This morning, waiting for the London Bridge via Forest Hill service at
Streatham Hill, I noticed the conductor rail had been replaced. I suppose
they do eventually wear out but most I observed look like they dated from at
least SR days, if not earlier.
Martin J.

On the underground they progressively jack up the conductor rails with shims
as they wear.

"Martin J" wrote in message
...
This morning, waiting for the London Bridge via Forest Hill service at
Streatham Hill, I noticed the conductor rail had been replaced. I suppose
they do eventually wear out but most I observed look like they dated from
at
least SR days, if not earlier.
Martin J.

I noticed at Brent Cross the other day that a section of conductor rail
about 20 feet long had been welded in. Seemed odd that a short section
of conductor needed changing, now track I can understand.

Kevin

wrote in message
oups.com...
I noticed at Brent Cross the other day that a section of conductor rail
about 20 feet long had been welded in. Seemed odd that a short section
of conductor needed changing, now track I can understand.

Could it have been badly burned by excessive arcing between rail and shoe?
If it had been at a point where many trains suddenly applied power (eg as
the train was starting from station or signal) it could have become so
pitted that it caused further arcing through poor contact - cue vicious
circle!

Martin Underwood wrote:
wrote in message
oups.com...
I noticed at Brent Cross the other day that a section of conductor rail
about 20 feet long had been welded in. Seemed odd that a short section
of conductor needed changing, now track I can understand.

Could it have been badly burned by excessive arcing between rail and shoe?
If it had been at a point where many trains suddenly applied power (eg as
the train was starting from station or signal) it could have become so
pitted that it caused further arcing through poor contact - cue vicious
circle!

There's a gap by the outer rail platform at Farringdon like that - it's
rare for a train to pull away without lightning effects, smoke etc.
Regulars are used to it and barely bat an eyelid now, but surely it
can't be good for the traction motors?

You should have seen 4-SUBs at Tulse Hill. On the London Bridge side
there was a porter's crossing about half way along the platforms and I
used to watch trains start off & groan out of the station with
satisfying fireworks every time a shoe reached the gap. In daylight you
could see showers of orange incandescent fragments of something (shoe?
rail?). At night the blue flash would be too bright for these the be
easily seen. (I can still hear what the French call le chant des
moteurs...)

One evening in 1964 I was at the Victoria end of the island platform at
Streatham Common, and I could see (and hear!) some kind of PUL/PAN
formation approaching at speed on the down fast. It was belting along.
It was always satisfactory to be on the platform when they rushed
through. As the train came into view, I could not help noticing (it was
dark) that each shoe on the juice rail side was making its own little
shower of sparks. They were yellow-orange rather than blue, and I
wondered if they were caused by brief loss of contact due to the
swaying bouncy ride these sets had especially at speed.

wrote in message
oups.com...
You should have seen 4-SUBs at Tulse Hill. On the London Bridge side
there was a porter's crossing about half way along the platforms and I
used to watch trains start off & groan out of the station with
satisfying fireworks every time a shoe reached the gap. In daylight you
could see showers of orange incandescent fragments of something (shoe?
rail?). At night the blue flash would be too bright for these the be
easily seen. (I can still hear what the French call le chant des
moteurs...)

One evening in 1964 I was at the Victoria end of the island platform at
Streatham Common, and I could see (and hear!) some kind of PUL/PAN
formation approaching at speed on the down fast. It was belting along.
It was always satisfactory to be on the platform when they rushed
through. As the train came into view, I could not help noticing (it was
dark) that each shoe on the juice rail side was making its own little
shower of sparks. They were yellow-orange rather than blue, and I
wondered if they were caused by brief loss of contact due to the
swaying bouncy ride these sets had especially at speed.

I've always wondered: with third-rail EMUs such as VEPs, are all the shoes
connected together along a common bus that runs the full length of the
train, or does each powered carriage have its own shoe(s) which are separate
from other power carriages? In other words, is it possible for one power car
to lose its supply (if all its shoes hit a gap) while another power car is
fully powered? Or does a gapped shoe simply mean that less current can flow
equally through every motor on the train? Given that trains usually have
shoes opposite each other on either side of a train, and the third rail is
usually overlapped where it changes from one side of the track to the other,
why do you get such magnificent firework displays when a shoe hits a gap?

(I am not an expert, so don't flame me if this account contains
howlers). In general, 3rd rail, (non-Underground) emus have what is
called a 'bus line' linking all of the shoes (on both sides) (via fuses
and the 'line breakers') within each unit. Therefore the shoes on the
side of the unit away from the juice rail are likely to be live &
should be treated as such. In this way, as long as one shoe of a set
touches the juice rail, all the motors of that set receive juice. If
multiple shoes of a set are receiving current, that current will divide
itself up between the shoes more or less equally, in this simple
description. Should a shoe encounter a gap, its share of the total
current is not instantaneously transferred to the other shoes. There
will be an arc, and more current will start to flow through the
remaining shoe(s). Once the arc becomes extinguished the whole of the
current demand will be carried by the remaining shoe(s).

If a section of third rail has to be isolated to allow work to take
place, that section could be energised by an emu's shoes and bus line
bridging the gap. I think I read somewhere that staff used to become
aware of this happening if MG sets on nearby emus were heard to start
up. (Do modern emus have MG sets?) I expect there are monitoring
devices. Or shorting bars to bring out the breakers. Didn't Underground
workers have 'lamp boards' with sets of bulbs in series?.

The bus line is not carried between sets running in multiple however.

Units intended for tunnel use such as Class 313 units, and LUL stock
are not allowed bus lines. Reasons are mainly to do with fire risk I
think. I seem to recall there was a nasty fire in the Paris Métro in
the 1900s blamed on insulation breakdown & arcing on wooden bodied
stock.

I think that the shoes attached to bogies on LUL stock only feed the
motors on that bogie, but I stand to be corrected.

wrote:

pretty good general description snipped

I think that the shoes attached to bogies on LUL stock only feed the
motors on that bogie, but I stand to be corrected.

On LU there is a busline within each car (so all poss shoes are connected,
likewise both negative shoes) and from one motor car to the adjacent trailer
to feed the compressor/s.

wrote to uk.transport.london on Fri, 17 Jun 2005:

One evening in 1964 I was at the Victoria end of the island platform at
Streatham Common, and I could see (and hear!) some kind of PUL/PAN
formation approaching at speed on the down fast. It was belting along.
It was always satisfactory to be on the platform when they rushed
through. As the train came into view, I could not help noticing (it was
dark) that each shoe on the juice rail side was making its own little
shower of sparks. They were yellow-orange rather than blue, and I
wondered if they were caused by brief loss of contact due to the
swaying bouncy ride these sets had especially at speed.

My father, in the very late 1950s/early 1960s commuted to London from
the Sussex coast. Although it wasn't, and isn't, his nearest station,
he invariably went from Arundel on the mid-Sussex line (still utterly
delightful, and incredibly pretty south of Horsham), which in those days
called at Pulborough, Horsham, Dorking North, Epsom, Sutton & Victoria -
we nearly always travelled the same way when visiting my grandmother in
London. On the rare occasions we went via the Brighton lines, there
were always showers of sparks and blue flashes - my father told me,
years later, that it wasn't just the beauty of the mid-Sussex that
attracted him, but the fact that the trains on that line had "less
square wheels" than those on the Brighton run!
--
"Mrs Redboots"
http://www.amsmyth.demon.co.uk/
Website updated 23 May 2005