Question about P32DM-AC Third Rail Operation

1. With the gaps in the underrunning third rail in the tunnel approaches to GCT, I was wondering how this affects the operation of the dual-mode push-pulled trains. When the P32 locomotive goes through a switch (assuming that there is enough of a gap so that the contact shoes do not contact the third rail) does the train take power or does it coast? How does the train get HEP? How many of these switches are there in which trains would get into this situation? (It seems hard for me to believe that trains would coast given the slow speed)

2. Where do push-pulls switch from electric to diesal outbound and diesal to electric inbound? When trains switch inbound, is there extra leeway? (I believe that the LIRR switches inbound in Nassau County, because if there is a problem, passengers can get onto another train at Jamaica for Penn)

Thanks in advance
Kyle

(First Post, but I've been roaming the forums for quite a while)

The train gaps at every switch and just coast, no HEP .
Inbound the trains usually swich near 125 street but leave engine running at idle icase train stalls.
Outbound the engine is started at mouth of tunnel and switchover is done after leaving 125 street.

I remember reading on LIRR forum that 3rd rail gaps in NYP are why trains are run with a DM engine on each end instead of with one engine and a cab car. Dutch - why is the same thing not an apparent issue with MN at GCT? (or do they run an engine on each end too?)

flexliner wrote:I remember reading on LIRR forum that 3rd rail gaps in NYP are why trains are run with a DM engine on each end instead of with one engine and a cab car. Dutch - why is the same thing not an apparent issue with MN at GCT? (or do they run an engine on each end too?)

I was about to ask the same thing, since Metro-North only uses locomotives on one end....

The grade from East river tunnel to Penn station is much greater than the grade in GCT. So LIRR does need two engines to get thru their gaps.
In GCT the grades are not even half as much so we just coast.
besides we do not like the noise of engines at the bumper block, it echoes tru the main hall.

Inbound the trains usually swich near 125 street but leave engine running at idle icase train stalls.

Dutchrailnut, so the engine would idle all the way inbound from 125th to GCT, and then while the train is waiting for its next departure, and then back outbound up to 125th? Wouldn't this create emmisions in the tunnel?

While we are talking about diesal engines, I was not sure if the term 'prime mover' is used in reference to just the actual diesal engine that is used to turn the generator, which power the traction motors or does it mean the entire system, the engine, generator, and motors. I guess if the term 'prime mover' is used to describe the entire system, then would it also include the third rail electrical equipment?

I'm guessing that the same motors used in diesal mode are used in electric mode? Do the motors run on the third rail voltage or is it stepped down using a transformer?

I read on the LIRR forum that push/pull trains including those that don't run to Penn and over 6 cars use a DE/DM on each end for HEP purposes.

The diesel(prime mover) only runs till cab car goes by the North end access. then engineer shuts it down.
On platform the engines are still noisy with all their fans, they sound like 3200 hp vacuuum cleaners.

The AC locomotives work like this:
The Engine powers a AC alternator.
The Alternator feeds a thru a rectifier and feeds the 1400 V DC buss.
The buss feeds 5 inverters, 4 variable frequency traction inverters and one 60 Hz HEP inverter
Each traction inverter feeds one AC traction motor
the HEP inverter powers the 480 volt 3 phase 60 hz power for the cars and engine auxiliaries.

In third rail mode the dynamic brake inverter is used to step up 700 volt DC from third rail to 1400 volt DC buss but rest stays the same.

as comparison the DE/DM's only have 3 inverters, 2 traction inverters feeding 2 traction motors each and the HEP inverter.

for our technophiles I am trying to keep it simple here.

Dutch -

thanks again for sharing your considerable knowledge with the forum.

Paul

Thanks Dutch

Kyle