General Discussion

In (another) good book I found,Black Gold-Black Diamond by Eric Hirsimaki, I ran accross a term, that I can't quite get the meaning of from the context of the writing.
What does the term "duplex" mean, in relation to a steam locomotive? In this case, it's used in a description of the "one and only" PRR S-1 class of locomotive, (according to the book, "the most powerfull steam locomotive ever built"?). Thanks

Duplex in this context referred to a rigid-frame four-cylinder locomotive with divided groups of driving wheels; each pair of cylinders drove its own group. They appeared in the following wheel arrangements: 4-4-4-4, 6-4-4-6 (the PRR S1 referred to), 4-6-4-4 (PRR Q1) and 4-4-6-4 (PRR Q2). The 4-4-4-4s were all PRR T1s except one; the Baltimore and Ohio had one class N-1 4-4-4-4 whose rear cylinders were located beneath the firebox and drove the rear two pairs of driving wheels. The only 4-6-4-4 also had this arrangement. All were "one-offs" except the T1 and Q2.

The theory behind it was to reduce the weight of the reciprocating parts of each engine by dividing the power among two sets of driving wheels. Whether the Q2 and T1 were successful or not depends upon whom you ask. The others were not considered successful.

BTW - the Pennsy did not use a dash in its class designations; it was S1, not S-1.

Old Timer

Re: the PRR T1...
I've always read mixed reviews about them. From what I've been able to gather, they could run two miles a minute with a 16 car BROADWAY LIMITED but were so slippery starting that they couldn't make it over their own shadow without sand and a pusher. I suspect the truth lies between the extremes. What are the opinions here on the board? Greatest thing since the GG1 or biggest disappointment until Penn Central?

I thought that the main reason for developing the the duplex locomotives was because the piston thrust on the crankpins of the conventional 4-8-4s was about as high as it could get and sheared off crankpins were becoming a problem. By dividing the drive and using smaller cylinders, the piston thrusts were greatly reduced without a corresponding loss of power.
Malc.

The piston thrust force was one of the reasons for dividing the drive. Old Timer's summary is probably about the most succinct we'll see on this thread.

Most would not and could not call the PRR T1 successful in the Niagara or N&W J sense of the word. The main problem with the T1's history in the past was the lack of original source documents and the complete willingness of some authors to publish unsupported hearsay or make a lot of vast assumptions with only half-..... well, you know the rest of the phrase. The T1's history has been the subject of more entertainment than fact. Believe me. its actual story is considerably more interesting than what's been published generally.

Eric Hirsimaki's book is one of the best for giving the overall picture of what PRR was going through and what some of the circumstances were surrounding the T1. His overall mission in both volumes of BGBD was much broader than the T1 (or Q2) so he didn't get into the details enough to adequately support some of his opinions IMO. However, from a corporate, financial and operations standpoint, it's an exceptional read.

Most of the stories about the T1 have been repeated over and over for almost two generations. That still doesn't make them fact, nor does it explore the extenuating circumstances related to the event. The best I can do in a single sentence is this: the T1 could not be considered successful, but neither was it as ineffectual as some would have us believe.

The Q2 wasn't a better performer than the J1 on a 50-mph freight RR, and cost more to operate. The Q2 (and the T1 as well) were higher speed locomotives and if they couldn't operate at that speed range, they tended to use more coal and water per unit of out put than conventional, similar sized locomotives. This observation is based in part on comparative tests between the PRR T1/N&W J and PRR Q2/N&W A on N&W in 1948. That's why the Q2s only lasted a few years while the J1's continued on until the end of steam on PRR.

QUOTE: Originally posted by Kevin C. Smith Re: the PRR T1... I've always read mixed reviews about them. From what I've been able to gather, they could run two miles a minute with a 16 car BROADWAY LIMITED but were so slippery starting that they couldn't make it over their own shadow without sand and a pusher. I suspect the truth lies between the extremes. What are the opinions here on the board? Greatest thing since the GG1 or biggest disappointment until Penn Central?

Suggests an excellent boiler and steam distribution, but too much reduction in adhesive weight . Does this accord with others opinions, or am I stating the obvious ?

The T1 had an excellent although somewhat smallish boiler, and very low pressure losses from the drypipe to the steam chests. Made for a potent combination as far as power went, but required skill in its application.

As far as adhesive weight is concerned, the average axle load on the drivers was 67,050 lbs for the two prototypes to 69,978 lbs for the production lot of 50, depending on which source you use for WOD. This is typical for a 4-8-4, although some had up to 74,000 lbs per driving axle (SP&S E1's).

Part of the T1's reputation for slipperiness came from the inability or unwillingness of many enginemen to handle the T1 differently from the K4 when starting. Sort of like driving a Ferrari the same way you'd drive your average go-to-work transportation. Probably wouldn't work out too well. But would you blame the car or the driver??

In hindsight (and IMO) PRR was wrong in going with the 50 production T1's. If the co. wanted to stick with steam they should have built a straightforward 4-8-4 (maybe similar to a UP FEF1 or 2). Many have equated the T1's to a great disaster. Mistake yes, disaster, I'm not so sure.

PRR lost money in 1945/46 just as the T1 production order was being delivered. Nothing will change a corporation's mind quicker than that. Plus PRR was under considerable competitive pressure from NYC in passenger service, and Central was already dieselizing its trains. PRR changed direction and committed to diesels about the time the final T1 was placed in service.

From that point on the T1 didn't matter, nor did any other steam locomotive on PRR. The company needed to cut costs quickly and diesels were the way to do it. Had PRR duplicated NYC's success with the NIagara or somehow adapted N&W's J to its load guage, it wouldn't have made any significant difference. On a cost basis, nothing could compete with the E7's that were already on the property in late 1945. Future PRR President Jim Symes already recognized this. The die was cast. It was just a matter of time.

QUOTE: Originally posted by Old Timer Duplex in this context referred to a rigid-frame four-cylinder locomotive with divided groups of driving wheels; each pair of cylinders drove its own group. They appeared in the following wheel arrangements: 4-4-4-4, 6-4-4-6 (the PRR S1 referred to), 4-6-4-4 (PRR Q1) and 4-4-6-4 (PRR Q2). The 4-4-4-4s were all PRR T1s except one; the Baltimore and Ohio had one class N-1 4-4-4-4 whose rear cylinders were located beneath the firebox and drove the rear two pairs of driving wheels. The only 4-6-4-4 also had this arrangement. All were "one-offs" except the T1 and Q2. The theory behind it was to reduce the weight of the reciprocating parts of each engine by dividing the power among two sets of driving wheels. Whether the Q2 and T1 were successful or not depends upon whom you ask. The others were not considered successful. BTW - the Pennsy did not use a dash in its class designations; it was S1, not S-1. Old Timer

It would seem to me, that this would be something of a "rail straightener" on curves? What would be the advantage of this type of layout over an articulated frame set-up?.
Thanks

germanium,

One of your fellow countrymen, Philip Atkins, wrote what is probably the most lucid comparison of the PRR T1 and NYC Niagara in his book -

Dropping the Fire, the Decline and Fall of the Steam Locomotive

He is/was associated with the National Railway Museum in York.

André Chapelon designed a duplex, too. It was a 2-10-2 for heavy coal and ore trains. However, in Chapelons design, the 2nd and the 3rd axle were coupled by inside-rods, unlike the T1

Somewhere on here, a fellow opined that the "problem" with the T1 lay not with its design but rather with the men operating it. Let me float what I remember of the post, and get it commented upon:

-The T1 was a good locomotive, designed to replace doubleheaded K4/K4s locomotives on the premier passenger trains on a 1 for 2 basis. Eliminating the second locomotive meant a 50% cut in crews and salaries, thus eliminating work.
-Conscious of the above, a lot of veteran PRR engineers suddenly found themselves incapable of handling the T1, but were quite capable of handling a two-crew train. "Gee, boss, that new locomotive is slippery. How about we go back to the pair?" "We'd have to call two crews." "Huh. Imagine that. Ain't that a shame?"
-With the locomotives being deliberately mishandled, of course there would be problems.

Eh, an ignominous end for arguably the best-looking non-Norfolk and Western steam locomotive ever built. It looks like something from H.R. Giger's sketchpad-in a word, evil.

To support NW611's recall and my earlier statement regarding T1 operation, here's a quote from a PRR internal memo dated 9/29/45 (from Hagley Library):

After we had taken sand at Conemaugh the engineman had the train moving and if he had left the throttle in its position, the locomotive would have hauled the train away, but he jerked it open, the locomotive slipped, the train stalled and we had to put a pusher on to get the train away.

This quote was take from a report by Asst. ME Decker who was riding the locomotive during an extensive over-the-road test period where 6110 and 6111 were being used on regularly scheduled trains.

Previous paragraphs in the same memo describe this engineman's insistence on using a heavy throttle during poor rail condtions east of Pittsburgh, where he allowed the locomotive to slip so badly that Decker stated:

...I was afraid we would do some damage to the locomotive before the engineman noticed the slip and closed the throttle.

On the other hand, given one of the best crews, things were different. Three days before the above run, #6110 took a 21-car passenger train over the Middle Division, rain and fog the whole way, with two slips recorded between Harrisburg and Altoona. They left Harrisburg six minutes late and arrived two minutes early at Altoona. There were at least three intermediate stops and no difficulties were encountered at any of them. This run is described in PRR memo dated 9/24/45. It is based on a report by a Special Duty Enginman who was riding 6110 during the run.

The above contrasting operations were recorded during a two month test period during Sept and Oct 1945. Most or all of the reports of runs during this period have survived. How the crews operated the T1's had a major impact on their performance.

murphysiding -

Rigid frame layout of a duplex eliminated all of the high pressure jointed connections in the steam lines to each of the four cylinders. It also eliminated the hinged joint and pin in the frame at the rear cylinder saddle. This reduced the maintenance costs associated with articulated power. On a high speed loco such as the T1 the rigid wheelbase would add stability. There were lateral motion devices on #1 adn #3 axles IIRC. This enabled the T1 to get around any normal mainline curve. On the way to tests,5511 managed to traverse the entire N&W main from Columbus to Roanoke without incident. There were and are several curves that exceed 12 deg 30min

On the downside, the rigid frame didn't allow each engine set to find its footing on track that was not ideally surfaced. The design and maintenance of the loco's suspension was critical to its performance on average track. PRR changed the suspension design between the prototypes and the production lot, but it didn't always have the internal discipline to get the servicing done on a consistent basis.

Feltonhill - thanks for the info. I traced the details, and I'll try my local bookshop.
On another issue, regarding slipping - if those heavy-handed steam hoggers had tried throwing the throttle open in a similar manner on a diesel, would slippage then occur, or are there overrides built-in to stop "Hank the Yank" doing this ?

feltonhill:(and Old Timer) Thanks for the explanations. Would it be correct to assume that a duplex locomotive could be a rough rider on less than perfect track?
Thanks