Compressed Air 0-4-0 No. 1
Builder: H.K. Porter – Pittsburgh, PA
Built: November 1915
Serial No: #5731
Wheel Arrangement: 0-4-0 3-tank Compressed Air (Pneumatic)
Driver Diameter: 36"
Cylinder Bore x Stroke: 11" x 18" high pressure; 22" x 18" low pressure
Boiler Pressure: 800 psi, reduced to 250 psi (HP cylinder) and 50 psi (LP Cylinder)
Pulling Power: 10,000 lbs. tractive effort
Engine Weight: 30 tons
Engine Length: 22 feet
Class: PPP ("Pneumatic - 3 storage tanks")
Fuel: Compressed Air, pressurized from on-site storage tank
Status: Non-operational


H. K. Porter had established a reputation as a builder of rugged, specialized locomotives for small industries and short line railroads. It could custom-build a steam locomotive quickly and efficiently, with a system of interchangeable parts—pistons, wheels and boilers in various sizes—that could be combined to suit a customer's specific requirements. During 1890 Porter built its first compressed-air locomotive, having two cylindrical tanks that held stored, pressurized air instead of steam to move the pistons. This allowed locomotive use inside enclosed areas without the fumes, heat and sparks associated with burning coal. Porter built more than 400 compressed air locomotives for use in mines, factories, textile mills, refineries, munitions plants, food handlers, sugar cane plantations and even the street railways of New Orleans. Other companies constructed compressed air locos, but by 1900 Porter had captured 90% of the market and built about 400 such lokies during 1890-1930.


A typical Porter compressed air engine had one storage tank (800 to 1200 psi) that used a reducing valve that throttled-down the air to about 150 psi at the cylinders. Larger air locomotives were compound with an 11x18-inch, 250 psi high-pressure cylinder located on the left side that used a special Porter-design, ball-bearing, balanced slide valve.  The 22x18-inch, 50 psi low-pressure cylinder with a plain slide valve was carried on the locomotive’s right side to reuse the exhausted air from the left side cylinder. Such two-stage engines employed a reheater between the two piston stages to warm the still partially exhausted (but cooled) compressed air. This air passed through a heat exchanger that was warmed by ambient air drawn through it by using the low pressure exhaust air in an ejector. Note that 800 psi is a much higher pressure than normally used in steam boilers, which rarely exceeded 300 psi. This is why compressed air locomotives were constructed with inch-thick steel tanks held together with large rivets, an obvious characteristic of all such machines. Air for locos was compressed in multi-stage machines, stored and distributed by trackside pipes to recharging stations along the tracks. Such extra piping was a more expensive way to distribute the compressed air to distant recharging locations. A compound loco operating on a sugar plantation could haul 13 carloads of cane seven miles on one charge of compressed air, and saved paying the wages of a fireman and $10 worth of coal during each day of operation.


Porter in 1915 built its first fireless locomotive (for a railroad tie creosote treating plant in Orrville, Ohio) using a large, heavily-insulated tank containing piped-in, boiling hot water in place of a fire-tube boiler. As the steam was used the pressure inside the tank was reduced, thus lowering the internal pressure which allowed the water to begin boiling again and generate additional steam. As the locomotive’s internal steam pressure built-up, the water stopped boiling until that steam was used-up, and the cycle would repeat. It was ingenious!  Such “fireless cookers” were less expensive to build, proved more useful and reliable than compressed air locomotives, and did not require miles of trackside pipes carrying compressed air in order to recharge a locomotive.  Soon, Porter dominated this niche market, as well, and the fireless cooker began replacing the compressed air locomotive.


That same year (1915) Porter built a large, three-tank, compressed air locomotive for use on a sugar plantation in Camaguey Province in Cuba. It was designated as a class “B-PPP”—the “B” means that it has an 0-4-0 wheel arrangement, “P” stands for “pneumatic” and the three-P symbol “PPP” indicated that the locomotive had three tanks or cylinders containing the compressed air. Carrying boiler serial number 5731, this particular loco was ordered by Dibert, Bancroft & Ross, a large Louisiana iron foundry that manufactured, among other things, machinery for the processing of sugar from cane. With its first attempt at standardization, during 1915 the company designed, constructed and completely equipped four ingenios azucareros (sugar mills) in Cuba for the Palma Sugar Company, whose principal owner at that time was none other than General Mario G. Menocal, el presidente of Cuba. He nixed the use of old-fashioned, steam-powered machinery of any kind on the ingenio, and ordered that electric motors be used throughout the new sugar processing installation.


A sugar industry newspaper said that the new locomotive “will be operated by compressed air furnished by an electrically driven compressor in one of the places the owners calculate that the liberal use of electric drive will cut down the bagasse [woody fibers from crushed cane used as boiler fuel] consumption in the house [factory] to the point where an excess will be available for generating [electric] power to be used outside the factory proper.  Beside the calculated fuel economy that will result in the use of this compressed air locomotive, the owners of the factory in question will be in a position to know with absolute certainty that no flying sparks will start cane fires, for the new locomotive is to be used not only in a batey [a sugar workers’ town consisting of barracks located close to the cane fields], but also for hauls of several kilometers from the fields.”


On November 6, 1915, this PPP curiosity was placed onto a flatcar at the H.K. Porter shops in Pittsburgh, and went directly to New Orleans where it was loaded aboard a ferry for the sea voyage to Cuba. Delivered to the ingenio on Thursday morning, December 16, this was the first compressed air locomotive of its type used anywhere in Cuba.  A three-inch pipeline was laid along the seven miles of track out in the cane fields so that this lokie could be recharged whenever it needed a fresh supply of compressed air.  For the first time fears of fires consuming contiguous fields of cane were unfounded, as the new compressed air locomotive performed flawlessly with no flying sparks because there was no fire.


As a result of the drop in sugar prices at the end of World War I, economies of scale and the growing 2,500-mile network of railroads in eastern Cuba (versus 360 miles in Cuba’s western end), distant cane fields became easily connected to the larger, more efficient foreign-owned sugar mills, while the small, domestically-owned mills located in western Cuba quickly became unprofitable. However, that transition also precluded further investment and diversification of the Cuban economy since the foreign-owned industrial mills transferred their profits back home to the U.S. As a result, export-led growth based on high capacity sugar production ultimately doomed the Cuban economy to the enormous boom/bust cycles (the “Dance of Millions”) inherent in export-led primary product production and a lack of diversified development.  Consequently, Cuba’s once-profitable sugar industry went bust during 1921.


Reportedly, this odd-looking lokie was repatriated back to the United States sometime after 1921, and during 1935 was working for the New Orleans Sewage & Water Board where it switched freight cars. After being retired, this lokie, along with other unusual rolling stock from the New Orleans’-area, was placed on display in Mel Ott Park in Gretna, Louisiana.  This compressed air locomotive was acquired by the Louisiana Steam Train Association (owner and sometime-operator of ex-Southern Pacific 2-8-2 #745).  During 2015—its 100th anniversary year—this now one-of-a-kind PPP compressed air locomotive was purchased from LSTA by Age of Steam Roundhouse.  It arrived by highway truck at the roundhouse on November 10, 2015, but won’t be running anytime soon, as our AoSRH air compressors do not generate enough pressure to make this critter crawl.


Most compressed air locomotives were small, narrow-gauge affairs that had just one or two tanks to carry the high-pressure, compressed air for operation in mines, factories and mills, but this is one of the largest, three-tank locomotives ever designed for extended outdoor use with heavier loads. The U.S. Navy was a big user of these Porter-built, unusual appearing, three-tank beasts for the movement of live ammunition at stateside naval piers. Three-tank compressed air locomotives switched railroad boxcars of munitions—cannon shells, depth charges, torpedoes, etc.—at naval shipyards on both coasts of the U.S.  They were nearly perfect for such potentially dangerous environments, producing no sparks as found in most other fire-breathing steam locomotives.  Resembling a stack of three torpedoes, motorists turned their heads to watch the low-boy trailer head up the highway from New Orleans to Ohio with a load even stranger than naval ordnance. Two of the 40-inch diameter compressed air storage tanks are 15 feet long, while the third is 17 feet in length.  Ironically, these locomotives’ storage tanks became heated from the hot, high-pressure compressed air, while ice formed at the opposite end from that same hot compressed air being exhausted and quickly losing its heat.


Compressed air becomes very warm under pressure, and immediately can chill to below freezing temperatures when exhausted quickly into the atmosphere.  Therefore, the used, frigid air that has been exhausted from the high-pressure cylinder has to be heated before it can be used a second time in the low-pressure cylinder. After its use in the high-pressure cylinder on the locomotive’s left side, the freezing-cold, low-pressure exhaust air passes to the interheater, a device similar to a heat exchanger whose complex of small tubing allows the higher ambient temperature of atmospheric air to heat this exhausted, low-pressure air.  A horizontal conduit above the right side driving wheels serves as the exhausted low-pressure air’s delivery pipe from the interheater to the right side, low-pressure cylinder.  There, the low-pressure air is used at 50 pounds psi in order to wrench every last ounce of power from the once-compressed air before it is exhausted into the atmosphere.


Our newly arrived compressed air locomotive was lifted off the low-boy trailer by nylon web straps attached to Age of Steam Roundhouse back shop’s travelling overhead crane, and the truck was driven out of the back shop. Little by little the loco’s 36-inch diameter driving wheels were lowered gently onto the standard-gauge rails, and the peripatetic compressed air lokie was at its new (and final) home.  At exactly 30 tons in weight, this little loco was the heaviest object ever lifted by our 30-ton capacity shop crane.  During regular service this particular loco produced 10,000 pounds of tractive effort.


Several single- and double-tank narrow-gauge compressed air locos survive from the South Dakota mining industry, but, as far as is known, this is the only standard-gauge compressed air locomotive surviving in the U.S.  It is certainly the sole remaining, Porter-built, three-tank compressed air locomotive in the United States, if not the world.