Explosions, Mishaps, and Lessons Learned


#1

Continuing the discussion from How to ship a 6-inch neodymium magnet:

Share your mishap stories.

My very very first such lesson was wiring up a transistor for the first time the wrong way and looking at the plastic enclosure start to bubble. I remember my first thought being, “Oh wow. I wonder if I-” before it popped alarmingly close to my face and unprotected eyeballs. .

My first lesson was: If it’s boiling, bubbling, hot, or things are going unpredictably, immediately shut it the fuck down. I also learned to have a quick shut off method ready when I wasn’t sure what I was doing. Transistors are a dime a dozen, but when I was a kid first learning about this stuff, I didn’t have a lot of money to burn (literally) on components. It’s pretty boring as stories go, but you always remember your first.

In terms of harrowing experiences, I’ve been pretty fortunate. I did have a table saw bind and throw a 3X3 directly into the left side of my chest and leave a giant bruise once. I shouldn’t have been standing where I was and I should have been using a sled for what I was trying to do.


#2

When I was a kid, I was building a Tesla coil. One of the early lessons with the car ignition coil on the primary side was that high voltage pulses can jump almost a half inch.

Similar lesson, occasionally relearned, is that a metal screwdriver is conductive.

Another Tesla coil lesson was quite noisy. I had a car battery charger as its power supply, homemade one my dad designed, and with no capacitor on the output; the pulsing voltage is better for the charging. So I added a cap. The first day it worked well. The next day when I rebuilt the rig it was rather underperforming; the power was low, it was not what it used to be even at the highest output setting (custom-wound transformer with taps from 8 to 18 volts, I think). Then suddenly,
#BANG
and all I saw was grey. Before the shock that I don’t see sunk in, a green light of the main power (the charger) poke through, then the red light of the aux PSU (a model train transformer) made itself visible. I switched them off, and only then the startle reaction came in and the electrolyte started burning in my eyes.
The fog disappeared shortly, enough to see the workbench being all covered with something that looked like spilled grey guts; that was the guts of the capacitor. Its casing was on the other end of the room.
In the haste to get it running, I connected the cap the wrong way. For a while it sunk power like a lousy diode, generating heat and gas, while I fed it more and more energy in attempts to bruteforce the original performance.

When I was making a stepper motor driver, I used four H-bridges with those little epoxy-capped transistors. Controlled from a parallel port, each base to one pin. And it all worked well - until I touched something wrong and reset the computer. All the D0…D7 went H, all the transistors opened, and I never found the caps from most of them.

A minor explosion of a pill bottle with electrolysis rig when hydrogen decided to have fun. Startling but inconsequential.

Some minor chemical and solvent spills. Some smoke. Some overheating electronics that burned and stank; nothing that would even remotely compare with my mom forgetting a pot of milk on the stove, that stench lingered for DAYS.

Gulping a 0.1M HCl when pipetting when distracted. No lasting harm but my pride dissolved.

Testing a neon lamp with a resistor, for a keychain for mains sensing. I have an adapter, with lightbulbs to limit current that can be connected in series with the load; one of the handiest toys I designed. I had the bulb-resistor assembly in series on the top output clamp that was supposed to be L, the bottom being N. It was not shining when I touched the free end. It was shining when touching the N pin. I touched the ground pin and touched the free end, to lower the resistance (DUMB!, what was I thinking!), nothing. After a while of messing, I touched the N pin, and
#ZZZZAP
and I got one. A horse kicks less, I’d reckon. After I recovered a bit and the rest of my hair settled back on my head, I did a post-mortem analysis; the whole mishap hinged on the assumption that the L and N pins are where they are (the N one was live, and vice versa). Major oops. Tracing to the sockets, it turned out that while the first power strip is wired correctly, with L in the left hole, the next one (you run out of sockets rather quickly here) was not. I used a piece of a computer power supply cord, remain from a project where I need a cable with one wall socket and several IEC sockets, and trusted the wire colors; that was a mistake, Chinaman swapped the blue and the brown so in the second power strip the right was L and the left was N.
I upgraded the lightbulb limiter, added a L/N swapping switch to the back, and a pair of neon bulbs to the pins on the front (against the safety ground) to indicate which one is live. Always strive to indicate where the voltage is.

Welding a long weld, I did not button up my shirt. Got a rather intense first, almost-second degree V-shaped sunburn on my chest. In the middle of winter. (Twice.)

Welding a shorter weld, I laid a nice “caterpillar”, and knocked off the hot slag, which broke off in a nice big piece and landed on my shirt sleeve. And was getting warm through the thick flannel. No worries, I brushed it off gracefully. It landed in my glove. I still have the scar.

Making a movie prop (a display for a timebomb) from a smart display (expensive 4-digit part) and a microcontroller that needed 12 volts for programming. Iterating through the software, switching the power supply between 5 and 12 volts. Once I did not switch it back; killed a $50 part and wiped my profit from the project. The $4 microcontroller (I think it was PIC16C84) survived.

Repairing a display in my boss’s laptop. One of the wires to the lid was chewed and the image was getting distorted. (One of the LVDS lanes.) I repaired it, all goes well, at the final test I pushed the board and disconnected something when I was not supposed to; the whole thing died and couldn’t get switched on anymore. Luckily it was scheduled for upgrade anyway, so we did data migration from the old one and the upgrade was done a couple weeks ahead of schedule. The wounded pride still hurts several years later.

I may remember more.


#3

Mine isn’t harrowing, really. And not explosive, but messy.

The first place I lived that had a garbage disposal was pretty nice for a broke 20something. it had a whole separate bedroom. I was making stew with some low end veggies from the discount market. There were plenty of bruises to cut out, so I put all the trimmings in the sink and ran the disposer at the end.

There was a weird noise from the undersink cabinet so I opened it. It looked like gazpacho, more or less, and it was shooting across the kitchen floor to the carpeted section / living room. All I could do was laugh because it was just ridiculous. A sorta boyfriend was there and he was super annoyed and left.

That’s how I made gazpacho in a garbage disposal and dodged a bad relationship all in one go.


#4

I was disasseming some stainless tubing, without gloves. Sliced my thumb to the bone, which I then passed out due to the sight of (only a few seconds). Last year I was moving a Volvo engine with gloves, and the engine sheared my gloved hands in the exact place.

Three inch slice through leather, perfectly fine thumb. I always wear gloves.

Ran 2000 watts of 110 through a long, rubber coated 16 gauge extension cord. Yeah, it caught on fire. Inside my shop. Next to 150 proof alcohol.

Speaking of fire, there are reason why meat smokers have water pans in the bottom. I had one that had evaporated, and when I opened the door it was a scene out of backdraft. Almost caught the house on fire. Always check your water pans.

I don’t even count solder burns anymore. (And I only solder/braze with gas, not a namby pamby iron)


#5

At this point I’m not even sure I can remember if they hurt anymore, and I burned myself last week.


#6

What about a water presence detector that’d run an alarm or even shutdown the smoker automatically?

Carried a power bank for my phone. (Back then the thing needed 7.2 volts, two Li-ion batteries; the battery pack died, so it was replaced with a 7805 stabilizer with a yellow LED in its “base” to rise its output by two volts. And a two-amphour 12V lead-acid battery, the UPS-grade sealed kind. Powered also my walkman from it, which had a built-in 3V stabilizer (so I wouldn’t have to feed it with AA cells; was an alternative to an adapter using two D cells, as it was bigger but way WAY cheaper per hour of music). Used electrical tape (didn’t know the Gospel of Heat Shrinks back then) for insulating the connector. The tape slid when I was riding subway. The passengers were treated to a sight of a guy in fatigue pants and tactical vest, emanating grey smoke and curses. Fortunately locals aren’t so terrorized as Americans so nobody annoyed me about it. The same day I added a Polyswitch fuse right to the battery.

I was making a jewel, from copper and brass and glass “gems”. A tiara. I spent almost 24 hours on it, straight. Got yelled at for occupying the table, attempted to clean the crap off, grabbed the 150-watt roofing-grade soldering iron by its head. Wondered for a while why it feels so wrong, dropped it before lasting damage was absorbed. Ouch. (It was a high-power high-precision iron; the copper shaft was cut flush, a hole drilled axially, and a thread cut, and a tip from a fine-electronics iron installed there. Ideal for precision soldering of sheetmetal jewellery.)

(I said I could remember more.)

Edit: Also, hot-melt glue. I usually use it with a torch; heat the end of the stick, smear where it should be. Reheat with flame again as needed, apply the other part. The glue is hotter this way, and sticks way better to things than when used with a glue gun. Also, no waiting for the gun to heat.

I found my shoes are leaking (again). They were a wreck, with more repairs than original material (I hate shoe-shopping, another ad-hoc repair is always more attractive than the ordeal of buying new. And they add up… and this was promised to be the last repair before decommissioning (again)). I used a white glue stick, which got nicely low-viscosity at high temperature. Applied liberally to the crack and to the area where the sole was almost missing. But it was getting through in a bit higher amount than expected. So I took a piece of something to put at the hole from the other side, stuck my hand into the shoe… and laid the upper side of my finger right into a pool of napalm-hot glue that accumulated in the shoe tongue. That was… not pleasant.

Hot glue and molten rosin are napalm-grade substances to be highly careful around. They stick.


#7

I was making tomato cages out of galvanized wire. The legs of the cage were sticking out every which way. My dog then decides it would be a good idea to jump at my face and give me a kiss, which made me stumble into the cage and slice my calf open. That was (looks at scar) four inches long, and I should have had stitches. And a tetanus shot.

That was the last time I did any metal working while wearing shorts.


#8

In 2000, a rich friend asked me to install ethernet lines in his big fat 6000 s/f house. I was alllllmost done with the job, just had to get a cable hole from first floor down to the area in the basement that was serving as a small data center. I had my sawzall and was cutting a carefully measured hole in the baseboard, when all of a sudden

#PSSSSSSSS!!!

I was getting wet with hot fucking water!!! Shit!!!

I had cut into one of the copper heat lines for their forced hot water heating system that I couldn’t see from my pilot hole. Fuck fuck fuck !!! I called out and he came running and water is spraying every fucking where and dripping into the basement and we can’t find the shutoff and then realize it’s dripping onto the power panels and his wife runs outside to throw the breaker at the meter…

I was fucked but not nearly as fucked as I would have been if I had sawed just one more centimeter, because right on the other side of that copper heating pipe was the main power line to the house.

Here I sit, instead of rotting away in a coffin.

He claimed he wasn’t pissed but I knew he was and I really fucked up that house. I’m not in IT anymore and I’m glad I’m not. God that was dumb.


#9

Jebus. My SO once clipped a 20 amp line she thought was turned off (why should she check?) and it blew the blades off her wire cutters.


#10

We need portable xray backscatter cameras for jobs like this.

I have a number of socks covered with little airflow holes. That’s what welding in sandals (“just that little one, that spot weld won’t do anything bad, it’s just a 2mm electrode…”) will end up as. The burns are so small they can be ignored safely, the feeling of discomfort of most of them ends within seconds anyway if they are even noticeable; the sparks are small enough to not worry. Thicker electrodes are worse, the stuff from 3.2mm ones starts commanding respect.

I also have a hole burned into one flannel shirt. Was angle-grinding a steel tube in a vise, felt warmth on my stomach, found that the normally cool and harmless sparks were impacting said shirt from about one inch distance, too many in too small area to add their individually minuscule effects up. The hole had brown edges and was smoking. There were enough holes to not worry anyway, and the only thing I regret was that I did not photograph it.

If said shirt was soaked with something easily flammable (e.g. oil or grease) it’d be worse. Don’t let that to happen, don’t wear much fuel, there’s always an ignition source.

Another little story, this time EMI. I am making a little Cockroft-Walton multiplier on a solderless breadboard, watching TV on the background. I switch it on, the TV - about 2-3 meters away, connected via cable to a roof antenna - starts losing signal, the digital signal suffers bad drop-outs and sometimes vanishes. The CW multiplier hisses quietly, which it shouldn’t. The effect is repeatable. Further examination found a corona discharge on one of the diodes, a salvage with a sharp spike of solder remaining on the side of one leg. Such discharge can apparently broadcast a mean wideband.


#11

Mom did something similar, with a neon bulb tester. At the ceiling, where after painting the lamp was to be reconnected. She was making sure the wires are unpowered; they weren’t, and she touched both of them with the tester tip and almost fell from the stepladder.

Something tamer happened to me when I was connecting a phone line when on a stepladder, and the phone rang. Instant 100V AC. Not that bad on its own but the surprise almost knocked me down too. Often the surprise is worse than the act of danger itself.


#12

Don’t staple your thumb to the wall, it’s… weird.

Also don’t saw toward the gap between your thumb and index finger. The hand span of my left hand is about an inch larger than my right.


#13

When I was around seven I had just watched Frankenstein on the TV, had heard that nerves used electricity somehow, and figured this could be a great experiment. So I decided to bring a dead fly back to life. I found a fly corpse on a window sill, floated the fly in some water in a bottle cap, unfolded two paperclips, and then fed both clips into a wall socket with their ends in the water. Sparks flew, outlets singed badly, and I got an agonizing shock and singed fingers from the paperclips, though the fly remained dead. Happily the circuit breaker tripped quickly.

Lessons learned:
Electrical shocks do not actually bring the dead back to life, but do have the potential to make the living dead.
Do not play with wall sockets.
If you move furniture around you can hide scorched sockets and avoid uncomfortable questions from parents.
Seven year old me had some terrifyingly bad ideas.


#14

On my right hand there’s a nub of thicker flesh at the edge of precisely that location.

I was setting up a generator on a prototype wind power plant; three fiberglass spiral helixes several meters long, vertical, coupled through bicycle freewheels to the horizontal shaft that was coupled to the generator. The generator had to be lifted into position, and it was about as heavy as me. The prototype was dry-assembled in a warehouse.

Having capability to deal with people (and by extension to command them around) as low as I have, I had to engineer around. I figured out that I can lift the thing on a threaded rod. The thing had a lifting lug, with a M12 thread, which dictated the diameter of the rod. So, M12 rod it was. A beam was installed above the generator, with a hole going through. A large washer went over the hole, to spread the load over the fairly thin steel box beam (not having that many experiences I decided to underestimate the steel strength; when you fly blind, try to fly high). That was not really a problem.

So, the wooden pallet with the generator is pushed to the position, the rod is lowered through the hole and screwed onto the generator body and secured with a jam nut. So far so good.

Another nut is placed onto the rod. It’s screwed almost down.

And, when putting the wrench on the nut, the generator slipped. I got my hand trapped by that quarter-inch spot, don’t remember if between the nut and the washer or the washer and the beam, with the full weight of the generator.

After a while of silent cursing I managed to extract my hand, mildly bleeding and in pain disproportional to the minuscule size of the injury, as it usually goes. Remembering the war heroes, who despite grave wounds remained at their machine guns, I decided to focus at the task on hand - a good choice, usually, as it takes more heroism points to feel the pain than to distract yourself with pew pewing the targets. It’s surprising how much you can ignore when your brain is busy with even a routine task; when in pain, distract yourself. So, many turns of the wrench later, the generator was lifted by the two feet I needed, and it could be mounted to the welded sockets screwed on the other horizontal beams and with some gentle hammer strokes shifted into the position and clamped down.

The plant was later moved and ran for a short time, yielding mixed results. The generator needed higher speed, the location had lousy wind, and at higher rpms the whole superstructure was shaking like it was having a really good orgasm, or maybe windgasm. Lessons were learned, overall idea was found somewhat viable, Mk.2 is now outsourced to somewhere where they can make way better turbines and the superstructure needs a vastly better design.


#15

When I was twelve or so, I was at home alone watching a discovery or history channel special on steam power and steam engines. They kept throwing up this graphic of a bottle of water on a bunsen burner with a cork in the top. Heating until the steam blew the cork out. I thought that was really cool and wanted to try it myself.

About 2 minutes later I had my dad’s blowtorch in hand and half-full bottle of wine that’d been sitting on its side in the fridge for probably several years (the folks aren’t big drinkers)

I just stuck it on the concrete patio, pointed the roaring blowtorch at its base and waited in anticipation. Until the whole bottle shattered leaving the cork still in the neck of the bottle. I looked down at myself and saw several long slivers of glass stuck to my shirt. They keyholed at me and that prevented them from embedding in my flesh. I cleaned up the crime scene before the parents got home.


#16

#KA-BOOM!!!

(sorry, it got too quiet here…)


#17

Love it. Narrowly missed disaster that the narrowly-missed can laugh about is always good.

Used a hand-cranked lift to raise a main landing gear assembly for a Boeing 707. Here’s some brosefs changing a tire on one, and it’s not rocket science to know that it’s a bigass, heavy piece of machinery. Think the tires, brakes, and that big white column (shock strut) coming up from the central beam between the tires.

Finish working on the gear, and instead of cranking the assembly down, I simply click the latch over to “DOWN” on the lift, without removing the 1.5 foot metal crank handle from the crank.

In .5 seconds, the weight of the landing gear assembly is such that the handle, for that .5 seconds, begins spinning madly…and then it goes away at high speed and in a path that felt remarkably close to my head. I found the crank handle about 50 yards away on the flightline. Had it impacted 1) my head, or 2) any of the other aircraft in the area, bad things all around.

Working with a coworker on an aileron (a flight surface about 4 feet long in this case) that was binding. I see the problem, and with my coworker at the opposite end of the flight surface, I push up on the surface to get at the problematic area (corrosion on a pin inside the wing), but find that the flight surface doesn’t want to move. “It’s binding again, the damn thing,” I think to myself, and push harder on it without results. Look over at my coworker to wonder what’s going on, only to find his face has gone slightly blue-ish and his eyes seem to be bulging out of his head because his finger is trapped between the aileron I’m trying to push up and the wing of the aircraft. He was greatly unhappy with the stitches and bruising.

Lesson learned: aircraft has fuel pump problems, so we fly to a base with necessary fuel system maintainers so they can remove 1) the exterior cover panel–a skinny aluminum cover with lots of screws, 2) the interior tank door–a heavy-ass piece of aluminum, and 3) mess around inside the tank itself. After the jet is returned to us, I check make sure the exterior panel is properly attached and the paperwork signed off (it is and it is), and then begin refueling, intending a ~100,000 lb load of JP-8. Probably ten minutes in, I hear a loud splashing noise, and turn to see JP-8 quite literally pouring out from every hole in the near vicinity of the original work. Tell brosef upstairs in the cockpit to notify the tower of emergency, call the fire dept, cut A/C power and run away all emergency-like, while I close valves and then run away emergency-like (fuel pump operator did not need to be told to run away).

Fuel depot bros never put the main tank door back on the tank, but they DID put the flimsy cover on and signed off on the paperwork. Lesson learned: never trust the godamn fuel depot people–rolling around in JP-8 cooks their brains–and always remove the outer cover if major maintenance has been performed to double check their work.

Set up to do a maintenance engine run, two people in the cockpit working gauges, calling tower, etc., one downstairs on headset ensuring the area is clear of debris or other objects. It was a windy day, and with engines (from the right) 4, 3, and 2 running, I began turning number 1. Dude downstairs bends down to pick up something on the ground, and as I watch, his headset comes off, as does his hairpiece (!). Engine number 2 happily ingests said hairpiece. Lesson learned: bald dudes working on the flightline need to stay bald while working on the flightline.

Lastly: take 1 uncooked egg, tap a small hole in one end and insert generic firecracker almost all the way inside the egg. When ready, light fuse and throw. However, if you throw with your right, do not hold the egg in your left hand to light it with your right, because following the realization that it’s in the wrong hand, you will still attempt to throw that egg with your left hand, even though it will explode right at the point your hand is level with your head. Hearing in the left ear will be gone for a short while and certainly more than half your head and body will now be covered in egg. Lesson: the egg is enough–no need for the explosives.

EDIT: 707 landing gear:


#18

A quickie: When buying perfume for a loved one, maybe you’d like to smell it on your skin first. If so, make sure the nozzle is pointed AWAY from your eyes before trying to spray your wrist. Perfume directed into the eyes had the nasty effect of making the now-blinded and in-pain person drop the test bottle of perfume on the floor, where it shattered and covered that person’s legs with glass shards and perfume. Laughs were heard all 'round.


#19

Fine.

Yes, when I was younger I took a soccer ball, cut a slice in it, half filled it with gas, and lit it on fire.

Then me and a few friends played soccer with it. Since the slit was thin it had a miniscule flame, till you kicked it. Then it would should jets of flame. How we didn’t end up like zoolander is beyond me.

Is that that you wanted to hear!? :wink:


#20

Keys forgotten in chucks. Didn’t happen to me (edit: YET) but fairly common, reportedly.

A badly chucked workpiece. First day with my lathe, mercifully small (read: unusably tiny, after a year and after getting used to it) one. I did not tighten the aluminium stub enough, and did not use the tailstock tip to hold it in place. (Inexperience. Double oops.)

I spun the workpiece up. So far so good. Moved the tool bit into position, it bit into the metal… good for few seconds, then it jammed, the workpiece pried out from the chuck, and went straight for the desk lamp. Crack, goes the lightbulb. Luckily the breakers did not trip.

But trip them I did, later, rather hard. I rigged the lathe with buttons for rotating the motor when a button is pressed, in one or the other direction (useful for thread cutting). But the motor acts also as a generator - oops. And the whole setup has considerable inertia, so there’s quite some energy stored in the rotation of all the coupled parts. The electrical interlock was done well, so no short if I press both buttons. But if I release one and press the other one while the thing is still spinning, the motor-cum-generator connects right to the mains, and feeds its out-of-phase waveform with considerable current right into the power line. POP goes the shop breaker - and the apartment line breaker I tapped for the shop, and the whole apartment 3x25amp breaker in the basement. I have to replace the motor with an ESC brushless one. Or, better, replace the whole lathe for something bigger’n’better.