New Haven 4-6-2 "Pacific" Locomotives

Class Details by Steve Llanso of Sweat House Media

Class I-1 (Locobase 157)

Data from table in June 1908 American Engineer and Railroad Journal (p. 230). Baldwin built 21, Alco-Schenectady built 11.

Used on the Merchants, Bay State, and Knickerbocker Limiteds in the 1st two decades of the 20th century. Slide valves were replaced in 1917 by piston valves, at which time superheaters were added; see Locobase 8116.

Class I-1-a (Locobase 8116)

Data from NH 1962 Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive Raildata collection.

Locobase 157 describes the first New Haven Pacific class as delivered in its saturated-boiler form. Beginning in 1917, the railroad began modifying these engines by installing a superheated boiler. The usual decrease in total heating surface induced by swapping many small tubes for a fewer larger flues was held to a relatively small figure. At the same time, the firebox gained some area with the addition of more arch tubes (the total impact on firebox heating surface now came to 29 sq ft) and the cylinders gained a little volume by growing an inch in diameter.

Interestingly, the 4-4-2 upgrade described in Locobase 8115 achieved almost the same power at speed because although the boiler was a bit smaller, the cylinders were smaller as well, which reduced demand. Moreover, the direct heating surface was little different. Total water evaporation was a bit higher in the 4-6-2 at 38,330 lb/hour, but the direct heating surface contributed only 11,045 lb/hour. Steam consumption could overmatch the boiler by achieving a theoretical 39,600 lb/hour; thus the boiler factor was 96.2%.

But of course the Pacific put more weight on the drivers and that proved a decisive advantage.

The superheat upgrade proved to be the last big change for the I-1s and they served the New Haven for decades more in that form. The first left service in 1944 and the last retired in 1951.

Class I-2 (Locobase 7590)

Data from reproduction of 1913 Alco Bulletin 1016 on Richard Leonard's (accessed 16 June 2006).

Drury (1993) says this class replaced the I-1s (Locobase 157) in mainline passenger service and also worked fast freights. Certainly it's a bigger locomotive with excellent proportions -- an adequate superheat ratio, large boiler, good factor of adhesion. Yet maximum water evaporation increased very little, up only 1,422 lb/hour to 39,752 lb/hour. Steam consumption grew at a faster rate, however, reaching 43,180 lb/hour and the boiler factor fell to 92.1%

Perhaps because of the lack of any real margin growth, the I-2s were overshadowed by the I-4s (Locobase 5465) that came on the road just 3 years later and relegated to secondary passenger traffic. In that role they served the line until the end of steam, being retired in 1948-1952.

Class I-3 (Locobase 9400)

Data from NH 1962 Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive Raildata collection. See also DeGolyer, Vol 43, pp. 1+. Works numbers were 39173-39174 in January 1913, 39175-39178 in February 1913.

To work the express-passenger Shoreliner service, the I-2 design discussed in Locobase 7590 was placed on taller drivers and given a boiler with longer tubes but four fewer flues. So the evaporative heating surface grew slightly, but the superheater area shrank. Total maximum evaporation rates changed little from the I-2, reaching 39,695 lb/hour. Maximum possible steam consumption remained 43,180 lb/hour.

It's little wonder, therefore, that the Shoreline duties were quickly filled by the I-4s when they began entering service in 1916 (Locobase 5465). The I-3s were relegated to secondary pasenger runs, they nevertheless served until the late 1940s.

Class I-4 (Locobase 5465)

Data from table in January 1917 issue of Railway Mechanical Engineer (RME).

Express Pacifics for the New York, New Haven & Hartford that headed the varnish between New York and Boston. For some very long trains (as many as 23 cars, e.g.), the New Haven would double up on I-4 power.

Compared to Brooks's I-2s (Locobase 7590), these engines had taller drivers and larger-diameter cylinders. RME shows the class as having 71 1/4 sq ft of grate area, but Locobase later ascertained through the NH 1962 Locomotive Diagram book (supplied in May 2005 by Allen Stanley from his extensive Raildata collection) that this was mistaken. In later years, they were easily distinguished by the Elesco feedwater heater mounted athwart the smokebox and, more unusually, by the air tanks laid longitudinally on each upper half of the boiler just behind the stack.

Later on, the New Haven made over some number (Locobase isn't sure how many) into superpower engines; see Locobase 7591.

Class I-4-E (Locobase 12721)

Data from NH 1962 Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive Raildata collection.

As noted in Locobase 7591, the New Haven met the burgeoning demand for heavy passenger trains led to upgrades of some of the I-4s to a superpower standard (see Locobase 7591). This entry reflects another subset that used the original boiler layout but added 3 thermic syphons of 91 sq ft and modernized the Baker valve gear by fitting it with roller bearings.

As in the more extensive makeover, boiler pressure remained the same, but the cylinders shrank by 1" in diameter. The tender was much bigger and heavier.

The New Haven calculated that the augmented boiler evaporated water at the maximum rate of 49,730 lb/hour, of which the direct heating surface contributed 20,130 lb/hour. Compared to the maximum steam consumption rate of 46,840 lb/hour, the boiler factor came to 106%.

Class I-4-F (Locobase 7591)

Data from NH 1962 Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive Raildata collection.

When delivered in 1916, the I-4 class (Locobase 5465) was a pretty potent express locomotive design. But as trains grew longer and heavier still, the New Haven began double-heading them. To meet the demand, the railroad procured the famed I-5 4-6-4s (Locobase 187) and modified some of the I-4s beyond the modest updates that appeared on the I-4-E (Locobase 12721).

The I-4-F rose to a superpower standard. In the makeover, boiler pressure remained the same, but the cylinders shrank by 1" in diameter, the Baker gear now used roller bearings, and the firebox received 91 sq ft of thermic syphons added to the firebox and combustion chamber. The tender was much bigger and heavier.

The big change came in the boiler. A redesign of the layout added considerable evaporative heating surface in not only the new combination of 2 1/4" tubes and 3 1/2" flue. Altogether, the design added about 25% in heating surface to the original I-4 boiler.

The New Haven calculated that the new boiler evaporated water at the maximum rate of 51,180 lb/hour, of which the direct heating surface contributed 20,130 lb/hour. Compared to the maximum steam consumption rate, the boiler factor came to 109.2%.

Specifications by Steve Llanso of Sweat House Media
Locobase ID157 8116 7590 9400 5465 12721 7591
RailroadNew Haven (NYNH&H)New Haven (NYNH&H)New Haven (NYNH&H)New Haven (NYNH&H)New Haven (NYNH&H)New Haven (NYNH&H)New Haven (NYNH&H)
Road Numbers1000-10311000-10311300-13491090-10951350-13991350+1353+
BuilderseveralNew HavenAlco-BrooksBaldwinAlcoNew HavenNew Haven
Valve GearWalschaertWalschaertWalschaertWalschaertBakerBakerBaker
Locomotive Length and Weight
Driver Wheelbase13.08'13.08'14.08'14.08'14.08'14.08'14.08'
Engine Wheelbase33.45'33.46'34.46'36.10'36.10'36.10'36.10'
Ratio of driving wheelbase to overall engine wheebase 0.39 0.39 0.41 0.39 0.39 0.39 0.39
Overall Wheelbase (engine & tender)61.17'61.17'62.33'66.77'66.77'79.92'79.92'
Axle Loading (Maximum Weight per Axle)46400 lbs54150 lbs60700 lbs60300 lbs61400 lbs
Weight on Drivers142500 lbs142800 lbs154000 lbs161100 lbs165000 lbs178600 lbs180800 lbs
Engine Weight229500 lbs234400 lbs251500 lbs259000 lbs266000 lbs287500 lbs291000 lbs
Tender Light Weight134000 lbs134000 lbs132600 lbs132600 lbs154000 lbs298000 lbs298000 lbs
Total Engine and Tender Weight363500 lbs368400 lbs384100 lbs391600 lbs420000 lbs585500 lbs589000 lbs
Tender Water Capacity6000 gals6000 gals6000 gals6000 gals7500 gals16000 gals16000 gals
Tender Fuel Capacity (oil/coal)14 tons14 tons13 tons13 tons12 tons16 tons16 tons
Minimum weight of rail (calculated) on which locomotive could run79 lb/yard79 lb/yard86 lb/yard90 lb/yard92 lb/yard99 lb/yard100 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter73"73"73"79"79"79"79"
Boiler Pressure200 psi200 psi200 psi200 psi200 psi200 psi200 psi
Cylinders (dia x stroke)22" x 28"23" x 28"24" x 28"24" x 28"26" x 28"25" x 28"25" x 28"
Tractive Effort31559 lbs34494 lbs37558 lbs34706 lbs40731 lbs37658 lbs37658 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.52 4.14 4.10 4.64 4.05 4.74 4.80
Heating Ability
Firebox Area204.40 sq. ft219 sq. ft217 sq. ft223 sq. ft298 sq. ft366 sq. ft366 sq. ft
Grate Area53.40 sq. ft53.50 sq. ft53.20 sq. ft53.20 sq. ft59.20 sq. ft59.20 sq. ft59.20 sq. ft
Evaporative Heating Surface3947 sq. ft3133 sq. ft3309 sq. ft3356 sq. ft3315 sq. ft3383 sq. ft3576 sq. ft
Superheating Surface670 sq. ft780 sq. ft730 sq. ft776 sq. ft776 sq. ft1425 sq. ft
Combined Heating Surface3947 sq. ft3803 sq. ft4089 sq. ft4086 sq. ft4091 sq. ft4159 sq. ft5001 sq. ft
Evaporative Heating Surface/Cylinder Volume320.40232.69225.70228.91192.66212.66224.79
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation10680107001064010640118401184011840
Same as above plus superheater percentage10680126261266212555140901409015155
Same as above but substitute firebox area for grate area40880516845164652628709248710893696
Power L19815185381894419832180432019030179
Power MT455.54858.60813.59814.19723.24747.671103.98


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