My Seaboard and Western Virginia Railroad, an Appalachian Crossing railroad which operates dynamic brake equipped locomotives, recently acquired a plains states short line which operated with non-dynamic brake equipped locomotives. My modelled portion of this (freelanced) railroad drops down off of the Appalachian Plateau, crosses the Ohio River - the low point on the layout - in the vicinity of New Martinsville, West Virginia and then climbs westward through the hill country of eastern Ohio en route to Columbus, Chicago, and now St. Louis and Kansas City. The grade is expected to be less than 1.5% max. Is there a reason why dynamic brake and non-dynamic brake equipped units cannot be operated together?
Dynamic and non-dynamic brake locomotives can operate together in a consist and railroads have done so as common practice since the 1950s. However, if the dynamic brake is to function, the lead locomotive has to be dynamic brake equipped. On modern locomotives the dynamic brake control will pass through on the M.U. through non-dynamic equipped trailing locomotives to another dynamic-brake locomotive deeper in the consist. Older EMD locomotives (pre-1953) used field-loop dynamic braking which required a separate M.U. cable, the consist was limited to four units for dynamic braking, and all of the dynamic locomotives had to be together in the consist.
1.5% grades are not mild and most railroads that encounter descending grades of that stiffness with heavy trains require the use of dynamic brakes or limit speed on descending trains depending on tons per operative brake (the air brake), if the dynamic brake is not functioning or not present. Up to 1980 Class I railroads without heavy grades – Canadian National, Illinois Central, MoPac – saw no need to purchase new locomotives with dynamic brakes except for certain pool services, but that practice died out on Class Is due to the economic imperative for universal locomotives. Short lines and regionals are another matter; many short lines often do not buy locomotives with dynamic brakes even when operating on former Class I lines where dynamic brakes was the practice, and limit train tonnage and speed to make this possible.
S. Hadid
S. Hadid has already answered your question, but I would just like to add that I have a video about the Union Pacific operations in the western U.S. that shows a non-dynamic brake Illinois Central SD70 in the middle of the consist. The narration comments that the IC locomotive has no dynamic brakes because it is from a midwestern railroad that operates over relatively flat terrain, but there are still enough dynamic brake equipped engines to keep the train under control.
It would probably be up to the Yardmaster to determine whether a train has enough dynamic braking capacity for the tonnage and grades involved, and assign locomotives accordingly.
Glad you brought up the question of power assignments. Traditionally this was the purview of the chief dispatcher (not the yardmaster), while the roundhouse foreman kept himself out of trouble by making sure he’d made ready enough power for the typical day’s traffic plus a little extra. Today power dispatching is usually assigned to a power desk in the dispatching center, usually staffed by people also qualified as assistant chief or chief dispatchers.
Yardmasters run the yard, dispatcher run the main line, and their interests are often not aligned.
If you take a close look at a train – it’s number of loads and empties (look at the springs), the gross weight of the cars, and the commodities hauled – it’s not difficult to approximate the train’s gross weight. From that you can calculate the tons per operative brake (each ordinary four-axle car counts as one operative brake; a five-well double-stack car counts as three operative brakes). The employee timetable and special instructions includes a chart stating the number of axles of effective dynamic brake for each locomotive type. From that you can go to another chart specific to each subdivision and determine the maximum authorized speed on descending grades for that train’s TPOB and #axles dynamic brake.
S. Hadid
Appreciate the responses gang and I thank you so very much. You have certainly facilitated some future purchases of some N-Scale locomotives.
Minor quibble, if the locomotive is a IC SD70 then it DOES have dynamic brakes, no EMD 60 series or newer locomotive for North American service was built without dynamic brakes.
Although, the power assignments are handled by the Power Desk, the local Trainmaster can have a large impact on what power is assigned, because he is THERE.
If something goes hinkey with the Power Plan, he is the one on the spot, and knows what power is on hand, what power can be spared, and what power will be available in the near future. I’ve done this bob and weave often enough, to know that the Power Desk screws up, as often as, they get it right.
In addition, the Yardmaster, under the Trainmaster’s direction, should build the train with-in the loading limits of the locomotive consist. This is usually based on pulling power, rather then dynamic braking force.
Nick
Sorry, my mistake on the IC locomotive identity – I watched the video again a couple of night ago and it was identified as an SD40.