DM30s At Both Ends

[JamesRR]

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?

[DutchRailnut]

the both are on line, the cars have control lines.

[rr503]

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.

[JamesRR]

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.

[Head-end View]

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.

[MACTRAXX]

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

[geico]

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

[DaveBarraza]

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.

[JamesRR]

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.

[Backshophoss]

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.