"This is a true story which I saw with my own eyes. In Arkansas... It was in the afternoon, at a boiler plant. Boilers have an induced draft fan that pulls combustion products from the combustion chamber. A big, big fan with an electric operated throttling damper.
The damper began behaving erratically and the operator jumped up, grabbed a firehose and started hosing down the actuator housing. I asked him what was going on. He said that the actuator had overheated and he was cooling it down and went on about it being a bad design.
Anyway, the actuator began working properly. He said this happens when the sun shines on the unit etc. And it was a bad design etc., Etc.etc
Then it happened again at 11:00 PM. Same story. I asked him about the fact it was cooler and the sun wasn't shining on it. Don't recall his answer but he explained it all away, got the fire hose out and fixed it and I got the bad design lecture again.
Turned out to be a loose wire. The shaking from the fire hose always fixed the problem temporarily and reinforced his belief.
He was truly disappointed."
> [O]ne of the earliest [applications] of dither came in World War II. Airplane bombers used mechanical computers to perform navigation and bomb trajectory calculations. Curiously, these computers (boxes filled with hundreds of gears and cogs) performed more accurately when flying on board the aircraft, and less well on ground. Engineers realized that the vibration from the aircraft reduced the error from sticky moving parts. Instead of moving in short jerks, they moved more continuously. Small vibrating motors were built into the computers, and their vibration was called dither from the Middle English verb "didderen," meaning "to tremble." Today, when you tap a mechanical meter to increase its accuracy, you are applying dither, and modern dictionaries define dither as a highly nervous, confused, or agitated state. In minute quantities, dither successfully makes a digitization system a little more analog in the good sense of the word.
— Ken Pohlmann, Principles of Digital Audio
Oh, indeed. I remember my father, a disabled former engineer, having an expensive McIntosh audio system. He was always fiddling with it, fixing it, applying anti oxidation spray, etc. My parents decided the large wall furniture (in which the audio system was, together with books, TV, etc) was to be replaced.
It turned out that during the giant relocation one of the compartments of his system (IIRC it was the tuner, but it might have been the pre-amplifier or amplifier as well) had become broken. My father, who was nearly blind, made it his project to repair the installation. He was failing, and my parents discussed sending the broken part of the audio system back for repair which would set us back a large sum of money.
Then, at some point, there was an earthquake of 5,5 on the Richter scale. (Having just looked it up the epicenter being 5,8 it was the largest earthquake ever registered in The Netherlands.)
The damage: a photo of a family member, protected by glass, had fallen and the glass was broken. In our wall, a rift appeared. Many things just weren't on their correct place. The radio? Ah, the radio. It worked again when it was put on!!
After a few weeks I narrowed the problem down, it happeneed in the late afternoon, but it worked fine in the evening. It also worked when it was raining.
So it had something to do with the sun shining through the window.
So I took the mouse apart and found that it had little rollers inside, each roller had a small black disc with holes in it. An LED one one side and a photoreceptor on the other... I assume it worked by counting the flashes of light through the holes in the disc.
The plastic cover on the mouse must be semi transparent and when hit by the sun, the photoreceptor was giving weird readings. I covered the mouse in black tape and never had the problem again.
I heard a story about a terminal in a public terminal room that a user was able to consistently log in to if they were sitting down in a chair in front if the terminal, but never if they were standing up.
They thought it might be static electricity, or some mechanical problem, or "problem exists between keyboard and chair", but finally they noticed something else was amiss...
It turns out some joker had re-arranged the 1234567890 keys to be 0123456789, so when the user was standing up, they looked down at the keyboard and typed their password (which contained a digit, of course) by looking at the keys. But when they were sitting down, they touch typed without looking at the keys, and got their password correct!
Edit to add: It appears my parent and I had different assumptions regarding the setup, which we cleared up below.
Admittedly I've not looked hard, but never saw a desk for sale as good as the ones Southwestern Bell had for everyone back then.
What do you know? I google "snopes car allergic to ice cream" and find that it's an urban legend: http://www.snopes.com/autos/techno/icecream.asp
I had a an old motorcycle years ago that was the same way as this guy's car. If I stopped to grab a snack, my bike would not start again. If I stopped for lunch, then it would fire back up no problem. Sure enough the problem was vapor lock. However the time needed for the bike to cool enough was about 15-20 minutes, not the couple minutes mentioned in this story.
What could it be? Nothing that was done was related to ignition or electrical systems at all. Yet it wouldn't start.
<spoiler> the new floor mats were too thick. Couldn't push the clutch down far enough, and this manual car you had to have the clutch in to enable the ignition. Just nudged the new mat back, problem solved.
Isn't it relevant to note that this problem was not real? It seems to kind of undermine the point if the author did not know of any insane-looking problem that was actually real, and had to make one up...
If you're hung up on the fact that the story isn't real, it means you aren't thinking about the moral of the story. You're focusing on the wrong thing despite the fact that the insight is being spoon-fed to you...
Incidentally (though respectfully... really!), this is a textbook example of pedantry, and it's the bane of our profession.
More to the point, fiction often points to truth in ways non-fiction cannot.
It's fine if the author uses a fictional story because it flows better. It not fine if the author uses a fictional story because they can't source a single real one.
There's no reason to make things up. Just listen to the old car talk shows - you hear one almost every episode.
Stories can be insightful or not-insightful based on what they teach.
Some kinds of thought patterns are useful to consider even if there is no basis in reality. Some aren't.
This story is in the latter group. If insane problems never happened, then this story would not be insightful.
Re read the story, it has a lot of darkness to it.
It also teaches a bad idea. No, more often than not things have simple solutions. Not the highly complicated version here of sending out an employee.
Just get the car serviced.
Driving to the store every night for Ice Cream seems like a waste of time, unless he really needs to get out of the house.
The 500 mile email
(Also mildly upset that units on OS X only has 586 units and 56 prefixes, fortunately brew install gnu-units to the rescue!)
If you're interested in computer stupidities this website (lynx friendly) is one of my favs: http://www.rinkworks.com/stupid/
Most of them aren't related to engineering; rather computer helpdesk stories from the previous century.
There was another that amused me about the server rebooting in a haunted data center:
We had a piece of software that would present a dialog for the user to select a file, then parse and send the contents to an embedded device. This software was an internal tool and not very reliable, so it would crash if you selected a file with invalid contents.
Two engineers, Dan and Brian, came to me with a tricky problem. Every time Dan would open a specific file everything would work fine. Every time Brian selected the same file the program would crash. I was obviously skeptical and went to watch. We tried it 10-20 times and sure enough, it always failed for Brian and worked for Dan. I watched them perform the exact same steps.
Eventually I gave it a try myself and realized what was going on. Dan would click "open", select the file, then click OK. Brian would click "open" then double click the file.
I recently filed a bug with Chromium. It took me about 3 hours to isolate the problem and build a simple test case when I could have just reported "My HTML5 game fails to load when I refresh the page" - making it extremely time consuming for the Chrome maintainers (much more so than it was for me) to find the culprit.
Please isolate the problem when reporting bugs!
I bring a replacement but first sit town and test-drive it without any issue, to her surprise. Next, I watch her type. Now, this user happens to be a rather large woman, working at a somewhat cramped desk. After typing for a bit, she exclaims, "See, it's doing it again!" Sure enough, spaces are appearing in her word processor, and her thumbs are not pushing the spacebar. Her breasts, however, are. I delicately explained to her that she is "leaning" on the keyboard. By rearranging her desk and seat, the problem was happily solved.
Probably the most apt PEBKAC I've witnessed.
> Knight, seeing what the student was doing, spoke sternly: "You cannot fix a machine by just power-cycling it with no understanding of what is going wrong."
> Knight turned the machine off and on.
> The machine worked.
One day while processing a batch, he noticed one parcel was giving the most awkward results. Totally different that anything he ever saw. This bug troubled him for almost a week, he couldn't figure out wether the satellite malfunctioned or if something was amiss in his calculation. Then it clicked, and a quick internet search confirmed his intuition. The satellite took the picture right in the middle of a solar eclipse!
About half a year later we were working in the server room, replacing a server when a colleague unplugged the old UPS in there. Unplugging the UPS for a minute shouldn't be a problem. The battery would take over and nothing would go down.
But well, the two servers attached to it immediately went down. It took me a minute, and then it dawned to me that this was the problem. The UPS did a test every other Friday, shut the power off as a test, which caused the two attached servers to restart, after which the webserver didn't start...
We removed the UPS as we didn't need it in the first place, problem solved.
This doesn't happen every time I drive home. It might depend on environmental conditions. It won't ever happen if I just go for a quick drive up and down the hill. The dealership has not been able to find anything wrong with it or come up with any explanation. This has been happening for over two years, it's a 2013 Honda hybrid, bought new. I've speculated if it could some brake-related issue that only manifests when braking regeneration is suppressed when the battery is full. Has me at my wit's end. When I get home from work the dealership is closed, and even if I could make it into the dealership with the thing clanking away, by the time I could get in and talk to someone the noise would go away unless I had them on the phone and ready to hop into the car at a moment's notice. So much for the warranty.
It was a rusty/incorrectly installed brake pin. Sometimes brake pads wouldn't return after you stop pressing the brake pedal. After brake system rebuild everything moves smoothly and brake pads always return to the initial position - no more weird sounds.
Also, when changing the brake pads, I've noticed that one of the pads (that was failing to return) was much thinner than the others.
Problem is: when they change the brake pads in the dealership/garage, they don't rebuild the whole system or grease the pins properly. You will not notice and they're not paid for the extra quality work. So things like this happen quite often.
The only way to do everything properly is to do it yourself. In case of a brake rebuild it's not very difficult but very time-consuming. Most difficult part was to insert the new piston back in the caliper.
If the latter, it'll likely be a caliper & disk getting hot and expanding, and rubbing, which can make an almighty racket - and then when they cool again they contract, meaning that a cold inspection would reveal little.
Alternately it's a wheel bearing on its way out, but that's unlikely on a new vehicle.
Does it get any better or worse when you apply steering, or not change at all?
I had wheel bearing issues with a previous older car, under similar circumstances. I checked steering, it doesn't seem to make much difference. The dealership dismissed wheel bearings as a possibility and said they checked the CV joint.
Their only theory the first time around was a small rock or something getting stuck in there and working its way out. The old "mud in your tires" sort of thing I guess (Joe Pesci reference). That's a mighty devilish rock.
I don't know if it is the same noise, but I had a loud, fast paced, 'whoom, whoom, whoom' sound on my Honda Civic Hybrid from 2008 when going downhill a lot.
Living in the Netherlands (mostly flat) I only had this during holidays in less flat parts of Europe. Never thought much of it and when asking the dealership they never heard about the problem, but also could not see anything wrong with the car. And it only was reproducable in mountain areas, and took a while to surface...
Then after about 3,5 years, after a holiday, the sound was almost always present. Drove to the dealership and the brake discs needed te be replaced, they were 'square'.
I was not allowed to drive another mile (kilometer in my case ;) with the car.
I always brake as less as possible going downhill, and always use the L (low) gear position, but can't prevent it. The roads in the Swiss Alps are so steep, only low gearing does not help, at least not with a Civic Hybrid. I don't drive with my foot on the brake all the time, but pump the brakes when really needed.
(in comparison, the Seat Ibiza Diesel car I had before could slow down a lot better in low gear, almost no braking was needed, but when going downhill with the Civic in low gear, it goes faster and faster, until you just must brake. Also the Ibiza was manual gear, like most cars in Europe, the Civic had a CVT)
The dealership thought it could be a result of the brakes getting hot when going downhill (cannot be prevented) and then keeping the foot on the brakes when standing still deforms the braking discs.
Using neutral gear position and if needed the handbrake when stopped, could be prevent it from happening again.
After replacing the discs I drove the car another 1,5 years until October 2013 and never heard the sound again.
The last stretch where it goes down to 40 and then 30 is steep enough that engine braking without any brake pressure at all is not going to happen safely. And there are lights too, I almost always (but not always) hit at least a couple of them coming into town, so stopping is kind of mandatory there (and unpredictable).
I don't have a habit of riding the brakes though, I'm either gently depressing them or my foot is off. But without gearing down there's going to be a significant amount of intermittent braking; just not continuous.
Now I could start the car fine, usually. But after driving for a few minutes, if I came to a stop the car would stutter, lurch and stall. I would then restart the car with a bit more effort and continue to the next stop, where the problem got worse and it would take longer and longer to get the car restarted. But eventually the car WOULD restart and I would continue on.
It was the perfect confluence of conditions to promote all kinds of stupid behavior. I always said, "I'm not driving again until I get this fixed" and two days later saying, "wellll, I can make it to the supermarket before it stalls!"
This went on for MONTHS, with the overall problem getting steadily worse. I could feel the car fighting to stay running as I slowed down. I became a master of giving myself a huge lead up to red lights and slowwwwly lurching up to them, desperately hoping the light would turn. One time I took a rolling right turn at a red, did a u-turn, took another right and kept going. One time I stalled at a tollbooth for 10 minutes. Like I said, I was an idiot.
I was certain this was going to be some tragic $1000 repair that I could ill-afford. When I finally brought the car in, the mechanic could find nothing wrong - except my air filter was exceptionally dirty. The car had simply been choked to death and needed more and more WIND to provide oxygen for combustion.
A family friend was a service advisor for a GM dealership in the 60's and early 70's. He told this same story to me in the late 70's.
Whether its true, or, was used to teach service advisors not to dismiss 'crazy claims I don't know. But it's been around longer than year 2000 cited in the story.
Edit: So its an urban legend. At least this one predates the Internet
I might not always be able to figure it out, but I at least try.
We had a small clock that we kept in the closet. When you got up in the morning to get your clothes you could also see the time of day. In a quiet night, you could hear it ticking away.
One night it stopped ticking.
In the morning, we opened the closet to see if the battery had died. We gave it a good 3 seconds to make sure the needle wouldn't move, ... It did. It started ticking away.
The night that followed we stayed quiet and listened. It was quiet. So battery first thing in the morning. Morning came, we opened the closet door. 3 seconds later, it ticked. That was odd.
In the middle of the day we came to the closet, opened the door, the needle was still. Some seconds passed, the little clock started ticking.
Now it became knowledge in the whole family. We were kids so we would take it for a game. From time to time we would just stop talking and listen and hear nothing, we open the closet the clock is still, then it starts suddenly. We called it a ghost.
Years went by, new batteries were put in place, the clock still behaved the same. Everytime you started looking at it, it would start ticking.
It became a boring thing. No one cared about the little clock any more. I would open the closet, see it still, take my stuff and close it and it wouldn't even tick. But then i open it back up and it starts ticking two seconds later. Meh.
Then i had an idea. It was an idea so crazy that i was scared to try. I consulted with my brothers their eyes grew wide... So we did it... We removed the battery from the clock and closed the door.
Thr next morning was quiet. We were getting ready to go to school. All three of us stood in front of the closet door. Ready to see what was going to happen. My older brother opened the door. And the clock was there, quiet.
One second passed. I was afraid of what was going to happen. Two seconds passed. Lord please... Three ... Tick.
I'm sure that's not the only possible explanation.
It is just an alarm clock that runs on batteries. I'm unsure if the alarm function still works or if it keeps time, even though it runs the wrong way. It is weirdly one of my favorite possessions - in fact, "The Clock which keeps Untime" is generally the only visible clock in the house save for computer monitors.
Can you explain this a bit more?
I heard this in a presentation that was emphasizing the need to actually speak to the Ops folks before deploying the solutions that dev dreamed up:
A toothpaste factory had a problem: Due to the way the production line was set up, sometimes empty boxes were shipped without the tube inside. People with experience in designing production lines will tell you how difficult it is to have everything happen with timings so precise that every single unit coming off of it is perfect 100% of the time. Small variations in the environment (which cannot be controlled in a cost-effective fashion) mean quality assurance checks must be smartly distributed across the production line so that customers all the way down to the supermarket won’t get frustrated and purchase another product instead.
Understanding how important that was, the CEO of the toothpaste factory gathered the top people in the company together. Since their own engineering department was already stretched too thin, they decided to hire an external engineering company to solve their empty boxes problem.
The project followed the usual process: budget and project sponsor allocated, RFP (request for proposal), third-parties selected, and six months (and $8 million) later a fantastic solution was delivered — on time, on budget, high quality and everyone in the project had a great time. The problem was solved by using high-tech precision scales that would sound a bell and flash lights whenever a toothpaste box would weigh less than it should. The line would stop, and someone had to walk over and yank the defective box off the line, then press another button to re-start the line.
A short time later, the CEO decided to have a look at the ROI (return on investment) of the project: amazing results! No empty boxes ever shipped out of the factory after the scales were put in place. There were very few customer complaints, and they were gaining market share. “That was some money well spent!” he said, before looking closely at the other statistics in the report.
The number of defects picked up by the scales was 0 after three weeks of production use. How could that be? It should have been picking up at least a dozen a day, so maybe there was something wrong with the report. He filed a bug against it, and after some investigation, the engineers indicated the statistics were indeed correct. The scales were NOT picking up any defects, because all boxes that got to that point in the conveyor belt were good.
Perplexed, the CEO traveled down to the factory and walked up to the part of the line where the precision scales were installed. A few feet before the scale, a $20 desk fan was blowing any empty boxes off the belt and into a bin. Puzzled, the CEO turned to one of the workers who stated, “Oh, that…One of the guys put it there ’cause he was tired of walking over every time the bell rang!”
You do also need to factor in the electricity costs for the desk fan, although it probably still is a lot more economical than the $8 million solution.
Natural languages are ambiguous...
Only to spend 3+ hours troubleshooting other things, discovering in fact, it was the simple dumb thing.
I TA'd a course in college that (among other things) was the first introduction that CS students at my school had to C programming. Since most students had no prior experience with anything besides Java (and a little OCaml, because one of the intro courses was half Java and half OCaml), they often would be at a complete loss of how to debug errors with pointers, string handling, etc. Whenever I tried to help students debug something in office hours, they would try to steer me away from looking in certain parts of their code because they "knew that was correct", and quite often the error would be in one of those parts of the code. The lesson I tried to teach them was that if you thought you wrote all your code correctly but it still doesn't work correctly, then you must have been wrong about something, so you have to be ready to challenge your assumptions about what's working and what isn't.
After running for decades, it was finally retired in 2012. The archives remain, in my opinion, some of the finest exercises in logical problem solving.
fun story though.
My theory is that the USB hub had a bad capacitor or some such which needed to discharge fully before communication on that port could happen. Funny thing is that she worked in tech support and would give this advice to others all the time.
If I made a quick stop then got back in my vehicle the automatic transmission wouldn't shift from 1st gear. I had to do all kinds of shifting stopping voodoo to get it to work.
I had brought it to the dealership several times but their mechanic said nothing was wrong or he couldn't find anything wrong. I didn't tell them it was the ATM a using it I said it was quick stop and go situations.
It still does it ocasionally but it seems age and wear are helping diminish the occurrences.
Pleased to see it again