• So, how long was an HH-1000?

  • Discussion of products from the American Locomotive Company. A web site with current Alco 251 information can be found here: Fairbanks-Morse/Alco 251.
Discussion of products from the American Locomotive Company. A web site with current Alco 251 information can be found here: Fairbanks-Morse/Alco 251.

Moderator: Alcoman

  by Allen Hazen
The latest (April 2008) issue of "Railroad Model Craftsman" has drawings of an Alco HH-660 switcher, and since the November 1985 issue had drawings of an HH-1000, I thought I'd compare dimensions. The HH-1000 is clearly longer (see below for details & comment), but... how much longer? The newer drawing of the HH-660 shows a length over coupler pulling faces of 43', 4.75" for the HH-660, and 39', 5" over the pilot faces. The older drawing of the HH-1000 shows a length of 42', 3", but it is neither of these: it appears to be the length over the ?? draft gear bosses ?? (I don't know the correct term for this: I mean the metal around the draft gear pocket, which protrudes several inches out from the pilot face).
Looking at my other sources... there seems to have been a slight but steady growth in length-- for which I can imagine reasons-- of 531/538/539 engined switchers. The prototype of the whole series, Alco demonstrator 600, which became New Haven 0900, was 40', 10" over the couplers. (Source: 1. I am assuming "over the couplers" means over pulling faces.) There was apparently some variation in later units: Alco demonstrator 602 (subsequently B&M 1102), the first with a welded rather than a cast frame, was 42', 8.75" over the couplers. And the late production (rounded hood ends, which were introduced some time in 1938) HH-660 illustrated in the new "RMC" was 20', 2" between truck centers, 43', 4.75" over pulling faces.(2)

Now the turbocharged units. The HH-1000 was a bit longer: 21', 3" between truck centers, maybe about 45" over pulling faces.(3) This makes sense: a much larger radiator had to be incorported, and the generator was a bit bigger. Further, the total weight was greater (approx. 115 tons instead of 98 tons): all told, it is surprising the length didn't increase more! (Some HH-600, HH-660, HH-900 and HH-1000 were built with Westinghouse electrical equipment instead of GE, but there is no suggestion in my various sources that this required any change in frame or external dimensions.)

Now the 1940 "low profile" carbody: the S1 and S2 were both(?) 22', 6" between truck centers, 41', 6" over pilot faces, (4) and 45', 5.75" over pulling faces (4,1). These dimensions seem to have been unchanged for the successor S3 and S4, and even for the Canada-only S-10 and S7 variants (1). Perhaps dropping the oil pan of the engine between the frames required other changes that increased the length a bit? Or perhaps Alco "decompressed" the internal machinery arrangement for improved maintenance accessibility? Or perhaps components that could be "stacked" under a high hood had to spread out under the lower hood: the rear sandbox was over the electrical cabinet in the HH series. Using the same length for the two models would have been a matter of standardization.

The final, Canada-only, 539-engined switchers with end radiators and raised underframe, were longer again: the 660hp S-11 was 45', 9.75" over the couplers and the 1000hp S-12 was 46', 3.75" (1).

(1) "The Diesel Builders, vol. II" by John F. Kirkland
(2) "RMC" April 2010
(3) "RMC" November 1985
(4) "Model Railroader Cyclopedia, vol. II: Diesel Locomotives" (This is my only source for truck-center and pilot-face length, and only shows the S2. It agrees with (1) on pulling face length; (1) says the S1 and S2 had the same length over couplers.)
  by Allen Hazen
Leading to source (5): the Pennsylvania and New York Central locomotive diagrams accessible at George Elwood's marvelous "Fallen Flags" railphoto site,

Although (1), page 68, explicitly says the S1 and S2 were the same length, PRR and NYCRR diagrams show the S1 as a foot shorter: 6" less between truck centers (so: 22' instead of 22', 6"), and another 6" less between the front truck and the front of the locomotive, for a length over couplers of only 44', 5.75". (Though the NYCRR scrupulously notes that this can go up to 44', 11" with a different coupler.)

(I'll admit to having been a BIT suspicious of (1): it records that in 1954 there was a design change, incorporating a longer-shanked coupler (for both S3 and S4 in Canada, and for S4 in the U.S., Schenectady having already ceased to build S3), but with no comment on the effect this might have had on over-all length.)


On the other hand, the New York Central did have some HH-660, and their diagram card agrees with the dimensions given in (2).
  by Kuyahoora Valley
For S1 and S2, the ALCO manual says length (inside knuckles) is 44' 5 3/4" and 45' 5 3/4" respectively. The truck centers are 22' and 22' 6"...the extra 6" on the S2 is between the truck center and the pilot on the long hood end, apparently to accomodate the radiators.
  by Allen Hazen
Kuyahoora Valley--
Thank you! Those dimensions tally with what the PRR and NYCRR diagrams show.
(Hmm. George Elwood's site also has a bunch of locomotive operating and maintenance manuals: I didn't think to check there. Is the Alco manual you looked at6 one of the ones on "Fallen Flags"?)
  by Kuyahoora Valley
No I have the ALCO Operation and Service Manual for the S1/S2/RS1...if you go to this site it has lots of manuals, including the "Manual for Enginemen" for the S1/S2/RS1...it shows the basic dimensions: