In any sensible engineering design, you have the *deliberate* inclusion of the fusible / weak link in the chain, in any complex engineering design, you have a cascade of them.
One of the peculiarities of english domestic electric wiring came about after the last war, and it was the ring main, as opposed to the spur main you get most places in the world.
One of the misconceptions going around nowadays is that this came about because it was just after the war, and copper was in short supply, the theory being that you *can* use thinner conductors in a ring main than a spur main for the same current carrying capacity.
The truth is that yes, there were post war shortages of all kinds of things, but the ring main was chosen because it was more robust, remember, we’d just come out of a war where everything had been bombed to shit…
So each floor had a ring main to the power sockets, and a separate ring main to the lighting circuit, typically the power ring mains came with 32 ampere breakers on the consumer unit, and the lighting circuit with 8 ampere breakers (which is why you could back in the day plug your new electric clothes iron into the lighting circuit) plus any additional heavy 40 amp duty spurs/rings to things like electric cookers or electric immersion water heaters or night storage heaters, eg shit that was permanently wired in, the ring mains per se were for stuff with plugs that could be plugged in or unplugged at will.
Voltage was always somewhere in the region of 220-250 volts AC, and frequency was always 50 hertz because you run a 4 pole genny at 1,500 rpm to get that as opposed to the US 60 Hz which required 1,600 rpm.
Again you’ll be told a lot of shit today about 50 Hz being chosen because it was “metric” but that is total bollocks, transformers and stuff tend to be bulkier to handle a given load at 50 Hz vs 60 Hz, but the real reason was at 50 Hz capacitance and inductance in the conductor make it a better frequency for power transmission over distance than 60 Hz… but Edison liked Tesla’s 60 Hz because it gave a more solid light with an arc lamp than 50 Hz, but Tesla favoured 240 volt three phase, and Edison already having put out 110 volt DC Tesla / Westinghouse / Edison went with 110 volt AC @ 60 Hz.
There were *lots* of others, any closed off system such as a city tram or a mine could have some completely proprietary system, because it fitted better that specific use.
Today if you want to make something really cheap and nasty and light you’ll spin a 2 pole gen head at 3,000 RPM to get 50 Hz and 3,200 to get 60 Hz, a direct couple it to some piece of shit engine screaming it’s tits off at the same RPM.
If you want your grandkids to still be using it you’d go 8 pole and 750 RPM for 50 Hz or 800 RPM for 60 Hz, voltage is of course controlled by the field current intensity.
Of course with AC and a properly designed transformer each side of the transformer is isolated from the other, so you can trade current and voltage across the transformer, but of course you can never trade frequency.
Of course, if you measure ACTUAL mains with an oscilloscope, you do not get a perfect sine wave, same as when you measure DC in your car or PC, it’s anything but a perfect flat line…
However, one of the peculiarities of a ring main with a 32 ampere breaker is that potentially every socket can deliver 32 amperes, and 32 x 230 = 7,360 VA/W, so we get the other peculiarity, which is the fused plug, and the fuse is there *only* to protect the plug and wire, not the device at the end of the wire or the person using it.
(As an aside I grew up seeing two sizes of round pin 3 pin plugs and sockets, smaller 5 amp ones and full size 13 amp ones, both in use at the same time, in the same houses..)
Then there are fuses etc within devices themselves, current and earth leak breakers for each circuit in the consumer unit, another bigger breaker between the consumer unit and the mains supply, and then more “weak links” back up the mains supply.
So, right up until you get to the actual national grid itself, you’re basically tripping over a whole series of weak links that both isolate things and limit propagation outside the thing with the issue.
*Your* house can burn to the ground, your neighbours can run an extension lead out to power the water pump to draw from the pool to try and put the fire out.
It was the same with your car and the brakes, two separate circuits, doing wheels at opposite corners, lifts had to have cables that would carry 8x the max load you could put in the lift, but they also had speed actuated brakes so even if you cut the cables…. trucks took air pressure to keep the brakes off, so any leak and on they come…. boilers and plane wings had holes where cracks might develop, to arrest their growth, the first pipes that came out of a boiler had a bursting pressure somewhere in between the pressure at which the relief valve blew off and the bursting pressure of the boiler itself, it went on and on and on and on.
Everywhere you looked, there were deliberate weak links, you could not get a Ford dealership from the factory unless you also carried 80% of the drivetrain parts catalogue in stores in actual stock, and if the required part was in the 20% you didn’t have you’d be as likely to check the nearest two Ford dealers as the factory for the item… thus eliminating the weak link that the factory had to carry all the stock for everything all the time… and the weak link of the delivery of that item to the dealer.
Preppers are big on canned and dried foodstuffs, because the weak link in frozen is the power to run the freezer.
We *used* to have a fridge that would run on kerosene *or* electricity, it worked a damn sight better on electric, but it did work on kerosene, two separate circuits of course, I believe it was ammonia in the kerosene side.
In the kitchen now I have an “instant” gas powered water heater that does hot water and central heating water, these are two separate water circuits, and they have two separate heating circuits, in summer you turn on a “hot” tap and the central heating water isn’t touched… so yeah, the central heating circuit needs a mains powered circulating pump, but the hot tap water works on mains pressure, so why the fuck does the whole thing stop working when the mains goes off? There is FUCKING NOTHING in that circuit that *requires* any kind of electricity, so even if you use electronic controls all you need is a backup DC battery for when the power is off, even if all it is is 4 x D cells to get 6 VDC….
So now when the power goes off, so does the gas water heating, and the gas cooker (in this house I can just feed it inverted 230 VAC from a 12 VDC battery) I mean what the fucking fuck is that all about…
This isn’t a “weak link” from a safety perspective like a fuse, that isolates the bad system, this is a fucking weak design, so whether it be a safety fuse blowing or a power cut, we now get a cascade failure to a *totally* separate system.
IT / Computers and interconnected databases are a prime example of this.
Here in the UK, if you are unemployed, you can claim unemployment benefit (I think the latest rebranding is calling it job seekers allowance or some shit), and if you are unemployed, or UNDER employed (part time or low wage) you can claim housing benefit assistance, and if you claim housing benefit assistance, you can claim council tax reduction.
I knew someone a few years ago, the DSS sent him a letter (they claim) saying come in, we want to talk to you, he did not get it so he went in as usual to sign on on his usual day.
To be told his unemployment claim had been cancelled… he spent the rest of that day and much of the next getting it re-instated.
Little did he know, that 94 microseconds after he missed his appointment and his unemployment claim was shut down, the unemployment computer told the housing benefit computer that he was no longer unemployed, so his housing benefit stopped, so he did not know it yet, but he would not be able to pay his rent that month… and a few milliseconds later the housing benefit computer told the council tax computer that he as no longer getting housing benefit, so the council tax computer cancelled his council tax discount, and sent him a bill for 700 quid for council tax…
In actual fact there were a few more automated things involved, a complete cascade failure, as it happened he was able to borrow 500 from me and 500 from another guy and 250 from his mum and a few weeks later it was all sorted out… he was lucky… he could have been on the streets, and started an entirely new set of cascade failures, because no address is “No Fixed Address” and that triggers a whole new bunch of shit, and trying to claw your way outta that is hard.
The recent BA debacle was a classic cascade failure, the head of BA IT says it has fuck all to do with cost cutting, in principle it doesn’t, until cost cutting throws out the rule books and starts cutting no matter what/// which *is* what happened.
Here is a small pop quiz.
1/ How do you start a manual gearbox car with a dead starter?
jack up one rear wheel, put it in top gear, turn ignition on, grab rear wheel and turn smartly, the diff will do the rest… if the battery is flat but starter is good two 6 volt lantern batteries in series will energise the coil enough to get her going, mechanical diesel even better.
2/ How do you move a car with a dead engine / no fuel off the carriageway?
Put in first gear, release all brakes, crank starter and steer
3/ How do you get a car that has lost traction on snow / mud / sand etc moving?
Deflate all tyres to 5 psi and move off slowly with minimum engine rpm
OK, a lot of this shit is defeated in a modern electronic computery whizzbang car, but it’s symptomatic of a society where nowadays basically nobody knows what used to be basic shit that everyone knew, my dad used to say when I was a boy that the definition of a good car battery was it would crank the vehicle 400 yards on the starter alone.
If nobody knows it, nobody can build in weak links to prevent cascade failures, fucking keyless entry and keyless ignition is a case in point, ain’t fuck all it does that a key cannot do better.
Can’t blame key technology for people like Ford making keys and locks so weak any escort key fitted any escort.. lost track of how many cars I head where the ignition switches went south so I just broke off the steering lock and added an ignition and a starter switch to the centre console somewhere.
The current HD is an ’02 model so it has one of the older systems with a button / proximity fob with a CR2032 battery for the alarm, and a non retained key for the ignition, so I have to replace the fucking 2032 in each fob every two years, (and a spare fob hidden in my jacket lining) otherwise it will die and I’ll be fucked because no cunt can remember the sequence of indicators and so on to get to the point where you can manually type in the fucking security code to be able to ride away.
The new ones are ten times worse, but thankfully the 883’s are blowing cranks so early you won’t want to ride anyway.
I actually know one cunt with a ’14 HD who got on his bike, which started because the fob was only 3 feet away on the shelf in his garage, so he rides off and stops for gas 50 miles away, and it won’t start and the alarm goes off every time he goes near it, because the fob is still 50 miles away in his garage….
I took huge pleasure. while he was getting stick from some lads, in walking up and telling him the old joke, “90% of all harleys ever made are still on the road….. 2% of them made it home….” LMFAO
It did *not* go down well.
The *first* thing I did was put my spare fob in the secret pocket in the lining of my jacket, which I *never* ride without (along with a £20 note) because *some* cunts don’t need to actually make a cunt of themselves to see an obvious failure mode and take steps to prevent it.
I still think it’s a fucking asshole system, and maybe one day I’ll rip into the wiring loom and make it old school, fuck it I’m back to carb and everything else on it.
Bottom line is it is still basically a pre-unit motor with OHV and pushrods and so on, so there is a lot worse shit to have to rebuild (like the new HD M8 motor)
Oh fuck, my left indicator bulb just blew so now the ECU has cut the power to the ignition circuit, I’m only *slightly* taking the piss here.
I’m waiting for the stories about the guy who decided to play some kraftwerk / electro-pop and acoustic tone coupled to his amazon echo in binary and managed to order a giant horse dildo…