Pans: front or back

Is there any difference as to which pantograph is raised on a dual pan engine? This was just a little oddity I noticed the other day, it seems the SEPTA push/pulls run with the front pan raised while my memory is Amtk uses the rear one. Now I realize they both will work, but is there any concerns with the direction the supporting arms face as far as deflecting, snagging anything? Without photos as supporting evidence in front of me, I seem to think Amtk even changes the pans when a train like a Keystone reverses, but I will need to pay attention to that detail as I am uncertain.

Just curious what the professional electric RRers think of this. Obviously it works as SEPTA has been doing it for a long time. Just interested to know if Amtak does it the other way is simply their rules, or ares their concerns as to how the pans are used?

Back in the day the word was that on the PRR the pantographs were designed to break free of the locomotive if one of them snagged in the wire, in hope that a whole extent of wire wouldn't be brought down, and locomotives ran with the rear pan so that if it snagged, the forward pan would still be usable whereas if the forward pan snagged it would remain hanging in the wire and take out the rear pan as well (under icing conditions both pans were used). I don't know what the situation is with today's power, but not infrequently you would see Amtrak and SEPTA operating differently in the same territory at the same time. This was dealt with in a thread some years ago, but I can't remember which forum. Of course the one-armed pans of today introduce another factor, in that as far as I know there are 4 pans on each unit with elbows in both locations facing in opposite directions. I'd like to hear what the different practices are and the reason.

Faiveleys work the same in either direction. They do in France, they do on SEPTA's Silverliners. There's occasionally differences because of aerodynamics, but there's no mechanical reason why they can't run in either direction. Most EMUs in the US and overseas have only one pan, where you see multiple ones overseas, it's often because of multiple power systems. Locomotives overseas with 4 pans have that because there's little standardization among power systems in Europe. Even within a country - France has two somewhat incompatible pan standards, one for each voltage they run. IIRC, the TGV has multiple pans on each power car for this reason, but typically only runs the 25kv one on the rear car, on the LGVs. IIRC, at least on some, that one has the arm trailing.

In a pinch, they can use the 'wrong' pan, and in some places (Netherlands), they'll use two pans at low speeds/standing, and one while running. seen it was Rotterdam services in Amsterdam - the loco had 2 pans up at low speeds, then dropped the second one as it left the station. I think this is to keep localized wire heating down under high current loads...

train2 wrote:Is there any difference as to which pantograph is raised on a dual pan engine? This was just a little oddity I noticed the other day, it seems the SEPTA push/pulls run with the front pan raised while my memory is Amtk uses the rear one. Now I realize they both will work, but is there any concerns with the direction the supporting arms face as far as deflecting, snagging anything? Without photos as supporting evidence in front of me, I seem to think Amtk even changes the pans when a train like a Keystone reverses, but I will need to pay attention to that detail as I am uncertain.

Just curious what the professional electric RRers think of this. Obviously it works as SEPTA has been doing it for a long time. Just interested to know if Amtak does it the other way is simply their rules, or ares their concerns as to how the pans are used?

Besides the operational recovery referenced above, it just makes common sense to run rear pan up vs. the risk of damaging the rear pan in the event of a front pan failure. I have actually been on a Amtrak train where the AEM-7 lost it's rear pan. After tying down the remains of the damaged pan and re-energizing the catenary, we were able to proceed, albeit at lower speed but it beat being stranded between stations.

SEPTA, for whatever reasons, has always seemed to have a propensity for running with the front pan raised.

Pans these days also have a failsafe for in the event it gets damaged, a mechanism is activated and lowers the pan.

running with front pan up also increases wear on carbon strips, as air displacement of car body pushes pantograph up against wire.

so why does septa run their engines with front pan?

The pans on the AEM-7's have little aerofoils on them- basically little wings to help them keep contact with the catenary at high speeds. The direction the aerofoils face is set to run front pan up in the direction of travel.
When Septa was leasing the ACS 64's from Amtrak they were told they run the rear pan up in case something took the pan out it wouldn't take out the other one and leave you dead in the water.