Question about engines used to help push a train

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If engines are used to help push a train, is there some risk that cars may be pushed off the rails?

ETA: I got a good answer from another informed source: "The risk is extremely low. The Engineer has a DPU Panel they use to set the Pushing/Pulling force on the train."
 
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Donvana

New Member
Obviously the risk is low because otherwise they wouldn't do it but the logic escapes me. With engines pulling from the front and others pushing from the rear there has to be slack somewhere in the middle. Because the engines can't possibly be perfectly matched the slack point will be moving constantly. In effect the train will be going in and out like an accordian.
It must be a philosophical thing. UP puts additional engines at the end of the train. CP puts them in the middle. CN runs trains so long they put them at the end and in the middle.
 

Donvana

New Member
Glad I didn't have to wait for that at a level crossing. Never seen a train with four sets of engines. Too many eggs in one basket and why? To save the cost of a crew?
To haul the freight on that train would take 296 truck drivers plus one additional for every container double stacked. Yet with ports flooded with containers I see relatively few trains on the UP southern main line while I-10 is a river of trucks.
Having a little trouble understanding the economics.
 
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bnsf971

Roadmaster
Driving trains of increased weight and length along with improved use of locomotive power leads to increased load on components and parts and, consequently, to their increased wear and tear.
Not really sure what this has to do with the topic at hand...
 

Railmonkey

New Member
Obviously the risk is low because otherwise they wouldn't do it but the logic escapes me. With engines pulling from the front and others pushing from the rear there has to be slack somewhere in the middle. Because the engines can't possibly be perfectly matched the slack point will be moving constantly. In effect the train will be going in and out like an accordian.
It must be a philosophical thing. UP puts additional engines at the end of the train. CP puts them in the middle. CN runs trains so long they put them at the end and in the middle.
You are wrong- there is no slack in middle. When they train on using DP they tell you to keep the "fence" up which allows independent operation of DP unit from head end and they want the DP unit throttled up at all times to bunch the train- even when dynamic braking on head end. That is part of what makes running DP trains easier than most other types of consist, they ride smoother through undulating territory due to no slack in them. If you drop the fence on a hill you can rip the train apart easier due to uneven forces if you have the train strung out on two sides of a hill.
 




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