How did push-pull work with the old equipment?

How did the old push pull trians work? Specifically the FA/S-3, like the ones on the Oyster Bay line in the 70's. Did the FA provide heat, power to the coaches? Were there controls for the S-? in the FA, were they added or was the old controls for multible units used? Did the traction motors work in the FA, were they even installed? How are the new DE/C3's diferent? Thanks in advance.....Mac

Although I don't know much about the older push/pulls (all of these units were retired long before I started riding the rails), I can say with some certainty that the FA units did not have traction motors. As far as I know, they were control cabs only; the power was provided by another locomotive, often an MP15AC.

I know for sure, however, that the DE/DM's act as the sole power supply for their consists. The C-3 at the opposite end is only a control cab.

As I recall the cab units did provide HEP. We're all agreed they provided no traction power.

to put it simple the FA's and F's were overweight cab cars not producing revenue.
Only thing they did other than playing cab car was they had the HEP unit in them.

Push pull is exactly what it sounds like - in one direction the locomotive pushes, in the other, it pulls. The cab car at the end did nothing. I wonder why the LIRR never just put cab controls in the old MP cars as they demotyored them, and bought HEP locomotives...

Greetings All,
The Alco FA locos were rebuilt units that were stripped of all related traction functions including the traction motors. They served as a control/power unit supplying 600volts DC through two train line jumper cables, 600VDC+ and 600VDC-. They also had a 27 point jumper cable trainlined to communicate with the traction locomotive on the other end of the train. The coaches in between were once MU cars utilizing the third rail, thus technically the FA became the source of the 600volt generation. The term Push-Pull meant that when operating from the FA heading west the train was being "pushed" and conversly when operating heading east from the traction loco (MP15ac, GP38-2) the train was being "pulled". The FA's had a totally fuctional air brake stand as well as speed control. Throughout the years many mods were done to these FA units and many MP15ac's were modified to replace these FA's using them for either hotel power or traction but not both at the same time. The MP's that were modified were known as "P" units. Hope this helped
KRO52

kro52 wrote:The MP's that were modified were known as "P" units.

I never knew that! That would explain why some of the MP15 in MTA colors had a "P" before their road number; I had always just assumed this was a designation for a protect engine. Thanks for the great info kro52!

MP15 171 is still in old paint and the "P" is still there, 161 was also a "P" unit and I think that 154? was a "P" unit also. I dont rem them all but I know for shure that the 161/171 were both "P"units

I'm pretty sure #169 was also.

Greetings All,

The MP15ac's that were "P" units were 161-172.

KRO52

kro52,

Do you know what specifically was done to the MP15's designated as "P" units? As I'm sure you know, many (if not all) of the "P" units are still active and appear to function in the same capicity as those which were not modified. A prime example is with the circus train; #154 was paired with #165 and they were seemingly identical.

Prior to the MP15 units, the powered end would be C420 and RS3 units.

Here's a 1971 shot at Port Jeff with a C420 on the west end:


Dave Keller

Greetings All,

The MP's that were "P" units that are still in service have had the mods for power unit removed from them. They are back to their original function as they were intended. In a nutshell, the original mod to "P" unit was supposed to be temporary, lasting only 6 month's to a year, while the shops were modifying the FA's and EMD F units. The "temporary" mod lasted more than 10 years. The mod to "P" unit which was difficult, but thanks to some very talented shop personel they made it work. The mod included isolating the traction circuit, isolating the throttle circuit to allow control of the traction loco on the opposite end through the 27 point trainline jumper, modifying the the governor circuit to allow the motor to maintain the correct speed to allow the alternator to produce 600 plus VDC for hotel power to the coaches, applying 600 volt, 4 point (positive) and single point (negative) trainline jumper cables and of course all of it's related electrical relays etc. to make it work. This was just to use the loco as a "P" unit. To return it to a loco status a few switches had to thrown and once again it was in loco mode. As note you could NEVER have both features engaged at the same time unlike the DE/DM loco's.

KRO52

Kro 52,

It has been said that Larry V. figured out a lot of the "P" unit stuff. Is that correct? Is that why his name was on the side of a locomotive engine for awhile?

Thanks,
Tom

Tom,
Actually it was a backshop electrical foreman Al P. who figured it out. Larry V. was a brilliant running repair Foreman with many years of service.

KRO52