4-8-2s replaced by 4-8-4s

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4-8-2s replaced by 4-8-4s
Posted by SPer on Tuesday, July 13, 2021 10:58 PM

Why did some railroads replaced 4-8-2 Mountains with 4-8-4 Northerns on passenger and freight trains.

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Posted by Overmod on Wednesday, July 14, 2021 12:36 AM

Same advantages the replacement of 2-8-2s by 2-8-4s did.

The early generation of 4-8-4 was in fact a heavier Mountain, and the ATSF called the original 3751 class 'heavy Mountains' when first built.  Later with higher drivers and better balance eight-drivered engines became at least the equal of Hudsons for high-speed work...

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Posted by daveklepper on Wednesday, July 14, 2021 2:54 AM

The equal of Hudsons for speed anbd the equal of Mountains for tractive-effort.

Just like Hudsons generally had larger fireboxes than Pacifics, so Northerns vs. Mountains (and Birkshires vs. Mikados, and Texans vs. Santa Fes).

Usually resulting in more horsepoiwer and higher top speed.

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Posted by BEAUSABRE on Wednesday, July 14, 2021 7:13 PM

Usually resulting in more horsepoiwer and higher top speed.

But not until the Erie instituted what I call "Second Generation Superpower" or "Real Superpower" with 70 inch drivers on its Berkshires

The original Lima built low driver (63/64 inch) 2-8-4's and 2-10-4's were more "Super Mikados" and "Super Santa Fe's" with one foot still in the drag era. 

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Posted by 7j43k on Wednesday, July 14, 2021 7:41 PM

GN O-8 2-8-2


T. E.--75,900


Grate area--98.5

Weight on drivers--325,000



NKP S-3 2-8-4




Grate area--90

Weight on drivers--266,000



Erie S-4 2-8-4


T.E. 78,900


Grate area--100

Weight on drivers--286,000


Pretty impressive, for a Mikado, eh?  Note in particular the weight on drivers.



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Posted by M636C on Wednesday, July 14, 2021 9:07 PM

On the other hand, Canadian National had fleets of both 4-8-2s and 4-8-4s.

It appears that the 4-8-2s were intended for lighter track than the 4-8-4s.

An enthusiast can spend many happy hours carefully comparing the boiler dimensions of the two types, checking variations in boiler diameter, grate area and lrength of the combustion chamber.

While in general, the 4-8-4s were newer, the "Bullet Nose Betties" were amongst the last steam locomotives built for CN (who didn't buy steam locomotives as late as CP).

I have always been struck by the similarity of the 6060 class 4-8-2s and the 5700 class 4-6-4s, particularly after the conical nose was removed from the 6060 class and a close comparison of the boiler dimensions on those two types is interesting.


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Posted by Shadow the Cats owner on Wednesday, July 14, 2021 9:51 PM

All you have to do is look at the so called War Baby 2900s of 4-8-4s delivered to the Santa Fe to see just what a hi powered hi speed Northern could do.  They were rated at 85 percent of the actual power output when it came to tonnage ratings to allow a safety factor in train weight.  Heck look up the 5010 series of Texas types the Santa Fe had.  Those were the most powerful non articulated engines produced.  They came close to the Big Boys in horses and had more tractive effort than a challenger.  Some where leased to the Pennsylvania railroad in the mid 50s and they out pulled the J class Texas type the Pennsylvania had by 25 percent hauling ore and coal trains.  

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Posted by CSSHEGEWISCH on Thursday, July 15, 2021 10:00 AM

It could easily be argued that Santa Fe's Big 3 (4-6-4, 4-8-4 and 2-10-4) were the ultimate non-articulated steam power.

The daily commute is part of everyday life but I get two rides a day out of it. Paul
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Posted by daveklepper on Thursday, July 15, 2021 11:45 AM

Yes, Definitely.  But also the N&W J.

And for articulated steam the N&W Y-6 and A certainly givre the Big Boy some serious competition.

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