"Amtrak phases out overhauls at Indiana shop"?

[AlanB]

Personally what I'd like to see more of is the F59PHI style of providing HEP. Those engines have a seperate, smaller diesel that provides the HEP to the train. This way if the prime mover fails, power is still maintained in the cars, even if the train isn't going anywhere. And if the HEP engine dies, they can draw power off of the prime mover to keep hotel power on in the cars, even though it will decrease performance of the engine.

Huh, I was always under the impression that the engine that provided the HEP was always separate, so as not to require the prime mover to idle at a higher rate than normal when the train wasn't moving (or some sort of similar reasoning). Am I wrong about this? While we're on this topic, am I correct in understanding that the P32s are the only units that can use current from dynamic breaking to reduce the load on the HEP generator? And, one final question: I was reviewing the latest copy of Amtrak Ink and there an article on how increased use of dynamic breaking is saving Amtrak fuel. I understand using dynamics reduces wear on the equipment's brakes, but how does it save fuel?

I'm definately not the right guy to answer all of your questions, but I can tackle the first one. In the case of the GE Genesis series, there is no seperate engine to provide HEP. If the prime mover fails, the train looses all power, both motive and hotel. That includes the P32-ACDM, the P40, and the P42. Now in the case of the P32-ACDM, if they were lucky enough that the prime mover failed in an area where there is LIRR third rail, then they could probably still provide hotel power, as well as move the train, at least so long as they don't run off the third rail.

This is why if you ever find yourself standing next to a P40 or P42, as well as a P32-ACDM not sitting on third rail, that you will hear the engine running at a much higher rate than would normally be required for just standing still. Or at least one of the units will be reving, even if the other's are at low idle.

 

[transit54]

I ended up googling the issue out of curiosity, and located this:

http://www.trains.com/trn/default.aspx?c=a&id=198

Answered just about all of my questions, so I figured I'd post it here in case anyone else was interested.

 

[jackal]

I ended up googling the issue out of curiosity, and located this:
http://www.trains.com/trn/default.aspx?c=a&id=198

Answered just about all of my questions, so I figured I'd post it here in case anyone else was interested.

Still didn't answer one of your questions: how does increased dynamic break usage reduce fuel consumption? I'd heard that before, too, and was wondering how that worked.

Maybe if they were using a Green Goat or other hybrid (battery-powered) locomotive, but all I would think dynamic braking would do is reduce the wear on the friction brakes...

 

[AmtrakWPK]

I'll make a guess at the dynamic braking issue. Frequently, if not "normally", Amtrak engineers use stretch braking. That means they are still applying motive power (and burning a slightly higher rate of fuel) while applying the brakes to the passenger cars. This keeps tension on the couplers of all the cars, and reducing jostling the passengers by preventing the couplers from going from tension into compression. I would imagine it is a little more difficult to do that if instead of using stretch braking while still applying "pull" from the loco they use dynamic braking. Dynamic braking, for those who don't recognize the term, means that the direct-current traction motors located on the trucks (the wheel assemblies) of the locomotive, are used in a different mode. A direct-current motor, when you apply power to it, will turn, and therefore pull the locomotive (and of course the passenger cars attached to it). As long as the locomotive is moving (the wheels, and therefore, those direct-current motors, are turning), if you stop applying power TO the motors, they act as generators, generating power. There is a network of resistive assemblies built into the roof of those locomotives, which can take the power generated by the traction motors when the train is moving but power is NOT being applied to the motors, and those resistive assemblies (with big fans blowing air through them to dissipate the heat generated thereby) use the power generated by the traction motors when in "dynamic braking", or generator mode. When you do that, those traction motors (now actually traction "generators") act as brakes on the engine, dissipating the kinetic energy of the train by generating direct-current electrical energy which is then dissipated as heat in the resistive assemblies in the roof of the locomotive. While doing so, the prime mover (the diesel engine) uses less fuel, just enough to maintain a high enough idle speed to keep providing hotel power (alternating current) to the passenger cars. And you also save some wear-and-tear on the brake pads.

That is my understanding of how things work. There may be some minor errors (other than my usual dyslexic spelling but for those who were wondering what "dynamic braking" is, that may help.

 

[Guest_Yerry_*]

WPK's dead-on on how dynamic braking works. By avoiding massive airbrake pumping operations at higher loco speeds, a fair amount of fuel can be saved.

But, unlike REGENERATION, DB merely takes excess energy and blows it out the top of the loco as heat, with this energy loss creating drag on the traction motors & wheels. The old Milwaukee Road Pacific Extension's electric service used regeneration; the electricity generated by a slowing (or descending off a mountain) loco was put back up on the catenary. MILW used to advertise that all their downhill trains therefore helped pull the uphill trains.

Regeneration required a lot more control equipment to keep the power in-phase and the same voltage as the power plant juice.

 

[Guest_Yerry_*]

New? Hardly. My county highway department has been counting traffic light cycles for the past 15 years, predicting when each bulb will burn out, and replacing it right beforehand. Now overtime for the TC crews has been minimal, ands I've seen maybe two burned-out bulbs in the eight years since I've lived here.

Of course, this depends on DATA IN. Before I moved here, Riverside County, CA had a nearly-identical system where data people manually entered numbers pulled off counters. But, their data entry people routinely faked their work, and suddenly they had HUNDREDS of bulbs out.

My only concern is when too many "We'll get that one next time" episodes catch up with everyone, but heck, that's happened already.

Question:

Relating to "if it doesn't die immediately after delivery, it'll last forever"; wasn't there a brief article in TRAINS about P42's suddenly dying en masse and GE was having difficulty figuring out why, in spite of the diagnostics computers on board?

 

[Mark]

It will be interesting to see how many people from Indiana, 'follow thier jobs' to Chicago or Delaware. I have a feeling that not too many will. Folks from Indiana tend to be repulsed by cities like Chicago. How will this effect Amtrak's maintenance plan if say half of thier skilled mechanical work force applies for jobs on other lines, like 'OBS gone freight'? Of course that could be part of the plan, ditch the 'high-seni' guys with 4 and 5 weeks vacation for new highers with no vacation and lower pay.

 

[Crescent ATN & TCL]

I'll make a guess at the dynamic braking issue. Frequently, if not "normally", Amtrak engineers use stretch braking. That means they are still applying motive power (and burning a slightly higher rate of fuel) while applying the brakes to the passenger cars. This keeps tension on the couplers of all the cars, and reducing jostling the passengers by preventing the couplers from going from tension into compression. I would imagine it is a little more difficult to do that if instead of using stretch braking while still applying "pull" from the loco they use dynamic braking. Dynamic braking, for those who don't recognize the term, means that the direct-current traction motors located on the trucks (the wheel assemblies) of the locomotive, are used in a different mode. A direct-current motor, when you apply power to it, will turn, and therefore pull the locomotive (and of course the passenger cars attached to it). As long as the locomotive is moving (the wheels, and therefore, those direct-current motors, are turning), if you stop applying power TO the motors, they act as generators, generating power. There is a network of resistive assemblies built into the roof of those locomotives, which can take the power generated by the traction motors when the train is moving but power is NOT being applied to the motors, and those resistive assemblies (with big fans blowing air through them to dissipate the heat generated thereby) use the power generated by the traction motors when in "dynamic braking", or generator mode. When you do that, those traction motors (now actually traction "generators") act as brakes on the engine, dissipating the kinetic energy of the train by generating direct-current electrical energy which is then dissipated as heat in the resistive assemblies in the roof of the locomotive. While doing so, the prime mover (the diesel engine) uses less fuel, just enough to maintain a high enough idle speed to keep providing hotel power (alternating current) to the passenger cars. And you also save some wear-and-tear on the brake pads.That is my understanding of how things work. There may be some minor errors (other than my usual dyslexic spelling but for those who were wondering what "dynamic braking" is, that may help.

Is it possible that Amtrak is using some of the power generated from dynamic braking to provide HEP? That would account for the fuel savings.

 

[transit54]

Is it possible that Amtrak is using some of the power generated from dynamic braking to provide HEP? That would account for the fuel savings.

Only with a P32, according to the Trains link I posted. A P40 or a P42 don't have the capability to do that.

 

[yarrow]

It will be interesting to see how many people from Indiana, 'follow thier jobs' to Chicago or Delaware. I have a feeling that not too many will. Folks from Indiana tend to be repulsed by cities like Chicago. How will this effect Amtrak's maintenance plan if say half of thier skilled mechanical work force applies for jobs on other lines, like 'OBS gone freight'? Of course that could be part of the plan, ditch the 'high-seni' guys with 4 and 5 weeks vacation for new highers with no vacation and lower pay.

good point. i don't think managment is doing this for the benefit of labor or the customer. to me, as i noted above who knows nothing about locomotives, this looks short sighted. i appreciated alan's comments above on how this approach has worked with acela but i trust amtrak workers to get me safely there not managment

 

[jackal]

Is it possible that Amtrak is using some of the power generated from dynamic braking to provide HEP? That would account for the fuel savings.

As far as I know, that's only possible on the P32AC-DM engines (the ones that can switch to third-rail electric power), which are only used on certain long-distance (normally diesel-powered) trains that terminate at NYP (no diesel allowed due to the tunnels). The P32s also use a computer-controlled inverter to provide HEP, so the engine doesn't need to run at a precise RPM to maintain the 60Hz AC current required for HEP, which is another fuel-saving item. But the P32s are, as I said, in limited use, so they would not account for much of the total fuel savings.

On all other diesel-electric engines (P42s, etc.), the prime mover still generates HEP even in dynamic braking mode.

I think AmtrakWPK is spot on with the primary fuel reduction coming from the elimination of stretch braking, something I didn't think about but that should have been obvious to me. Back to the other thread about jostling in the rear cars: I'll bet some passengers in the rear cars are rethinking their decision to take Amtrak...

(Edit: I now see rnizlek's reply beat mine--that's what happens when you try to catch up on 12 hours of posting on two busy forums over lunch on a slow cell phone connection...I swear I started the reply before rnizlek did! :lol: )

Question: since the P32AC locomotive offers more advanced fuel-saving features (specifically the two I mentioned), why when Amtrak ordered the P42s didn't they have GE build them with AC traction and using similar fuel-saving technology? Plus, the ACs would handle better on grades like Raton Pass--I heard some Amtrak engineers saying that, especially in the past when Amtrak carried mail and express cars on the back of the SWC, the traction motors would occasionally overheat and shut off to protect themselves during the long, slow climb up Raton. That wouldn't happen with AC motors.

 

[transit54]

Question: since the P32AC locomotive offers more advanced fuel-saving features (specifically the two I mentioned), why when Amtrak ordered the P42s didn't they have GE build them with AC traction and using similar fuel-saving technology? Plus, the ACs would handle better on grades like Raton Pass--I heard some Amtrak engineers saying that, especially in the past when Amtrak carried mail and express cars on the back of the SWC, the traction motors would occasionally overheat and shut off to protect themselves during the long, slow climb up Raton. That wouldn't happen with AC motors.

I know that AC locomotives are substantially more expensive than DC locomotives. I forget by how much, but its a lot. And I would have to guess with Amtrak's limited appropriation they simply didn't have the funds to get all the equipment they needed. Perhaps someone with more knowledge can chime in here, but if I had to guess, I'd say it would be the increased cost, without question.

 

[George Harris]

The old Milwaukee Road Pacific Extension's electric service used regeneration; the electricity generated by a slowing (or descending off a mountain) loco was put back up on the catenary. MILW used to advertise that all their downhill trains therefore helped pull the uphill trains.
Regeneration required a lot more control equipment to keep the power in-phase and the same voltage as the power plant juice.

I don't think the AC systems do regenerative braking either. (If someone can correct me on that, feel free.) The Milwaukee electrification was DC, 3000 volt, I think, so regeneration was not problem. No phase or cycle issues at all.

 

[transit54]

To briefly shift this post back to the original topic, Obama visited Beach Grove today to discuss the loss of jobs:

http://www.wlfi.com/Global/story.asp?S=8250882

 

[AmtrakWPK]

(continuing OT :lol: )

I think the reason the AC's are so expensive is that they are a lot more complicated. The standard DC loco has a diesel which drives an alternator which generates AC which is then put through a solid-state rectifier stack and fed to the traction motors. Pretty straightforward. The explanation I have for how the AC's work is: diesel, driving an alternator that produces AC, rectifiers to convert to the AC to DC [to this point the same basic system as DC locos] , but then you add a high-power, high-voltage solid-state inverter system that take that rectified DC and converts it to high-voltage, high current AC to drive the AC tractions motors with. I was told it was necessary to do that, and that they could not simply take the direct AC from the main alternator and drive the motors with it. SO as a result you have a much more complex system, but it does apparently give you more tractive effort than a DC loco of the same (diesel) horsepower with less heat generated by the traction motors themselves. This being the case, I personally would expect that eventually all diesel-electric locos would end up as AC-traction systems. And then, perhaps eventually, all-electric with universal catenary. (by which time, probably most of us will long since have been pushing up daisies from under the ground.

 

[Joel N. Weber II]

Alan, that is a wonderful photograph.

It's possible that the person who posted the criticisms of Amtrak's changes simply hadn't been informed of all of the subtle issues that can make less maintenance improve reliability if it's carefully planned out. It looks to me like ``reliability centered maintenance'' contradicts what had been the common wisdom for decades.

I hadn't realized that on the locomotives that have a separate diesel for HEP that the prime mover still has the ability to produce HEP if needed, but that does seem like an elegant, reliable design.

If you look up the ``head end power'' article in Wikipedia and start following links, I'm pretty sure that one of the companies that sells equipment for converting old cars to HEP does have options for generators on each car. But indeed, that adds a bunch of potential safety issues (how do you make sure those generators don't start in tunnels no matter what? how do you make sure you don't get carbon monoxide leaking into the passenger area? what if the fuel catches fire?). I believe the individual cars already have batteries for some lights (and I think I've read somewhere that they do catch fire on rare occasions), and so the main issues are that if the single HEP source is lost, the HVAC stops running (which I tend to think is fine for 20 minutes while the HEP cables are adjusted, and not so fine for three hours), and possibly that on the long distance routes the batteries may eventually die.

(Back in the days of steam heat, I believe that each passenger car had a generator driven by the car's wheels which recharged the batteries.)

Does constant tension catenary pretty much put an end to the problems with the wires being ripped down?

 

[AlanB]

Does constant tension catenary pretty much put an end to the problems with the wires being ripped down?

Well it reduces the likely hood, since the catenary doesn't sag in the heat of the summer or get stretched too tightly that it pulls out of position during a very cold day. However, it doesn't eliminate all of the potential for having a wire(s) pulled down. A bad pantograph won't care if you've got constant tension or not, if it catches the wire, it's probably coming down.

 

[Green Maned Lion]

And then, perhaps eventually, all-electric with universal catenary. (by which time, probably most of us will long since have been pushing up daisies from under the ground.

Our great grandchildren will be pushing up daisies before that happens!

Edit: put in quote. thought I was quoting last poster.

 

[AlanB]

Our great grandchildren will be pushing up daisies before that happens!

Before what happens? :unsure:

Wires stop falling down? Each car get's its own generator? Or something else?

Please remember that we have a quote function available on this board. It makes it so much easier and clearer for people to know what you're referring to. If you're unsure how to use it, please don't hesitate to contact me privately.

 

[jis]

I don't think the AC systems do regenerative braking either. (If someone can correct me on that, feel free.) The Milwaukee electrification was DC, 3000 volt, I think, so regeneration was not problem. No phase or cycle issues at all.

At least the NJT ALP-46s do regenerative braking returning power to both 11kV 25Hz and 25kV 60Hz AC supply.

 

[transit54]

Not the mention the Acela and the HHP-8s.