NFR Train physics question

[Yard Sale]

From my office near the mighty Columbia river I can see the railroad running up both sides. I've noticed that almost every train has either engines in the middle or at the rear end helping the lead engine, sometimes both. What I'm wondering is if that rear engine is pushing some cars and the lead engine is pulling some cars, is there a car or cars in the middle that are basically floating? As in getting a little push and a little pull? I'm sure this is a silly question, but for some reason my mind just won't accept an obvious answer.

Follow up: If its more efficient to pull than to push why they don't break it into 2 trains and just pull on both? Aerodynamics? Simplicity?

 

[Long_Rod_Silvers]

I was told years back that on higher slope tracks they put an engine in the back to lessen the stress on the couplers. E.g. when one engine is pulling up the hill, there's twice as much stress on the couplers than when there's also an engine pushing. Helps reduce stress.

I don't know, it made sense to me so I stopped looking for answers.

I have to imagine it helps going downhill as well, having extra control/help at the back end.

 

[albula]

Just a guess and a completely uneducated one at that. Perhaps it takes only one engine to get them up to speed but two to slow them down if necessary.

 

[O' Clarkii Stomias]

Mid and tail end locomotives reduce the latitudinal stress on the cars and the tracks. A set of locomotives pulling on the front is the most efficient, but they want to pull in a straight line which puts a lot of sideload in curved sections of trackage.

 

[Yard Sale]

So the rear engine is pushing the last car, but the last car is still being pulled by the second to last car?

 

[O' Clarkii Stomias]

Everything is being pulled by the head unit(s) including the mid and tail locomotives. The mid and tail locomotives are there just to lighten the strain.

 

[Mossback]

Why railroads put locomotives in the middle of a train - Trains

See why railroads put locomotives in the middle of a train and how it plays into model railroading.

www.trains.com

 

[DimeBrite]

If you guessed "Distributed Power", you are correct.

 

[Divad]

If the front engine is fighting with the rear it’s considered domestic caboose.

 

[BriGuy]

If the front engine is fighting with the rear it’s considered domestic caboose.

Best dad joke in a long while.

 

[Canuck from Kansas]

Do they have to be pulling and pushing the exact same? ie, what happens if the rear engine is pushing harder than the front is pulling, wouldn't this cause buckling? Or if the front is pulling harder than the rear is pushing, wouldn't his cause the middle and end cars to want to straighten on a curve? (this has kept me awake at night for many years).

cheers

 

[_WW_]

Do they have to be pulling and pushing the exact same? ie, what happens if the rear engine is pushing harder than the front is pulling, wouldn't this cause buckling? Or if the front is pulling harder than the rear is pushing, wouldn't his cause the middle and end cars to want to straighten on a curve? (this has kept me awake at night for many years).

cheers

It's called software...like what's in your phone.

 

[Canuck from Kansas]

It's called software...like what's in your phone.

I believe they've been push/pulling for a lot longer than software for this, though I could be wrong (it does occasionally happen).

cheers

 

[Yard Sale]

The article above says they have been doing it for a long time using radios.

 

[_WW_]

I believe they've been push/pulling for a lot longer than software for this, though I could be wrong (it does occasionally happen).

cheers

Beginning in the 1960s, mid-train distributed power units – DPU – and pushers have been operated using radio signals. Southern Railway pioneered this technology, adopting an early form of Locotrol...Originally, the electronics were placed in a separate railcar as the equipment was bulky and generally did not fit inside a standard locomotive cab or nose. Over time, the radio gear was condensed into relatively small cabinets, with most of the functions being controlled by software.

In fact, some railroads have gone even further and have implemented advanced systems that use sophisticated algorithms and computer software to optimize the train’s performance and reduce fuel consumption.

Okay...go to sleep now.

 

[DoesItFloat]

Two gummies this morning, eh?

 

[kmudgn]

Its a railroad sex thing

 

[Canuck from Kansas]

Beginning in the 1960s, mid-train distributed power units – DPU – and pushers have been operated using radio signals. Southern Railway pioneered this technology, adopting an early form of Locotrol...Originally, the electronics were placed in a separate railcar as the equipment was bulky and generally did not fit inside a standard locomotive cab or nose. Over time, the radio gear was condensed into relatively small cabinets, with most of the functions being controlled by software.

In fact, some railroads have gone even further and have implemented advanced systems that use sophisticated algorithms and computer software to optimize the train’s performance and reduce fuel consumption.

Okay...go to sleep now.

Ahhh, that's a relief, it's been years of restlessness over this.

 

[O' Clarkii Stomias]

Beginning in the 1960s, mid-train distributed power units – DPU – and pushers have been operated using radio signals. Southern Railway pioneered this technology, adopting an early form of Locotrol...Originally, the electronics were placed in a separate railcar as the equipment was bulky and generally did not fit inside a standard locomotive cab or nose. Over time, the radio gear was condensed into relatively small cabinets, with most of the functions being controlled by software.

In fact, some railroads have gone even further and have implemented advanced systems that use sophisticated algorithms and computer software to optimize the train’s performance and reduce fuel consumption.

Okay...go to sleep now.

DPU technology has been around for a long time, but the incorporation if Variable Frequency AC drive in locomotives have revolutionized remote power units.