I have always wondered if railroads actually calculate the weight of the train and find the appropriate power for the train, or do they just slap 2 or 3 dash 9s on there. I know a sd-40 can pull a 50 car train with ease, but I always see 2? And sometimes I have seen a single ex-conrail dash 9 pull a 70 car train (going slow of course [:D]). It would seem it would be more cost effecient to try to find the appopriate power for the train, do railroads do this?
All railroads have tonnage charts for different engines based on the severest grade in the district. Obviously the steeper the uphill grade the less tonnage an engine can pull. Now couple that with a few other factors like how many set outs and pick ups it will make and are there engine terminals between the starting point and the destination as well as is there assigned helper power on the grade and you have your answer. It would be very foolish to waste the fuel alone without even considering engine wear and tear if not needed. Conversely it would be very foolish to underpower a train but believe it or not that probably happens as much or more than overpowering a train.
…I’m sure calculation is involved to power a given train to travel over a certain profile of track with a certain measured load.
Of course, if that is all they did there would be a lot of engines sitting at the coal fired power plant and too few at the mine. (Personal opinion, “Balancing power” across the whole railroad is the difficult job and is more “art” than “science” and the Dispatcher’s job is one that is very hard to master.)
I have a chart that tells me how much tonnage each class of locomotive can handle. Our power tends to cycle, one train’s inbound power is usually the power for it’s counterpart going back. So when the power comes in, I look at my chart, and build the outbound train based on the tonnage the chart tells me and taking into account any work the train has to preform line of road.
The Power Bureau controls locomotive assignments. Although the power plan usually works, I (and most anyone else in the field) have been known to disregard the power plan because locomotives are out of place, shopped, there isn’t enough power for a train, somebody else stole my locomotives, etc.
Nick
Very good topic.
On Class 1 railroads, such as CSX and MKT, which person or persons at the locomotives terminals within the “Power Bureau” mentioned actually assigns the units? Would that be a Trainmaster?
From my limited understanding of this in the past, the person had to have very good analytical/computation skills and be familiar with the strange characteristics of using various types of units on the same train (GE, EMD, Alco) (6 axle vs. 4 axle). Also had to be familiar with the routes (curves, grades, axle load weight on bridges).
Example: A knowledgeable friend of mine shared with me that back in the 1970s, GE U36Bs on the Seaboard Coast Line were notorious for spinning their wheels when throttling up on heavy trains. So then I understood why in most photos I see of that era, those U-Boats were almost always put on the point of MU lashups in front of 4 and 6 axle EMDs by the Trainmaster or person in charge of the power.
Thoughts?
The Power Bureau is a system level department.
At the local level, the area Trainmaster is responsible for carrying out the “Plan” and making last minute changes if needed. You’re suppose to clear any changes with the Power Bureau, but in critical situations, we just do it, and tell them later.
Nick
A figure I’ve seen used is horsepower per ton. I would assume that this is given to a specific schedule based on the territory it covers (with the accompanying grades, etc.) and the type of train it is. I’ve really only seen this figure for one train (for some reason, it comes up when all I can get is a consist for any other train). UP’s ZWASKP (the weekly perishable train) is supposed to get 2.5 horsepower per ton. In real life, it generally gets closer to 2.3.
I’ve mentioned here before an ICG train I saw back in the 70’s, headed south through Rantoul, Ill. It was empty hoppers, and apparently there was a power shortage somewhere 'cause the consist was two unit trains worth of hoppers, but they only had one train worth of power at the head end (and nothing pushing). Wish I could remember what the two units were at the head end - they were on their knees. For some reason I counted the cars and remember the total being up around 180…
So, when assigning power, do you also have an up to date total of trailing tons on that specific train, or is it a best guess based on history of loads vs empties, max wt vs empty weight, etc?
With all the automation inuse, conceptually, it would easy to aggregate any data put into the system about a given cars state, and total it up at the end. Is this what actually happens?
If you have such a list, are the weights based on actual scale readings, customers reports, or what else would they be based on…
When a crew gets on there train they should have the paperwork in hand that tells them exactly how many tons the train is and exactly how much horsepower they have. The conductor should also walk through the power to make sure everything is running and good to go. In hill or mountain territory inspecting the condition of the dynamic brakes is very important also. If a train doesn’t have the horsepower to ton ratio (HP/T) to make the ruleing grade then something must be arranged like setting out tonage or adding units (and in some cases plans could be made to “double the hill”). In most mountain territory it is critical to have the minimum HP/T for the ruleing grade. In the flatland it is not as critical but a train short on horsepower might run at significantly lower speed and can hold up other trains. Remember horsepower is speed, so even in the flats you want your hotshots to have relatively high HP/T, say 3-5, while lower priority trains like grain & coal drags might get by with 1-2.
Also it should be noted that some railroads make there power assignment decisions based on tractive effort rather then horsepower.
I’ve heard powered axles mentioned as well.
I have a computer screen that gives the total length and tonnage for all cars in my terminal classed to a given train. I also have a screen that shows the train’s current length and tonnage, the trains theoretical maximums, length and tonnage available for to fill out, the number and location of cars in my terminal scheduled to make the train.
Note that not all the cars classed to a train, may be scheduled for today’s train. In practice, if the length/tonnage is available, we send the cars regardless of the date of the scheduled train. Sending cars in advance of schedule is a good thing.
Nick
Our tonnage charts are based on T/E rather then raw horsepower.
Nick
It was briefly mentioned but traffic isn;t always equal in both directions so sometimes extra units are either added to existing trains or run light to reallocate them. Pennsy Power by Stauffer shows a PRR train of just engines that must have twenty running light. I once saw a Penn Central train many years ago southbound through Middletown Ohio with sixteen engines on it. I suspect the origin was either Toledo or Detroit with auto parts northbound and not much southbound.
Power assignment is by turns very simple and very complex for Class I railroads. In addition to the tonnage of the train there are a number of other considerations that enter into assigning power to a train. Some of them are, is the train originating from a locomotive shop terminal, if so a train may be ‘overpowered’ in order to be able to distribute engines to other areas of the network, conversely, some trains from outlying terminals may appear ‘overpowered’ enroute to locomotive shop terminals as they are transporting engines that need shop attention and those engines may or may not be working. A secondary consideration in assigning power is when an engine is due for its required 92 day maintenance.
Many railroads attempt to ‘power plan’ their scheduled train networks and thus power that takes train 1 to a terminal is scheduled to take train 2 out of that terminal. While scheduled trains have a fairly stable traffic volume, there are fluctuations in traffic and sometimes the power assigned to train 1 will be handling full drag tonnage for the territory, and other times the traffic may only be a hand full of cars, however the requirement to have the power in place to handle train 2 requires the normal complement of power to be used on the train, even though train 1 will now be vastly overpowered.
The real ‘Wild Card’ in power utilization is in the handling of bulk commodities, coal, coke, iron ore, grain and all the other train load commodities that the carriers handle. Since these moves are relatively erratic, when compared to scheduled trains, it may take special engine scheduling to get the necessary power on hand to handle these moves from time to time. Power that handles a bulk commodity train will normally stay with that train through the trains ‘life cycle’ from empties enroute to be loaded, the loaded trip to destination and the
Lots of good info, some from people who do this daily. But I have not yet seen a comment about adjusting for weather conditions. In the west strong winds hitting a train at a 45 degree angle can substantially affect the amount of power needed, and if Murphy’s Law prevails this may happen on ruling grades. Also, different configurations of trailing equipment catch more wind than others, auto racks for example. Also snow and blizzard conditions require planning beyond the norm.
If the ‘Powers that be’ are to be believed, the tonnage ratings for the various classes of engines take into consideration the normal gamut of weather conditions, rain, snow, wet leaves, etc. Wind conditions, being more variable than any other weather conditions are normally accounted for by noting delays for the train as being unable to maintain line speed account wind conditions. While winds (tornadoes) may derail trains, they are not a factor in calculating tonnage ratings.
I, too, recall the SCL practice of mixing the GE U36Bs with EMD power. It was explained to me once that the GEs were slow to get moving, as their throttle response was not as good as the EMD (perhaps it was toned down to compat the wheel-slip issue!). However, once the GEs got moving, they were quite fast and more fuel efficient than the EMDs. So, SCL would often use two U36Bs and a GP40 to lead a crack piggyback train. The GP40 would pull harder quicker to get the train moving, then the GEs could easily maintain 70+ mph. This practice continued through the 80s with the B36-7s (although it was more common to see three of them together).