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BlastOButter42

LIRR DM30AC dual-mode operation and diesel-to-electric switchover

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Hi folks,

Hoping anyone who knows a bit about DM30AC operations on the LIRR could provide some information on the changeover from electric to diesel power and vice-versa. When/where does the changeover generally occur? Do they operate in electric mode only in and around the East River tunnels and switch to diesel as soon as possible eastbound/as late as possible westbound? Or do they operate in electric mode as much as possible where electrification is present? Also, does the changeover occur at line speed or only while stopped?

Asking in part because I know Metro North and Amtrak's P32AC-DMs operate in electric mode as little as possible -- even though (in the case of MNR) electrification extends all the way to Croton-Harmon and Southeast on the Hudson and Harlem lines, a northbound train will switch to diesel before hitting the Bronx. At least one unofficial source I found attributed this to operational restrictions due to the need to draw power for the entire train from low-voltage third rail from one locomotive, with the resulting high current causing lots of arcing and possible damage. Consistent with this is the fact that NJT's ALP-45DPs operate in electric mode from 25 kV AC catenary and don't have this restriction. So I'm wondering if it also applies to the DM30ACs.

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Yep what @trainfan22 said is correct. 

The diesels don't get there maximum power running in electric mode. The reason why when heading to the city the switch is done right before Jamaica, is so that if there's problems the train can be canceled at Jamaica. Heading east bound, the switch happens as soon as possible, and the Harold interlocking in between the East River Tunnels and Woodside station is the perfect location since a full 12 car set with two engines can be completely out of the tunnel. 

The changeover happens while in motion. I've never personally seen it happen, but I guess the diesel engine shuts off pretty fast. 

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I imagine the DMs fail because they are trying to draw current for the traction motor and generate the HEP for the entire train through two contact shoes?

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17 minutes ago, Jsunflyguy said:

I imagine the DMs fail because they are trying to draw current for the traction motor and generate the HEP for the entire train through two contact shoes?

No, they are designed to do that. The DMs fail because EMD hasn't built a decent passenger locomotive since GM sold it to the banks.

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18 hours ago, Fan Railer said:

No, they are designed to do that. The DMs fail because EMD hasn't built a decent passenger locomotive since GM sold it to the banks.

in 1998 EMD was GM owned

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The dumdums suck because the LIRR basically designed them. The railroad, making some trumped up excuse about exceptional conditions on its system, elected to build a clean sheet dual mode design when they could have just suited the gennies to their need. Of course, they did this while woefully underestimating the size of diesel territory demand, so what we have today is a puny fleet of weak (3000hp before HEP draw), HEP-impotent (only 6 cars/locomotive) and unreliable (MDBF on the order of 10k) locomotives. Three cheers for bureaucratic chauvinism!  

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15 hours ago, RR503 said:

The dumdums suck because the LIRR basically designed them. The railroad, making some trumped up excuse about exceptional conditions on its system, elected to build a clean sheet dual mode design when they could have just suited the gennies to their need. Of course, they did this while woefully underestimating the size of diesel territory demand, so what we have today is a puny fleet of weak (3000hp before HEP draw), HEP-impotent (only 6 cars/locomotive) and unreliable (MDBF on the order of 10k) locomotives. Three cheers for bureaucratic chauvinism!  

To add onto this, I remember reading from The LIRR Today that the MTA is looking to procure a replacement fleet of exactly the same size.

So they could give less of a shit about running the actual service specified by their own guidelines. (E.g., Stony Brook theoretically should see half hourly trains off peak)

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2 hours ago, bobtehpanda said:

To add onto this, I remember reading from The LIRR Today that the MTA is looking to procure a replacement fleet of exactly the same size.

So they could give less of a shit about running the actual service specified by their own guidelines. (E.g., Stony Brook theoretically should see half hourly trains off peak)

Yup! As usual, the railroad is unable to recognize its mistakes...

The way they get away with a lot of the diesel territory short-changing is through classifying those areas as non-commuter territory, which basically voids all guidelines. Not sure if this is the case on the PJ, but I know Greenport and Montauk beyond Patchogue face that issue. 

Long term, what needs to be done is electrification of the South Shore to Speonk and the PJ to the end of the line. The amount of money and equipment wasted on the Patchogue scoot is...troubling, and as you say, the PJ is an embarrassment. 

Edit: here are the guidelines

http://web.mta.info/mta/compliance/pdf/Title-VI-Railroad-Policies.pdf

Edited by RR503
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