October 20th, 2007

You may have noticed a "new" section on the site called United States Patent Drawings The drawings displayed are part of a group I've been collecting from http://www.uspto.gov/ , the patent office site. As I mention in the introduction, there are drawings in that database that cannot be found anywhere else on the web. Some  are probably not available anywhere.

Case in point, Baldwin Locomotive Works "polyplex" locomotives. While drawings for the Triplex may be found in old magazines, the derivatives of that design are impossible to find outside the Baldwin archives.

As far as the original tripex goes, the patent office has two different sets of drawings, The one on the left dates from 1912 and was submitted by George Henderson,  a consulting engineer for the Baldwin Locomotive works. Judging by the cab windows and wheel arrangement this drawing is not of any of the engines actually built. Alll the Erie locomotives had different window spacing. None of the Triplexes were built with reversed cylinders under the tender. On the Virginian, the wheel arrangment was actually 2-8-8-8-4. The Virginian engine, #700, was not a compound.

The first of these behemoths was delivered to the Erie in 1914. It was assigned to pusher service on the Gulf Summit grade near Susquehanna, Pennsylvania. Numbered 2603 and known to most railfans as the "Matt H. Shay" the engine developed a whopping 160,000 pounds of tractive force. She weighed in at nearly 854,000 pounds, most of it (about 90%)available for adhesion due to the number of drivers. The tractor drive, the driver set under the tenders, was thought to give the locomotive an advantage over engines with conventional tenders. The extra drivers could take advantage of the weight of the fuel and water, normally a part of the total weight of the train being pulled or pushed. While many authorities assert that the tractor drive would be almost useless as the coal and water ran out, Baldwin considered the short runs the locomotives were assigned to. Most of the time, the tender would be full while the engine was operating.

Because of the large amounts of steam required to feed all those cylinders the Triplexi were among the first locomotives to use mechanical stokers. Theengines could not be hand fired when running under full steam. They used a Street's stoker with steam jets to distribute the coal on the grates. Unlike more modern stokers which used a screw to feed coal to the firebox, the Street used a continuous chain conveyor of moving small buckets.

Two other Tripexi were built for the Erie. None of the locomotives were considered successful. Despite it's size, the boiler was just not big enough to supply steam for all six cylinders . Part of this problem is now thought to be because the tender stack impaired the draft from the firebox. This cut down the efficiency of the boiler. In short, the Triplexes were unable to keep the fire hot enough to maintain full steam.

The drawing on the right was submitted a few years later in 1916 by Sam Vulcain, a long time director of the Baldwin Locomotive Works. This may be the patent for the "simple" version of the Triplex used on the Virginian, though the drawing suggests the front and second cylinders are still compound. Like the Erie engines, the Virginian version suffered from the inability to generate full steam. Once again, Baldwin has chosen to use the tender stack, thus cutting down on the amount of draft available to the firebox.  Unlike the Erie locomotives, which were scrapped, the Virginian locomotives were rebuilt in to smaller, more efficient engines. The resulting 2-8-8-0 and 2-8-0 locomotives served the railroad until it was absorbed by the Norfolk and Western.

Both these "tripexi" are pretty common as "polyplexi" go. Far more rare is this drawing of yet another "triplex". Probably only part of a "quadraplex" the drawing is minus the tender, which could have been conventional with no underlaying "tractor" drive, This  would make it a VERY interesting example of the breed. Without the tender stack, this variant might have actually worked.  Might have, that is, except for the fact that it's boiler is actually articulated in two places. Experience with similar Santa Fe engines would have taught Baldwin engineers that this isn't really a workable idea. While the forward section of the boiler would be full of smokebox, superheater, and other equipment the two other portions would actually contain water (and firetubes). This proved to be a shortcoming on the Santa Fe engines, where the flexible connection developed leaks. It would undoubtedly have been a problem here also. So we end up with just another Triplex unable to make full steam. Although the Santa Fe flexi-boilers were actually built, no examples of this design ever left the drawing board.

In may be that this particular design was actually meant to see service on the Santa Fe, the only road to ever use flexible boilers on any locomotive.

If the previous locomotive was actually meant to have a tractor drive, it would be a direct cousin to the  locomotive pictured to the right. Patent #1100563 is a "true" quadraplex. Like #976014 this engine has a flexible boiler. The tender also sports it's on stack. Both items would have been enough to add this locomotive to the stack of failures the Triplexi would become. This engine would have been a compound with the exhaust from the center cylinders feeding the outer sets. An unusual aspect of this locomotive (as far as polyplexes are concerned) is the front cab. By 1913, the date of application, fifteen cab-forwards had been running on the Southern Pacific for three years.

If we speculate that the previous patent could have been for a Santa Fe engine, is there a possiblity this drawing was for a new Southern Pacific engine?

#1100563 is probably largest of the polyplex breed. There are stories of a "quintaplex" having five sets of drivers. Almost certainly it would have incorporated the weaknesses of its brethren. Certainly too, it would have added additional complexity to the already intricate collection of cylinders, valve gear and rods. Adding another eight drivers to the bulky length of that boiler may have warranted yet another flexible joint in the boiler, introducing more potential for trouble.  If we note that these locomotive have two cabs, we may speculate that two crews might be neccessary to run such a monster, in which case it would be just as labor intensive as two seperate locomotives.

It turns out that the quadraplex drawing is not the last in the series. In 1927, Sam Vulcain attempted to resurrect the species by submitting this drawing for yet  another Triplex. The drawing displays improvements on the original design, particularly the elimination of draft robbing tender stack. The critter istill appears to be a compound, with the first set of cylinder exhausting into the second. The third set, under the tender in the tractor drive are smaller low pressure cylinders. This begs the question of whether Baldwin had solved many of the issues inherent in the earlier engines.

By 1927, however, this would have been a moot point. "Super Power" locomotives had begun the appear. Types like the Berkshire, Mountain, and Northern were becoming common and displacing the big articulateds for all but the heaviest trains. Simple articulateds like Norfolk & Westerns A and Y class were proving that the complexity of a compound (especially one with six cylinders) wasn't necessarily the solution to the problem.

By 1930, diesels would be making strong inroads into the realm of steam. It would be the beginning of the end, especially for giants like the "optiplexi". Like the dinosaurs, the triplex and kin vanished from the face of the earth.

Well I think that's about it for now...Thanks for listening.