Steam & Excursion > What is a saturated steam compound locomotive?

I was advised to post this here.  

Picture 1, Title:  Northern Pacific steam locomotive #1263, Fall City, ca. 1920.  Photographer: Longworth, George.  Date: circa 1920.  Caption: Northern Pacific Railway locomotive #1263 and a caboose tie up for the day in a spur near Fall City. It is shown here as a saturated steam compound locomotive. It was rebuilt with superheating and simple cylinders around 1923. 
 

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In thiis picture the steam engine is a compound steam engine.  The steam is is used first at high pressure, but then it is is exhausted to be used a second time at lower pressure.  Since it is lower pressure the pistons (cylinders) are bigger to provide more surface area.  This is more commonly seen on articulated locomotives known as malets, named after the inventor.  (not all articulated locomitives are mallets)  C&O 1309 will be entering service and is a compound.  A saturated steam locomotive also sometimes refers to a non superheated steam engine, aka soaker.  I'll let others explain the workings of how this was done and their acceptance.  Hint, you sure don't see many non articulated compound engines like this. 

Tominde Wrote:

> Hint, you sure don't see many non articulated compound engines like this. 

Santa Fe had hundreds of them in various wheel arrangements: 4-4-2, 4-6-0, 2-6-2, 4-6-2, 2-8-0, 2-8-2, 2-10-0, and 2-10-2.  They tried a number of different compounding schemes including tandem compounds (same setup as NP 1263), Vauclain compounds with the high and low pressure cylinders stacked and driving a common crosshead on each side, balanced compounds with the low pressure cylinders in the usual place and the high pressure cylinders inside the frames driving a cranked axle, and even a couple of cross compounds with just two cylinders: high pressure on one side and low pressure on the other.  The reason you don't see many photos of them was that the railroad rapidly grew disenchanted with the frequent, time-consuming maintenance these beasts required.  Santa Fe even fitted some tandem compound 2-10-2's with permanently-mounted jib cranes to swing the high pressure cylinders out of the way in the shops:

https://digital.denverlibrary.org/digital/collection/p15330coll22/id/57506
https://digital.denverlibrary.org/digital/collection/p15330coll22/id/57308

Santa Fe bought its last new compounds in 1914, and began a massive program of simpling a few years later that saw most of these locomotives converted to two-cylinder, single-expansion machines (or scrap metal in the case of many of the 4-4-2's) by the end of the 1920's.  There weren't a lot of railfans taking pictures that early, so photos are somewhat scarce.

While not operated by steam, the compressed air, standard-gauge, 0-4-0 #1 on display inside the Age of Steam Roundhouse Museum in Sugarcreek, Ohio, is a rare, cross-compound locomotive having just two cylinders, an 11"x18" 250 psi high-pressure cylinder on the "fireman's" side and a 22"x18" 50 psi low-pressure cylinder on the opposite (engineer's) side. It carried 800 psi of compressed air in three heavily reinforced tanks, and used a reducing valve to lower that air pressure for its first use in the 250 psi high-pressure cylinder. Before that pressurized air could be exhausted and reused in the 50 psi low-pressure cylinder, it had to pass through a heat exchanger that warmed the expanding-but-freezing-cold gas to prevent ice from forming on the locomotive's piping! (If you remember your high school physics class, when a gas is compressed and pressurized it gets hotter, and when a gas is decompressed and depressurized it gets colder.)

This ugly duckling locomotive wins the hearts of everyone who sees it, hears its interesting story and appreciates all the physics that went into its design, use and eventual replacement by new technology (the fireless cooker). If you have an opportunity, you should plan to see it and the other steam locomotives, diesel engines, passenger cars, freight equipment and cabooses displayed at the Age of Steam Roundhouse Museum. [url=http:// www.ageofsteamroundhousemuseum.org​ ] www.ageofsteamroundhousemuseum.org​ [/url] Be safe.

John B. Corns


 

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That's wild.   Took a serious compressor to fill that puppy. 

Does it ever operate?   Who built it?

So, technically, when that little 0-4-0 is charged, it is indeed a load of hot air.

Mary McPherson
Dongola, IL
Diverging Clear Productions

Compressed air operated locomotives were used in places where you just couldn't have a fire, like inside a mine.
Since it didn't consume oxygen or expell carbon monoxide it was "safe" to use underground since it wouldn't kill the miners.

"The Age of Air Roundhouse" just doesn't have the same ring to it...