Helper engines?

[Anonymous]

I live along the Wayzata subdivsion of BNSF, about half way between willmar and Minneapolis.
Normally, the coal trains I see have two or three engines, usually SD70s. Lately, I've seen coal
trains go thru with one engine in front, and one pushing on the rear. Does anyone know the
reason for this?

[kwboehm]

I have seen the same thing out the front window of my house. From what has been explained to me, those units are Distributed Power Units. If I remember correctly, I believe th DPU's help with reducing slack since they are in radio contact with the lead locomotive. I'm not sure of any other purposes of DPU's if someone else could help out.

[Anonymous]

Thats right - its called distubuted power units. They are put in the back or even in the middle of a long train to help out the locomotives on the point (in front).
So if the train is going up the steep hill, the front engines will pull the train, the back engines will pu***he train, and the engines in the middle will do a little bit of everything. Doesn't this also increase the fuel efficiency?

[Anonymous]

Oh, by the way - Welcome to the forums![:)][:D][:p] Enjoy.

[AltonFan]

Some years ago, UP coal trains coming through the Chicago area typically had three of the latest diesel engines on the point. (I'm not up on my modern diesels, so please bear with me.) A friend who is involved in steam locomotive restoration and excursions told me that when UP was surveying for their Challenger's visit to the Chicago area, it was discovered that three of these diesels, when lashed together, exceeded the weight limits for a number of bridges in the area. Since then, it has become common to see two units on the point, and one in the rear.

BNSF may have similar problems in Minnesota.

[Mookie]

DPU's are put on BNSF trains because the Mookie gets a 2nd chance to look at an engine as it is going by! (Plus the fact that it is uphill between here and everywhere else!)

Mookie

[Modelcar]

...DPU application would surely distribute the load on draw-bar activity throughout the train and wouldn't it reduce the chance of pulling the train apart as compared to having all the power at the head end, especially in mountainous territory...

[jchnhtfd]

DPU has lots of advantages, and not all that many disadvantages (assuming that the engineer knows what he is doing!) -- and almost all of them relate to evening out the pulling forces throughout the length of the train. Problem being that while the air brakes go on on every car (we hope) and, with a little planning, can be made sort of vaguely even throughout the length, the pulling/pushing for moving comes only from the engines. And there is a definite limit on what a coupler drawbar will take. Ask any of the guys on this forum about what happens when a coupler breaks on a cold snowy windy night! So distributing the pull throughout the train reduces the pull on any given coupler (assuming, again, the engineer knows what he is doing!) and reduces the chance of busted couplers. Also reduces slack action, and potential damage from that source...