Frolicing critters

Thanks that's very much what I had suspected, I was just sure I'd seen situations of front paws on the rail, rear paws on the ground, but maybe they were just too quick for me and were managing to avoid touching the conductor rails whilst grounded

Indeed, especially with enough current to propel a 150-200 tonne train...Does anyone know how much current is used, while we're on the subject?

I can't find figures for any Tube train but a 4 -car class 378 can deliver 2400hp, (1800kW), so say 4800hp (max) 3.6MW for an S stock. At 630V that's 3,600,000/630 = about 6000 amps. Of course no one circuit or shoe on the train would take the whole current.

Oh and while googling I happened to find this page and on it a joke I thought was so good it had to be shared:

Q: What do you do if you see a Central Line train coming towards you?
A: Make a bolt for it!

one other thing re 'completing a circuit' is that skin (and fur) is actually a *very* good insulator. It turns into a conductor with the tiniest cut though...

An interesting thread!

Lots of things die on the railway! Leaving out those things that cannot be discussed leaves birds, animals, insects, equipment and electricity!

Pigeons spend their lives on the system often travelling on the trains and generally living on ledges, girders etc in stations, even the pigeon netting and spikes do not stop them so they often die and rot on the netting unless they plummet to the track to be carried off by a scavenger or cleaned up by the P-Way staff.

It's not unknown to see dead cats, dogs, hedgehogs, rats etc on the track, sometimes electrocuted and sometimes crushed to death like the hedgehog caught between switch and stock rails as points were reversed, causing a point failure. Signal staff have been known to lose fingers the same way! Most animals tend to be unlucky if they get electrocuted on the track, however, dogs tend to have a death wish because getting a 'belt' from the pozi may only shock them and then they will try and bite what 'bit' them!

Foxes are more likely to simply be run over when attempting to cross a track with a high line speed.

Rats are everywhere of course living on stations, using the air main and cable runs as highways to travel between stations and by urinating everywhere have the potential to kill anyone with leptospirosis. They also love to use the duct routes in stations, nest in footway boxes and in inverts under platforms and various other nooks and crannies. Mice have a penchant for nesting inside weatherproof phones found at tube station headwalls as well as any available void and they just love all the food and rubbish left by passengers.

Bugs, well they are everywhere but I've never forgotten the one that caused a signal failure west of Boston Manor by getting inside a Q relay and getting caught between a pair of carbon contacts adding extra resistance to the circuit. Although it had been juiced at 100 volts it was still alive but welded to the contacts and was still wriggling a couple of days later after the relay was brought back to the depot!

Wasps can be very nasty, they used to like to live in the power room at Acton West IMR and were quite angry attacking everyone that entered.

When it comes to staff walking and working on the track it is always best to avoid proximity to juice rails indeed it is best not to be on the track at all as it is a very hazardous environment whether trains are running or not. As a lineman like hundreds before me attending signal failures in tube tunnels I would step out of the cab straight onto the negative rail as a step to the track and use the same step again when boarding. When testing track circuits it was quite normal to place the multimeter on the neggi to read the voltage across the running rails. It was not unusual to 'feel' the juice, for me if my key chain got close to a current rail I could feel it and when my point fitter rested the point of his bar inadvertantly on the live neggi in the winter he felt it and also had a nice blue halo!
Back in the day cable linemen making traction disconnections for possessions would often work live and with bare hands unbolting the knuckles from the juice rails. Some staff once upon a time would test the juice by touching the pozi with a bare hand. These practices were only as safe as the resistance of ones safety boots and the amount of moisture underfoot. I knew one chargehand 35 years ago who always walked on all the rails when crossing the track, one winter's morning he did that once too often and was thrown across a track and over a cable run. He couldn't understand it as he had been doing the same all week in the snow and ice trusting his safety boots. When he examined his boots there was a drawing pin stuck in the sole which he had obviously 'collected' somewhere between shifts!
Getting 'juiced' was an almost daily occurrence working on signals, but at 100 volts ac rather than dc traction. Lifting relay contacts to test circuitry one was bound to contact an earth at some point, usually the relay top hanger above. Wearing gloves was not a real option as it made one sweat and then any contact with earth would lead to a much worse shock. One learnt to keep one hand in one's pocket and then unless really unlucky any shock would be localised to the working hand and little worse than being stuck with a pin somewhat unexpectedly.

When things go wrong there is the potential for very dangerous high voltages to appear on LU tracks in some areas which are otherwise isolated electrically (immunised) from the rest of the system as they can carry very high amperage fault currents under certain conditions.

For the untrained and unfamiliar the message loud and clear has to be that traction current is always on and the voltage and current are potentially fatal. Add to that the health hazards created by vermin and other creatures, the slip, trip and fall hazards as a result of the loose cabling, trackside drainage, ballast and trackside equipment as well as moving trains at any speed and know that even with correct training and familiarisation the railway is a very very dangerous environment to work in and worse than that in bad weather.

AFAIR 2000 amps was the figure that used to be quoted as the current drawn when a train pulls away and my recollection is that the signalling trackside earth cabling, 19/064 imperial, could carry a 2000 Amp fault current. I suspect things are somewhat different nowadays.

An interesting post! Thank you

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Relatedly (I think), when standing on a platform on a little-used section of line (such as Roding Valley) before the train arrives, but as it is approaching, you can hear a very distinctive click-clicking noise, presumably from the rails. Does anyone know what precisely causes this? You can hear them in this admittedly slightly poor quality video (around 13 secs)

I was gonna ask about other noises you can hear coming from the rails but I can't really describe them, like the knock knock sound you hear around 7 secs here.

A really interesting post, thanks RT.

This happened about forty years ago, the pole carrying the telephone line had been knocked over in a RTA and the GPO (as it was then) would not touch it as it was close to the overhead, they actually watched the pigeon settle on the wire, and then start to poop. I worked for the GPO at the time and heard all about it.

Well how else are you going to test if a 9v battery is "still good" other than by touching the two terminals with your tongue?

I remember a few years ago changing a light bulb without a torch and feeling the tingle of 230v AC across my finger tip, luckily I was stood on a wooden stool in my hiking boots at the time!

Any shock can be nasty, it all depends not only upon voltage and available current but the impedance of an individual to earth which itself is subject to other factors such as how wet a person may be, that's why non-isolated 240v supplies are specifically disallowed in bathrooms and for additional protection the supply for an electric razor is an isolated 110v supply. There are also rules that should ensure one cannot stand in a bath or shower and reach the metal parts of any light fitting, extractor fan, heater etc and why pull cord switches are used.

These days in a workplace just about any electrical shock is enough to warrant attending hospital to have one's heart monitored for stability for several hours after the event. I believe in that regard voltages as low as 6v are assumed to be as dangerous as any other.

When I was at primary school we used to lick pp3 batteries for 'the tingle'. Some stood it better than others, personally I didn't like it so I didn't play that game more than a handful of times. As a young PO apprentice one often had to suffer the trials and tribulations of 'initiation' when joining a new department or exchange, being tied up was common, having one's tool wallet zip soldered up or worse having one's toolbox filled with beeswax, the lid closed and welded shut and the lock filled with solder also happened. There were many other examples of the treatment but the most common was being invited to test one's resistance on a standard exchange tester. One would be invited to hold the clips at the end of the leads, one in each hand and observe the reading on the ohmmeter, then one's tormentor would throw the ring key giving a 75v ac shock at 20Hz and it did hurt.
Working in the exchange, my field was exchange installation following my apprenticeship, I did copious amounts of wiring work on main and intermediate distribution frames and suffered tag rash from the 50v dc belts causing me to move my hand involuntarily at speed into the adjacent vertical and being stabbed in the back of the hand by multiple tags simultaneously. I had leather protectors but didn't like wearing one as the elastic used to constrict the blood flow to my fingers making the job harder.

Keeping one hand in one's pocket when doing electrical work is good advice, the worst shocks generally occur when current travels through the body and the heart muscle which can lead to irregular heartbeat hours after the event which in turn can be fatal. The idea is never to take a shock across the heart if it can be avoided. Even so single handed shocks can be dangerous in other ways, getting a shock while gripping can mean that one cannot free oneself as the alternating voltage will cause muscle spasm which is why the first thing to do when attending such a casualty it to turn off the power.

In the case of traction current a casualty may fall onto the current rail as a result of a shock and continue to be electrocuted until the current is taken off. I speak from experience when I say that it is not pleasant to open one's eyes and realise that one has landed on or next to a current rail. I have 'flown' head first into the suicide pit and landed on the neggi after slipping on a patch of grease on the platform, I have landed across pozi and continuous rails after tripping on unseen newly installed footpath edging but on both occasions the current was off so I got with nothing worse than some rather bad bruising from chest to ankles.
Worse was an incident where I could well have been electrocuted following attendance to a trainstop failure at Sudbury Town in several inches of snow. One second I was retracing my footprints back to the station, next I was flat on my face nursing a sore neck as my heavy toolbag hit me in the back of the head as I went down. My head was no further than an inch from the pozi and the current was on, I think my guardian angel was looking out for me on that day and I soon forgot my sore neck as I thanked my lucky stars.

When I began my LT Career one was warned to keep both hands in one's pockets in equipment rooms unless instructed to do something useful with them. Standing clear of equipment and terminations and not leaning on or against anything including plain walls was also a requirement that was strictly enforced. Of course at that time the emphasis was on not causing a signal failure and had little to do with personal safety!

As for telephones, unless there is a fault they are always live at a nominal 50v dc except when ringing and the voltage rises to 75 volts and falls towards zero with the ringing cadence. With the handset off hook the circuit carries around 10 milliamps but telephone lines are generally not dangerous due to the resistance of the line, the allowable signalling loop resistance being 1000 ohms and most lines will have a few hundred ohms because the main cable will typically have a loop resistance of about 176 ohms per mile.

I've had that. Idiotic way to do it, but I isolated the circuits at my aunt's house by flipping the breakers one by one until my co-worker upstairs shouted that the light had gone off. They proceeded to remove the bulb from the fitting to be changed whilst I labelled the breaker and re-energised the other circuits. I removed the old fitting and was just preparing the wiring for the new fitting when I felt something wasn't right on the back of my hand, so I checked the live with a sensor-screwdriver. Lit up light the proverbial Xmas tree.
Back to the DB and no matter which breaker I toggled, the damned live stayed on.
Worked it out in the end. Some DIY moron didn't understand ring circuits and had taken one leg out of one breaker and brought it back into the adjacent breaker. This meant you had to flip off two breakers in order to isolate any circuit.
£700 of rewiring later...

Amateur wiring is always a risk. I bear the scars on two fingers from a 15 amp socket which had the single pole switch wired in the negative side. So when I connected positive and earth with my fingers on an apparently switched off electric fire I nearly ended my days! I was three at the time but still remember the lesson.

Positive and negative in a 15A socket? My recollection of 15A 3 pin sockets was that they distributed an ac supply, we had them in our house in the 1950s along with 2A and 5A 2 pin sockets all supplying 240v ac.