Why don't we use bidirectional diesel locomotives in the US?

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Re: Why don't we use bidirectional diesel locomotives in the

Postby dowlingm » Wed Dec 13, 2017 11:36 pm

Irish Rail's 141, 181 (GMD La Grange) and 071, 201 classes (GM/EMD London) are all North American built twin cabs. Irish practice (though receding with the advent of DMUs and push pulls) was to run around rather than wye.
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Re: Why don't we use bidirectional diesel locomotives in the

Postby bostontrainguy » Tue Dec 19, 2017 4:22 pm

So would using double-cab diesel locomotives on the Cascades lessen the damage? How much carnage occurred because there was a heavy trailing locomotive to push those cars off the bridge? Another reason to reconsider the way we do things here maybe?
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Re: Why don't we use bidirectional diesel locomotives in the

Postby F-line to Dudley via Park » Tue Dec 19, 2017 4:53 pm

bostontrainguy wrote:So would using double-cab diesel locomotives on the Cascades lessen the damage? How much carnage occurred because there was a heavy trailing locomotive to push those cars off the bridge? Another reason to reconsider the way we do things here maybe?


None. The Talgo coaches are too lightweight to run with any unprotected ends, so for FRA head-on/rear-end crashworthiness they must run with any of the following:

-- With one of those ridiculous-looking "lego brick" Talgo cab cars that are basically just a giant overbuilt paperweight with a cab.

-- With an F40 (or other suitable ex-loco convert) NPCU. Baggage bay goes unused because the Talgo fleet has their own baggage cars, so it's operated strictly as a cab and counterweight just like the "lego brick" paperweights.

-- Double-draft with locos on each end.


Any which way you're running something much heavier than a passenger car and approaching or equal to that of a locomotive because that's required to use the Pendulars on FRA rails. And it's illegal to run them without the super-fortified ends of a true loco, gutted loco, or 'facsimile' inert weight like the "lego bricks".

In the geometry of that accident, at that rate of overspeeding, the end result is most likely the same or extremely similar in any of those 3 consist configurations. And reproducible in simulation in any of the 3 configurations. The only thing we're waiting on from the NTSB that would be a critical difference maker is if some other unrelated catastrophic equipment fault created similar final accident conditions...but for wholly different reasons than a Philly-like overspeed on a curve jumping the train off the tracks (i.e. something that mimics that scene, but is sourced from totally different faults).
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Re: Why don't we use bidirectional diesel locomotives in the

Postby andrewjw » Tue Dec 19, 2017 5:32 pm

Also, as noted, the trailing loco would have cut in the brakes once it lost MU connection, which is why it stayed on the tracks.
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Re: Why don't we use bidirectional diesel locomotives in the

Postby dowlingm » Thu Dec 21, 2017 10:38 am

F-line to Dudley via Park wrote:
bostontrainguy wrote:-- With one of those ridiculous-looking "lego brick" Talgo cab cars that are basically just a giant overbuilt paperweight with a cab.
Is there a regulatory reason why Amtrak NPCUs/Talgo cabs don't have a HEP engine, like this CAF example? https://www.youtube.com/watch?v=SfpLi0ASPCk
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Re: Why don't we use bidirectional diesel locomotives in the

Postby NorthWest » Thu Dec 21, 2017 11:42 am

The Talgo sets do have HEP generators in either the cab car (Series 8) or in one of the end cars (Series VII).
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Re: Why don't we use bidirectional diesel locomotives in the

Postby mtuandrew » Thu Dec 21, 2017 1:38 pm

And as for the NPCUs, Amtrak has apparently decided there isn't a need since it's more efficient to supply from the Genesis' prime mover. As far as I know, 406 is the only F40 with a HEP generator installed, so it can power the Exhibit Train without using as much fuel as a conventional prime mover (whether 16-645 or 7FDL-16.)
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Re: Why don't we use bidirectional diesel locomotives in the

Postby F-line to Dudley via Park » Thu Dec 21, 2017 2:21 pm

mtuandrew wrote:And as for the NPCUs, Amtrak has apparently decided there isn't a need since it's more efficient to supply from the Genesis' prime mover. As far as I know, 406 is the only F40 with a HEP generator installed, so it can power the Exhibit Train without using as much fuel as a conventional prime mover (whether 16-645 or 7FDL-16.)



The Exhibit Train's HEP generator is of special design for plugging into extremely old cars incompatible with the standard loco-supplied hookup. That's the only reason why they rigged up that special cabbage. With any post- A-Day built/rebuilt rolling stock they don't need anything and just run off the loco's inverter.
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Re: Why don't we use bidirectional diesel locomotives in the

Postby Alcochaser » Thu Dec 21, 2017 2:26 pm

F-line to Dudley via Park wrote:
The Exhibit Train's HEP generator is of special design for plugging into extremely old cars incompatible with the standard loco-supplied hookup. That's the only reason why they rigged up that special cabbage. With any post- A-Day built/rebuilt rolling stock they don't need anything and just run off the loco's inverter.


WRONG. (like a lot of your info)

AMTK 406 has a standard HEP skid that was a spare for the F59PHI fleet. It was sitting around the grove parts supply. It was a bit of an afterthought/compromise as the Grove guys were a bit disappointed about not fully restoring it.

It wasn't even used all that much for the Exhibit train. 822 provided the HEP for the most part. Most of the crews were not familiar with the F59PHI hep unit installed in the 406. Particularly in the east. 406 didn't even lead a lot.

The only place the 406 HEP got used frequently was sitting idle at a place that didn't have ground HEP power. But while moving 822 provided the HEP most times.
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Re: Why don't we use bidirectional diesel locomotives in the

Postby mtuandrew » Thu Dec 21, 2017 11:22 pm

Mod Note: moved to General Discussion: Locomotives, Rolling Stock and Equipment (via General Discussion: Passenger Rail.)
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Re: Why don't we use bidirectional diesel locomotives in the

Postby trainiac » Tue Jan 09, 2018 5:58 pm

Going back to the original topic, here are a few issues, not all of which have been clearly dealt with yet:

1) When road switchers became popular in the US and Canada the 1950's, they were indeed designed to be bi-directional - but with only one cab. In an early high-nosed hood unit like a GP9 or RS11, visibility would not have been significantly different going in either direction. The idea was that a narrow hood (lowered on units like the ALCO RS-1) afforded adequate visibility in both directions. European mainline locomotives tend to have full-width carbodies, making a second cab necessary for bidirectional operation.

2) Cabs and controls are an added expense. Although probably not a huge portion of the locomotive's cost, the expense nonetheless spurred some roads to order cabless hood units, ending with the GP60B's purchased by ATSF in the 1990s.

3) Cabs take up space, and most double-cab locomotives seen in Europe have the cab at the very end of the frame. North American hood units tend to have a walkway and short hood, and having a second cab of the same dimensions would require another 6-7 feet of length for the cab alone and 10-15 feet if the short hood is included. Not a problem on a unit like an SD40-2 - but modern road units fill most of the available space on frames that are already 73-76 feet long.

4) Cabs at the end of the frame offer less collision protection than if they are behind a hood. Collision protection spurred some roads to run hood units long-hood forward - essentially going in the opposite direction from having double cabs.

5) When equipped for collision protection, cabs are heavy. Wide-nosed cabs maxed out the weight on 4-axle units like the GP40-2(W), GP60M and Dash 8-40BW, so they were built with smaller, rear-mounted fuel tanks and/or lighter underframes to compensate. It would be very difficult to build a comparable 4-axle unit of similar size and power with two wide-nosed cabs without exceeding axle load limits.
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Re: Why don't we use bidirectional diesel locomotives in the

Postby talltim » Tue Jan 09, 2018 6:46 pm

There are some modern single cab mainline diesels in use in Europe, I think the biggest class the is the Vossloh Mak G1206 which is used by lots of operator in France, Benelux, Germany and Switzerland although there are other types of varying vintage https://www.flickr.com/photos/elsdanni/ ... 67544@N22/ The replacement model, the G1700 is also used by lots of operators https://en.wikipedia.org/wiki/Vossloh_G1700_BB
France had some centre cab electrics but I think they have gone now. https://en.wikipedia.org/wiki/SNCF_Class_BB_13000
The Swedish Iore electrics are single cab, but that is because they work in permanently coupled pairs https://en.wikipedia.org/wiki/Iore These might look familiar as they are related the the ALP 45/45/46A
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Re: Why don't we use bidirectional diesel locomotives in the

Postby dowlingm » Thu Jan 11, 2018 1:06 pm

Irish Rail used to run 121 Class locomotives "bonnet first" but after an incident that practice was stopped. The successor locomotive classes had / have dual cabs.
http://www.irrs.ie/Journal%20175/175%20B121.htm ("DIFFICULTIES CAUSED BY B121’s SINGLE CAB ARRANGEMENT")
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Re: Why don't we use bidirectional diesel locomotives in the

Postby EuroStar » Tue Aug 14, 2018 3:06 pm

NJT could make use of some bidirectional diesels right now given the crunch for equipment it seems that the practice of running the engines around the trains is making a come back at least for some runs as I observed a geep leading a train long hood forward into Hoboken on a set with no trailing cab car.
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