East Coast Overhead line

[Barrett M95]

Thank you for the welcome.

I see - I'm perhaps not tuned in to the level of audience yet.

Yes, I believe that while increasing tension is always welcome from our point of view as vehicle engineers as it makes life easier on high speed current collection, oscillations are inevitable and detrimental to a second collector. There is an interesting IMechE paper I have on pan-head bounce and current collection that goes in to a lot of mathematical detail based on uplift force, wire tension and even cross-winds.

 

[GNER 373]

Thanks Old Timer, interesting read indeed!

 

[Old Timer]

Thank you for the welcome.

I see - I'm perhaps not tuned in to the level of audience yet.

Yes, I believe that while increasing tension is always welcome from our point of view as vehicle engineers as it makes life easier on high speed current collection, oscillations are inevitable and detrimental to a second collector. There is an interesting IMechE paper I have on pan-head bounce and current collection that goes in to a lot of mathematical detail based on uplift force, wire tension and even cross-winds.

Thank you for the input.

I am sure it is way beyond my intellectual capability to comprehend. I always find those sorts of papers very dry indeed.

I leave such things to the clever OHL Engineers and chaps like yourself.

 

[captainbigun]

I have 20N in my head for some reason, from running MENTOR. Not being primarily a MENTOR/OLE guy and basically being reduced to twiddling telemetry and making sure we didn't rip the wires down, I can't exactly remember what the 20N actually refers to. It uses a B/W high-speed pan if that helps.

BW high speed should have a mean force of 90N +/- 3N. That's independant of the vehicle. There are some difference in the angle of the aerofoils between vehicles to take account of differing characteristics of operation (i.e. speed and airflow).

20N sounds like something friction related.

It's interesting watching the pan on the rear loco of a pair. It has to work very hard to maintain contact, but it's not a problem. The biggest issue is carbon wear.

 

[Hydro]

Possibly, there's a medley of measurements taken on MENTOR. I'd like to get back out on it and not fall asleep in the observation dome this time. Maybe then I'd remember what all the pretty flashing numbers and wavy lines mean.

 

[Barrett M95]

BW high speed should have a mean force of 90N +/- 3N. That's independant of the vehicle. There are some difference in the angle of the aerofoils between vehicles to take account of differing characteristics of operation (i.e. speed and airflow).

20N sounds like something friction related.

It's interesting watching the pan on the rear loco of a pair. It has to work very hard to maintain contact, but it's not a problem. The biggest issue is carbon wear.

20N is in the zone for a friction figure I would say, yes.

I should point out that not all BW high speed pantographs have that nominal figure. I know one vehicle fitted with one that is (or at least was) 70N nominal static, but it is not 25kV.

It does vary a lot with speed but the main worry is over-stressing the contact wire by creating too much vertical displacement but some units have a height stop to prevent catenery damage. In a case where you have two vehicles running in close formation at high speed (200km/h for example) the mean force of the first pan head on the wire will be, say 100N with fluctuations between 60N and 140N. The second vehicle however will have the same mean force of 100N, but you will find the peaks and troughs to be as high as 180N or low as 40N. The 180N figure may over stress the wire, and the 40N figure is at risk of losing contact which will result in arc damage.

I know of tests that have resulted in wire displacements of 350mm at 300km/h.

 

[Old Timer]

The OHL design is based upon a maximum uplift force, as not all clearances are maintained by registration arrangements.

There are some bridges which are free-running but there is minimal clearance from uplift. The very last thing that the OHL Engineer wants is a high uplift force pan running around.

Pan Uplift values are provided for us in the handback acceptance criteria, so we have to assume that the pans running are within whatever the agreed criteria is.