Lightning strike

Mother had a close call back in the 60's. The house was almost the highest point on a hill and Lightning often struck nearby, being on overhead lines the power often went so an oil lamp was made ready and placed on the dining table which was close to the window. Unplugging the aerial for the TV was std procedure but Mother got it wrong one day and unplugged it from the socket and not the less accessible back of the TV, the socket like many back in early VHF days was mounted on the wooden window frame. It was about

15 mins later that arc leapt from the socket and hit the metal base of the Aladdin oil lamp about 3 ft away which as Mother was sat at the table made her jump a bit the lamp at least intercepting the arc before it reached her. Could not have been a direct hit but the old extra large VHF aerial dad installed to get ITV before the area was officially covered gathered a charge on more than one occasion,Mother never really understood unplugging the aerial as on another occasion she unplugged from the back of the set but being a tidy type rather than leave the end on the floor coiled it up and placed it on the wide internal sill. A while later Dad placed a cup of Coffee on the sill while doing some p/work at the table not really noticing the aerial lead which having been slightly knocked unwound itself from behind the curtain where mother had hid it coming to rest in the saucer wet from some spilt tea. Dad got stimulated by the coffee in a way never before when he picked the cup up grounded the lead and saucer most of the coffee being flung around the room. It was painful for him but quite funny to watch.

G.Harman

Reply to
damduck-egg
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There are the apocryphal (for me) tales of people who made sure every socket had a plug in it, or the electrickery would leak out ...

Reply to
Jethro_uk

There was an apocalyptic cover to "Electronics Today International" (I used to subscribe !) in the 80s, with a mushroom cloud, and a special article detailing the damage the EMP from a nuclear blast could do ... transistorised equipment - particularly MOSFET - was very vulnerable. While valve equipment was effectively immune.

All of a sudden those stories about Russkies and pre 1960s technology didn't seem so funny ....

Reply to
Jethro_uk

One night, in the 80s, I was walking, with some friends across Harrow Hill. It was summer. Warm, not too humid, and dry. There had been no hint of any thunderstorm.

We stopped and sat on bench about halfway up the hill, to have a cigarette. It was just after kicking out time.

Out of nowhere, a lightening strike hit a nearby (about 10m away) tree. There was an almighty crack, and a branch *jumped* off.

A minute and a mile later, and my friends and I all agreed we had never seen anything like it. Nor have I since.

It still puzzles me how a lightening bolt chose a tree halfway up a hill with a sodding pointy church on the top with the mother of all lightening rods.

Reply to
Jethro_uk

External aerials are the biggest risk factor. You could be unlucky with cable, but the strike will likely find an easier path to ground first.

It is worth remembering that a TV aerial on top of a house can have a noticeable potential difference to ground on its aerial lead. Enough to easily light an neon screwdriver and on active days I have had the odd minor belt off one from the nominally outer case earthy side!

Only really a problem when installing aerials and tweaking satellite dishes when there is some unsuspected electrical storm activity about.

Regards, Martin Brown

Reply to
Martin Brown

Lightening rods/protection work by enabling the building up charge to leak into the atmosphere from the nice pointy tips. The idea being that the voltage doesn't rise high enough to flash over. The charge is dissipated over minutes rather than ms. A dry, relatively round and high resistance, tree doesn't leak the charge so the voltage can build up to the atmospheric breakdown point.

Reply to
Dave Liquorice

Pretty much my understanding also about 'lightening conductors', which is actually a bit of a misnomer. AIUI they aren't intended to conduct the lightening, but to prevent it happening in the first place. I do wonder whether the copper strip often used could actually cope with the currents involved anyway, or would it just vaporise.

Reply to
Chris Hogg

Were you really that ugly as a kid ;-)

sorry couldn't resist the obvious.

Reply to
whisky-dave

Jethro_uk brought next idea :

I remember the article well. The Russkies continued to use and develop valves long after we abandoned them, likely for their tolerance of EMP.

Reply to
Harry Bloomfield

Jethro_uk explained on 29/07/2014 :

It chooses both the best and most direct route to discharge itself. Obviously, that was the tree.

Reply to
Harry Bloomfield

I had a (female) friend who joined the RAF in the 80s. She had to learn valve engineering to work on the radar systems ..

Reply to
Jethro_uk

Quiet an appropriate word, discharge ... we almost "discharged" in our pants !

Reply to
Jethro_uk

It happens that Chris Hogg formulated :

They do on occasion vaporise. The church close to us which was struck, which I mentioned earlier, had a lightning conductor. The copper had vaporised and the discharge then made its way via the stone work of the steeple, through the wall and had then tracked its way down inside, via the plaster.

Reply to
Harry Bloomfield

My father had a 23ft radio mast on the roof. The house was halfway down a hill, and even with the mast, there were taller things nearby...lightning struck the mast, travelled down three storeys, and vaporised the glass fuse in his two-way radio. There was no melted glass visible - the fuse simply disappeared.

Reply to
S Viemeister

No she covered up the mirrors, not me :-?

Another thing she did, was open windows too. The explanation I was given, was to let out the ball lightning should it come down the chimney. I seem to remember the explanation for covering the mirrors, was that bare mirrors attracted ball lightening, but not sure on that point.

Bless, she was very superstitious, but I have not come across similar before or since.

Reply to
Harry Bloomfield

No, it takes the path of least "resistance", that may or may not be the most direct route. Think about it, if lightening took the most direct route why is it all squiggly not a straight line?

Reply to
Dave Liquorice

You Migh laugh but valves in the form of TWT's (travelling wave tubes) are now in a lot of new digital TV transmitters!...

Reply to
tony sayer

In article , mail- snipped-for-privacy@btinternet.com scribeth thus

Wow I'd loved to have seen that !...

Reply to
tony sayer

Its just where the electric field was and where the resistance was less. The old saying a Bolt from the blue has its origins in that.

I have seen a church get walloped, the catholic in Cambridge half way up its spire around the 30 odd metre mark the spire topping out at 65..

The highest object isn't always the one that has the last path resistance of where the field is highest...

Reply to
tony sayer

Furse who make most lightning protection in the UK now have rounded ones than pointy ones they aren't any better so that say!..

I know which I'd prefer;)..

Reply to
tony sayer

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