4-6-2 "Pacific" Steam Locomotives in the USA

Class P-1 (Locobase 7938)

Data from "Passenger and Freight Locomotives - Central of Georgia Railway," American Engineer and Railroad Journal, Volume 81, No 1 (January 1907), pp. 31-33. See also DeGolyer, Volume 27, p. 243 and Volume 29, 9. 216. (Thanks to Ivo Rutishauser for his 7 July 2026 email noting the differences between the two batches.) Works numbers were 25793-25794, 25889, 25903 in June 1905; 25967 in July. P-1s with 20" cylinders works numbers 29300-29301, 29360, 29365-29366 in October 1906; and 29380, 29454, 29466-29468 in November.

At the time, the AERJ described them as "well proportioned throughout, and have ample boiler power for the service required of them."

Drury (1993) describes these as "typical early Pacifics" that had slide valves and inside bearings; cylinder diameter for the five 1905 engines measured 21" (533 mm); starting tractive effort was 38,870 lb (14,000 kg; 137.3 kN). The specs included the builder's guarantee that the engines would "haul 12 cars not exceeding 675 tons at an average speed of 40 mph between Macon and Atlanta, a helper to be used on the 40 ft [sic] grade out of Macon."

Ivo Rutishauser found the later Baldwin specification, which revealed that the cylinder diameter had been reduced by an inch to 20" (508 mm) for the ten 1906 engines. Locobase looked into the new spec and found a possible reason for the change.

In describing the cylinders for the 1906 engine, the specification said to use the same cylinder heads as the first five, but bore the cylinders to a 20" diameter. It added "Strengthen [cast] cylinder saddles as breakage has occurred as sketch." The sketch showed that the cracks began in the casting between the half saddle boiler support and the horizontal extension holding the cylinder. Locobase supposes that the builder and the railroad concluded that thickening the cylinder walls and strengthening the saddle would solve the problem.

The diagram book shows the superheated upgrade (Locobase 4227). Most received 12" (305 mm) piston valves.

Class P-1 - superheated (Locobase 4227)

Data from Central of Georgia's 1927 locomotive diagram book, supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange

When the C of Ga superheated its slide-valve, Stephenson-motion Pacifics (Locobase 7938), they transacted the usual trade-off between boiler tubes and superheater flues. Unlike many such Pacific overhauls, the resulting heating surface total dropped considerably because of the boiler's small diameter. Most received 12" (305 mm) piston valves in new cylinder castings bored to the origina 21" (533 mm) diameter..

The class lasted throughout the steam era. 419 (ex-1619 and 425 (ex-1625)wrecked in a head-on collision on 23 July 1937 near Ogeechee, Ga. Casualties totalled 27: four train crew died and 25 passengers suffered injuries. A photograph published at the time showed the violence of the impact that destroyed both engines

The CofGa retired the 422 in March 1939. World War II demands delayed any more withdrawals until March 1947 when 414, 424, 426, and 428 left the roster. July 1948 saw the retirement of 416 and 421. The last five closed out the class in 1950-1952.

Class P-2 (Locobase 4228)

Data from CofGa 12-1925 locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Volume 42, pp. 195+; and "Pacific Type Locomotives, Central of Georgia Railway", Railway and Engineering Review, Volume 53, No 47 (22 November 1912, 1080-1081); and J T Anthony, "Combustion in Locomotive Practice", Railway Age Gazette, Volume 54, No 23 (6 June 1913), pp. 1220-1225. Baldwin works numbers were 37619-37624 in April 1912 and 40660-40684 in September 1913. Lima's works numbers were 5217-5220 in 1916.

Drury (1993) comments that despite the higher weight these engines were still light Pacifics. Still, these P-2s had much bigger grates and larger cylinders (and superheaters when delivered) than the P-1s they joined on the C of Ga (Locobase 7938).

Direct heating surface area in the spacious modified-Wootten firebox included a short Gaines half-wall combustion chamber that subdivided the 132" (3.35 m) length of the firebox. The R&ER's 1912 description of the Gaines half-wall is about as clear as any Locobase has seen. An even more detailed discussion is available in J T Anthony's dissection of combustion in fireboxes.

As noted in other entries, the wall's height fell well short of the internal firebox dimensions. In this case, it stood 31" (787 mm) behind the boiler's rear tube sheet. Its top included a ledge that extended 6" (152 mm) to the rear. Five equally spaced 2" (50.8 mm) diameter ducts standing vertically within the wall drew air from below and let it escape through openings under the ledge.

"This air," the description explained, "mingles with the gases just as they pass over the [Gaines brick ] arch and furnishes the oxygen needed to complete combustion. At the same time, the projecting ledge tends to deflect the [heated] gases against the back sheet and the rear of the crown sheet, and so increases the value of these parts as heating surfaces."

Locobase wonders if deflecting hot gas so it struck part of the back sheet and crown sheet caused problems through stresses induced by differing temperatures.

The grate area was figured on the 88" (2.235 m) length behind the Gaines wall.

Class P-2 - syphons (Locobase 6677)

Data from CofGa 4-1932 locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Vol 42, pp. 195+.

Some time after the Lima quartet was delivered to fill out the P-2 stud in 1916 (Locobase 4228), all of the engines were updated beginning in the late 1920s or early 1930s with more grate area and firebox heating surface area. It now included 13.3 sq ft (1.25 sq m) of arch tubes and 53 sq ft (4.9 sq m) of syphons. Tube count decreased by 12 while adhesion weight rose by over four tons.

Most ran to the end of steam in the early 1950s, although at least one engine was scrapped in 1935. (Likely a casualty of some accident ...).