Quote:
Originally Posted by DAEpperson
I saw the UP's articulated mallet come over and down Cajon Pass some 18 years ago. That was a machine to behold!
There is a cab-forward Big Boy at the California Train Museum in Sacramento - another articulated double boiler engine. They actually took the cabs off the rear and transferred them to the front. A Baldwin I think. Seems the snow tunnels were so long in the Sierras that the engineers would pass out from asphyxiation and smoke - so they put the cab on the front!
Also, the thing is so sophisticated for it's time that it won some prestigious engineering award.
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All of the later UP articulated engines were technically not "mallets". A true "mallet" is a "compound" engine, wherein the front low pressure cylinders run off of the exhaust steam from the rear, high pressure cylinders. Later articulated engines, like the Big Boys and Challengers, ran high pressure steam to both the front and rear cylinders, directly from the boiler.
None of these were "double boilered" engines. All ran a single boiler. The cab forward engines were on the Southern Pacific, not the Union Pacific, and they were not "Big Boys". Yes, they were built specifically for the long tunnels.
Compound mallet. Notice the size difference between the front and rear cylinders:
Modern compound mallet on the Norfolk and Western, the Y6B. While not "bigger" than the Big Boy, it had more tractive effort available:
A modern simple articulated engine, a Great Norther R2 (which would also out-pull the Big Boy). Notice the front and rear cylinders are the same size:
And, finally, the Southern Pacific cab forward. Also a simple articulated. They didn't so much put the cab on the front as turn the whole darn thing around. Notice the smokebox is on the back and the firebox is on the front:
