What does the Amtrak Auto train weigh?

@PRR 5841 posted:

I knew this was Amtrak’s biggest train but I didn’t know it could regularly operate with 50 cars pulled by 2 P40DC locomotives.  I saw a video showing 17 Superliners, 33 Autoracks with 2 locomotives.   Just a guess but I’d estimate the total weight of a train this size to be 4000 to 4500 tons.  Anyone know what a 50-car Auto-train usually weighs in at?

Thanks

Doesn't sound logical that those cars are 100 tons each. More like 50 to 60 tons per car, thus maybe a max of 3200 to 3500 tons for the whole train. Just my guess.

Figure the 17 passenger cars at 80 tons each - 1,360 tons.

The 33 auto carriers around 60 tons each - 1,980 tons.

3,300 to 3,500 tons for the whole train. That’s easily handled with two P40s. There are no serious grades on the route, either. Coastal plain all the way.

I had read, about a year ago, that 30 car carriers was the max., for a total of 300 automobiles.

@Joe Hohmann posted:

I had read, about a year ago, that 30 car carriers was the max., for a total of 300 automobiles.

We've been on the end of a long unload once or twice. Waited in Lorton once for three hours. Our car was # 260 of 270 on the train. Still better than driving from NY to Fla and back.

It is advertised as the longest regularly scheduled passenger train in the nation. Never seen more than 2 P40's either.

I find it interesting that the train is almost always P40s and not P42s. I guess it's the lack of grades that Rich mentioned.

Due to the auto racks, is the AT a "mixed" train....?

Their words, not mine

@Dominic Mazoch posted:

Due to the auto racks, is the AT a "mixed" train....?

Not if one considers the enclosed auto carriers as over-glorified baggage cars with drive-on baggage.

Rusty

@Will Ebbert posted:

I find it interesting that the train is almost always P40s and not P42s. I guess it's the lack of grades that Rich mentioned.

The brake control system is different and I think the P40s play nicer with the auto carriers.  

@Boilermaker1 posted:

The brake control system is different and I think the P40s play nicer with the auto carriers.  

You have my attention.  What is different in the brake control system?

When Superliner cars were new, they had the option of using the electropneumatic brake system, but that was all disabled after a near-runaway on the SP.  So, has Amtrak equipped the Auto Train cars with electropneumatic braking?

The ex RF&P mainline runs right by my boat slip, a few miles south of Lorton.  I occasionally see 3 locos at the head, sometimes not a Genesis series.

My understanding is that the Amtrak-CSX agreement limits the number of cars.

@Number 90 posted:

You have my attention.  What is different in the brake control system?

When Superliner cars were new, they had the option of using the electropneumatic brake system, but that was all disabled after a near-runaway on the SP.  So, has Amtrak equipped the Auto Train cars with electropneumatic braking?

P40s have mechanical air brakes, whereas the P42s are electronic.  Apparently the arrangement on the control stand also differs and the air pressure gauges in the cab are more sensitive/accurate in the P40s as well. 
Having never been in the cab of one, let alone run one (or any other locomotive for that matter). I would presume the gauges must help over the significantly longer than normal Amtrak train length, as well as the fact that the auto cars are “freight cars” and probably handle differently than a passenger car. 
I defer to you, Tom, on how that would make the train act differently...

And I would think with the auto racks at the rear, most of the weight is thete.

Read my post above. The auto racks are lighter than the coaches.

I would assume the autoracks have a different braking system than a typical freight car. For starters, they will be using 110 pounds of air rather than 90 since it is a passenger train.

@Will Ebbert posted:

I would assume the autoracks have a different braking system than a typical freight car. For starters, they will be using 110 pounds of air rather than 90 since it is a passenger train.

Please explain what different car brake valve components would be needed/required for using a 110 brake pipe pressure vs. a 90 pound brake pipe pressure.

@Hot Water posted:

Please explain what different car brake valve components would be needed/required for using a 110 brake pipe pressure vs. a 90 pound brake pipe pressure.

There's a reason I used the word assume. It was an assumption. I'm not intimately familiar with any air brake system and I've never worked on freight car brakes, only locomotives and passenger cars. If I'm wrong feel free to plainly state it rather than your signature passive aggressive comments. 

@Will Ebbert posted:

I would assume the autoracks have a different braking system than a typical freight car. For starters, they will be using 110 pounds of air rather than 90 since it is a passenger train.

It's been a few years since I was conversant with Auto Train operations and as a result my reply may be a little dated, but I'll try to give a short answer. The major difference between AMTRAK's multilevel auto racks and the Superliners is in the individual car's air brake control valves. Regular passenger  equipment air brake control valves are equipped with a "Graduated Release" feature or component, whereas normal freight car air brake control valves are only equipped with a "Direct Release" type control valve. The graduated release feature allows the air brakes to be partially released on rail cars so equipped after a service application, very similar to releasing the pressure on the brake pedal of your automobile, yet still keeping some pressure applied, after hitting the brakes a little too hard. Graduated release works very well with short trains made up of cars of somewhat similar weight, however it does not work well for long freight trains made up of different types of equipment and weight loadings. The controlling locomotive's automatic brake schedule also must have a "Graduated Release"or "PASS" position and be cut in in order for this feature to function.

Normal freight cars are equipped with an air brake control valve which is only capable of "Direct Release" that is, once the brakes have been applied, you cannot partially release the brake application. Any increase in brake pipe pressure will trigger a complete release of the freight car brakes. Most of the older freight locomotive's brake schedules are only equipped for "Direct Release".  Since AMTRAK's auto racks were not equipped with the "Graduated Release" feature, they must operate the train with the locomotive controlling brake valve in the "Freight" or "Direct Release" position.  

The difference in Feed Valve/Regulator Valve (110 p.s.i. vs. 90 p.s.i.) Brake Pipe pressure settings has little to do with the actual operation of the individual car's air brake control valves, and more to do with the maximum amount of air pressure provided into each car's brake cylinder during braking operations.   

Hope this helps, 

C.J.

@Will Ebbert posted:

There's a reason I used the word assume. It was an assumption. I'm not intimately familiar with any air brake system and I've never worked on freight car brakes, only locomotives and passenger cars. If I'm wrong feel free to plainly state it rather than your signature passive aggressive comments. 

Well, just maybe if you try and ask questions, rather than posting/making "assumptions",  you might learn a LOT more.

@Rich Melvin posted:

Read my post above. The auto racks are lighter than the coaches.

Many years ago, an article about the AT stated that the auto racks were heavier than the passenger cars. That stuck in my head.  Thanks for correction.

@Will Ebbert posted:

There's a reason I used the word assume. It was an assumption. I'm not intimately familiar with any air brake system and I've never worked on freight car brakes, only locomotives and passenger cars. If I'm wrong feel free to plainly state it rather than your signature passive aggressive comments. 

Will, well done. Don

Want to get a better understanding of train weigh vs. tractive effort of the locomotive...

Tractive effort is the amount of force that the locomotive can exert in the horizontal direction (am I correct about this?)

Weight on the rails is a vertically applied force by the rail cars 

So how do can you tell the horizontal force that the locomotive sees as a result of the weight of the railcars? Also how would roller bearings vs. plain bearings factor into this? I've tried finding answers on google but every site I found were answering different questions than that ones above 

Tractive effort is the CALCULATED amount of force that a locomotive can exert "at the rims of its driving wheels".  (The only way to measure actual tractive effort is to place the locomotive on a chassis dynamometer, and there are few of these in the USA.  I am aware of one at the Test Center in Pueblo, CO.)  The "horizontal component" of this vertical force is drawbar pull, and that is the amount of force a locomotive will exert at its coupler AFTER the energy used to move the locomotive is deducted. 

Everything "ahead/in front of" that drawbar/coupler is just used to generate that drawbar pull. The locomotive's "job" is to convert the energy in #2 diesel fuel and the resultant engine torque/power, converted by the alternator and inverter(s) into volts and amps, into "pull".  That is one major reason why locomotive builders (and the railroads!) are obsessed with fuel efficiency and locomotive system efficiency.  The lowest cost that any system can achieve to deliver the max "pull" is what makes railroads profitable in terms of train operation.

The effort required to move a rail car is the sum of the journal friction and flange friction as a result of the weight of the car itself.  Wind resistance of each car is also a factor and becomes THE predominant factor in the car's resistance to motion as speed increases, since this "car resistance" increases as the square of the speed in the car resistance formula.

The AAR and Davis freight car resistance formulae actually indicates that friction bearing cars actually have a lower INITIAL resistance to motion than a roller bearing car

BUT

that difference is slight and makes no adjustment for cold weather when friction bearing lubricants have greater viscosity, giving friction journals greater resistance to motion

the rolling resistance of an antifriction (roller bearing) car is lower than a friction bearing equipped  car once that car is in motion

Here is some simple math on how tractive effort is calculated:

1) Back in the days of DC traction units, the EMD Engineering Dept. determined that about a 17% adhesion level was obtainable under virtually all conditions. Thus, a GP40-2 weighing 250,000 pounds, for example, would have a continuous tractive effort of 42,500 pounds at the coupler, while and SD40-2 weighing 390,000 pounds would have a continuous tractive effort of 66,300 pounds at the coupler. 

Now, under ideal rail conditions, i.e. hot & dry, adhesion levels approaching 20% to as high as 25% were attainable, with corresponding dramatic increases in tractive effort (the GP40-2 would thus be 62,500 pounds TE, and the SD40-2 would be 97,500 pounds TE, both at 25% adhesion). The weight of the locomotive multiplied by the percent of adhesion, gives the tractive effort.

2) Now, in the modern era of AC traction and highly sophisticated wheel speed control systems, adhesion levels of over 40% are readily obtained. Thus, for example, a BN/BNSF SD70MAC, weighing about 400,000 pounds, can achieve a tractive effort of 160,000 pounds! Sometimes even more on a nice hot dry day in the northern Wyoming coal fields.

Such tractive effort number have been recorded in the EMD Engineering Test Car, with the use of an instrumented coupler equipped with strain gauge, which sends data to the computers in the test car. 

Slightly off topic but how much can a single coupler handle? Obviously at least 160,000 lbs. 

Pete

@Norton posted:

Slightly off topic but how much can a single coupler handle? Obviously at least 160,000 lbs. 

Pete

Just from memory; I seem to remember that the BN specifically ordered "high strength couplers" on their units, good for something like 500,000 pounds. I remember being on a coal train out in the Powder River Coal Basin, with 3 SD70MAC units on the headend of a 19,000 ton coal train, and one DPU SD70MAC on the rear. All three of the lead units exceeded slightly over 160,000 pounds each, thus pulling 480,000 pounds, starting the loaded train on White Tail Hill, just south of Donkey Creek, Wyoming. It was about 95 degrees F, with extremely low humidity, and we had to stop prior to the top of the Hill, since the traction inverters got too hot, at 8 MPH, and finally reduced power, so we stopped. After cooling the inverters by revving up the engines in neutral, we were able to restart the train and accelerate back to 8 to 10 MPH prior to reaching the top.

I read in EMD literature years ago discussing the advantages of AC over DC, about a heavy BNSF PRB coal train going uphill after a motor pinion gear disintegrated.  Unlike DC whereupon the sudden release of torque causes instant motor destruction, the AC armature simply catches up the the stator field, never exceeding redline.  The loss of a single traction motor was enough to cause speed degradation to the point where the locomotive computer, sensing ever increasing motor/inverter heat, automatically reduced power eventually resulting in a stall within sight of the summit.  After time spent to cool, the train was started again, crested the grade and continued on to destination.  I’ll assume that changing a motor pinion gear is a lot easier than replacing the motor.  Did you happen to be on this trip?

@PRR 5841 posted:

I read in EMD literature years ago discussing the advantages of AC over DC, about a heavy BNSF PRB coal train going uphill after a motor pinion gear disintegrated.  Unlike DC whereupon the sudden release of torque causes instant motor destruction, the AC armature simply catches up the the stator field, never exceeding redline.  The loss of a single traction motor was enough to cause speed degradation to the point where the locomotive computer, sensing ever increasing motor/inverter heat, automatically reduced power eventually resulting in a stall within sight of the summit.  After time spent to cool, the train was started again, crested the grade and continued on to destination.  I’ll assume that changing a motor pinion gear is a lot easier than replacing the motor.

No, as the pinion gear can NOT be replaced without removal of that complete traction motor, wheel axle gear set. The pinion gear on the AC motor is a "plug" type, which has a long tapered snout that is hydraulically "inserted" into the corresponding tapered bore in the rotor shaft. All such work must be done on the shop floor, with the entire gear case assembly removed. Lots of work involved.  

 Did you happen to be on this trip?

Can't remember for sure, but I was on a number of trips, out in the Powder River area, where we "stalled" and then restarted the train. From the beginning of the delivery of the SD70MAC units to BN (1991?), I spent pretty much every other week in the Gillette, WY area, training Road Foremen of Engines and Engineers, on the operation of the SD70MAC units. As more and more units were delivered, the use of DPU eventually became more wide spread. Train tonnages slowly increased from the "normal" 13,500 tons to the eventual 135 car 18,500 to 19,000 ton trains, of the late 1990s. 

Can I then assume that at least the AC motor can be reused for a significant savings?

@PRR 5841 posted:

Can I then assume that at least the AC motor can be reused for a significant savings?

Absolutely. Just like a DC traction motor, if the armature shaft, or rotor shaft, is not damaged, and new pinion gear can be installed. Now, the bull gear on the wheel axle pair, is a whole different story, as the gear side wheel must be pressed off, then the bull gear pressed off, then a new bull gear pressed on, then the wheel pressed back on. Obviously such work can only be accomplished at an experienced, and FRA qualified/certified, wheel shop.

Was there TE increases with DC motors on Super Series equiped 50, 60 and 70 series EMD's?

@Dominic Mazoch posted:

Was there TE increases with DC motors on Super Series equiped 50, 60 and 70 series EMD's?

Yes.

I remember that the latest MCB couplers were rated continuously at 560,000 lb of pull, but the buff strength was lower, and I believe three AC diesels with a starting calculated tractive effort of 180,000 lb each, and all on the head end of the train, were a good match for the required drawbar pull with getting a knuckle.  This also assumes the engineer was not acting in an "off or max" mode.  One huge advantage of distributed power (one or more units buried in the train) more evenly distributes drawbar pull and permits the operation of a higher tonnage train.  The downside to this is, in unit coal train service, the tipple at times has tried to bury the mid-train units with coal, that is, until the railroads and the loader operator paid greater attention and realized that only hopper cars should be loaded.

I also remember that when CSX AC4400's were assigned to unit coal trains, we discovered one member of the train crew always armed with a crescent wrench.  When I inquired, he told me that at one tipple, new units or units with new wheels hit the tipple, and it was his job to remove the firecracker antenna and at times the horn until the train loaded.  As a result, CSX tweaked their clearance diagram and also restricted tipple loading at this location to specific road numbers.  The main reason for the "gull-wing" cab of many BNSF AC4400's was one old tipple with limited clearance.  The redesign cost (and non standardization) was an impediment, and GE actually offered to defray the cost to modify the tipple, but BNSF decided to proceed with a redesign of the locomotive.