(1) In real world, I observe most of the eloks run with the front
pantograph down and the rear one up. Is that because of aerodynamic
considerations?
(Answer - Tom Orle, Joerg Bruehe, & Marout Yasuo Sluijter-Borms, Greg Proctor) It has nothing to do with aerodynamics.
Normally the rear panto is
used unless the loco, as noted above and below, is coupled to a tank car, another loco or a car
transporter. The reasoning is as follows - if the front panto is up
and somehow gets damaged while speeding along, the broken panto could
damage the rear panto. But if the rear panto is used and gets damaged,
then the loco can continue to the next stop using the front panto. A fault in the catenary could tear
the pantograph. (Click on the underlined text to see a video of a damaged pantograph and what it does to the catenary.) If thee leading panto is damaged then it will probably
catch the second panto and destroy it also, leaving the Lok without
power. As catenary has become more robust this worry has diminished to the
point where many Loks are only fitted with one panto.
If a flammable liquid or gas tank car follows the loco it becomes a
safety issue. If the train is double headed, then the first loco will have the front
one up and the second loco will use the rear unless the above
mentioned cars are behind it.
Loks like E44, E93, E94 etc all ran with two pantos up because the
technology of the carbon block panto sliders wasn't far enough advanced.
In the 1950s/60s the technology advanced and new Loks were built where
one panto was enough to collect the required current. The older Loks got
upgrades when replacements were required.
The 1200 series used to automatically raise front panto upon station hold
and lower it, once the train had reached low enough power consumption
to enable single panto running.
Jens Wulf and others have shared links to e-loks with front pantos up, some with several loks and only one panto on the loks is up, and pictures with several pantos up. Go to the links below to see these pictures. These are followed by a youtube video of a panto and catenary being destroyed.
Pantographs have a graphite piece to make the contact with the
catenary wire (so that the wire stays intact, and the wear is on
the graphite which can easily be replaced). As the panto slides under the catenary it gives off sparks of melted carbon and metal. To prevent the resulting melted
graphite dust from falling on the lok's roof the rear pantograph is used. The forward panto
is normally used when piloting another lok or there is sensitive cargo
immediately behind.
But they don't use the rear panto when an automobile transporter is
the first car behind the loco because the carbon deposits from the
panto's wiper will dirty the automobiles.
Since the NL uses only 1500V DC, many locos and triebwagen
use both pantos during shunting, to have greater area of contact when
using heavy current to set in motion the vehicle.
Iwan Blom's answer to a question whether there are cables between loks with no pantos up: "No, there are no cables. The DB loks use certain systems for double or
multple heading. One of these systems is ZMS. ZMS is used on both 151 and
185, but 185 is not allowed use it when it's running with dissimilar loks.
The 140 has a different system, hence the 185 and 140 are ballast here :-)
They're probably be moved as a repositioning item."
Tom Torle further explains repositioning loks. "Me thinks they are just along for the ride as in a repositioning move. That way they don't have to create separate schedules just to move
loks around and tie up the track (I think that's called Lz for
'Lokzug'). I don't think these loks have provisions for sharing catenary power."
Below is a link to a video of a multiple Lz:
Used to be until the 50's. It has been replaced by '1' and '2'. 'V' stands for 'Vorne' (front) and 'H' stands for 'Hinten' or rear. Btw - in those days the locos used both panto's up. If you look carefully at older pictures, you'll notice that the old panto's only had one slider making contact with the catenary wire. Any loco using that kind of panto always ran with both up. Newer panto's have 2 sliders and therefore can get away with using only one panto up. (3) Which way should the single arm pantograph run? With the elbow joint facing front or rear? (Answer - Tom Orle)
Either way - however they're designed. Some don't have the space on
the roof for the elbow to go in one direction or other due to
placement of the main circuit breaker, hydraulic panto raising
cylinders or other stuff.
(Answer - Jacques Vuye AKA Dr. Eisenbahn)
In fact it originally had four!
This because it is essentially two loks, permanently coupled sharing a large
part of their main components with the Ae4/7 (motors, transmissions,
compressors, etc).
It was running on two pantographs for most of its life and the same rules
apply as Tom described in his [answers].
The third one, seen currently on the Museum lok in Erstfeld, is in fact a dummy
and serve no practical purpose! The "functional" ones are those at the "rear" of each half lok.
They are raised by compressed air and the engineer has controls in the
cabs.
Upon arrival at the station he lowers the rear panto and after he
himself moved to the other end pushes the button to raise the other.
Note also, that when a train is coupled or uncoupled by the worker
standing between the loco and the first car - the panto is dropped.
This is to prevent any possibility of electrical shock to the coupler
if there were any defect or leakage in the loco's electrical system.
You can see this at dead-end stations like Munich, Stuttgart and
Frankfurt all the time.
THis is a safety precaution, necessary when the train needs electrical
power:
On the buffer plate there is a large single-pole connector with big
insulation.
It carries between 1500V in NL (full catenary load) or 3000V in other
UIC compliant locos.
It is locked into a holder on the buffer plate and the lock uses the same
key as the main circuit switch on the loco.
The key can only be removed from the main control panel if:
That way, it is certain, the connector has potential 0 V and
can safely be hooked to or unhooked from the carriages.
-the loco is totally dead (all systems set to OFF)
-Catenary circuit breaker is in the OFF position
-Both pantos are lowered
-Main circuit control is set 0