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What’s the big deal with DPU’s

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What’s the big deal with DPU’s
Posted by JDawg on Thursday, April 29, 2021 6:42 PM

So, I happened to glance over at the trains magazine forum(the rail fanning one). And I saw this big discussion over DPU's and locomotives in the middle of a train. I was perplexed because it seemed people were going nuts over the fact that there was a locomotive in the middle of a train, a DPU. I found it odd because although I am not a rail fan, I do enjoy watching trains.
     The rail line that runs near my house in MN always has trains with DPU's at the middle and the end of trains. I'd see at least one a week, for years and years, still happening today, although the line's traffic has slowed overall. Am I just lucky, or is it more common than this one thread let on? A bit off topic for the MR forum, but I dared not ask in the other forum for fear of being eaten alive!Whistling

JJF


Prototypically modeling the Great Northern in Minnesota with just a hint of freelancing. Smile, Wink & Grin

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Posted by JDawg on Thursday, April 29, 2021 6:43 PM

JDawg

So, I happened to glance over at the trains magazine forum(the rail fanning one). And I saw this big discussion over DPU's and locomotives in the middle of a train. I was perplexed because it seemed people were going nuts over the fact that there was a locomotive in the middle of a train, a DPU. I found it odd because although I am not a rail fan, I do enjoy watching trains.
     The rail line that runs near my house in MN always has trains with DPU's at the middle and the end of trains. I'd see at least one a week, for years and years, still happening today, although the line's traffic has slowed overall. Am I just lucky, or is it more common than this one thread let on? A bit off topic for the MR forum, but I dared not ask in the other forum for fear of being eaten alive!Whistling

 

JJF


Prototypically modeling the Great Northern in Minnesota with just a hint of freelancing. Smile, Wink & Grin

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Posted by BigDaddy on Thursday, April 29, 2021 6:51 PM

I'm a fan of Virtural Railfan, although not a subscriber.  DPU's are everywhere.  They are more common than undiversity in a TV commercial.

Henry

COB Potomac & Northern

Shenandoah Valley

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Posted by Outsailing86 on Thursday, April 29, 2021 8:15 PM

They are getting more common. One at front, one at end is easier. There is science behind the middle locomotive that it is pushing 1/3 and pulling 2/3. There is a "push zone" of train forces, which does affect curve forces slightly. The big benefit is air can be deployed to the consist much faster for braking.

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Posted by MARTIN STATION on Thursday, April 29, 2021 9:33 PM

 I for one am glad to see DPUs. It seems I was always reaching the RR crossing after the motive power had already passed. Now it does't matter, I can look forward to seeing some motive power in the middle or on the end of the train. Now it really is better late than never.

Ralph

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Posted by FRRYKid on Friday, April 30, 2021 2:30 AM

The rail line (BNSF ex-BN exx-NP) that runs near my house always has DPUs on almost all the trains I see. (Depending on the train, it's usually 2 on front and 2 on back but there are times it's 3 and 1.) While many people think the line is flat as it's Eastern Montana, I was told there is an almost 1% grade on that line. With as long as those trains are (102 on grain hoppers, probably somewhere close to that on coal trains and tank trains), the extra power is needed to move them.

"The only stupid question is the unasked question."
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Posted by dehusman on Friday, April 30, 2021 10:29 AM

The original Distributed Power was a Canadian system.  The UP first used it in the Blue Mountains to increase capacity and eliminate splitting trains and using helpers.

From there it spread to bulk trains and then trains in general (mostly based on how many engines were equipped.)

That's why ex-SP C44AC's were always in the #2 position on a unit coal train.  Since they were C44AC's they were in coal, since they didn't have UP cab signals, they couldn't lead, since they didn't have DPU they couldn't trail, so the only place they could be used was as the trailing unit in the head end consist.

DPU trains stop quicker than a conventional train, accelerate better and actually have better fuel economy, plus they can handle more tonnage because the drawbar forces are reduced.

Dave H. Painted side goes up. My website : wnbranch.com

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Posted by zugmann on Friday, April 30, 2021 10:39 AM

dehusman
DPU trains stop quicker than a conventional train, accelerate better and actually have better fuel economy, plus they can handle more tonnage because the drawbar forces are reduced.

They can also create a bigger mess if the DPU engines act up. 

 The opinions expressed here represent my own and not those of my employer or any other railroad, company, or person.

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Posted by NittanyLion on Friday, April 30, 2021 11:26 PM

Context is important. Until very recently, they were almost unheard of in the Eastern US. It only really emerged as part of the operational model changes that happened over the last five years or so. 

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Posted by KibuFox on Sunday, May 2, 2021 5:00 PM

dehusman

The original Distributed Power was a Canadian system.  The UP first used it in the Blue Mountains to increase capacity and eliminate splitting trains and using helpers.

 

Southern Railway in the US was one of the pioneers of DPU, starting in the late 60's, early 70's. With the idea, doing it primarily over the Saluda grade. To do it, they used special boxcars converted to recievers, which they'd MU into a pair of locomotives which would be put mid train.  Everything was controlled from the cab of the lead locomotive.

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Posted by cv_acr on Monday, May 3, 2021 12:07 PM

NittanyLion

Context is important. Until very recently, they were almost unheard of in the Eastern US. It only really emerged as part of the operational model changes that happened over the last five years or so. 

"Helpers" were common in mountainous areas, but as trains get bigger and heavier, even relatively flat territories are using extensive DPU on long and heavy trains.

I live in Ontario on the CN main between Toronto, ON and Chicago/Detroit/Toledo (Chicago and Detroit lines diverge on the other side of the border). 10 years ago DPU was pretty much unheard of here, and it was sort of an "event" to see it. Now it's pretty much 1 in every 3 through trains.

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Posted by cv_acr on Monday, May 3, 2021 12:08 PM

KibuFox

 

 
dehusman

The original Distributed Power was a Canadian system.  The UP first used it in the Blue Mountains to increase capacity and eliminate splitting trains and using helpers.

 

 

Southern Railway in the US was one of the pioneers of DPU, starting in the late 60's, early 70's. With the idea, doing it primarily over the Saluda grade. To do it, they used special boxcars converted to recievers, which they'd MU into a pair of locomotives which would be put mid train.  Everything was controlled from the cab of the lead locomotive.

 

Canadian Pacific was doing the same thing in the same time frame with "robot" cars and remote helpers over the Rocky Mountains.

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