# What engine pushes UP 844?



## Isaac (May 9, 2017)

I want to know which engine most often pushes 844 as when a cheaper version comes out I want to model it. It seems to mostly have the Rio Grande 1989 heritage unit but sometimes has a GE AC4400CW instead.


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## highvoltage (Apr 6, 2014)

Isaac said:


> I want to know which engine most often pushes 844 as when a cheaper version comes out I want to model it. It seems to mostly have the Rio Grande 1989 heritage unit but sometimes has a GE AC4400CW instead.


Not sure about most often, but a video showed 844 connected to UP 6936, which is an EMD DDA40X.


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## Deane Johnson (Sep 19, 2016)

I always assumed the extra engine was for additional power. It doesn't actually push the 844 along does it? Is "pushes" simply a way to refer to additional power?

I've just never heard the term used this way before, but that's not surprising for me.


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## Isaac (May 9, 2017)

Deane Johnson said:


> I always assumed the extra engine was for additional power. It doesn't actually push the 844 along does it? Is "pushes" simply a way to refer to additional power?
> 
> I've just never heard the term used this way before, but that's not surprising for me.


Be it a helper or being dragged I want to know which one is most often used with 844 for modeling purposes.


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## highvoltage (Apr 6, 2014)

Deane Johnson said:


> I always assumed the extra engine was for additional power. It doesn't actually push the 844 along does it? Is "pushes" simply a way to refer to additional power?
> 
> I've just never heard the term used this way before, but that's not surprising for me.


From UP's website:

"Because the Frontier Days train is long, diesel locomotive No. 6936 will assist in providing No. 844 some extra power and braking on the runs between Cheyenne and Denver."


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## mesenteria (Oct 29, 2015)

I don't think there is a 'most often'. If there is a convenient heritage unit with sufficient capacity, they'll use it. If not, the DDX is most often seen behind #844.

Why a diesel at all? Insurance against breakdowns, to assist with dynamic braking descending grades (saves maintenance on the friction brakes for all rolling stock in the consist, not just the steamer) and power provision when there isn't a power wagon in the consist to generate electricity for air conditioners and lighting. On the rare occasion #844 can't handle the drag on the trailing tonnage by itself, say on a grade or on slick rails, the attendant diesel can be drafted to provide some oomph.


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## Isaac (May 9, 2017)

Guys I really dont care why there is a diesel behind it or if it is needed or even a good idea I just want to know which one to get to model it correctly. If you look at theese pictures with newest first it looks like you have an sp diesel, the rio grande heritadge, and a normal up engine. I dont think the DDX runs anymore does it? I just wanna know which engine is most likely to be paired with 844 in 2017. http://www.railpictures.net/showphotos.php?offset=0&where=search|Steam%204-8-4|Union%20Pacific|-2||-2||180|1||||||||Steam%204-8-4|-2||Union%20Pacific|-2|||180|-2|-2||||||1||2|||||||&newdisplay=10


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## santafe158 (Jul 14, 2010)

I don't think you're going to find a "normal" engine behind it. They probably grab whatever is available for the excursions. You've listed several options, and they've probably all been used at one time or another.


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## CTValleyRR (Jul 26, 2014)

Isaac, you've fallen into the trap of thinking that because no one is giving you the answer you want, it must mean that we don't understand the question. Actually, you're the one who doesn't understand the answers.

UP844 doesn't have a dedicated helper loco. It roams around the UP system. Whatever division is hosting it assigns motive power as it is available, with preference being given to heritage units (although I've seen plenty of pictures of it with Armour Yellow behind it). It's a crap shoot. If you want a rigid statistical analysis of what loco, or model of loco, has the greatest odds of being behind it, at any given time, well, have fun with that.

From a modeling perspective cosider this: if you ALWAYS use the loco that is statisitcally most likely, yet you know that several different locos perform this task in reality, then your model will be INACCURATE for whatever percentage of time that your chosen loco ISN'T performing helper duties. To be truly accurate, you would need to alternate locos, just like the prototype. Or you could just pick a model which has been used and say that, on the day /week/ whatever you chose to model, THAT loco is providing helper duties.

And, just for the record, steam locos are often pushed by deisels. Since it takes more than 24 hrs to bring a steam loco up to operating pressure, it is often easier to just shove it around with a diesel.


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## mesenteria (Oct 29, 2015)

As CTV says, there is no correct answer. You could just as easily cover your eyes at a display showing scale models of every modern and serviceable road engine UP has on its roster currently, and pick one to slip into the head of the consist behind 844. I have seen SD40's, SD45's, Dash 8's, Dash 9's, AC4400's, and the DDX some of us have mentioned.


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## highvoltage (Apr 6, 2014)

Isaac said:


> ...I don't think the DDX runs anymore does it?..


Yes, it's still in operation.

https://en.wikipedia.org/wiki/Union_Pacific_6936


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## 1905dave (Sep 18, 2016)

As a former UP Locomotive Director, the engine paired with the steam engine,if there was one, was a clean new unit, or another heritage unit. That narrows it down to about 1000 possible units.


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## santafe158 (Jul 14, 2010)

CTValleyRR said:


> And, just for the record, steam locos are often pushed by deisels. Since it takes more than 24 hrs to bring a steam loco up to operating pressure, it is often easier to just shove it around with a diesel.


WHAT?! I don't know where you got that information but it is definitely not true, save for a few unfortunate situations.

Occasionally they'll put one behind a locomotive for extra power when needed, or to stretch out the coal supply on long distance ferry moves, but it's definitely not because of the amount of time it takes to bring a steam locomotive up to pressure, and they don't just "shove it around." The amount of time it takes to bring one up to pressure also depends on the size of the boiler. Large engines might be done in 24 hours or more, but smaller ones like what I work on can be ready, safely, in 5-6 hours.


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## mesenteria (Oct 29, 2015)

Jake, I read that comment and concluded that the poster assumed the OP was asking about shoving moves at the maintenance facility. If he did mean that a diesel takes the consist out on the main while the boiler is brought up to temperature, he's woefully mistaken.


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## santafe158 (Jul 14, 2010)

mesenteria said:


> Jake, I read that comment and concluded that the poster assumed the OP was asking about shoving moves at the maintenance facility. If he did mean that a diesel takes the consist out on the main while the boiler is brought up to temperature, he's woefully mistaken.


That is a good point, and I apologize if that was the case. That is definitely true.


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## CTValleyRR (Jul 26, 2014)

mesenteria said:


> Jake, I read that comment and concluded that the poster assumed the OP was asking about shoving moves at the maintenance facility. If he did mean that a diesel takes the consist out on the main while the boiler is brought up to temperature, he's woefully mistaken.


Exactly. I'm not talking about road moves, except in one case that I know of where the steam loco was out of commission. At the Valley Railroad, we shove steam locomotives around with the diesel switchers all the time in the yard area.

And obviously, the size of the boiler will directly affect how long it takes to bring a steam locomotive to operating pressure.

Sorry if I confused anybody.


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## mesenteria (Oct 29, 2015)

We're stepping from one patch of weeds to another (okay, I am...), but there is considerable variance from institute to institute as to how to fire a locomotive from cold. I have seen credible articles saying it can be done in as little as four hours to some insisting the hostler is inviting big troubles down the line if he heats the boiler to operating temperature in less than about 10 hours.

The fact is that, like diesels, steam locomotives should be kept at working temperature all the time. It isn't possible or practical, but ideally steam locomotives should be kept hot. Not long ago, diesels were left running 24/7 because to start them again was the worst thing for them.

Each 15 degree drop or rise on the stay bolts, the seals around the tubes on the tubesheets, and changes to the rivets around the boiler casings, causes stress and even minor leaks. It's especially bad for the flues. That is why the expert and skilled fireman or hostler ensures an even fire, and why the hogger does his damnedest not to spin the drivers when the engine is pulling hard. When the drivers spin, the pulsed intake of air through the gratings lifts the coal bed and much of it gets sucked into the flues. That leaves holes in the fire where now non-heated air chases the crud down the flues, but rapidly cooling the flanges and welds or seals as it does so.

To conclude, especially with older metallurgy, boilers need to be brought up to temperature over several hours. They sure as aitch would not be taken out to the main and either shoved or towed while the firemen keeps building steam and the hogger has little to do for a few hours but blow the crossings.


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## CTValleyRR (Jul 26, 2014)

No worries -- good discussion, at least as far as I'm concerned.

You're right, though -- I'm thinking of it from the perspective of a tourist operation, where the locos are run periodically, rather than an ongoing operation where the loco would likely be needed again within a day or two at worst.

At least on the ValleyRR, the locos don't steam from mid-Oct until the holiday schedule starts up, and they go cold again from January to April. And, to be fair, we probably baby them somewhat when we start firing them in the Spring. And when they're just running weekends, they do bring in people to keep them hot through the week rather than cool down and start up again.


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## santafe158 (Jul 14, 2010)

CTValleyRR said:


> No worries -- good discussion, at least as far as I'm concerned.
> 
> You're right, though -- I'm thinking of it from the perspective of a tourist operation, where the locos are run periodically, rather than an ongoing operation where the loco would likely be needed again within a day or two at worst.
> 
> At least on the ValleyRR, the locos don't steam from mid-Oct until the holiday schedule starts up, and they go cold again from January to April. And, to be fair, we probably baby them somewhat when we start firing them in the Spring. And when they're just running weekends, they do bring in people to keep them hot through the week rather than cool down and start up again.


Yeah that's a bit more understandable. We run 3 locomotives from the late 1800's, so they're fairly small compared to a lot of other places. Our rule of thumb is a minimum of four hours from cold on our smaller engine, and a minimum of two hours if it's banked and hot from the day before. Usually we try to take a little longer than that if the time is available, since it does put less stress on the boilers.


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## Isaac (May 9, 2017)

Thank you all for your answers. I do now realize that UP will usually try to throw a special unit on the back but they will just throw whatever on to provide braking not motive power. Thanks again everyone!


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## CTValleyRR (Jul 26, 2014)

Isaac said:


> Thank you all for your answers. I do now realize that UP will usually try to throw a special unit on the back but they will just throw whatever on to provide braking not motive power. Thanks again everyone!


Wow! 2-1/4 years later, the OP responds! I'm impressed! Usually, these things just kind of fade out.


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## Isaac (May 9, 2017)

CTValleyRR said:


> Wow! 2-1/4 years later, the OP responds! I'm impressed! Usually, these things just kind of fade out.


Yea I had another question so I came back. As for which engine powers 844, it turns out noone makes a steaming version of UP 844 so I am waiting and hopefully BLI or MTH comes out with one


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