saw blade, but I ascribed that to, oh, maybe weakening a few teeth when I soldered up the blade.
I had our daughter run the trig to generate coordinates for the six holes, then lay out the center bore and bolt holes on the plate for practice. Drilling the first hole prompted me to resharpen the drill, but poking the remaining five holes into that plate produced vast clouds of wood smoke from the sacrificial plate underneath, despite boiling copious quantities of cutting fluid off the top.
I finally admitted defeat when the “angle iron” rubbed the teeth right off a 2-inch hole saw.
As nearly as I can tell, that plate is un-machinable stainless steel, hand-forged by the Devil himself specifically to taunt me, and is good for nothing. Obviously, I hadn’t used it for anything in the years it had been in my pile and, perhaps as an omen, it didn’t have any other holes in it from anybody else’s efforts. I’ll keep the pieces around just to sneer at them; won’t get fooled again.
So, at this point, I am out a bandsaw blade, a drill bit, and a hole saw. We won’t discuss the circle cutter or my abortive attempt to lash the damn thing down to the Sherline and perform helix-milling upon it.
Unstuck backplate with beating bolt
While licking my wounds, I wondered if the bolt circle on the backplate would provide enough lever arm to make any difference. I tightened a sacrificial bolt & nut with one face of the bolt aligned along a radius from the spindle center, then deployed a big drift punch and the two-pound ball-peen hammer (a.k.a., The BFH).
A half-dozen good shots later, the backplate spun free. Notice the very small gap between spindle and backplate… that’s all it takes!
I added a closed-cell foam washer to fill the gap between the backplate nose and the butt end of the chuck; there was a remarkable amount of crud built up in there.
I am so happy that it even makes up for the death toll among the tools…
It’s worth noting that the headstock has two honkin’ big bronze spindle bearings, no delicate balls, and a few mighty thwacks didn’t do them a bit of harm.
They’re doing well in their new home, building out comb on the foundation. The queen is in good shape, laying eggs as soon as the workers finish the cells. The workers seem to be feeding pollen directly to the larvae rather than storing it, which makes perfect sense. They’re taking two quarts of 1:1 sugar water every day!
Either you already know what this is all about or you really don’t want to know.
The Smell of Molten Projects in the Morning 