Passenger Trains > One P42DC can pull how many cars?

Was watching the Horseshoe Curve cam as today's no. 43 climbed the "hill". The train today consisted of 9 cars (the usual 6 car 
Amfleet consist, plus 3 private cars). The train ran at the usual speed and seemed to have no issues with the heavier than usual 
consist. This made me curious as to how many cars a single P42DC can handle on the grade.  The P42DC has basically the same 
horsepower as two E8 units. However while two E8's had more traction motors in use they also had idler axles. I wonder how many 
cars the PRR rated two E8 units without assistance on the "hill" and how many does Amtrak rate a single P42DC for? 



Edited 1 time(s). Last edit at 07/12/19 18:10 by mp109.

Let me try to make this comparison.........not sure how relevant since there's likely been some modifications done to the E8's. 

Few years back, Bennett Levin partnered with another non-profit group (PRR Technical and Historical Society I believe) for a trip that ran from Harrisburg to Altoona on the NS (old PRR) Main and up around Horseshoe Curve. Using the the figure eight loop tracks at the crest of the mountain crossing, we looped back around and down Horseshoe Curve to Altoona. From Altoona we then took the shortcut route from either Lewistown or Tyrone that heads up to Sunbury and Selinsgrove (forget the name of this short line route). From Sunbury we took the ole PRR Buffalo Day Express Route down the Susquehanna River and back on the NS Main Line (on the east side of the Rockville bridge), to Altoona. Overnight in Altoona. The next day - another climb over Horseshoe Curve and out to Pittsburgh to tour various and former PRR (and a little B&O) trackage around Pittsburgh. Great excusion trip. Got to enjoy it from Warrior Ridge and PRR 120.
 
The consist was a Keystone trainset (five coaches), Kitchi Gamma Club, Warrior Ridge, PRR Business Car 120. It was very identical to what over Horseshoe Curve today actually. Powering the consist - Levin's E8's!!! We went up and over Horseshoe Curve with no problem with the Amfleets and heavy-weight private cars on the rear. Course Levin - via son Eric who was the engineer (on one or both days, not 100% sure) and his connection with NS - had two helper NS diesels following behind the consist (but not attached!) that could swoop in and assist in any power needs just in case we stalled out going over Horseshoe Curve. But we didn't. The E8s performed beautifully. 

So nearly same consist as the re-created "Broadway Limited" I would say could be pulled by an E8 (two in the consist) or P42DC.

when i was working at auto train sometimes 1 p-42 would brake down close to Fla 1 p-42 was able to pull the entire auto-train at 55mph  that could be up to a full  48 cars... so they are vary powerful

There is no one real answer for this.  It's all based on the grade, weight of the cars, condition of the locomotive, whether it's providing HEP or not, etc.  I've heard somewhere that the rule of thumb is seven cars, although that may be Superliner cars and while providing HEP.  Pretty much whatever it'll haul.

The Texas Eagle will frequently have 9 cars with 1 P42 between Chicago and St. Louis:

P42, baggage, transition sleeper, regular sleeper, diner, lounge, 3 thru coaches and a St. Louis coach on the end.

one unit can handle the cz east of denver, cofNO all the time

I was told by mechanical the limit is 12 cars with HEP running. Anything more and a second unit is to be assigned.

My experience on my territory (mainly flat) was that you could haul 9 cars and stay on schedule. Any more than that you would lose a little time getting back up to speed between station stops, speed restrictions etc. Ususally padding in the schedule helped you depart the stations on time but if you were late already you were just going to get later.



Edited 1 time(s). Last edit at 07/13/19 16:50 by AmHog.

Yesterday 7/12 #22 NB Eagle was 7 Hours Late arriving Normal, Il It had 2 P42's, with a U.P. unit leading. Anyone know why ? The Day before it was quite late like that, due to a Tree Hit according to others here on Trainorders. I'm assuming the Freight Units are not able to run the 79MPH.

Nine cars ... so maybe 600 tons? So the P42
has to put out 30000 pounds of TE, or a bit more,
which is getting close to its limit, all right.

How long are the longest Chiefs up Raton,
with their two P42s?

The base line for the builder is anymore than ten cars on the seattle side and a second locomotive is required.  But that solely because a single locomotive and ten cars can barely do track speed in the montians

A 'ballpark' DC tractive effort rating is 25% of weight on drivers, so a unit that weighs somewhere in the range of 250,000 lbs will produce about 60,000 of tractive effort.  That is on clean, dry, straight track.

Next to consider is the type of wheel slip control.  The much newer types of control compared to an early 1st generation unit will also give considerably greater tractive effort.  An E8 unit, as with most of those generation units, just compared amperage between the two traction motors on each truck.  When the current differential got to a certain amount, it would light the wheel slip light, sound the buzzer, and open the battery field contactor, which drops all the load on that truck.  As soon as the load drops, the wheel slip indication clears, and full power comes back on.  The lunging will continue until the engineer reduces the throttle until the engine can hold the rail.

One of EMD's first electronic controls from the 60's was called IDAC, for Instantaneous Detection and Correction.  This system monitors all the axles, and catches the wheel slip before it spins, and reduces the excitation just enough to control the slip without taking off all the load.

Bottom line is that any of the much newer electronically controlled units will greatly out pull a 1st gen unit with the same number of axles, and weight on drivers, and a  P42-DC will produce over 60,000lbs of T/E.
G  

> a  P42-DC will produce over 60,000lbs of T/E.

Not with gearing for 100+ miles/hour.

timz Wrote:
-------------------------------------------------------
> > a  P42-DC will produce over 60,000lbs of T/E.
>
> Not with gearing for 100+ miles/hour.

I think you have 'minimum continuous speed' confused with 'tractive effort.'
Wikipedia shows VIA's units rated at 63,000lbs...
Please tell all of us what gearing has to do with tractive effort, and how you figure it!
G



Edited 1 time(s). Last edit at 07/15/19 15:15 by ExSPCondr.

The unit's control system sends up to...
1500 amps? 1600 amps? thru each
traction motor, whatever the gearing.
Same maximum amperage, so same
maximum torque at the traction motor
pinion, whatever the gearing.

So if the engine is geared for 50% higher
speed, maximum TE is 33% less.

timz Wrote:
-------------------------------------------------------
> The unit's control system sends up to...
> 1500 amps? 1600 amps? thru each
> traction motor, whatever the gearing.
> Same maximum amperage, so same
> maximum torque at the traction motor
> pinion, whatever the gearing.

Not whatever the gearing, WHATEVER THE ENGINE HAS FOR ADHESION, THE HARDER THE TRACTION MOTOR HAS TO TRY TO TURN THE WHEEL, THE MORE AMPERAGE WILL FLOW, AND THE VOLTAGE WILL BE LESS.
> So if the engine is geared for 50% higher
> speed, maximum TE is 33% less.

Unfortunately there is an error in your logic.
Electrical horsepower requires Amps to be multiplied by Volts to get Watts, which is horsepower.  You haven't mentioned either Volts or Watts...  
STARTING TRACTIVE EFFORT, and CONTINUOUS TRACTIVE EFFORT are two different things, and continuous tractive effort is a function of horsepower.

Again, Wikipedia is your friend!
G

> THE HARDER THE TRACTION MOTOR HAS
> TO TRY TO TURN THE WHEEL, THE MORE
> AMPERAGE WILL FLOW

Up to the limit -- 1500 amps or whatever it is.

> continuous tractive effort is a function of horsepower

Tractive effort at a given speed is a function
of horsepower, you mean. A function of
actual horsepower -- not rated horsepower.

> Up to the limit -- 1500 amps or whatever it is.
This says that you have never watched the loadmeter on a DC  locomotive, or are at all familiar with the short time rating posted on the control stand next to it.
> > continuous tractive effort is a function of
> horsepower
>
> Tractive effort at a given speed is a function
> of horsepower, you mean. A function of
> actual horsepower -- not rated horsepower. 

NO I DON'T MEAN, and I'm not going to argue with you any more here.  Everything I have posted here is on Wikipedia. 

STARTING TRACTIVE EFFORT IS A FUNCTION OF WEIGHT ON DRIVERS, WHEEL SLIP CONTROL, AND A/C or D/C traction.
CONTINUOUS TRACTIVE EFFORT IS A FUNCTION OF WEIGHT ON DRIVERS, WHEEL SLIP CONTROL, AND A/C OR D/C TRACTION, AND HORSEPOWER.  
Published on Wikipedia are the following two figures:   Weight on drivers 268,000lbs.  Starting tractive effort 63,000lbs, THAT'S 23.5% THE WAY I DO MATH, and in line with what I posted in my 1st, and right in line with industry standards.
G
 



Edited 1 time(s). Last edit at 07/15/19 20:26 by ExSPCondr.

You've watched loadmeters that showed unlimited amps?

Wonder how many amps a P42 would need, to do 63000 lb TE. Over 2000?