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 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. 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 http://www.railarchive.net/alcopacifics/index.html (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. Even so, they 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 collection. Produced in a single batch in January 1913 as works #39173-39178.

Although this sextet was intended for the express-passenger Shoreliner service, those duties were quickly filled by the I-4s when they began entering service in 1916. 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 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-F (Locobase 7591)

Data from NH 1962 Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive 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 to a superpower standard.

In the makeover, boiler pressure remained the same, but the cylinders shrank by 1" in diameter. 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" flues, but also the addition of 91 sq ft in 3 Nicholson thermic syphons in the firebox and combustion chamber. Altogether, the design added about 25% in heating surface to the original I-4 boiler.