I noticed recently that BNSF is using pusher power units in our flat land country in ND.
Anyone know the reason for adding power unit to the rear instead of the head end?
Gramps in North Dakota
I suspect these are not ‘manned’ helper engines, but ‘DPU’ remote control engines.
Jim
What you’re seeing is generally referred to as “distributed power” as opposed to “pushers.” Pushers are manned, DPU are controlled by the engineer at the head end via radio signals.
As flat as your land may be, there may be places where two units can’t move a train over the profile. And, the train may travel through areas that simply aren’t flat as it goes from A to B.
DP spreads the horsepower out, which can reduce the possibility of things like pulled drawbars and broken knuckles. Putting all three units on the head end means all 100+ cars are hanging on that first coupler. Pushing from the rear with a DPU (and from the middle, too, with in-train units) reduces those forces.
The DPU’s can also assist with braking with their dynamic brakes.
Adding and removing units also takes time (thus, money). Running a DPU straight through and only using it when it’s needed can be a time (and money) saver in the long run.
The first reason would be that knuckles can only stand so much pulling power before they break. That is why the units go on the rear.
The second reason would be that these are “Unit” trains that stay together for the entire length of their journey. Even though the head end power may be enough to pull the train across some flat land, the train may not encounter flat land the entire way and so the DP power is needed where grades are more severe.
BNSF doesn’t call them “pushers”, rather they are “helpers”. They are almost extinct in the crossing of the Maria’s Pass (5,213’). What helpers that are left are based in Essex, MT and used on ‘conventional’ trains. With the advent of Distributed Power (DP), many of the 2 (head end) + 1 (DP, end-of-train) westbounds take on an additional DP unit in Shelby, MT, making them 2+2, in the venacular. No mid-train helpers, out here. Conversely, many eastbounds drop the 4th unit in Shelby and go east 2+1 into the “flatlands”. The “Canpotex” (potash) westbounds came out of Canada as 2+2 and headed west as 3+2. Very long and heavy trains! CP and BNSF power was mixed, run-through. Almost all units were Dash 9-44CWs, with an occasional leaser. North- , then west-bound coal trains and grainers do the same. 1.3 hp/ton seems to be the minimum, over the “hill”.
Hays – wdh@mcn.net
Improved train handling and saves fuel.
Thanks for the speedy reply, question answered and curiosity satified.
Gramps in North Dakota
It also depends on where you live in North Dakota, if you live along the Jamestown Subdivision (between Bismarck and Fargo) then you are seeing the power needed to get them up and over Buffalo Hill and Dickinson Hill in the Badlands. BNSF switched to using DPU throughout on these trains since DPU allowed an increase of 10 to 15 cars per train without any additional motive power. This is due to reduced curve drag created by dividing the power between two locations rather than concentrated at the front.