The Front Pantograph is up again

Well Amtrak and it's wisdom has decided to put in this week's bulletin order that ALL AEM-7 and HHP motors should run with the front pantograph up instead of the rear. There is no logic in this! If you run with the rear pantograph up and snag the wire and tear the pan off, no problem you simply put up the front and continue. Now that you run with the front pan up and snag the wire you will now tear the front pan off and the good rear one with it! DUH! This rule now changes 20 plus years of common sense. My money says after the front pan tears the rear pan off the rule will go back to the smart way! Somebody got a raise!

The front pan up also will increase amount of failures, since the updraft of air from front end of engine will actually increase pressure that pan has on wire.
But what the heck there is always a Office manager who knows better than any field man.

$2 says some idiot manager saw a train with the rear up, thought it looked 'backwards' and insisted everyone run the 'correct' pan up.

Actually, most, if not all pans work equally as well in either direction, and that certainly includes the types Amtrak uses. The bent arm trailling looks like it shouldn't work, but it works just fine.

I've tried to make sense of these practices for years, and I can't. It seems to make sense for a MU to put front pan up when each MU has more than one pan, because that puts about 60' between the up pan and down pan, while if back pans are used and a pan dewires and makes a mess, you've only got about 10' between the up pan and down pan. However, on a locomotive, it seems back pans would be the best to raise - a snagged pan will trail out over the train, and the front pan will remain untouched.

However, I'm not remotely clear as to why the policies actually ARE what they ARE. CSS has changed a few times, and most stuff out east only has one pan. It seems when PRR had two pans, the back was always used except on E44, where front was used.

Well I can't wait till the front pan gets snagged and tears the rear pan off with it. 500 people sweltering in the hot sun on a July day! I'm actually suprised that Metro North lets Amtrak run like that Between NRO and NHV! MY 2 bucks says MNCRR tells Amtrak No !!! Put the rear one up! Especially with thier old wire that tends to sag something bad in the hot days of summer! tick-tick-tick.....

Hi All,

A little piece of PRR trivia, carried over to Amtrak etc. In the dead of winter, with ice and snow all around, and icicles hanging off the catenary, BOTH pantographs were raised. The lead pantograph was an ice scraper, and also picked up juice, and the rear pantograph ensured a clean pantograph and also picked up juice. Both pantographs therefore ensured that the train would NOT stall, and the catenary would be kept clean for the next train, etc.

I do agree that there is a danger in running with only the lead pantograph up in good weather, and if it gets snagged, the rear pantograph is in jeopardy as was previously stated.

Actually, on the AEM-7, and I think on the '44, '46 and HHP-8, the front pan can run isolated, to keep the arcing down. I'm guessing this feature was carried over from the RC-4s, which are probably no stranger to ice scraper service!

When running with both pans up for sleet scrapping, only one is suppose to be energized. Running with both energized can cause damage to the locomotive.

So there seems to be some agreement on why NOT to run with the front pan up instead of the rear (because pan/wire trouble could subsequently ensnare the rear pan as well). But can anybody think of a good reason to run just the front pan besides "some dumb manager thinks it will look better?" I certainly cannot due to a lack of experience/knowledge, but I'd like to believe that Amtrak is doing this for a legitimate reason.

AEM7AC920 wrote: When running with both pans up for sleet scrapping, only one is suppose to be energized. Running with both energized can cause damage to the locomotive.

What kind of damage, and why? I know of no electrical reason, excepting that if a phase break between different system voltages (11kV vs 25kV) or frequencies (25Hz vs 60Hz) was shorter than the space between the two pans, that fault current between the different systems would travel through the two pans and the internal engine HV wiring.

I hate to steer this from a Amtrak discussion to a tech discussion, but how does it damage a locomotive when both pans are raised AND energized? In the electric crane industry, the cranes are powered by three parallel conductor bars, similar to the electrification method used by B&O in the really early days. Each bar has a leg of 3ph 440vac. Those cranes using inverters MUST have tandem collectors on each bar/leg, which would be the equivelent of two pans being raised and energized. I guess I'm at a loss as to how this works in one place, but not in others.

Two live pantographs will bridge any insulators and short phase gaps causing a direct short between the two power sources.
same problem occures when traveling thru interlockings etc the two pans will bridge section insulators and can hurt people working on isolated sections, yes those people are supose to ground the isolated section ,but you can never be sure.
When sleet operations are done usually the front pantograph is isolated from the locomotive.

First off... I know that the pantograph selector switch on AEM-7s is either in FRONT-BOTH-REAR. There is no "isolation switch" to a pantograph. If the raised pan is "hot" so is the lowered one. Running with both pans up is indeed possible and is referred to in the Amtrak AMT-2 book (electrical instructions). IT would be only done fore icicle removal.
Getting back to the front pantograph subject... There is NO good reason to run with the front one up. NONE. If you look close at a pantograph you will see small aerofoils on the arm. The aerofoils work like a spoiler on a racecar but in reverse. They are designed to push up on the wire. Soooooo, If the front pan is up the aerofoils are now having the opposite effect. They are causing the pantograph to droop under higher speeds! This front pantoraph running is rediculous to say the least. Tick,tick, tick....

DutchRailnut wrote:Two live pantographs will bridge any insulators and short phase gaps causing a direct short between the two power sources.
same problem occures when traveling thru interlockings etc the two pans will bridge section insulators and can hurt people working on isolated sections, yes those people are supose to ground the isolated section ,but you can never be sure.
When sleet operations are done usually the front pantograph is isolated from the locomotive.

Wouldn't there be a risk of this bridging from two locomotives (each powered) heading a train?