12-volt fatal shock Re:'snow-clearing train'

I got the belt of my life breaking a circuit from my toy train transformer to an electric motor in my Meccano set.

Wasn't till ten years later I learnt about inductive flyback voltages. Easy to get 250v+ out of breaking an inductive circuit carrying current from a 12v source,. That's what a car coil is anyway. starts at 12v, break it, primary goes to -300 to -400v and secondary goes to 25KV or more if the spark gap don't short it.

IF the starter was stalled and on and someone disconnected the battery, then easily a very big current 400+ volt spike for a few milliseconds.

Normally not enough to kill, but with a hearty condition..?

We are told that there was no underlying health condition.

Within reason, the body can withstand some very high voltages - the killer is current.

The EHT on monochrome TVs, for example, was from about 10 to 16kV but from a high impedance source, so you got a belt and cursed, but that was all there was to it.

The introduction of colour with its power hungry shadowmask tubes was a differnt matter entirely as not only was the voltage much higher, at 25kV, but it was generated by a relatively low impedance source. It's surprising how safety conscious one becomes overnight when you realise you are now dealing with something that is lethal ...

Going back to your Meccano motor, I had a Trix construction set from which I built bells and buzzers. One project in the manual modified a buzzer by adding two wires connected to metal 'handles' to turn it into an electric shock machine ...!

iffernt matter

h I built bells

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Funny how things have changed, that sort of thing was normal but now quite unacceptable.

NT

It's volts that jolts, but mills(*) that kills.

(* milliamperes)

Could have been a Wimshurst Machine? (also require a couple of Leydon Jars). On list of 'one day' projects...

jon N

built bells

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Not sure if this delivers real shocks or just vibrates...

Cheers,

Colin.

I've only had one shock from a colour TV, and it bloody hurt. Certainly not something I'd care to repeat. Mains shocks tickle in comparison :-)

cheers

Jules

My last mains "tickle" sent me 6' across a room, from a standing start, into a wall. Not sure what hurt the most, the shock or hitting the wall. Or possibly it was the embarrassment of being an idiot?

I had a 440v shock once, working out of hours testing a boiler control panel, crouching down holding the flame sensor (a bloody good earth) near a candle to simulate ignition, overbalanced and grabbed the nearest thing, a

The 600V DC on the third rail is enough to seriously burn and often kills outright.

A 12v supply and an inductor with wet hands and an arcing contact is quite enough to generate several seconds of 400vAC. Starter motors draw a few hundred amps on starting..

It would require some 'skill' to disconnect the battery while the starter was turning...

This story will turn out to be the usual urban myth. Where they've left out the faulty mains battery charger he was connecting - or whatever.

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I remember there being an electric shock machine outside the lower tram station on the Great Orme in Llandudno. I think it took pennies and there was a fixed brass handle, a rotating one, and a meter, and I suppose the idea was to see how high a voltage one could stand.

Regarding shocks from batteries, I recently heard of some chaps who claim to have been told on a Balfour Beatty site induction that the use of battery operated tools is not permitted if there is a drop of rain in the sky- it sounds a bitt OTT and of course they may have misunderstood...

Not really. You are playing with what you suspect is a dodgy terminal. You yell to someone in the drivers seat..'try that' and give the terminal a wiggle and momentarily break it and get 400v between the hand on the live terminal and the chassis which your other hand is grasping as you lean into the engine compartment.

You have set up the perfect conditions for a cardiac arrest. One hand to the other, both firmly in contact with the applied voltage. Both gripping hard, and probably sweaty.

I would say its almost certainly true. The inductance in a starter motor is massive as are the currents. The flyback pulse would be very energy rich. It PROBABLY would do a lot of damage in a modern car. And there may well be snubber networks these days, but an old car...yes.

You might. Others would have more sense. High current flow is likely to burn your hand if nothing else.

Have you no self preservation tendencies?

So where is the evidence of a 'helper'? 'No-one knows what happened' would be the clue.

It has often bemused me that the sides of the tracks aren't littered with dead cats and urban foxes (not to mention moles on the line). Does anyone know why?

Having said that, I was once standing on a platform when a fox walked its length to the footbridge where it crossed over and proceeded down the opposite platform. Perhaps their mummies tell them.

Chris

One of my drills tells me to remove the battery before changing the bit - yeah, sure! Then there was "unplug from the mains" on a packet of sheets of abrasive paper (prolly meant the sander), but could I find the lead?

they are.

Found most of my cat on a line.

Mind you it looked as though it had actually been caught in a gin trap, then tossed there to look like a train accident.

A cat will get blown way off line by a train hit.

Their ears tell them. Rails sing.

Corporate lawyers worried you might squeeze the trigger as you grab the bit and sue them for the lacerations.

Do they sell many records?