Pantograph contact strip

[L&Y Robert]

When riding a "cab-view" (particularly the Führerstandmitfahrt vieos) I note that the contact wire gently zig-zags from side to side, and read that it is to spread pantograph contact strip wear. What is a pantograph contact strip made of? Is it a single strip, or a double articulated strip (seems to be when examined from the platform, but can't be sure). I apprerciate that a streight wire would soon cut a groove in a moving contact strip.

 

[Tin Rocket]

carbon

 

[merlodlliw]

They are indeed made of carbon, the Swansea factory that makes them,is part of the Morgan advanced materials PLC
http://www.morganamt.com/gb/products-and-materials/collectors-transport/
the site tells you all about the product, I used to work for a Morgan sister Company in Ruabon.

 

[A-driver]

I believe most uk pantographs are a double strip. They are carbon strips and that is correct, the wires zig zag side to side to equal wear over the entire strip.

The carbons sit on a 'head gallery' which is a sort of trough filled with compressed air fed by an ADD pipe. If the air escapes (due to carbons breaking or being completely removed) dropping air pressure this is indicated by a light in the cab and tells the driver there may be damage to the pan so that s/he can drop pans rather than pulling miles of wire down (not what you asked but an interesting little fact).

 

[jopsuk]

By carbon, specifically it will be Graphite of some form

 

[Murph]

The carbons sit on a 'head gallery' which is a sort of trough filled with compressed air fed by an ADD pipe. If the air escapes (due to carbons breaking or being completely removed) dropping air pressure this is indicated by a light in the cab and tells the driver there may be damage to the pan so that s/he can drop pans rather than pulling miles of wire down (not what you asked but an interesting little fact).

Um, isn't "ADD" the automatic drop device? I.e. it should drop automatically on air loss, and not normally require action from the driver to drop it.

Edit: Or did you mean so that they can drop the other pans on multi units, to inspect for damage, etc?

 

[A-driver]

Um, isn't "ADD" the automatic drop device? I.e. it should drop automatically on air loss, and not normally require action from the driver to drop it.

Edit: Or did you mean so that they can drop the other pans on multi units, to inspect for damage, etc?

I don't know if they should drop but in any pan damage incidents I have known to happen from drivers they have had to manually drop the pans. Plus the rule book instruction for an ADD activation is to drop the pans, stop the train somewhere sensible if possible and contact the box.

 

[hairyhandedfool]

The A.D.D. is automatic as it's name suggests. The compressed air is the only thing holding the pan up, if air escapes from any of the A.D.D. devices the applicable pantograph drops.

In the drivers cab there is a 'line light' which is illuminated when the unit/loco being driven is receiving power from the over head wires (or third rail as appropriate) and goes out when the power supply is stopped for any reason.

If the A.D.D. is 'activated' then the pantograph cannot be raised again until it is repaired by a technician (fitter), which is unlikely to happen on the mainline.

 

[dtaylor84]

See also this informative RAIB report.

 

[A-driver]

The A.D.D. is automatic as it's name suggests. The compressed air is the only thing holding the pan up, if air escapes from any of the A.D.D. devices the applicable pantograph drops.

In the drivers cab there is a 'line light' which is illuminated when the unit/loco being driven is receiving power from the over head wires (or third rail as appropriate) and goes out when the power supply is stopped for any reason.

If the A.D.D. is 'activated' then the pantograph cannot be raised again until it is repaired by a technician (fitter), which is unlikely to happen on the mainline.

An add activation in most trains will set the VCB light flashing. The line light will only go out if it looses power as a result. Plus if you have units in multiple the line light only applies to that specific unit, not the ones behind you. Therefore if you get a flashing VCB and the line light remains on it indicates that the ADD is on the rear unit, not the one you are driving from.

As I say, I can only speak from experience, mess room talk and the three point rule for ADD (drop, stop, box) but an add activation dosnt always seem to drop the pan. As soon as a driver notices a flashing VCB they must press pan down to ensure it drops.

Some stock actually dosnt have any VCB indication-317s for example only have a line light and steady VCB light. If you have an ADD then the only way you will notice is if you loose line light but loosing line light dosnt always mean an ADD, it normally indicates that the wires have been de-energised. Infact on a 317 if you have an ADD activation on the rear unit you will get no Incab indication at all. The only way you may notice, apart from looking back out the window and seeing miles if cables down) is if the train feels a bit sluggish but again, an add activation wouldn't be your first guess.

 

[hairyhandedfool]

I realise I haven't driven a 317 for a decade or so, but I don't recall 317s having a VCB light, steady or otherwise, 319s definitely didn't have one back then (I doubt they do now either), but in any case, an A.D.D. which doesn't drop the pan doesn't sound like a very good A.D.D. imo, given that the whole point of them is to drop the pan.

 

[O L Leigh]

Cl317s have always had a VCB light, although it may have been labelled as "Breaker" rather than VCB.

I could be remembering it wrong, but I'm sure the flashing is a more recent innovation initiated as an in-service modification (at least on GA). Prior to that an ADD activation only resulted in a loss of the line light. As you say, when running in multiple you got no help whatsoever if it affected the rear unit other than a loss of power. The reason that you got no VCB/Breaker light with an ADD activation before was that the ADD dropped the pan to the roof but did not open the VCB.

Just to correct:

The ADD can be isolated by the driver to enable to pan to be raised. However, this would be under instruction from fleet support and only to permit inspection of the pan if this cannot be done any other way. It can also be isolated should the ADD develop an air leak or some other defect.

The standing instructions for drivers in the event of suspected dewirement or pan damage is to drop the pan. However, this is because the driver may be able to act quicker than the ADD and can pre-empt any damage due to obstruction of the OLE seen from the cab rather than relying on a reactive system such as ADD which will only activate once damage has been caused. This does not mean that the ADD is not an automatic system, because it is. The pan is held up by compressed air, and the ADD will vent the pan air system in the event that a carbon strip is lost or damaged, the pan goes over-height or is damaged in some other way meaning that the pan cannot be held up any longer and will lower itself without being requested by the driver.

O L Leigh

 

[D7666]

carbon

The OP referred to some German text :

(particularly the Führerstandmitfahrt vieos)

so is possibly asking not just about Uk but elsewhere.

Pantograph contact strips in UK may well be carbon, but this is not always the case elsewhere.

Some lands use copper, some use a copper-carbon mix, others carbon.

Even in the same land, a DC pan head may have a different strip to an AC pan head.

--
Nick