The proposed-but-unbuilt "C1a"

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Allen Hazen
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The proposed-but-unbuilt "C1a"

Post by Allen Hazen » Fri Sep 10, 2010 7:43 pm

Conventional wisdom has it that the PRR bought disastrously bad 4-4-4-4 Duplex locomotives as its post-war K4s replacement, while the New York Central more sensibly bought North America's best 4-8-4, the S1 (and S2) Niagara.
History is complicated. The PRR's T-1 may not have been quite as bad as people usually think (there has been a string about it on the PRR forum...), and, more surprisingly, the New York Central at least THOUGHT about getting a Duplex variant of the Niagara!

Alvin Stuaffer's 1981 book "New York Central's Later Power: 1910-1968" reproduces (p. 269) a New York Central engineering department diagram of a "Class C1A" 4-4-4-4. Richard leonard has a scan of this diagram (sent to him by someone else, and two small to read the lettering) on his excellent steam locomotive archive WWWebsite:
(There's MUCH more on his site: after looking at the diagram and photoshopped picture, explore: it's worth it.)

In the interest of ... promoting historical knowldege and enjoyable speculation? ... I will post some thoughts abut this "ghost" locomotive. Starting with the lettering on the diagram.
Upper right of diagram: Engine Designed for 18[degree] 30 [minute] curve
((Actual lettering is all capital letters.))
((Dimensional data written ON the diagram I'll put into a separate post.))

Bottom left: New York Central System
Office Eng'r Motive Power
New York, N.Y. Mar 28, 1945

Bottom right: Preliminary Diagram
Class C1A

My comment: March 1945 is when the prototype Niagara was delivered (with production S1b later that year). So apparently the C1a was considered as a possible follow-on, not as an alternative to, the 4-8-4.
(To be continued)

Allen Hazen
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Re: The proposed-but-unbuilt "C1a"

Post by Allen Hazen » Fri Sep 10, 2010 9:25 pm

Continuing the data from the diagram...
Near the center, blow the diagram:
Estimated weights
Engine truck 97000 lbs
Drivers 275000 "
Trailing truck 119000 "
Total engine 491000 lbs
Tender (Light) 181000
Tender (Loaded) 443000 "
Total engine & tender 934000 "

And, a bit to the right:
Max Tractive Force 64800 lbs
My comments:
Same weight on drivers as a 4-8-4 Niagara, but rather more on the trucks (where it wouldn't do any good for adhesion!): S1a was 91000 lbs on the endgine truck (S1b: 91400) and 105000 lbs on the trailing truck (S1b: 104600). And the tender is also somewhat heavier: the S1 had tenders that were 178000 lbs empty and 420000 loaded (about which, more anon).
Max tractive effort has been raised a bit from the S1 as well: NOT a good idea with a duplex!
(Weights for the Niagara from the New York Central 1946 locomotive diagram book, available at George Elwood's Fallen Flags site, )

For comparative purposes, PRR diagrams for their T-1 Duplex are available on the WWWeb at: ... z=sm&fr=ge
T-1 Engine truck: 99570 lbs
T-1 Drivers: 279910 lbs
T-1 Trailer: 122800 lbs
(At least post-1945: the T-1 prototypes had more weight on the trucks and less on the drivers: perhaps the equalization was modified to get better adhesion?)

How much of the weight difference was due to décore, I don't know: streamlined steam tended to be heavier than naked steam. But the PRR in general seems to have had a more relaxed attitude toward locomotive weight than the New York Central.

More anon.

Allen Hazen
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Re: The proposed-but-unbuilt "C1a"

Post by Allen Hazen » Fri Sep 10, 2010 9:40 pm

Lettering actually on (or in front of) the picture:
At rear of tender:
Water - 18000 Gals
Coal - 55 tons

On boiler:
--on rear course:
100" O D
--under sandbox:
Boiler pressure
290 lbs
--on front course:
90" I D

On cylinders (both sets):

In front of engine, height measurement:
(to the right of the height line "Max width" but the width given is illegible in the book: 10' plus ???)

Wheel diameters:
Tender and trailing truck: 41"
Drivers: 79"
Engine truck: 36"
My comments: (i) Wheel sizes are the same as on the S1b (S1a had different diameters on the two axles of the trailing truck): this is very much a Niagara variant!
(ii) Most S1 were operated with 275lbs boiler pressure, but at least one was tested at 290lbs: probably New York Central hadn't decided which would be best as of March 1945. And quite possibly C1a locomotives, had they been built, would have been operated at the slightly lower pressure-- New York Central seems to have thought that the advantages of pressures over 275 lbs weren't enough to compensate for the extra stress.

Lengths (given below the picture) in my next post.

Allen Hazen
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Re: The proposed-but-unbuilt "C1a"

Post by Allen Hazen » Fri Sep 10, 2010 11:33 pm

Lengths (shown below picture):
Front coupler to front axle of engine truck: 83.75" (given as a fraction: I'm using decimals as easier to type)
Engine truck wheel base: 90"
Rear axle of engine truck to first driving axle: 68"
1st to 2nd driving axle: 82"
2nd driving axle to c/l of rear cylinder: 62"
C/l of rear cylinder to 3rd driving axle: 76"
3rd driving axle to 4th: 82"
4th driving axle to front axle of trailing truck: 8' 10"
Trailing truck wheelbase: 66"
Rear axle of trailing truck to tender drawbar pivot (?): 95.5"
Tender drawbar pivot(?) to first axle of tender leading truck: 98"
((Comment: I assume the point measured here is the pivoting point, but not sure: anyway, it's somewhere in the neighborhood of the engine-to-tender flex point.))
Tender leading truck wheelbase: 86" (with center pin in middle, 43" from each axle)
Rear axle of tender leading truck to first of five "rigid" tender axle: 99"
Interval between neighboring tender "rigid" axles: 60"
Rear axle of tender to rear coupler: 11' 11"

Driving wheelbase: 25' 2"
((Comment: Ouch! The driving wheelbase of an S1 is only 20' 6". The driving wheelbase of the C1a would have been longer than that of a 69"-drivered 2-10-4 (if you can picture one of those on the Central!).))
Engine wheelbase: 52' 8"
Last axle of engine to first axle of tender: 16" 1.5"
Tender wheelbase: 35' 5"
Tender "rigid" wheelbase: 20'
Total wheelbase: 104' 2.5"
((Comment: a Niagara, spotted carefully, would fit on a 100 foot turntable, which was apparently system standard. (PRR had gone to 125 foot turntables to accommodate its biggest monsters.) So IF the New York Central had decided to build the C1a, they would have had to make further infrastructure investments to handle it. Somehow the "business case" for the Duplex ain't looking hot....))
Total length: 123' 1.25" over couplers.

Comments: from the front coupler to the 2nd driving axle, lengths are very similar to the S1. (The C1a was apparently designed with an outside bearing engine truck with two inches more wheelbase than the engine truck on an S1.) From the 3rd driving axle to the rear of the engine, again almost identical to an S1b (the point I have called the drawbar pivot seems to be an inch further back on the S1b; otherwise these lengths are identical. So (looking only at the engine, the big difference is the 138" gap between the 2nd and 3rd driving axles (on an S1 this was 82") necessitated by the second set of cylinders.

So how would it go around curves? The New York Central main line had lots of nice straight track, but at stations and in terminals... The 18 degree 30 minute curve the engine was "designed" to operate on seems to have been a New York Central standard: the same limiting curve is quoted for Hudsons, Pacifics, lots (though not all) Mikados, and the S1 Niagaras. My guess is that getting a C1a to go around a sharp curve in a yard would have involved more sweat and finger-crossing than with other classes.

Diagrams and dimensions for the S1a and S1b, by the way, can be found in the New York Central 1946 locomotive diagram book, available (as a large pdf file that takes some minutes to download) at George Elwood's marvelous site:

Another post-- tomorrow, maybe-- with further information (& speculation) about the C1a.

Allen Hazen
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Re: The proposed-but-unbuilt "C1a"

Post by Allen Hazen » Sat Sep 11, 2010 2:27 pm

O.k., my previous posts (except for explicitly labelled "comments") have pretty much been devoted to copying out data in sources: for the most part they are meant as an aid to following the 1945 diagram, which as available on the WWWeb isn't very legible. This time I'm going to make a few more inferences in interpreting the sources: I'm pretty confident about them, but this IS inference, not transcription.

About the boiler. The diameters shown (100" outside diameter for the largest, 90" inside diameter for the smallest course) are the same as for the S1. (This isn't record-breaking-- a couple of railroads had 4-8-4 with 102" boilers-- but it is big for a 4-8-4: make no mistake, the New York Central was fitting a BIG engine into its restricted loading gauge!) Since the lengths at the rear end are the same as on the S1, it looks as if the C1a boiler would have had the same firebox dimensions as the S1, with its 100-and-a-bit square feet of grate area. (Again, not record breaking-- ATSF and N&W had 4-8-4 with 108 sq ft of grate-- but good... and a lot better than the pathetic 92 square feet of THAT OTHER RAILROAD's 4-4-4-4.)

Now it gets a bit trickier. The S1b had a shorter combustion chamber than the S1a. (The dotted lines outlining the fireboxes in the diagrams in the 1946 diagram book don't show this -- my guess is that the S1b drawing was largely traced from the S1a drawing-- but it is revealed by the 11" greater tube length recorded for the S1b in the data tables.) My guess is that the decision to make this change (a change for the worse if a couple of old articles in "Trains" are to be believed...) had already been made by the time the S1a was delivered-- anyway, the dotted line on the C1a drawing suggests that it was intended to have the shorter combustion chamber.

I ***think*** (eyeballing the drawings: I haven't tried to measure these tiny reproductions) that the C1a would have had the same tube length as the S1b. The drawing doesn't show the front tube sheet, but it would be about where the boiler lagging stops and the unlagged smoke-box starts: if you look, you'll see that this transition is over the forward part of the first driver on an S1 and toward the rear of the first driver on the C1a drawing: I can't swear that the difference is exactly the 56" that gets added to the spacing between 2nd and 3rd drivers, but it's not far off.

So all or most of the extra length of the boiler is smoke-box, not water-filled volume. Otherwise put: the front end has in IMMENSE chamber to use up somehow. It looks, in the C1a drawing, as if this was put to at least one good use: double stack (or, at least, double blast-pipe under an elongated stack). The exhaust steam piping in a Duplex probably makes it easier to design a double stack than a single! But anyway, this is a good thing: multiple blast pipes make for more efficient "pumping" of the exhaust, and so give the same draft for the fire with less back-pressure in the steam system: this is the sort of thing that makes noticeable differences in locomotive performance.

Allen Hazen
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Re: The proposed-but-unbuilt "C1a"

Post by Allen Hazen » Sat Sep 11, 2010 2:43 pm

Last post in this series. (I'll be interested if it inspires some discussion!)

Stauffer's exposition isn't quite as clear as I'd like, and he doesn't cite his sources, but apparently the concept in the March 1945 drawing wasn't the final iteration of the C1a design. One change was to go to an 8-axle tender (Centipede plus trailing truck) to keep the loaded tender axle load down to 60,000 pounds. (Fear of the Lord may be the beginning of wisdom in general, but fear of the civil engineer seems to have been it for the New York Central's mechanical department!) ... Maybe somebody said "This locomotive is would require new turntables anyway, so why not lengthen the wheelbase AGAIN?"

And apparently the C1a was originally envisioned as using Franklin poppet valves (like the S2a), but a later iteration had piston valves with Baker valve gear. Probably a bad thing for performance: poppet valves were just better than conventional piston valves. (The tests which showed the S2a to be slightly less powerful than the S1b were run at settings that optimized fuel and water efficiency: they showed the S2a to be SO much more efficient than the S1b that it is almost certain that, operated at the same level of fuel usage, it would have been significantly more powerful.) But, particuloarly with the comparatively small cylinders of the Duplex, even the Baker-valve-gear C1a would have been an impressive performer.

Last remark: that tender is HUGE. Compared to tenders on most other railroads, it doesn't have much water capacity-- New York Central's main line had track pans, and the Centipede tenders had venting that allowed water pick-up at full speed (or with a minimal deceleration: 80 mph). But coal capacity was 66 tons! I think with many passenger trains this would have permitted a full trip, Harmon to Chicago, without refueling!

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Re: The proposed-but-unbuilt "C1a"

Post by erie2937 » Sat Sep 11, 2010 11:21 pm

I have in my possession a twenty-nine page document entitled: New York Central System Equipment Engineering Department Specification Number 577 Covering 4-4-4-4 Type Road Locomotive Class C1a.

It is dated April 2, 1945 and was issued over the signatures of the Engineer Motive Power, the Ass't Chief Engineer Motive Power and Rolling Stock and the Chief Engineer Motive Power and Rolling Stock(P.W. Kiefer).

The locomotive wheels are described as "Cast Steel Driving Wheel Centers, 72" diameter". Diameter of driving wheels 79". Trailer wheels, front and rear, are to be 41". Engine truck wheels are to be 36". The engine truck is of four-wheel, swing motion type, with outside roller bearings, and arranged for clasp brakes. A four-wheel Delta type trailing truck is to be used, arranged for single shoe brakes.

Total wheel base, engine and tender - 107'2".

Boiler pressure 290 pounds per square inch.

Smokebox arrangement: double stack with suitable netting arrangement is to be applied.

Smoke lifting arrangement: Engine is to be equipped with smoke lifting plates, arrangement to follow Railroad Class S-1A locomotive. NYC referred to "elephant ears" as Smoke Lifting Plates, not smoke lifters.

This document also calls out a change in the tender from a 4-10-0 wheel arrangement to a 4-10-2 wheel arrangement to handle 64 tons of coal and 18,000 gallons of water and a double-screw stoker instead of a single-screw device. There would be a separate 2-wheel truck at the rear of the revised tender with clasp type brake. Length of the revised tender: 56'6' front buffer to over rear coupler. Total wheel base 38'11".

Too bad the engine was never built.

I wonder whether or not a courageous importer could be persuaded to produce a model. I think it would sell, at least to me.

Hugh T. Guillaume

Allen Hazen
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Re: The proposed-but-unbuilt "C1a"

Post by Allen Hazen » Sun Sep 12, 2010 6:32 pm

Hugh T. Guillaume--
That sounds like an amazing document. It OUGHT to be published for the historical record. (I'm not a member of the New York Central Historical Society, and I don't know if this is the sort of thing they would publish in their "Central Headlight." If ***I*** were editing it, I know I'd leap at the chance of publishing a document like that (with an introduction by you saying how it came into your possession).)

(I have seen the booklet Kiefer published about the Niagara/E-7 comparison tests -- "A practical evaluation..."-- at a time in my life when nickels for photocopying were in short supply: I'd love it if someone would publish a facsimile edition. Since the booklet is quite short, the volume could be fattened up by including one or two things like your document as appendices. If this happens, I know what would be on MY railroadiana Christmas wish list!)

As for modeling... The PRR T-1 had running gear not too different from that proposed for the C1a in its dimensions (I think the T-1 trailing truck had a shorter wheelbase than the S1b/C1a truck, but I'd have to check to confirm). The boiler (from the back of the smokebox back) and cab seem to be about the same as on the S1. I think this might be a feasible "kit-bashing" project for somebody!

(Oh: 72" centers for 79" drivers seem to have been standard NY Central practice.)

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Re: The proposed-but-unbuilt "C1a"

Post by rlsteam » Wed Oct 13, 2010 11:38 pm

The scan of the drawing of the proposed C1a duplex ( ... _steam.htm) was sent to me in 2004 by a physicist in New Jersey; it was scanned from Staufer's "New York Central Later Power 1916-1968." As to the photos in my "NYC Fantasy Steam" collection, "photoshopped" is not the right term because I use Paint Shop Pro 7 (I have Adobe PhotoShop but have never learned to use it). For more "fantasy steam" on other railroads check out, where you can get a kick out of seeing the PRR T1 as a Garratt, the AT&SF "Blue Goose" 4-6-4 in the "war bonnet" paint scheme, the famous Erie Quadruplex, etc.
Dr. R. C. Leonard, "Richard Leonard's Rail Archive" ( )

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A Duplex on the NYC - The proposed-but-unbuilt "C1a"

Post by Juniatha » Wed Dec 08, 2010 12:39 am


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