Virginian Triplex

[fredswain]

You are correct. The middle set of cylinders received the high pressure steam and after leaving them it was divided equally to the front and rear cylinder sets. It was a bit strange how they did this though. The right hand side high pressure cylinder exhausted to the front set of low pressure cylinders. The left hand high pressure cylinder exhausted through the rear set of low pressure cylinders. The front set exhausted through the smoke box and out the stack and created the only draft for the firebox which was ultimately one of the problems with that engine. Not enough draft and not enough heat available to supply the engine with any appreciable steam above 10 mph or so. The rear set of cylinders passed through a feedwater heater and then exhausted out the stack on the rear of the tender. Another problem with that engine had to do with adhesion of the rear drivers. As the tender emptied, it obviously got lighter. This reduced the available adhesion on the rear drivers and they'd slip before the others would. Unfortunately the throttle pulls down all drivers so when the rears are at their limits the rest aren't which was a waste. Nice idea and it looks really neat but it didn't work that well in the real world.

[KCSfan]

The cylinders on both triplexes were the same size, (6) 36" x 32" for Erie and (6) 34" x 32" for VGN.   The center cylinders were HP and the front & rear were LP.

Felton,

I guess my eyes were deceiving me when I thought I noticed a difference in the cylinder diameters. Would I be wrong in assuming that the exhaust steam from the high pressure cylinders was shared equally by each of the two low pressure cylinder sets? That would explain the size of the low pressure cylinders on the triplexes as compared to a more conventional compound whose low pressure cylinders were much larger than the high pressure ones. I've always thought that the cylinders on a conventional compound were sized so that both the high and low pressure sets delivered an equal driving force to their respective driving wheels. Am I wrong in assuming this was also a design objective in the case of the triplexes?

Mark

[feltonhill]

The cylinders on both triplexes were the same size, (6) 36" x 32" for Erie and (6) 34" x 32" for VGN.   The center cylinders were HP and the front & rear were LP.

[KCSfan]

On conventional compound locomotives steam was exhausted from the high pressure rear cylinders to the larger diameter low pressure front cylinders. It's a bit difficult to tell from the photos but it appears to me that the Erie triplex's middle and rear cylinders are about the same size suggesting that they were both high pressure and and the front cylinders are larger and therefore were low pressure. On the Vgn's triplex the middle cylinders seen to be the smaller high pressure ones and both the front and rear appear to be larger low pressure cylinders. If that's correct, what was the steam flow on the triplexes of each road?

Mark

[timz]

In a test, one Triplex single-handedly hauled 250 loaded cars - that was 16025 tons - at a speed of 13.5 mph.

In May 1921 a Virginian 2-10+10-2 took 100 loaded six-axle gons, supposedly totalling 16000 tons, from Princeton to Roanoke (with pushers here and there). The Railway Age article made it sound like that was fairly unprecedented. Anybody know where and when the Triplex did whatever it did?

[dredmann]

For a decent on-line overview of the triplex locomotives, see http://www.steamlocomotive.com/articulated/virginianxa.shtml and http://www.steamlocomotive.com/articulated/eriep1.shtml.

 

[feltonhill]

N&W was regularly dispatching 16,000-18,000 ton coal trains from Williamson to Portsmouth behind a single Class A ca. 1955-1958. Peak speeds were 40-45 mph where grade and curves were favorable.  This performance became possible because of the increasing use of larger cars, which have less rolling resistance per ton.  The triplexes did not have that advantage and were stuck with many smaller cars.

Documentation for the Class A can be found in at least two books:  N&W Giant of Steam, Revisied Edition by Lewis I. Jeffries and the Rails Remembered series (Vol s. 3 and 4 IIRC) by Louis Newton.

I believe the Erie triplexes could be called semi-successful because they were in service several years.  The Virginian triplex was not successful by any known measure.  It was quickly returned to Baldwin and rebuilt into a 2-8-8-0 and a 2-8-2, both of which lasted to the end of steam.

[martin.knoepfel]

How long did the VGN and the Erie respectively keep their Triplexes in service? this would provide some information as to whether the operating departments considered them useful or a failure.

[tpatrick]

The core of the problem with the Erie Triplexes was not the size of the grate. Rather, it was the fact that the rear cylinders exhausted directly to the air. This means that only half of the exhaust went through the smokebox, resulting in inadequate draft. The grate was enlarged from 90 sq. ft. to 122, but even that was not enough to compensate for the dearth of draft.

Still, the Triplex was an awesome machine for its day. Its tractive effort was rated at 160,000 pounds. In a test, one Triplex single-handedly hauled 250 loaded cars - that was 16025 tons - at a speed of 13.5 mph. That may still stand as the record for the longest, if not the heaviest, train ever handled by a single engine. To be fair it must be noted that pushers were used to start the train because the Triplex was powerful enough to pull the train apart while starting.

That would be impressive even today.

[JonathanS]

Thanks.  If Erie got three of them, did they have better luck running them?  Sounds like it was a project that didn't go very far for the Virginian Railroad.

Most authorities state that the Triplexes were a flop on the Erie as well.  If that was true, why would the Erie go back for two more after testing the prototype for two years?

On the Erie the Triplexes were designed for and were used to replace double headed and triple headed pushers on one specific grade.  The Triplexes did that very well.  The fact that the firebox could not keep up with the cylinder demand was not a problem in this application.  By the time the boiler had lost pressure the train being pushed had already reached the summit and the Triplex was no longer needed.  The pressure was rebuilt while the engine was returning downgraded and while it waited for its next assignment. 

The Erie's opeating department (and for many other railroads) of the era was not interested in speed.  Rather they wanted to get every BTU of energy out of each pound of coal that they could.  A locomotive with a firebox that could keep up to the steam demand in the service that the Erie's Triplexes were assigned to would waste a lot of fuel in the idle times.  The Triplexes were designed to perform a specific job using a minimum of fuel.  They did that and did it for a number of years.  But since they couldn't run 100 miles at 30 mpg many "experts" consider them a failure.

[fredswain]

Here's a page with some info:

http://www.dself.dsl.pipex.com/MUSEUM/LOCOLOCO/triplex/triplex.htm

 

 

[DarkTalon]

if you need more photos, MTH Trains makes some models of them in both O and HO scale. As far as I've read they weren't very successful anywhere, hence why only 4-5 of them are known, and were never intended to actually haul trains, but rather be used as cut-ins or other such helper locomotives..

[Winant]

Thanks.  If Erie got three of them, did they have better luck running them?  Sounds like it was a project that didn't go very far for the Virginian Railroad.

[CSSHEGEWISCH]

The VGN Triplex (Erie also had three) was a compound locomotive built by Baldwin to the designs of George Henderson.  It had a surprisingly small firebox and used steam almost faster than the boiler could produce it.  On VGN it was considered to be a flop.  More information can be found in "Articulated Locomotives" by Lionel Wiener and "The Virginian Railway" by H Reid.

[Winant]

I recently saw a picture of a Virginian engine prototype, c. 1916 called a triplex.  Looked like a 2-8-8-8-4 with the final set of 8 drivers partially under the tender.  That's all the detail in the picture, no photo credit or anything.  Does anyone have further information on this type of engine?

 Thanks