Why did some railroads replaced 4-8-2 Mountains with 4-8-4 Northerns on passenger and freight trains.
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...
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.
daveklepperUsually 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.
GN O-8 2-8-2
T. E.--75,900
Drivers--69"
Grate area--98.5
Weight on drivers--325,000
NKP S-3 2-8-4
T.E.--64,135
Grate area--90
Weight on drivers--266,000
Erie S-4 2-8-4
T.E. 78,900
Drivers-69"
Grate area--100
Weight on drivers--286,000
Pretty impressive, for a Mikado, eh? Note in particular the weight on drivers.
Ed
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.
Peter
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.
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.
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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