Network Rail 'Ice-breakers'.
 

Looking through a copy of 'Railway Magazine' from March 2007 last night, I came across a picture of 86901 and 86902 stabled in York station. The caption referred to the fact that the loco's were ready to clear any ice that might form on the o/h wires. Does anyone have any more information on these two? Are they self propelled? And how does the ice breaking equipment actually work?

And you can see them here, courtesy of Google..http://www.departmentals.com/photo/8690186902
http://www.departmentals.com/photo/8690186902

I think the "ice breaking" equipment is simply the locos pantographs:)
Regular passage of electric trains would normally keep the overhead wires free from icing but from what I can gather the problem has got worse since overnight electrically-hauled mail trains stopped running. Although the two locos can also be used as load banks I believe that they can still operate under their own power.

Thanks for the info lads.

So, say they operate as a pair, would one use its pantographs to dislodge the ice, whilst the other one pushed?

Barclays, HSBC, and even Northern Rock banks I have heard about but what is a Load Bank and how does it function?
John (G) still in the days of steam.

I can't say for sure exactly how the locos are used but I imagine that the ice clearing is done with the pantograph/s actually taking current. This is obviously going to create a lot of sparking (and increased pantograph collector strip wear) which is probably why Network Rail have dedicated "ice breaking" locos. As these locos are running "light" they will be drawing less current and creating less sparks than a service train running at high speed and pulling a heavy train. 86901/902 might even be equipped with extra hard collector strips.

NR seems to be taking de-icing more seriously nowadays. Until fairly recently it was the TOCs who did it (and they still do).

I can't help wondering if there's going to be rather too much duplication going on when the weather gets nasty....at Tonbridge for example there's Southeastern running "Ghost train" ECS from Jubilee sidings, Amec operating MPVs out of Engineers Sidings, and GBRf running 73/GLVs out of the yard. Knowing the railway, I'll bet none of them talk to each other at the planning level, at it'll be the taxpayers and passengers who foot the bill for the overkill as usual.

:D

Hands up anyone who read the above link and understood it? :D

No, one loco running under its own power would clear the ice simply because the pantograph would 'wipe' the contact wire clean. Not forgetting of course that the OHLE is dyanmic, it bounces and sways under tension as a train pushes against it so it will be given a good shaking to agitate the ice as well.

Because the system is supplying large amounts of power, even a small build up of ice causes significant impedance, which manifests itself as arcing - even under steady state conditions. When you're driving in these conditions the motors can become very jerky indeed. Unfortunately something in the traction path usually gets upset (ie, a fuse or relay).

Of course this is just as much a problem on the DC side where conductor rail icing occurs. This can be even more disruptive to trains as the system needs many times more amps, with only a nominal 750 volts instead of 25kV available to drive it.

The answer is to keep trains running 24/7, hence my earlier comments about running 'ghost trains' throughout the night.
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With regards to the loadbank, I would imagine that it is used for testing the OHLE supply system.

A electric train which is motoring is a pretty horrible load - giving varying inductance, jittery power consumption & arcing, and high frequency ripple.

A far better tool for studying the network is a nice smooth steady state load, which is what I would guess the two locos have been configured to provide.