"Custos Custodum" wrote in message
...
On Wed, 31 Mar 2021 06:01:39 +1100, "Rod Speed"
wrote:

Brian Gaff (Sofa) wrote

Erm well are you suggesting bridging them with a charged up hv
capacitor?
Not nice, and probably dangerous, at least the ladies only picked them
up
in one hand then very quickly dropped them and swore.

Real ladies never swear.

They only swear when it slips out.

They should tell him to slip it back in again ;-)

On 01/04/2021 12:29, Andrew wrote:
On 31/03/2021 17:39, Steve Walker wrote:
On 31/03/2021 15:36, Adam Funk wrote:

Better testing devices are now available (but I'm told my grandfather
used to use that kind of technique to check whether wiring was on or
off).

So did my grandfather. Unfortunately for other people, he seemed to be
electricity proof and what he could touch without a problem would give
others a hell of a belt.

Ex IT colleague went to work for London underground. He got the chance
to go into the tunnels one night and to test that the power was off they
had an ancient bit of wood with a number of bayonet-fitting bulbs
fitted along it, connecting the power rail to the running rail.

Actually the Underground has two power rails (centre and side). The
running rails are somewhere in between in potential.

--
Max Demian

"Max Demian" wrote in message
o.uk...
On 01/04/2021 12:29, Andrew wrote:
On 31/03/2021 17:39, Steve Walker wrote:
On 31/03/2021 15:36, Adam Funk wrote:

Better testing devices are now available (but I'm told my grandfather
used to use that kind of technique to check whether wiring was on or
off).

So did my grandfather. Unfortunately for other people, he seemed to be
electricity proof and what he could touch without a problem would give
others a hell of a belt.

Ex IT colleague went to work for London underground. He got the chance
to go into the tunnels one night and to test that the power was off they
had an ancient bit of wood with a number of bayonet-fitting bulbs
fitted along it, connecting the power rail to the running rail.

Actually the Underground has two power rails (centre and side). The
running rails are somewhere in between in potential.

Although presumably testing either the positive or the negative rail wrt
ground would indicate that the line was still electrified. I wonder if the
strip of bulbs would work with either rail (they are different voltages wrt
ground), without blowing the bulbs (in one case) or failing to light
sufficiently to see (in the other case).

I know that the four-rail system is used to try to lessen electrolytic
corrosion in the tunnel linings and underground pipes, but I've always
wondered why the two rails are not symmetrical about 0V - ie +315 V and -315
V rather than +420 V and - 210 V.

On 01/04/2021 14:54, Max Demian wrote:
On 01/04/2021 12:29, Andrew wrote:
On 31/03/2021 17:39, Steve Walker wrote:
On 31/03/2021 15:36, Adam Funk wrote:

Better testing devices are now available (but I'm told my grandfather
used to use that kind of technique to check whether wiring was on or
off).

So did my grandfather. Unfortunately for other people, he seemed to
be electricity proof and what he could touch without a problem would
give others a hell of a belt.

Ex IT colleague went to work for London underground. He got the chance
to go into the tunnels one night and to test that the power was off they
had an ancient bit of wood with a number of bayonet-fitting bulbs
fitted along it, connecting the power rail to the running rail.

Actually the Underground has two power rails (centre and side). The
running rails are somewhere in between in potential.

No. the underground can run on either side rail *or* centre rail which
are both 'live' The running rails are earthed


--
Renewable energy: Expensive solutions that don't work to a problem that
doesn't exist instituted by self legalising protection rackets that
don't protect, masquerading as public servants who don't serve the public.

On 01/04/2021 15:05, NY wrote:
"Max Demian" wrote in message
o.uk...
On 01/04/2021 12:29, Andrew wrote:
On 31/03/2021 17:39, Steve Walker wrote:
On 31/03/2021 15:36, Adam Funk wrote:

Better testing devices are now available (but I'm told my grandfather
used to use that kind of technique to check whether wiring was on or
off).

So did my grandfather. Unfortunately for other people, he seemed to
be electricity proof and what he could touch without a problem would
give others a hell of a belt.

Ex IT colleague went to work for London underground. He got the chance
to go into the tunnels one night and to test that the power was off they
had an ancient bit of wood with a number of bayonet-fitting bulbs
fitted along it, connecting the power rail to the running rail.

Actually the Underground has two power rails (centre and side). The
running rails are somewhere in between in potential.

Although presumably testing either the positive or the negative rail wrt
ground would indicate that the line was still electrified. I wonder if
the strip of bulbs would work with either rail (they are different
voltages wrt ground), without blowing the bulbs (in one case) or failing
to light sufficiently to see (in the other case).

I know that the four-rail system is used to try to lessen electrolytic
corrosion in the tunnel linings and underground pipes, but I've always
wondered why the two rails are not symmetrical about 0V - ie +315 V and
-315 V rather than +420 V and - 210 V.

They are both at 630VDC


--
Religion is regarded by the common people as true, by the wise as
foolish, and by the rulers as useful.

(Seneca the Younger, 65 AD)

NY wrote:

I've always wondered why the two rails are not symmetrical about 0V - ie
+315 V and -315 V rather than +420 V and - 210 V.

"The positive rail is 3 inches higher than the running rails, while the
negative rail is 1.5 inches higher. The positive insulators are thus
twice the height of the negative ones and therefore have about twice the
earth leakage resistance, so the voltages are set with a proportional
disparity between the positive and negative voltage levels. The
positive rail is at a potential of 420 volts above earth and the
negative rail at 210 volts below earth."

http://www.trainweb.org/tubeprune/tractioncurr.htm

On 01/04/2021 16:06, Andy Burns wrote:
NY wrote:

I've always wondered why the two rails are not symmetrical about 0V -
ie +315 V and -315 V rather than +420 V and - 210 V.

"The positive rail is 3 inches higher than the running rails, while the
negative rail is 1.5 inches higher.Â* The positive insulators are thus
twice the height of the negative ones and therefore have about twice the
earth leakage resistance, so the voltages are set with a proportional
disparity between the positive and negative voltage levels.Â* The
positive rail is at a potential of 420 volts above earth and the
negative rail at 210 volts below earth."

http://www.trainweb.org/tubeprune/tractioncurr.htm

changed since my day then, when underground ran on SR three rail
systems quite happily...and could use either centre or side rail


--
"When a true genius appears in the world, you may know him by this sign,
that the dunces are all in confederacy against him."

Jonathan Swift.

On Thu, 1 Apr 2021 14:39:43 +0100, "NY" wrote:

"Custos Custodum" wrote in message
.. .
On Wed, 31 Mar 2021 06:01:39 +1100, "Rod Speed"
wrote:

Brian Gaff (Sofa) wrote

Erm well are you suggesting bridging them with a charged up hv
capacitor?
Not nice, and probably dangerous, at least the ladies only picked them
up
in one hand then very quickly dropped them and swore.

Real ladies never swear.

They only swear when it slips out.

They should tell him to slip it back in again ;-)

It's the world's fastest game for two pairs of hands. :-)

In article , Tim Streater
wrote:
On 01 Apr 2021 at 16:23:15 BST, The Natural Philosopher
wrote:

On 01/04/2021 16:06, Andy Burns wrote:
NY wrote:

I've always wondered why the two rails are not symmetrical about 0V
- ie +315 V and -315 V rather than +420 V and - 210 V.

"The positive rail is 3 inches higher than the running rails, while
the negative rail is 1.5 inches higher. The positive insulators are
thus twice the height of the negative ones and therefore have about
twice the earth leakage resistance, so the voltages are set with a
proportional disparity between the positive and negative voltage
levels. The positive rail is at a potential of 420 volts above
earth and the negative rail at 210 volts below earth."

http://www.trainweb.org/tubeprune/tractioncurr.htm

changed since my day then, when underground ran on SR three rail
systems quite happily...and could use either centre or side rail

I was always told that the centre rail was at earth to keep the
resistance down. SR trains run OK on underground lines (not in the
tunnels, obvs, too tall) but e.g. at East Putney you would sometimes see
an empty SR train switched from the Putney SR line that goes on to
Windsor, onto the District line going south to Wimbledon, where it could
rejoin SR lines.

One morning when taking the SR train to Waterloo, I suddenly noticed we
were in a tunnel. We were on the District Line between Wimbledon & East
Putney. we came through Wandsworth Town into Clapham Junction. Obviously
some tunnels will take standard trains, but not the deep tube ones.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

"Max Demian" wrote in message
o.uk...
On 31/03/2021 23:34, Rod Speed wrote:
"NY" wrote in message
...
"williamwright" wrote in message
...
On 31/03/2021 14:10, Tim Lamb wrote:

Electrified?


Electrifried?

Thank you, Bill. *That's* the word the English language needs ;-) Nice
one!

We mostly use zapped in normal conversation
as opposed to more formal stuff like the media.

Zapping is when you change channels with the TV remote.

Wrong, as always.

Don't you Aussies have a word ending with "o" for it?

Nope. Just like you poms dont have a word ending in "y" for it either.

"NY" wrote in message
...
"Jethro_uk" wrote in message
...
On Wed, 31 Mar 2021 22:06:03 +0100, NY wrote:

"Fredxx" wrote in message
...
We were told similar by our physics master, except I don't think the
advice was to regularly use the back of your hand instead of a neon
tester, just that if ever you were in a situation where you *had* to
find out whether something was live or not, and you had no
alternative, then use the back of your hand rather than pinching it
between fingers, or sticking your tongue on it!

I wonder how many kids of nowadays test PP3 batteries that way?

I knew a woman at university who could feel very low voltages with her
bare fingers (no need for tongues!). She could tell instantly whether an
AA battery was fully charged or almost flat. She always touched a door
handle or a car door with her elbow through her clothes to discharge
most of the static charge that she may have acquired walking across a
carpet or from the tyres rolling on the road.

SWMBO used to (interesting it's no longer the case) be able to sense
electric storms long before they happened.

My theory was it something to do with the ****ed nerves of MS being more
sensitive to electrickery.

There could well be a lot of truth to this. The woman I knew had
"hypermobile joints" (she could bend her hands a long way backwards at the
wrists etc) and later in life developed a strange syndrome which meant
that if she was ever injured (or had surgery) she would feel the pain for
a long time after the wound had healed - which was bad news as she needed
an operation for something and decided that the normally short-term pain
of an incision would go on for so long afterwards that she couldn't face
the operation.

Yeah, there was one of those with hypermobile joints on "Michael Mosley:
What's My Diagnosis" and they spelt out some real medical downsides with
that condition. Forget the detail now. Very interesting because I was
fascinated
by that condition as a teenager, presumably because someone I knew had it.

On Fri, 2 Apr 2021 04:54:56 +1100, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

FLUSH the trolling senile asshole's latest troll**** unread

--
Bod addressing abnormal senile quarreller Rodent Speed:
"Do you practice arguing with yourself in an empty room?"
MID:

"Who or What is Rod Speed?

Rod Speed is an entirely modern phenomenon. Essentially, Rod Speed
is an insecure and worthless individual who has discovered he can
enhance his own self-esteem in his own eyes by playing "the big, hard
man" on the InterNet."
https://www.pcreview.co.uk/threads/r...d-faq.2973853/

--
Sqwertz to Rodent Speed:
"This is just a hunch, but I'm betting you're kinda an argumentative
asshole.
MID:

When I was in the cadets at school many years ago I leant on the front
of an old military radio. It turned out the three pins I hadn't noticed
were for a supply to a matching transmitter.

At mains.

Across the palm of my hand.

It hurt, but didn't throw me anywhere.

I haven't had another shock since. Perhaps I'm paranoid enough.

Andy

On 31/03/2021 20:04, charles wrote:

In the analogue days we sometimes got hum on our pictures. Only after it
has been raining, I eventually traced the fault, The 120v on the VCR's
aerial connector found its way to my mast head preamp and then found a path
to ground down the wet wall of the house. This created a 2v drop between
the output and input connections. I earthed the coax outer at the bottom
and the problem went away. The VCR could only provide about 30uA.


Interesting.

Bill

On 31/03/2021 20:23, Steve Walker wrote:
Definitely nothing to do with static either, as once you'd touched it,
touching again immediately would give you another jolt.

What about a third and fourth time?

Bill

On 01/04/2021 18:54, Rod Speed wrote:
Nope. Just like you poms dont have a word ending in "y" for it either.

I'm going to avoid Australia in case they're all like you.

Bill

williamwright wrote
Rod Speed wrote

Nope. Just like you poms dont have a word ending in "y" for it either.

I'm going to avoid Australia

Great, the last thing we need is more ****wit poms like you.

On 03/04/2021 18:20, williamwright wrote:
On 31/03/2021 20:23, Steve Walker wrote:
Definitely nothing to do with static either, as once you'd touched it,
touching again immediately would give you another jolt.

What about a third and fourth time?

It's enough of a jolt that you don't do it more than twice.

On Sun, 4 Apr 2021 04:58:26 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

FLUSH yet more of the trolling senile asshole's latest troll**** unread

--
Richard about senile Rodent:
"Rod Speed, a bare faced pig and ignorant ****."
MID:

On Tuesday, 30 March 2021 at 09:02:48 UTC+1, Andy Bennet wrote:
On 29/03/2021 23:32, soup wrote:
Many have had a 'belt' from domestic 240Volt wiring through bad luck,
bad judgment or plain stupidity .
Whilst a shock from 240V CAN kill how often does that actually happen
and how many just get thrown across the room into a foetal position
whimpering and crying until the arm unknots and the tingling feeling
goes away.
Been there done that - once!
When I was about 8 years old I had a crystal set and thought I needed a
longer aerial on it to get better reception. Had seen pylons with wires
on them supplying electricity so thought that would be a lovely aerial!.
Went to mains socket in bedroom with metal meccano screwdiver in one
hand, bare wire to plug into socket in other. Pushed down the earth
shutter with screwdriver and inserted bare wire into now open shuttered
pin. I now know the difference between live and neutral! Seriously
thought I was going to die. Been extreemly cautious ever since and never
had another belt from the mains!


And I thought it was just me. At a similar age - maybe 10 - I decided to make an electric car. I knew motors had windings. That was all I knew. I wound a wire around the metal axle of a lego car, and attached both ends to a battery. Strangely, nothing happened.

OBVIOUSLY I needed more oomph. I opened up a plug. Observing that there were three terminals, I decided to splice the wire into all three to see what would happen. I then made the only good decision I made that day. Instead of plugging in to the switched on socket, I elected to switch it off, plug in, and THEN switch on. Just as well, it blew the thing off the wall and blew the fuse at the board. I saw a flash but avoided any shock, which was more than could be said for my parents.

I also remember that when the electrician came round to fix it, I ended up with a double in my room where I had previously had a single. So that was a win.

On 03/04/2021 20:13, Steve Walker wrote:
On 03/04/2021 18:20, williamwright wrote:
On 31/03/2021 20:23, Steve Walker wrote:
Definitely nothing to do with static either, as once you'd touched
it, touching again immediately would give you another jolt.

What about a third and fourth time?

It's enough of a jolt that you don't do it more than twice.

It was one of my jokes.

Bill

The Natural Philosopher wrote:
On 01/04/2021 16:06, Andy Burns wrote:
NY wrote:

I've always wondered why the two rails are not symmetrical about 0V -
ie +315 V and -315 V rather than +420 V and - 210 V.

"The positive rail is 3 inches higher than the running rails, while the
negative rail is 1.5 inches higher.Â* The positive insulators are thus
twice the height of the negative ones and therefore have about twice the
earth leakage resistance, so the voltages are set with a proportional
disparity between the positive and negative voltage levels.Â* The
positive rail is at a potential of 420 volts above earth and the
negative rail at 210 volts below earth."

http://www.trainweb.org/tubeprune/tractioncurr.htm

changed since my day then, when underground ran on SR three rail
systems quite happily...and could use either centre or side rail

You have a misunderstanding somewhere.
No either about it , Not now and not since they were electrified over a
100 years ago whatever your day was when you made a wrong assumption.
Underground passenger trains *, have to be in contact with both side and
centre rails
to complete their circuit, there is no path built in via the axles and
wheels with brush gear to by pass axle bearings so they dont get damaged
by high currents passing through them like 3rd rail ( and overhead equipped
) trains have.
What happens on the shared sections is the outer rail voltage is raised to
the full potential required , once 630 but often now the later 750 .the
centre rail is simply bonded to the running rails and is at ground
potential. The observant who used the shared sections around around Putney
may have noticed at one time to save money the centre rail was sometimes
mounted on wooden blocks rather than insulators. Special arrangement have
to be in place where the two systems meet so a train doesnt bridge both
system so there are long gaps in the live rails on Putney Bridge and
between Turnham Green and Gunnesbury. Photos of the Putney bridge ones and
a drivers description on this link.
http://www.trainweb.org/districtdave...ey_bridge.html

* some of the maintenance locos are switchable in case they get contract
work on the third rail system.

We are getting away from DIY but the technically nosy may find a detailed
description of how such systems in the UK were developed here.

http://www.clag.org.uk/3rd-4th.html


GH

On 29/03/2021 23:32, soup wrote:
Many have had a 'belt' from domestic 240Volt wiring through bad luck,
bad judgment or plain stupidity .
Â* Whilst a shock from 240V CAN kill how often does that actually happen
and how many just get thrown across the room into a foetal position
whimpering and crying until the arm unknots and the tingling feeling
goes away.

Hum... tricky one... each persons reaction is different.
Electric shock (no matter what voltage) can cause a bad reaction.
First Aid advice (via My current employers HS dept) is straight to A&E
for a cardiograph.

AC
110V (55-0-55) ouch
240V (Domestic, can be nasty - A&E for anything above a minor touch
advised but not forced to go)
415V (3 phase) = Dead.
Anything greater than 415V = Dead.

DC
Charged capacitor above 50V hurts
Microwave 5kV or more capacitor = very nasty, A&E strongly advised.


--
Ask how to email me.

Kellerman wrote:
On 29/03/2021 23:32, soup wrote:
Many have had a 'belt' from domestic 240Volt wiring through bad luck,
bad judgment or plain stupidity .
Â* Whilst a shock from 240V CAN kill how often does that actually happen
and how many just get thrown across the room into a foetal position
whimpering and crying until the arm unknots and the tingling feeling
goes away.

Hum... tricky one... each persons reaction is different.
Electric shock (no matter what voltage) can cause a bad reaction.
First Aid advice (via My current employers HS dept) is straight to A&E
for a cardiograph.

AC
110V (55-0-55) ouch
240V (Domestic, can be nasty - A&E for anything above a minor touch
advised but not forced to go)
415V (3 phase) = Dead.
Anything greater than 415V = Dead.

DC
Charged capacitor above 50V hurts
Microwave 5kV or more capacitor = very nasty, A&E strongly advised.

Other things much more relevant than the particular voltage you have
touched:-

Where the shock tracks through you, i.e. if it's from one hand to
the other across your chest it's much more likely to do damage
than if it's just across your hand or along a limb.

How dry your skin is and thus how much resistance you present to
the flow of electricity.

How good an earth the 'earthy' end of your shock is, if you're
barefoot on a wet floor it's going to be much worse than if you
have rubber soles on a dry floor.

--
Chris Green
·

On 26 May 2021 at 11:41:19 BST, "Chris Green" wrote:

Kellerman wrote:
On 29/03/2021 23:32, soup wrote:
Many have had a 'belt' from domestic 240Volt wiring through bad luck,
bad judgment or plain stupidity .
Â* Whilst a shock from 240V CAN kill how often does that actually happen
and how many just get thrown across the room into a foetal position
whimpering and crying until the arm unknots and the tingling feeling
goes away.

Hum... tricky one... each persons reaction is different.
Electric shock (no matter what voltage) can cause a bad reaction.
First Aid advice (via My current employers HS dept) is straight to A&E
for a cardiograph.

AC
110V (55-0-55) ouch
240V (Domestic, can be nasty - A&E for anything above a minor touch
advised but not forced to go)
415V (3 phase) = Dead.
Anything greater than 415V = Dead.

DC
Charged capacitor above 50V hurts
Microwave 5kV or more capacitor = very nasty, A&E strongly advised.

Other things much more relevant than the particular voltage you have
touched:-

Where the shock tracks through you, i.e. if it's from one hand to
the other across your chest it's much more likely to do damage
than if it's just across your hand or along a limb.

How dry your skin is and thus how much resistance you present to
the flow of electricity.

How good an earth the 'earthy' end of your shock is, if you're
barefoot on a wet floor it's going to be much worse than if you
have rubber soles on a dry floor.

In the case of shocks from capacitors the total stored energy is also very
important. That is why defibrillators are calibrated in Joules.

--
Roger Hayter