BNSF has been running DPU on several stack trains for acouple years now. most are around 10k feet long, however sometimes they run 12k-13k foot ones where there are 2 units in the middle and 1 on the back. saw 1 last night that had 196 wells.
It could also be two trains tied together that had different starting points and/or different end points but share a reasonably long route. The Reading did that before the distributed power era and could be spotted by a caboose in the middle of the train. Saves on crew costs.
Mid-train remotes ("slaves" in years gone by) used to be the norm, usually placed about 2/3 of the way back to equalize brake response. I'm not sure why the use of remotes fell out of favor until recently.
CPR frequently runs long intermodal trains with a couple of units up front, one in the middle and anopther on the end. It depends on tonnage and grades, but distributing the power reduces in-train forces that might otherwise cause derailments by stringlining, etc.
In the 200-car monsters CSX is running thru here now, there is usually one locomotive about midway in the train, and usually if there are autoracks in the train all or most of them will be behind the midtrain loco. Hadn't thought about trailing-tonnage limitations on the long cars, but sounds like that could be the reason.
DUP's in the mid-train position? Not really a new idea, just one gaining more railroads who will use it.
BNSF this past Winter started using mid-train DPU's on some of their West to East srackers off of the Southern Transcon. Nowadays they seem to be running them in both directions off of the Southern Transcon; in this area of South Central Kansas hey are running several days a week. Normally, the head-end power is three or four units, not quite halfway back will be two units in the mid train position and normally one unit on the rear DPU position. Most of these trains seem to approach the 10,000ft lengths(?).
There had been some mention around here that this was a tactic used in the cold weather/Winter to keep train/airline charged. No idea if that is the case, but that number of engines would certainly make for faster cycling of air pressure requirements(?) after a stop, faster.
I have no idea when BNSF adds the extra units in the trains through this area (Possibly, KCK area, Topeka, Argentine?), and do they stay with the move all the way into California? Most of the Domestic Container Stackers seem to run all their power on the head-ends, only occasionally does a rear DPU seem to run through this area. The main users of the mid train DPU's are the Import/Export Container consists.
Having the loco within the train is most likely account 'trailing tons' restrictions with long cars. Long cars, (89 foot & greater) if lightly loaded have a tendancy to 'stringline' when subjected to excessive trailing tonnage in curves ascending grades.
Never too old to have a happy childhood!
Can't tell for sure without further information. But the mid train loco is probably a distrubuted power unit. In fact, I just saw a container train yesterday with this configuration eastbound on the UP Geneva Sub just west of Chicago (the mid train unit was working, so it wasn't dead in tow).
There could be any number of reasons from putting the loco in the middle of the train rather than on the end. It could have been because of drawbar forces. Or, a cut of cars could have been added to the rear of the train behind the loco at the Rochelle intermodal facility ("Global" something or other). If this happened, there would have been no particular reason to move the DPU engine to the rear of the new cut of cars - it would work fine just where it was.
what is the idea of this?
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