Why does Amtrak run with 2 locomotives?

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Posted by Paul Milenkovic on Saturday, November 28, 2009 1:53 PM

blue streak 1

If there is either the 9 or 10 car limitation on one HEP power source or not beirg able to parallel the outputs please explain AMTRAK's Auto Train consists.??

 

I think the answer is 1) enough locomotive units to handle ruling grades without having to assign helpers, 2) the high gearing of the P42's and use of DC traction motors means, perhaps, half the tractive effort of a comparable freight locomotive unit, 3) enough power to get the acceleration required to keep schedules, and 4) some degree of redundancy as it isn't just mechanical failure to worry about, there is a high chance of a grade crossing collision stranding a train.

If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
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Posted by beaulieu on Saturday, November 28, 2009 3:34 PM


blue streak 1

If there is either the 9 or 10 car limitation on one HEP power source or not beirg able to parallel the outputs please explain AMTRAK's Auto Train consists.??

I believe Amtrak has a 14 car limit on HEP.

Paul Milenkovic

 

I think the answer is 1) enough locomotive units to handle ruling grades without having to assign helpers, 2) the high gearing of the P42's and use of DC traction motors means, perhaps, half the tractive effort of a comparable freight locomotive unit, 3) enough power to get the acceleration required to keep schedules, and 4) some degree of redundancy as it isn't just mechanical failure to worry about, there is a high chance of a grade crossing collision stranding a train.

 

The P42s would only be 2/3rds the TE of a typical DC motored freight locomotive like a Dash-9 if they had freight gearing, then toss in the effects of the 110 mph gearing and I think they have 40% or less, at useable speeds.

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Posted by aegrotatio on Tuesday, December 01, 2009 2:55 PM

 Does Metra's F40PH units have a dedicated engine powering the HEP?  I thought the newer (possibly rebuilt) units have dedicated engines for HEP.

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Posted by pennsy4430 on Saturday, December 12, 2009 2:05 PM

I am a retired Amtrak engineer. Worked the Northeast Corridor for most of my 33 yrs but moved to Myrtle Beach in 1998. I then learned the CSX RR from Washing ton South to Savannah ,Ga.  and ran my final 5 yrs there. Have been retired now for 7 yrs.

I noticed that no one person mentioned another theory of the 2 locos with 7-10 cars. They may be deadheading that 2nd loco West somewhere cause of a shortage of power. Certainly I am not familiar with rails West of Washington or New York, So not sure of how much power are used on the Trains.

Generally on the Corridor, an Aem 7 was good to haul about 10 cars max then they added a 2nd loco. Schedule was everything, on time or the dispatchers were on your case. Csx was not that concerned with the schedule just keep out of the way of of there hot shots which is understable.

One Thanksgiving I went on duty to return South from Richmond, VA. to Florence, SC. The train came in with 23 cars and a bad lead unit. We tryed to multiple a freight loco in front of the 2nd Genesis but could not get the air to work( 3 engineers and a road foreman tryed lol). So i was ordered South with 1 Genesis and 23 cars. Surprised me! That diesel was slow to accelerate but once up to speed cranked right along at track speed, hardly lost time.

Enough war stories for now. Hope I have answerd in another way your question. For all who read this on 12/12, have a great holiday  --  Herb Alban

 

 

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Posted by oltmannd on Monday, December 14, 2009 6:41 AM
timz

Paul Milenkovic
Do you mean to tell me that a booster-equiped Northern is a match for a pair of Genesis locomotives?

The 4-8-4 would produce the same tractive effort at 5-10 mph that the two P42s produce at 30-35 mph. If that means it's matching them, then maybe so.

The P42 weighs... at least 270,000 lb? So we could hope adhesion would allow more than 36,000 lb continuous TE, despite the monocoque frame; the low rating is the disadvantage of gearing all the P42s for the same maximum speed (110mph?).

The 36,450# TE is at the motor's continuous thermal limit which occurs at 37.8 mph. The locomotive weighs 268K and produces 4250 HP. The notch 8 (no HEP) adhesion demand at MCS works out to 13%, so the locomotive can easily produce higher TE, but only within the traction motor's short time rating. The gear ratio is 74:29 with a max speed of 110 mph.

-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/

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Posted by blue streak 1 on Monday, December 14, 2009 8:26 PM

pennsy4430
That diesel was slow to accelerate but once up to speed cranked right along at track speed, hardly lost time.

Would it be too much to guess that there were not many steep up slopes?

 

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Posted by daveklepper on Tuesday, December 15, 2009 5:10 AM

In advance of the person with the real answer (Pennsy 4430), having ridden the ACL main over 100 times, I'd say you are correct.   Pretty flat with no real steep grades.   The ACL frequenctly used Pacifics, passenger power, for 60 and 70 refer-car hot shot freights.   Track speed was 79 during Amtrak-SCL days days but there were spots of 90 and perhaps 100 earlier.

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Posted by DMUinCT on Tuesday, December 15, 2009 2:34 PM

aegrotatio

 Does Metra's F40PH units have a dedicated engine powering the HEP?  I thought the newer (possibly rebuilt) units have dedicated engines for HEP.

Boston's MBTA used F40PH built like Amtrak.  To maintain HEP in stations and between runs it was required it to have a "Fast Idle" speed.  (noise and smoke).    The next order was for F40 PHL (L for long).   The longer Carbody not only looks better but houses a separate diesel for HEP, and gives the locomotive a standard 8 notch throttle.

Don U. TCA 73-5735

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Posted by aegrotatio on Friday, December 18, 2009 10:09 AM

 Thanks for the data, Don!

 And, Pennsy, thanks for your info, too.  I understand that the new rebuilt AEM-7 "AC" units can pull as much as two unrebuilt units now.

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Posted by Deggesty on Friday, December 18, 2009 10:26 PM

daveklepper
The ACL frequenctly used Pacifics, passenger power, for 60 and 70 refer-car hot shot freights.   Track speed was 79 during Amtrak-SCL days days but there were spots of 90 and perhaps 100 earlier.

Dave,  you're right about the ACL's allowing 100 mph between Richmond and Jacksonville--and it was not just in spots. There was an article in Trains back in the sixties (Paul North may be able to tell us what issue) which covered the main line operation. I found it fascinating. Back then, the Coast Line was advertising that it could take you from New York to Florida without the possibility of a detour by way of Cuba. Some of the ads pointed out that these trains were faster than those of the road that went "Through the Heart of the South," even though the Richmond-Jacksonville route via the JSL cutoff was only about twelve miles longer.

Johnny

Johnny

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Posted by Yankingeorgia on Saturday, May 12, 2018 10:42 AM

A well designed 4-8-4 would maintain its starting tractive effort up to between 15 and 20 MPH.

A Santa Fe 3765, 3776 or 2900 class would be putting out considerably more than 36000 lbs TE at 35 MPH.

Most other big 4-8-4s would do the same.

I used the ATSF engines because one of the routes discussed was a historical Santa Fe routing.

What killed steam was maintenance costs and availability, compared with diesels.

Individual diesel units at the time they replaced steam were relatively small and produced far less horsepower than the steamers they displaced.

It took many decades before a single diesel unit could produce horsepower comparable to that of a single NKP Berkshire (4500 cylinder HP).

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