6roybatty61487 karma2013-01-30 08:32:20 UTC
I once had to order a small swimming pool filling amount of baby oil, and then the same quantity of K-Y jelly. On a corporate credit card. For a car company which shall remain nameless.
The story goes, we were working on a nondestructive testing system (phased array active voxel ultrasound tomography) and we discovered that at the high power levels we needed to use to get our material discrimination signal back with an adequate noise margin, we tended to get cavitation at the transducers. As the youngest and least-PhD-possessing member of the engineering team, I was dispatched to (a) figure out how to stop it and (b) stop it.
So nineteen-year-old me goes spelunking. The first thing I tried was downloading manuals for as many medical ultrasound systems as I could find (this was a long time ago, and the internet was a lot smaller). That didn't really get me anywhere, but I did notice that they use a small amount of water-based lubricant to couple between the subject and the transducer. So I figured that maybe the water we were using was too easy to cavitate.
I then scraped all the literature for anything I could find that related to cavitation, and found that the vapour pressure of the medium was the critical variable. I told my boss and he said we should try some kind of oil. Did I mention that our testing tank held tens of thousands of gallons of water?
So I went looking for reasonably cheap, reasonably dense, optically clear, non-toxic oil, and the first thing I found was baby oil. So I ordered up thirty thousand litres of it. It arrived in 55 gallon drums. We tried it. It was a little better, but still not good enough, and besides with the amount of baby oil mist we were producing from the ultrasonic agitation, everything was getting slippery and I was seriously concerned that it might be flammable, so we put it back in the drums and cleaned the tank (and the test array) down.
So, with nothing left to lose, I went back to my boss and told him that all the medical companies use K-Y or similar. He said "sure, go ahead". So I bought thirty thousand litres of cheap knock-off K-Y. When you buy that much, it doesn't arrive in tubes. It comes in sacks of powder, which you add to water- kinda like a gelatin dessert, except it never sets, it just gels up.
We tried it, and it was about 35% better than water. It was good enough, actually, to get through the first round of prototyping, and then one of the PhDs came up with a pulse shaping method that stopped even water from cavitating, so I designed a circuit to generate those pulses... and then had to get rid of thirty thousand gallons of old, somewhat nasty, used K-Y jelly.
That was only my fourth worst tech job, so hey, it paid the bills.
tl;dr: we were having problems with our giant ultrasound scanner, turns out regular ultrasound scanners use K-Y, so we tried it on ours
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6roybatty61099 karma2013-01-30 09:16:24 UTC
Well, there's the job where I got my now permanent acrophobia and also my astigmatism, due to a shithead and seagull shit; there's the job where I worked 140 hour weeks for a guy who believed I was moonlighting (while being literally the only software engineer on his entire product team); and there's the job where I had literally no idea what I was doing, supposed to do, or how the device I was supposed to test actually worked.
Two of them were monumentally shitty jobs, and did not involve actual shit. They are pretty boring stories, and the 140-hour-weeks job ended up putting me in hospital for a while due to critical levels of burnout. Nobody wants to hear about those. You're probably more interested in the first one; the literally shitty job.
I used to be a network tech. I still am, sometimes, but I used to be one too. Let me describe to you the nature of large manufacturing concerns: they do not have warehouses. In fact, they used to, but they don't any more. The way these systems work now, is that every component, every piece of every component, every cotton plant that goes into every piece of thread that's woven into every piece of fabric that goes into every cover for every seat that's assembled into a car is tracked from the time its raw materials are pulled out of the planet, to the time it rolls off the forecourt of the dealer.
Every step in this process is choreographed from start to finish by systems like Kanban and, broadly speaking, just-in-time systems. In these systems, the components arrive exactly as they are required by each manufacturing step, sometimes as close as five minutes before the robots and/or workers require them to be fitted to the assembly on its way through the stock chain.
So wind time back to the late 1990s, before the age of fat internet pipes and ubiquitous fibre, and think about just what is involved in tracking every screw, every nut, every prill of ABS, that goes into everything your factory handles. You're gonna need some badass network techs. You're gonna need a tower, with a big microwave dish at the top- actually, several, since if your link goes down for any reason, everything is completely fucked and it will cost you millions in downtime.
So you have these big dishes, about 3ft across, at the top of a 200 foot concrete tower, and you need to keep rain out of them, so you cover them in a radome- basically, a fibreglass covering over the dish. That's what those circular things you see on towers are- there's actually a dish inside them.
Now you stuff ten kilowatts or so of microwaves up a waveguide to the top of the tower, they come out in a beam from the radome, and you get your 100 Mbit link to the nearest town, where whatever telco can charge you an arm and a leg to ship it off to whichever destination you choose.
There's a problem with this, if you live anywhere near the sea. The problem is seagulls. They love to stand on top of the radome, because there's a little spill energy from the microwave beam, and it makes them get a little warm. So they perch up there and warm their arses, and this would not be a problem at all except that they tend to shit down the front of the radome.
Fibreglass is transparent to microwaves, but seagull shit is not. If any of the seagull shit lands on the radome- and it will- it will stick there and heat up. Eventually it'll dry out, and then it'll get really hot, carbonize, and destroy the radome- since carbonized seagull shit absorbs microwaves even better than the fresh variety. It'll burn holes in it.
We tried everything you can imagine to get them to stop perching up there- spikes, noisemakers, really bright strobe lights, etc., etc., but the seagulls were determined. They loved it up there because it was warm.
So the solution was to send me up there, in a climbing harness, with a (wooden! don't want to damage the fibreglass!) paint scraper to scrape the seagull shit off the radome. Obviously, tag out the PA running the dish before you go up there, because you do not want to get 10 kW of microwaves in the face.
It was a horrible, thankless job. It became even more horrible one day when someone removed my tag and re-enabled the PA while I was up there, hanging off the front of the radome; I caught the beam in the face and upper body. I let go of the edge of the radome that I was hanging onto, and hung from my harness, as it was the quickest way to get out of the beam. Worse still- the directions for eye exposure to microwaves is to keep them closed until medical help arrives. The blood circulation in the eyelids helps to cool the burns- corneas don't have much circulation of their own. The only problem with this is, it is not possible to climb down a 200 foot tower with your eyes closed.
It took two hours for the rescue services to figure out how to get me down, since I couldn't climb down on my own, and they didn't have a cherrypicker tall enough. In the end they sent a climber up with a 400 foot rope so that they could winch me down on it.
I had to spend several weeks with my eyes closed. It sucked. Blind people have it bad. The guy who removed my tag was instantly fired and his liability insurance ended up paying for the assistance I needed to do everything for six weeks. Fortunately I didn't lose my sight, but as I get older, the little tiny scars in my eyes tighten up a little more and a little more, giving me gradually worsening crazy nonlinear astigmatism.
I haven't been able to so much as climb a ladder since then.
tl;dr: I was employed to scrape seagull shit off of microwave towers until someone microwaved my face
Hey, thanks to whoever got me Gold for this. :-)
6roybatty6575 karma2017-11-28 17:41:32 UTC
He got arrested for putting a flamethrower on a scooter.
It all worked out okay in the end because it was obvious he wasn't actually intending to do any harm to anyone.
6roybatty6178 karma2013-01-30 09:59:50 UTC
Sure. I got a job working as a validation engineer for Hewlett-Packard in 2001. We were building a protocol converter for two different types of storage array. Until this point, I had never worked with either; I had never worked with high performance computing; I had never worked with logical volume management systems; I had never worked with SCSI above the electrical layer; I had never done validation work.
I was completely clueless. Fortunately, I'm also a quick study, so I was able to keep half a jump ahead of everyone else in the team for the six months or so I was there, at which point Carly Fiorina canned our entire division and gutted HP Labs, because she is a fucking moron.
6roybatty6137 karma2013-01-30 09:24:20 UTC
Yep, exactly correct.
In more detail:
phased array: we used an 8x8 array of ultrasound transducers, working as one. By triggering them each at slightly different times, you can change the shape of the beam and the direction it travels, without needing to physically move anything. This means you can scan the beam very quickly, and is how the missile warning radars work- we just used sound instead of radio waves. This technology is how those "3d" scanners work to give you 3d pictures of foetuses, etc.
active voxel: the way our system worked was to pump a bunch of energy into some small region of the test cell, and then listen to how it rang; from doing this (and believe me, I was just the solder monkey and far from understanding how they did it) you can tell the mechanical properties of the material, so you can tell ( for eg.) steel from aluminium, or ceramics from glass.
ultrasound: our system used sound at between 3 and 6 MHz; humans can hear up to about 20 kHz if they are young and haven't ruined their ears with motorcycles and rock concerts. The higher the frequency, the smaller the wavelength, and thus the better the resolution of your system; our system had a resolution of about one cubic millimetre.
tomography: the process of building up a 3d model by measuring slices of an object. MRI, CT, PET, etc., use tomography to image the insides of things.
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