|Nigel Graham 2||12/06/2019 13:21:07|
|434 forum posts|
A light-hearted look at real examples of a strange but common experience, inspired by another thread about simple mistakes.
Can sometimes we be too clever for our own good?
1) I worked in an acoustics laboratory with standard test-rigs used by scientists making experimental equipment. One visiting group became convinced their device had failed, for no clear reason.
Tactfully - these were people way above my educational and professional station in life - I suggested tracing the signals through the system. Each unit was chained through a patch-panel, allowing simple diagnosis by oscilloscope... Sure enough, a nice healthy transmit-side sine-wave from the signal-generator, cut into blocks by the pulse-generator, etc. Credible, low-level received signal, but not reaching the measuring volt-meter.
Hmm. Then the Eyeball, Mark One, spotted it....
The received signal was cleaned by an adjustable band-pass filter, with high-pass and low-pass halves. Normally the decade range switches would mirror each other's position. This time they both faced the same number, so the filter stopped all below, say 10kHz...., and everything above 10kHz. A stop-all setting revealed by mere switch-pattern!
Sighs of relief and several red faces among those of the Exalted Stations In Life.
2) My turn to be caught.
I helped a friend and fellow model-engineering society member restore a water-mill to flour production; but it suffered from strange surges in the stream, shock-loading the machinery, breaking wooden cogs (proper name for mill-gearing teeth), about £12 each.
We realised the sill needed a simple choke board of adjustable height for appropriate powers while diverting surges over the weir...
... so sketched arrangements of screws, wheels, bevel-gears, shafts, journals ....
On my next visit, my mate says, "Done it", pointing to the window-sill. Thereupon reposed the necessaries for setting the choke for milling, idling (demonstration-only) and driving the grain-cleaner...
... Just labelled pairs of plain wooden blocks.
3) Please take this as NOT undermining the memory of some very able, thorough craftsmen no longer with us. Instead it crystallises the above, showing how considerable shared and individual experience can mask the obvious, and prevent conceiving having made basic mistakes.
My society built a 7.25"g, all-fabricated version of LBSC's 'Juliet' for portable-track duty. It was assembled in the club workshop on the usual Tuesday evenings, by some very skilled people; but when they tested it on air, the chassis just would not run.
Things were re-measured, re-fitted; Reauleaux Diagrams sketched... the chassis could still only ooze round half a turn then violently leap the rest.
Some of us also used the workshop on Saturdays. On one such, by chance only I turned up, but I set the chassis running lest fresh eyes spot the oddity. My hand did: air puffing from an exhaust fitting's over-deep cross-drilling. LBSC recommended plugging such with a "weeny" brass screw anointed with sealant.
I left the air on while hand-drilling the tapping-size, to blow the chips outwards (exhaust side, remember). The drill broke through; the chassis nearly leapt off the bench!
Calm restored, cautiously edging the air back on made the engine run, roughly, but somewhere-nearer. Puzzled, I removed the exhaust branch-pipe... corrected the mistake, refitted the pipe, added the LBSC-approved weeny screw. Now it ran somewhere-much-nearer.
I think the ghostly chuckle was only the compressor water-trap.
May I be forgiven for arriving early on Tuesday so the main builders arrived to find me innocently engaged in my project while Juliet peacefully ticked over within tuning of all-correct.
With due modesty, I showed them the original paper gasket, with a tiny relief cut by moisture and pressure where the central hole wasn't.
Still, they say, the man who made no mistakes, made nowt.
I've certainly made many! Sometimes by not thinking sufficiently ahead.
At an exhibition, I was admiring one 3" scale traction-engine as a happily well built, well cared-for romper around the rally-field. The man next to me merely moaned about some minor solecism. Extra rivet...? No, I didn't ask, "Which one's your engine, guv?"
|Martin Kyte||12/06/2019 13:52:16|
|1511 forum posts|
Well it is definitely possible to overthink things, usually when you have a degree of expirience but are faced with something a little new. You can see exactly where things could go wrong but have not acquired any history of it going right which makes you over wary and reluctant to start the process. Generally when you do you wonder what all the fuss was about.
|Howard Lewis||12/06/2019 16:37:02|
|2439 forum posts|
Sometimes the painfully *****ing obvious isn't!
many years ago, a colleague was running engines on extended tests, and one was consuming oil at an alarming rate.
the engine was duly stripped for examination. The acknowledged experts all stood round, debating wall pressures and cross hatch angles, when my colleague asked "Shouldn't those rings be fitted the other way up?"
End of deep discussion.
We've all done it from time to time. I find that electrical equipment works better if switched on, and with a good fuse in the 13 amp plug!
My other silly trick is to remove the sink trap to unblock it and to pour the water into the sink. Shortly before it lands on me.
Edited By Howard Lewis on 12/06/2019 16:39:07
|Stuart Bridger||12/06/2019 17:10:46|
|361 forum posts|
Many years ago, I had a new Peugeot 405. I was doing a lot of traveling with work at the time. If I had been sitting in traffic before stopping, on returning to the car I would find a significant amount of the contents of the cooling system on the floor. It took 3 months of back and forth to the dealer with many tests and components being changed before a specialist from Peugeot was called in.
It was soon identified that the wrong specification radiator cap had been installed in the factory...
|Richard Marks||12/06/2019 17:31:57|
|184 forum posts|
A friend who was a central heating engineer asked me to look at a system that would not switch on, So I checked the mains and I had 240 volts all the way from the plug to the panel using a neon screwdriver, I then got the trusty avo out and I had NO volts anywhere with the positive probe on the positive line and the negative probe on the neutral line but still got a reading with the neon on the positive line, then for some reason I put the neon on the neutral line and it glowed so I switched it all off and did a resistance check from the mains plug to the board terminals positve was ok but the neutral was oc due to the screw in the neutral pin being on the lead insulation and not making contact, rewire and refit and all was well. WHY would I put the neon on the neutral terminal?
|Neil Wyatt||12/06/2019 17:44:33|
16738 forum posts
My dad had someone mock his model of HMS Cossack for whizzing around flying an alfa flag 'I have a diver down'.
Next meeting he produced an old manual of seamanship to demonstrate that in 1937 it meant 'I am undergoing speed trials'.
|237 forum posts|
A mate of mine used to have a Yamaha DT125 which had problems seizing up. The first time the engine seized he fixed it himself, new piston, new rings and gaskets. It lasted about a week before it seized up again. This time he took it to a garage. new piston, new rings, new gaskets and a wad of cash. About a week passed before it seized up again. He was starting to get a bit disheartened and was thinking of selling it so I told him I would take a look. Now i'm no mechanic but it took me about 10 minutes to discover a crack in the head letting water into the cylinder.
4787 forum posts
At school I was the first call for electrical problems in our boarding house. Could not understand the neutral being live until I found the overcautious installers probably in the twenties had put fuses in both live and neutral, perhaps running a balanced system off their own generator. naturally if the fuse went the typical electrician just put a thicker wire in the live fuse leaving the return fuse ready to blow next time.
|Guy Lamb||12/06/2019 22:53:47|
|68 forum posts||
It may be that your school was originally connected to a D.C. supply, as a negative fuse would be required in such a system.
|R Johns||21/06/2019 06:52:45|
|23 forum posts|
My claim to fame. 16 year old just started my apprenticeship and at the company for two weeks before I have to go off to a training centre for a year.
Just fitting a brand new state of the art computer controlled milling machine that takes material at one end and spits out a component at the other. The great and the good cannot get it to work. Two days of computer experts and my new engineering shop manager scratching their heads when I am taken along to see this new beast of a machine.
They were all nosing at the computer screen and seeing if the tool arms moved in the correct order as per the computer program. I am looking at the other end where the work is carried out and spotted a problem. Looking at how the tool holder moved towards where the work piece would be it appeared that when the arm was fully extended it started to spin round on the last 6 inches or so when approaching the work piece.
I did feel a ninny and expect a dressing down when I asked if the cutting tool was the right way up.
Lots of red faces but my reward, the machine program for that component was changed to my name.
|Nigel Graham 2||21/06/2019 07:49:33|
|434 forum posts|
Yes - that's a classic example, R Johns!
I'm surprised someone managed to put the tool the wrong way up though. Was it just the cutter the wrong way round in the collet, or the entire collet chuck upside down?
|Harry Wilkes||21/06/2019 09:14:25|
729 forum posts
A manager who was 'interfering' with a problem with a computer controlling a plant called me over to it and pointed out the on screen text 'Press Any Key To Continue' and bemoaned there was no any key on the key board to which I pointed out to him there were in fact 102 any keys
|colin hawes||21/06/2019 11:12:20|
|502 forum posts|
A company where I worked had frequent trouble with a radial drill motor randomly blowing one or more of it's three fuses. Electrical maintenance people were called in several times to solve the problem, checking everything with their test equipment and finding no fault as the motor would always run again with replacement fuses and their conclusion was that a rewind was required. I took the motor apart myself ( with some difficulty) and found the stator and rotor almost seized with accumulated sticky debris from years of use. It ran faultlessly after that was cleaned off.
|R Johns||21/06/2019 11:12:34|
|23 forum posts||
3770 forum posts
Two degreed engineers came down to the boilerhouse at the car factory to show us how it should be done after the gas company cut off the supply to repair a gas main. Two of the boilers were heavy bunker oil fired, water tube boilers the size of a small two-storey house.
The gas company when the gas is "cut off" keeps gas in the mains at one or two PSI to stop air getting back into the gas lines and causing a flammable mix that could explode easily.
So these two dudes try lighting one of the heavy oil fired boilers, after ordering the boiler attendant out of the way, using the feeble flickering flame from the gas ignitor. But the low-pressure gas flame was too feeble to touch off the heavy oil when they tried to start the boiler up. So they just kept running the boiler through its start cycle. Fan on. Gas ignitor flame on. Heavy oil valve open. Over and over again. Filling the furnace with unburnt heavy oil, which soaked into the brickwork.
After several hours of trying, they got lucky and touched off a flame. Ignited all that oil and fumes accumulated in there and blew two large explosion doors out the back of the boiler furnace, sending massive boiler-room window sheet glass across the main entrance road to the plant, minutes before 4pm knockoff siren and 4,000 workers streamed past cheering them as they skulked off, leaving the apprentice (me) coming in on afternoon shift to sweep up their mess.
Before the afternoon shift was half over, we had hooked up a barbecue gas bottle to the ignitor and got the other boiler started first try. Dunno what they teach those guys at university.
Edited By Hopper on 21/06/2019 11:33:00
|Howard Lewis||21/06/2019 21:12:01|
|2439 forum posts|
They could probably tell you a lot about the valency bonds, and electron orbits used in the hydrocarbons.
But don't ask about the flash point of the bunker fuel!
3770 forum posts
Oooh they wouldn't have expected mere mortals like us to understand anything like that.
|Dave Wootton||22/06/2019 07:21:24|
|15 forum posts|
I used to be a refrigeration engineer, working for the manufacturer of large industrial chillers, not a bad job, but the one thing I hated was being on standby one in every five weeks.
One bank holiday Monday I got a call to go to a research establishment in Cambridgeshire, so had to drive from home in Sussex to the site, took nearly four hours in horrendous traffic. On arrival was shown to the machine, swarming with all the highly qualified technicians they could muster, who from their description had a good idea of what they were doing and had thoroughly checked everything. The machine was important in their research process and things were about to get critical.
Feeling under a bit of pressure now I thought I might as well see what was going on with it, so switched on the small rocker on/off switch on the control panel, watch it time itself out ( anti-recycle timers) whereupon it started bringing the compressors on line. On hearing the noise I was surrounded by a crowd asking "what did you do?". " just switched it on" I replied.
Red faces all round, the machine was controlled via a computer control system, so they had never used the switch or registered it's presence. We made up some feasible excuse on the job sheet to save their blushes and I headed home in the traffic, took me five hours to get home!. Never did find out who switched it off or why.
Just goes to show we can all get it very wrong sometimes!
|martin perman||22/06/2019 09:24:57|
1684 forum posts
My father spent most of his working life as an engineering draftsman and for a while he worked at the company where I served my apprenticeship, one of the apprentices spent six months at university and six months in the factory learning about the busuiness. My father became his mentor and taught him to draw and one afternoon a special bolt from a machine needed to be drawn for manufacturer and it was given to the apprentice, my father said he made a lovely job of the drawing of the bolt but it couldnt be used as when he had been given the bolt the two broken parts were tapped together and that is how it had been drawn, the apprentice was described as being so clever he was thick as he could never see the wood for the tree's.
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