Questions on C&O J3a Boiler Statistics

[GP40-2]

I've recently been trying to determine the actual boiler dimensions of the C&O J3a Class 4-8-4s built in 1948 (#614) and have come across some new (and different) numbers that I have not seen elsewhere.

First, a little bit of history. I acquired a set of drawings of the 614 back in the Chessie Safety Express days (early 1980's) that listed the 614 as having 5595 sq.ft. total evaporative surface, 2305 sq.ft. superheater surface, and 520 sq.ft. firebox (direct) heating surface. Since these stats where on the drawings, I never questioned them until recently. 

It was brought to my attention by poster Feltonhill, that he had data showing the J3a had 4821 sq.ft. total evaporative heating surface, and 2058 sq.ft. superheater surface. He did not state firebox (direct) heating surface. This change was due to the J3a using larger diameter firetubes for higher gas flow than the earlier J3 Class. This was an "end of steam" design feature that found its way into a number of locomotive designs in the mid to late 1940's. Clearly, the data on my drawings from the 1980's were from the earlier J3 design, and not the J3a. I've seen the J3 specs associated with the J3a a number of times over the years on various sites, so this incorrect data has made its way around the community.

Now, to add to the puzzle. Over the holiday, I have had time to look at additional paperwork from the Chessie Safety Express days I had stored at another location in boxes. I have come across a copy of an additional, smaller,  drawing of the J3a Class that lists the total evaporative surface as 5005 sq.ft., superheater surface as 2120 sq.ft. and more importantly firebox (direct) heating surface as 589 sq.ft. 

The total evaporative surface and superheater surface are relatively the same as reported by Feltonhill. The larger firebox (direct) heating surface makes sense because not only did Lima use larger firetubes in the J3a, but they also shortened the length of the tubes to increase flow and increased the length of the firebox area. This is where things get interesting and at the same time maddening. The 589 sq.ft. firebox area, if correct, is the largest direct heating surface I have ever seen on a 4-8-4. This is important because direct heating surface is where the majority of steam production occurs. What is maddening about this is we still have a functional copy of the J3a Class here (the #614) and nobody seems to have concrete data on exactly how Lima updated the J3a vs. the older J3 Class. 

Comments? Feltonhill?

[feltonhill]

The only thing I can add is information from C&O locomotive diagrams

J3 600-604
Firebox HS - 396 SF
Arch tubes - 21 SF
Circulators - 0 SF
Syphons - 108 SF
Total Direct HS - 525 SF
Indirect HS - 4937 SF
Total Evaporative Surface - 5462
Superheater - 2342 SF
Combustion chamber - 54" est
Tube length - 21'
Tubes - 59 x 2-1/4"
Flues - 220 x 3-1/2"

J3 605, 606
Firebox HS - 395 SF
Arch tubes - 21 SF
Circulators - 0 SF
Syphons - 103 SF
Total Direct HS - 519 SF
Indirect HS - 4974 SF
Total Evaporative Surface - 5493
Superheater - 2315 SF
Combustion chamber - 54" est
Tube length - 21'
Tubes - 62 x 2-1/4"
Flues - 220 x 3-1/2"

J3a 610-614
Firebox HS - 417 SF
Arch tubes - 0 SF
Circulators - 65 SF
Syphons - 0 SF
Total Direct HS - 482 SF
Indirect HS - 4339 SF
Total Evaporative Surface - 4821
Superheater - 2058 SF
Combustion chamber - 66" est
Tube length - 20'
Tubes - 56 x 2-1/4"
Flues - 177 x 4"

IMO, the update took place within the same firebox and boiler shell, so there would be little if any visible difference in the J3's and J3a’s.  However, inside things changed.  The grate area remained the same; the firebox itself seems to be the same; the combustion chamber was increased 12", the tubes and flues were shortened 12", 177  4" flues were substituted for 220  3-1/2" flues, and the 2-1/4" tubes varied between 56 and 59.  The final figures for the J3a and NYC S1b boilers are very similar.  However, the firebox configuration of the Niagara is different because of the shallower angle of its grate.

FWIW, the NP A5's had 590 SF of direct HS, but this was due to the large grate area necessary for burning the low-grade coal NP used.

[GP40-2]

Thanks for the reply. I am almost temped to crawl inside the thing and measure it myself. LOL. 

[feltonhill]

You may well have than chance.  614 is due to be moved to Roanoke soon, and be placed on exhibition along with 611 at VMT for an undetermined length of time starting in Feb 2011.   Access may be possible then.  However, I have no reason to believe that C&O's diagrams are inaccurate.  On a similar note to what you discovered with 614, some of the information accumulated during 611's refurbishing for excursion service contained material what was developed back in March 1941, seven months prior to the first J, #600, being completed.   It contained several inaccuracies, including the HP figure that we've discussed before on this forum.

I intend to check the July 1948 issue of RME at the NWHS archives in two weeks  and see what it has to say about the J3a's.  I looked over it quickly in November but didn't make a copy.