GP40-2 freight vs. GP40-2 Passenger question.

[Steve F45]

While at Hoboken terminal a few months ago I was trying to do a panoramic shot of the train sheds from one of the middle platforms. While waiting there and setting up i noticed how loud it gets outside and hella loud inside from the trains idling. It wasn't till i was leaving that i started to notice that the overall engine speed at idle seemed kinda high on most of the gp/f40's that were in the sheds. Im not talking about the hep motor as that has a small exhaust and different tone to it.

Now when i goto the local spot to view NYSW i've seen there gp40-2 that they have at idle and it was nowhere near as loud or as high in engine speed at idle.

What are the main differences, not taking into account body shapes or HEP. Unless hep power is derived from the engine itself.

[Allen Hazen]

In the original EMD F40 (as on the GE Genesis and P32 locomotives, and the old U34CH and the Chicago area F40C), the HEP generator is rund by the main engine. Since HEP is provided as AC current at 60hz, this meant (with older units: more modern ones use solid state invertors to produce AC of the right frequency) that the engine had to be run at pretty much constant speed (often there was a setting that allowed the engine to be run at a lower speed for prolonged idling), with the traction output controlled by differences in excitation. As a result, when the locomotives are in a station, their engines, instead of runing at idle, are going full speed.

NJT has a variety of HEP-equipped locomtives, some rebuilt from freight units, some built new. I don't know what sort of system is used on which kinds.

[Jtgshu]

NJT's PL42's run at around a Notch 3 position when they are providing HEP for the train. But they do not have a seperate HEP motor, the power comes from the main prime mover.

NJT's F40's do have a seperate low idle switch, which lets the loco idle even lower than idle, but the GP40's do not

A Geep, freight or passenger, idles faster when the reverser is in Forward or Reverse. If its in Neutral, it idles lower. Its the opposite as in a car, when the cars engine runs at a higher RPM when in neutral or park, than Drive or reverse

Various noises could also be the cooling fans kicking on (not the HEP engine and fan, which is like 90 percent of the noise coming from an NJT passenger loco) or the number of fans running, also could be the air compressor loading or unloading

[conrail_engineer]

A Geep, freight or passenger, idles faster when the reverser is in Forward or Reverse. If its in Neutral, it idles lower. Its the opposite as in a car, when the cars engine runs at a higher RPM when in neutral or park, than Drive or reverse.

Not all of them. It depends on how the order was specified. I've seen as many that idle the same speed no matter the reverser position; and even a few where the idle speed kicks up when the reverser is centered.

A car idles slower in gear (automatic transmission) because the engine is under load. A locomotive has no additional load placed on it for the reverser, until the throttle is notched out.

[Jtgshu]

really? wow, I didn't konw that

Are there a lot of locos set up that way?

edit - hahaah I guess I never noticed, until last night, i had a GP40-2 last night which didn't idle down when the reverser was centered!!!

[MBTA F40PH-2C 1050]

the MBTA F40PH's 1000-1017, they are known as the screamers, they have their HEP's hooked with the main engine and they sound like they are in run 8 all the time, sitting in south station, making a station stop, etc. i love on the rebuild F40PhM-2C and the F40PH-2c's. the HEP is separate from the main engine

[Engineer Spike]

On CPR's SD40s, they have a summer/winter switch. It is on the control panel with the isolation switch. In the summer, the units have low idle, with the reverser centered.
One day I had a lengthy wait in a siding. This was in the early winter, on a cold day. My 3rd unit had lots of white smoke. It turned out that the shop did not flip the switch, which usually has a seal on it. I broke the seal, to put it in "winter", too permit high idle. Eventually the unit warmed up>
When I was on the Burlington, the Metra F40s had 3 positions on the HEP switch. The firs was for no HEP. The unit would rev up like any old GP40. The next was "stand by". It provided HEP from the AR10 traction alternator. It used a lower rpm, but could not provide traction power. The last normal HEP setting was the scream we all know, full rpm, HEP from HEP alternator.

[ridintherails]

the MBTA F40PH's 1000-1017, they are known as the screamers, they have their HEP's hooked with the main engine and they sound like they are in run 8 all the time, sitting in south station, making a station stop, etc. i love on the rebuild F40PhM-2C and the F40PH-2c's. the HEP is separate from the main engine

In the rebuilds i find that I can carry out a conversation with someone next to me no problem. Most geeps aswell. The seperate HEP generators keep things a little quieter in the back. The screamers are a different story. In the older f40's I can't here myself cough running in notch 8. Try walking through the engine room at that level.. it hits your gut.