BR(S) Class 71 Electrics - why did some operate without overhead pantographs fitted?

[Nearholmer]

Two-rail electrification was sort-of normal in the very formative years of electric traction. The first line that we would recognise as a “proper electric railway/tramway” was the one Siemens & Halske built at Lichterfelde, which was 2R, and it wasn’t until they had a lot of trouble with ground leakage at a line they were building for an exhibition in Paris that they developed the use of a separate positive conductor (they then ended-up using a separate negative too, for various reasons, abandoning using the running rails altogether for several years). Some of the other pioneers also used 2R, Egger being one.

 

 

Volks was a “fast follower”, rather than a real pioneer, and the first version of the VER was something of a quick and dirty job, so he was a bit behind the curve starting with 2R. Photos of it in that form are very rare, but this has been doing the rounds, and I’m fairly certain that it does show it during its brief life (the old Chain Pier in the background).

 

 

The voltages on these early lines were low, and the Victorian public didn’t know quite how dangerous electricity could be. There are contemporary accounts of people deliberately taking shocks on the Lichterfelde line, for instance, and of women accidentally getting shocks from their trailing skirts because they were looking at themselves in pocket mirrors and putting lipstick on, instead of looking where they were treading!

 

 

Edited January 26 by Nearholmer

[Wickham Green too]

1 hour ago, bécasse said:

You were clearly unaware that some bright spark in Network Rail thought that, because two-rail electrification has long been the norm for model railways, it ought to be tried on the real railway too.

Plays havoc with the track circuits though ......................... hence the trend towards axle counters nowadays.

[roythebus1]

3 hours ago, Artless Bodger said:

I think I read that Volk's at Brighton originally was 2 rail electrified, but changed to 3 partly due to current leakage. I can't imagine Sussex commuters accepting a Volk's style train though.

They may find the Volks stock more comfortable than some of the modern offerings.

[bécasse]

I am remained of a story that came out of the OURS many years ago. Someone with contacts managed to arrange a tour of the then new Underground depot at Upminster (which I wasn't on, I should add). As part of their tour they had cross the tracks at the throat of the depot, their guide checked that no movements were due and then explained how to cross stepping from rail to rail. When they safely reached the far side, one of the learned visitors mentioned that the technique expounded by the guide was much easier than he had anticipated but questioned how they crossed when the current was on (since the rails they had trodden on included the two raised live rails). The guide replied "What do you mean, what do we when the current is on, the current is on!" Quite an interesting exposé of the fact that the voltage on LT's conductor rails, one nominally positive, the other nominally negative, floated, although apparently at that time more so in the depot than on running lines.

[Flying Pig]

On 25/01/2024 at 20:49, Wickham Green too said:

Would it make sense to design one specially for lighter use though ..... I say design - they may have been off the shelf items from whoever supplied pans to Blackpool Trams etc. 

 

But were they lighter anyway ? - don't forget the 71 was a considerably more powerful loco than a 76 and working on half the voltage would have taken twice the current per kW. 

 

Relatively little power at yard speeds where the pantograph was used since

 

     power = tractive effort x speed

 

[Tom Burnham]

On 25/01/2024 at 20:49, Wickham Green too said:

Would it make sense to design one specially for lighter use though ..... I say design - they may have been off the shelf items from whoever supplied pans to Blackpool Trams etc. 

I'm not an expert on Blackpool trams but I'm pretty sure they used trolley poles rather than pantographs until comparatively recently.  No doubt pantographs were available off the shelf, though.  Bracknell Willis (sp?) comes to mind 

[kevinlms]

11 hours ago, Nearholmer said:

Two-rail electrification was sort-of normal in the very formative years of electric traction. The first line that we would recognise as a “proper electric railway/tramway” was the one Siemens & Halske built at Lichterfelde, which was 2R, and it wasn’t until they had a lot of trouble with ground leakage at a line they were building for an exhibition in Paris that they developed the use of a separate positive conductor (they then ended-up using a separate negative too, for various reasons, abandoning using the running rails altogether for several years). Some of the other pioneers also used 2R, Egger being one.

 

 

Volks was a “fast follower”, rather than a real pioneer, and the first version of the VER was something of a quick and dirty job, so he was a bit behind the curve starting with 2R. Photos of it in that form are very rare, but this has been doing the rounds, and I’m fairly certain that it does show it during its brief life (the old Chain Pier in the background).

 

 

The voltages on these early lines were low, and the Victorian public didn’t know quite how dangerous electricity could be. There are contemporary accounts of people deliberately taking shocks on the Lichterfelde line, for instance, and of women accidentally getting shocks from their trailing skirts because they were looking at themselves in pocket mirrors and putting lipstick on, instead of looking where they were treading!

 

 

2R kind of doesn't work well in wet weather.

[Nearholmer]

10 hours ago, bécasse said:

Quite an interesting exposé of the fact that the voltage on LT's conductor rails, one nominally positive, the other nominally negative, floated, although apparently at that time more so in the depot than on running lines.

Despite having had very close involvement with the system for nearly thirty years, I never quite got the bottom of the history of potential distribution on the 4-rail system. I know that initially the system floated, with the potential distribution being a byproduct of the different creepage distances on the positive and negative insulators, so that it varied according to circumstances, and I know that now both poles are earthed via resistors of determined values, so that it is fixed within tight limits, and potential distribution is monitored for change outside those limits, which indicate insulation failure of one kind or another. The bit I don’t know with certainty is when the move from one practice to the other was made, I could never find it from easily available records (I was too busy to go archive mining) and even “old boys” I asked about it weren’t totally sure. My best approximation at an answer is that it resulted from some horrendous fires on rolling stock in the 1950s, which occurred when initially highly resistive pole-earth-pole faults, so not detected by short-circuit protection, propagated to become sustained arcing faults between positive and negative lines below car floors, but I have an inkling that some areas may have had managed potential distribution, and monitoring before that, maybe from lessons learned the hard way during WW2, or perhaps even earlier. What I do know is that depot sections were the last to be “sorted out”, possibly as late as the 1970/80s, most likely because historically they tended to have high, and often very dirty, ballast, and some had ‘pots’ in very poor condition, so a lot of natural leakage going on, which would have confounded attempts to ‘pin’ the voltages and monitor them.

 

If anyone does know the exact batting order of events, I’d be interested to learn.

[Wickham Green too]

10 hours ago, Flying Pig said:

Relatively little power at yard speeds where the pantograph was used since ... power = tractive effort x speed

Starting a load of coal from Snowdown would have required quite a fair bit of grunt - far less once on the move.

 

7 hours ago, Tom Burnham said:

I'm not an expert on Blackpool trams but I'm pretty sure they used trolley poles rather than pantographs until comparatively recently.  ...

indeed, most Blackpool Cars did use poles - but a few had pans from the '20s.

[Michael Hodgson]

4 hours ago, kevinlms said:

2R kind of doesn't work well in wet weather.

That wouldn't worry the Volks Electric Railway.  Brighton doesn't get wet weather.  

Except on bank holidays.

[Flying Pig]

1 hour ago, Wickham Green too said:

Starting a load of coal from Snowdown would have required quite a fair bit of grunt - far less once on the move.

 

 

Grunt in this case is not power, it is tractive effort.  However in you are correct in that TE varies with traction current, so the driver would need to handle the loco carefully on starting a heavy train if there was a lower current limit when working on the pantograph.

[Artless Bodger]

2 hours ago, Nearholmer said:

high, and often very dirty, ballast,

Something I noticed one very wet night at Bearsted station (I'd gone to meet my wife off her train) soon after some reballasting, there was a hissing sound and a small spark arcing from the bottom of the 3rd rail to a prominent piece of ballast.

 

Rather more exciting was one morning waiting at Maidstone Barracks - someone emerged from the bothy at the end of the emu sidings there and, as far as I could make out, tossed the contents of the teapot across the tracks causing a momentary and very bright arc. Took a while for my eyes to recover.

[Oldddudders]

For real third rail drama, try being around when a pot explodes. The bang is impressive, not to mention the trajectory of the shrapnel.

 

My experience was in Grove Park shed, NYE 1976, where I was acting shunter. due to a lack of volunteers. Somewhere before midnight, in pouring rain, there was a huge bang and clatter, and the yard CB tripped out. Stepping out of the shunters' hut, smoke was still rising from the scene of the bang, and the juice rail was clearly  unsupported. My first attempt to reset the yard breaker was unsuccessful, so I had to pull a hook-switch or two. Then the breaker went back in. Murphy's Law obtains in SE London, so the now useless road was the only empty one, of course. Thus the last couple of trains in had to be split and shunted to put units on top of berthed stock. Drivers looking forward to getting home and celebrating 1977 were really chuffed to have to do the extra moves, of course.....

[Southernman46]

4 hours ago, Flying Pig said:

 

Grunt in this case is not power, it is tractive effort.  However in you are correct in that TE varies with traction current, so the driver would need to handle the loco carefully on starting a heavy train if there was a lower current limit when working on the pantograph.

Indeed ISTR there are 38 notches on a Class 71 controller to enable them to do precisely that. 

[DY444]

On 26/01/2024 at 02:34, adb968008 said:

Odd ball thought, but as laying more 3rd rail is a no-go.. why not extend 750vdc overhead instead ?.. Uckfield / Exeter etc..

 

Most SE/ SR /LSWR stock (Desiro/Electrostar) was built with pantograph wells in the roof design.

 

You would need a very hefty amount of copper in the air in terms of catenary/contact wire and suitably hefty structures to support it to power a modern emu.  Ground level exposed conductors aside it is pretty much the worst of both worlds.  You get none of the higher power and light weight structure/conductor advantages of AC and none of the cheapness to install of third rail.

 

Also, and it's early days I accept, but given the somewhat inauspicious start to battery operations over a non-electrified line barely half a mile long, I predict battery powered emus are going to prove themselves to be a massive operational headache and an expensive mistake which the industry is going to regret.  

[phil-b259]

57 minutes ago, DY444 said:

 

 

Also, and it's early days I accept, but given the somewhat inauspicious start to battery operations over a non-electrified line barely half a mile long, I predict battery powered emus are going to prove themselves to be a massive operational headache and an expensive mistake which the industry is going to regret.  

 

To be fair 'the industry' doesn't have much choice - if the DfT is refusing to stump up for electrification (and yes I know the GWML went baldly wrong, but the more you do something the better you get at it and by the end of the project its costs had been bought under control) yet also demanding the industry do something to cut carbon emissions....

Edited January 27 by phil-b259

[Southernman46]

32 minutes ago, phil-b259 said:

 

To be fair 'the industry' doesn't have much choice - if the DfT is refusing to stump up for electrification (and yes I know the GWML went baldly wrong, but the more you do something the better you get at it and by the end of the project it costs had been bought under control) yet also demanding the industry do something to cut carbon emissions....

Aye - I watched their possession planners tearing their hair out in the NR Reading planning meeting on many an occasion as the scheme slipped back and back ...........................................