DM30s At Both Ends

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DM30s At Both Ends

Postby JamesRR » Mon Mar 26, 2018 4:07 pm

The other night, leaving Penn to NJ, I saw a LIRR double decker consist with DM30s at both ends. Is the trailing one being towed, or is it running - and if so, is it helping to propel the train or just provide power?
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Re: DM30s At Both Ends

Postby DutchRailnut » Mon Mar 26, 2018 4:18 pm

the both are on line, the cars have control lines.
If Conductors are in charge, why are they promoted to be Engineer???

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Re: DM30s At Both Ends

Postby rr503 » Mon Mar 26, 2018 4:19 pm

JamesRR wrote:The other night, leaving Penn to NJ, I saw a LIRR double decker consist with DM30s at both ends. Is the trailing one being towed, or is it running - and if so, is it helping to propel the train or just provide power?


Nope both running. IIRC the LIRR decided DE/DMs can only provide traction power and HEP to 6 cars at a time (in theory they can do more, but beyond that HEP will eat too much into your traction hp, which is already low at 3000 hp) so when you want to do more than that # of cars, you're gonna need 2 of them.

The second engine definitely is providing traction power too, for the reasons above.
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Re: DM30s At Both Ends

Postby JamesRR » Mon Mar 26, 2018 4:59 pm

rr503 wrote:
JamesRR wrote:The other night, leaving Penn to NJ, I saw a LIRR double decker consist with DM30s at both ends. Is the trailing one being towed, or is it running - and if so, is it helping to propel the train or just provide power?


Nope both running. IIRC the LIRR decided DE/DMs can only provide traction power and HEP to 6 cars at a time (in theory they can do more, but beyond that HEP will eat too much into your traction hp, which is already low at 3000 hp) so when you want to do more than that # of cars, you're gonna need 2 of them.

The second engine definitely is providing traction power too, for the reasons above.



Well, if 6 is the effective limit, that makes sense - I believe this was a 10-car consist.

NJT has occasionally put a loco on the rear when they have no cab cars to spare, and again I've wondered if it was being towed or pushing, too. They don't have the power limit, though, as their ALP46's can pull 10 double decker cars.
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Re: DM30s At Both Ends

Postby Head-end View » Mon Mar 26, 2018 6:52 pm

There is another reason for the two DM-30's and that is to protect against third-rail gapping which I believe was a problem early-on when only one locomotive was used.
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Re: DM30s At Both Ends

Postby MACTRAXX » Mon Mar 26, 2018 9:02 pm

Head-End View: (and Everyone:)

Yes...Specifically the long gaps on both sides of Jamaica at Hall and Jay Interlockings is the prime
reason for using two DM30s on the through runs from diesel territory.

Dual mode trains usually change power sources on the Main Line west of Jamaica after they clear
Jay westbound and eastbound some change over right around Harold after they clear the tunnel.

What I always found interesting is that the rule book notes that if dual mode trains operate on the
Port Washington Branch they are clear to operate in electric mode on the entire branch.

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Re: DM30s At Both Ends

Postby geico » Tue Mar 27, 2018 7:23 am

MACTRAXX wrote:Head-End View: (and Everyone:)

Yes...Specifically the long gaps on both sides of Jamaica at Hall and Jay Interlockings is the prime
reason for using two DM30s on the through runs from diesel territory.

Dual mode trains usually change power sources on the Main Line west of Jamaica after they clear
Jay westbound and eastbound some change over right around Harold after they clear the tunnel.

What I always found interesting is that the rule book notes that if dual mode trains operate on the
Port Washington Branch they are clear to operate in electric mode on the entire branch.

MACTRAXX


2DMs were also required by Amtrak as not to block tracks in Penn and the surrounding interlockings. Of course Amtrak decided the rule only applied to LIRR and not themselves as Empire trains only have 1 engine on them.

Sometimes 2 DEs/DMs are assigned to a short consist because they are short on cab cars
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Re: DM30s At Both Ends

Postby DaveBarraza » Tue Mar 27, 2018 8:35 am

geico wrote:Sometimes 2 DEs/DMs are assigned to a short consist because they are short on cab cars


My favorite incarnation of that situation was the Greenport Scoot running with two DE30's and one coach. The C3 Cab Car had been involved in a grade crossing accident the afternoon before.
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Re: DM30s At Both Ends

Postby JamesRR » Tue Mar 27, 2018 10:38 am

geico wrote:
MACTRAXX wrote:Head-End View: (and Everyone:)

Yes...Specifically the long gaps on both sides of Jamaica at Hall and Jay Interlockings is the prime
reason for using two DM30s on the through runs from diesel territory.

Dual mode trains usually change power sources on the Main Line west of Jamaica after they clear
Jay westbound and eastbound some change over right around Harold after they clear the tunnel.

What I always found interesting is that the rule book notes that if dual mode trains operate on the
Port Washington Branch they are clear to operate in electric mode on the entire branch.

MACTRAXX


2DMs were also required by Amtrak as not to block tracks in Penn and the surrounding interlockings. Of course Amtrak decided the rule only applied to LIRR and not themselves as Empire trains only have 1 engine on them.

Sometimes 2 DEs/DMs are assigned to a short consist because they are short on cab cars


That's very interesting - Amtrak does only have 1 loco on its Empire trains. I wonder if the wheelbase is such that they don't gap out, or if they don't traverse any massive gaps on their typical routing through the station.
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Re: DM30s At Both Ends

Postby Backshophoss » Tue Mar 27, 2018 6:07 pm

The Amtrak P32's seem to gain enough speed to cross the gaps thru the puzzle switches from a standing start,the DM's are slow starters from
a standing start in Penn on a straight shot into West Side Yard.
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