Philadelphia & Reading 4-4-2 "Atlantic" Locomotives in the USA

Class 100 (Locobase 14994)

Data from"Atlantic Type Inspection Locomotive", Railway Age Gazette, Volume 55, No 10 (5 September 1913), pp. 404-405; "Inspection Locomotive on the Reading", Railway Age Gazette, Mechanical Edition, Volume 87, No. 9.(September 2013). See also Roy V Wright (Ed.) 1922 Locomotive Cyclopedia of American Practice, Sixth Edition (New York: Simmons-Boardman Publishing Company, 1922), p. 176. (Many thanks to Chris Hohl for his 18 August 2017 email supplying Locobase the links to two contemporary descriptions that filled in many of the details missing from the Locomotive Cyclopedia summary.) Works number was 544 in April 1913.

This inspection engine featured some unusual revisions to a standard Reading design to accommodate the eight seats in the observation section, the Reading used a small-diameter anthracite-burning boiler whose exceptional length-to-diameter ratio came from a shallow Wootten firebox with short combustion chamber and a full 14 feet of tubes. Another significant alteration to the typical boiler profile was the placement of the steam dome directly over the firebox. A combination lever allowed operation of the reverser either through a traditional lever or a screw.

Each of its eleven inch (279 mm) piston valves with 7" (178 mm) travel lay over and 7 1/2" (191 mm) outside of its cylinder partner

An inside view of the observation section showed a row of four chairs on either side, the rows separated by a wide center platform with sides rising to chair-arm height. Given the boiler's proximity to the observers' chairs, Locobase was surprised that "[a]mple provision for heating the observation room is made by means of steam pipes under the floor." In addition, the engine was rated to pull two private cars "on a good schedule".

The 100 operated until April 1929.

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Class 376/D-10a/P-1b (Locobase 15924)

Data from DeGolyer, Volume 21, p. 172. See also Alfred Bruce (1952). (Thanks to Chris Hohl for his 25 January 2014 email correcting the driver diameter.) Works numbers were 15880-15883 in April 1898.

This class was an immediate continuation of the Atlantic City's Camelback 4-4-2s (Locobase 2562). Like those engines, this quartet ran as Vauclain compound and had the camelback layout with the wide Wootten firebox. This accounts for the deceptively low firebox/grate area ratio. Firebox heating surface included 53.8 sq ft (4.2 sq m) in the combustion chamber.

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Class P-3b (Locobase 9456)

Data from RDG 11 - 1926 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Volume 24, p. 275. (Thanks to Chris Hohl for his suggested updates that led me to the Baldwin specs; and to Wes Barris of steamlocomotive.com for his 28 June 2018 email reporting the missing metric equivalents to cylinder diameter and stroke.) . Works number was 20531 in June 1902.

The Reading built these two high-drivered Atlantics to compare simple-expansion working (Locobase 9455) with that available to a Vauclain balanced compound with even more cylinder volume. Apparently, the 329 was even less successful than any of the earlier Reading compounds as it received two 21" cylinders in 1904. At that point it was a duplicate of the 328; see Locobase 9455.

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Class P1-c (Locobase 12415)

Data from Baldwin Locomotive Works Specification for Engines as digitized by the DeGolyer Library of Southern Methodist University Volume 23, p. 37. (Thanks to Wes Barris for his 9 July 2021 email catching confusing typos in the works number list.) Works numbers were 17787-17788 in May 1900, 17812-17813 in June.

Part of the Vauclain compound parade that reached its peak right about the time these were ordered, these Atlantics didn't retain that system for very long. Locobase 9450 shows the results of a later simplification and superheating.

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Class P1-e (Locobase 9449)

Data from RDG 11 - 1926 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

All four locomotives were built as Vauclain compounds (Locobase 15924). The Reading retained the large Wootten firebox in a rebuild the shops completed in 1904, but abandoned the compound cylinders and very tall 84 1/4" drivers in favor of two simple-expansion cylinders and 74" wheels.

So modified, the quartet supported fast passenger operations until the 311 was sent for scrap in February 1927 with 314 following in November. Five years later the second pair was sent to the ferro-knacker in August (312) and December (313).

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Class P1-f (Locobase 9450)

Data from RDG 11 - 1926 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

As noted in Locobase 12415, express Vauclain-compound locomotives on the Reading didn't operate for long in that setup. The Reading's shops took the quartet of tall-drivered engines with this boiler and converted them in 1904. At some point, probably later in their careers, the shops eliminated 27 tubes from the tubesheet. (If it was the product of installing a new boilerr, they may sought wider tube spacing for greater strength. Or they simply may have blocked off the extra tubes.)

They served the Reading for another 25 years before the 320-321 were scrapped in July 1930. The 318-319 followed in September 1933.

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Class P2-a (Locobase 9451)

Data from RDG 11 - 1926 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

These were all Reading-built express passenger engines with large Wootten fireboxes delivered with long combustion chambers, a boiler detail that the Reading reduced considerably in later variants. Otherwise, the class showed a classic camelback look.

All were rebuilt in 1913-1914; see Locobase 9452.

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Class P2-b (Locobase 9452)

Data from RDG 11 - 1926 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

P-2as built in 1907, redesignated in 1914 with the most apparent difference was a 15-psi reduction and the adoption of outside radial valve gear. Weight dropped on the drivers, but increased over the lead bogie and the trailing truck.

Later reduced to 276 tubes (for 2,088.7 sq ft of tube surface vs 2,139) . Most were scrapped in the mid-1930s.

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Class P3-a (Locobase 16161)

Data from DeGolyer, Volume 23, p. 38. (Thanks to Chris Hohl for his 10 December 2016 email noting the misplaced decimal in the LP stroke, which incorrectly reduced it to 2.4".) Works numbers were 17741-17742 and 17765-17768 in May 1900.

At nearly the height of the four-cylinder Vauclain compound infatuation, the Reading bought these six Atlantics. The power system took orthodox form: Each side had an HP and an LP cylinder cast together and supplied through a single relatively large 15" (381 mm) piston valve. The Reading also adopted 1 3/4" diameter tubes and a firebox with a 48" long combustion chamber contributing 61.1 sq ft (5.68 sq m) to the firebox heating surface area.

Regardless of the often breathless descriptions of the savings and performance, the railroad soon dispensed with the compound system; see Locobase 9453.

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Class P3-c (Locobase 9453)

Data from RDG 11 - 1926 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Works numbers were 17741-17742 and 17765-17768 in May 1900.

Only three years after the six Vauclain compound Atlantics were delivered to the Reading (Locobase 16161), the railroad simpled them and raised the boiler pressure (not a usual step).

A decade later, the Reading again reconfigured the boiler and wound up with fewer, but larger-diameter tubes resulting in much less heating surface; see Locobase 9454.

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Class P3-d (Locobase 9454)

Data from RDG 11 - 1926 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Apparently the idea of squeezing a lot of relatively small-bore (1 3/4") tubes into a boiler (Locobase 9453) didn't work out well in practice, so the Reading reconfigured the boiler to a more conventional layout. In the process, the engine lost about one-quarter of its heating surface.

The entire class was retired in 1933.

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Class P4-a/P4-d (Locobase 9455)

Data from RDG 11 - 1926 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Volume 24, p. 274. Thanks to Chris Hohl for his suggested updates that led me to the Baldwin specs. Works number was 20529 in June 1902.

The Reading built these two high-drivered Atlantics to compare simple-expansion working with that available to a Vauclain balanced compound with even more cylinder volume (Locobase 9456). As noted in the P3-b entry, this engine's performance was apparently more satisfactory.

After the compound's conversion in 1904, the two formed a small sub-class of their own, although the 329 now rolled on 80" drivers. In the teens, both were redesignated P4-d when they were refitted with new boilers pressed to 225 psi (328) in May 1914 and 220 psi (329) in February 1915. Their fireboxes had 4 fewer sq ft in the firebox and a slightly smaller grate area. Weight by now had increased to 107,825 lb (48,909 kg) on the drivers and 192,700 lb (87,407 kg) for the engine. With the higher BP, tractive effort stood at 24,100 lb (10,932 kg) for the 328 and 24,700 lb (11,204 kg) for 329.

The two were scrapped a month apart in 1933--February for 328, and March for 329.

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Class P4-b, P4-c (Locobase 9458)

Data from RDG 11 - 1926 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Volume 24, p. 274. Works numbers were 20529, 20531, 22266, 22267 in May 1903; 22274, 22287 in June; 24164, 24172 in April 1904; 24188, 24199, 24225, 24272 in May.

Baldwin blended the distinctive demands of an anthracite road burning light-drafted culm, the design philosophy of express Atlantic locomotion, and a waning interest in compounding in this decade of simple-expansion engines. Its defining element was the enormous Wootten firebox, whose width led the Reading to place the cab in the center of the boiler and ahead of the furnace.

The class was rebuilt by the Reading in 1914; see Locobase 9457.

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Class P4-e/P4-f (Locobase 9457)

Data from RDG 11 - 1926 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

In the mid-teens, the Reading overhauled all ten Baldwin 7-foot Atlantics originally supplied in 1903-1904 (Locobase 9458). P-4e refers to the 1903 batch, P4-f to the 1904s. Ot the 10, 7 received 80" drivers and that septet is represented in the specifications.

All ten were scrapped between July 1933 and June 1935.

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Class P5-c (Locobase 4100)

Data from Figure 55, "Atlantic Type (4-4-2) Three Cylinder Simple Locomotive for Passenger Service", in Roy V Wright (ed), Locomotive Dictionary 1916 (4th Ed) (New York: Simmons-Boardman Publishing Company, 1916), p. 172. Additional data from J Snowden Bell, "Individual Paper on Three-Cylinder Locomotives", Report of proceedings of the ... annual convention of the American Railway Master Mechanics' Association, (American Railway Master Mechanics' Association, 1913), pp. 276-280; and Paul T. Warner, "Three-Cylinder Locomotives." The Railway and Locomotive Historical Society Bulletin, no. 58 (1942), pp. 18-31.

It's hard to believe one could fit a larger grate on a camelback Atlantic that this one. Add to the novelty a three-cylinder layout and you have the third of three experiments by Edward Elliott of the Philadelphia & Reading. (The other two are described in Locobases 2809 .)and 4099

Note that the BP is slightly lower than that of 303. Snowden Bell reported that all of the Reading's three-cylinder locomotives had their cylinders arranged side-by-side with the center cylinder driving the front axle, the two outside cylinders turning the second. All cylinders were fed by piston valves. The two outside cylinders used Walschaert's valve gear while the center cylinder's valves were actuated by Joy gear.

Also, Warner notes that the heating surface includes the Schmidt superheater.

Warner's best time behind any locomotive came one morning when 344 clipped off 12 miles of descending grade in the Lehigh Valley in 8 min 4 sec or 89 mph.

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Class P5-sd/e (Locobase 6453)

Data from Philadelphia & Reading 9 Sept 1914 erecting diagram for this more conventional Atlantic camelback.

The two piston valves each measured 13"(330 mm) in diameter and had 7" travel with 5/16" lead and 1 3/8" lap. The diagram notes that the P-5d has 23" x 26" cylinders with 80" drivers while the P-5e had the 23" x 27" and 86" drivers shown in the specs.

The EHS dropped when the locomotives were superheated. Axle loadings ranged from 63,650 lb to the 68,125 lb shown in the specs. At a later date, the boiler saw the removal of 28 tubes and a drop in tube & flue heating surface area to 2,707 sq ft (251.49 sq m). Total EHS then came to 2,981 sq ft.

The RDG 11 - 1926 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange do not show superheater area. The figure given in the specs is an estimate based on installations of similar flue count and length.

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Class P6-a (Locobase 2809)

Data from J Snowden Bell, "Individual Paper on Three-Cylinder Locomotives", Report of proceedings of the ... annual convention of the American Railway Master Mechanics' Association, (American Railway Master Mechanics' Association, 1913), pp. 276-280; and Paul T. Warner, "Three-Cylinder Locomotives." The Railway and Locomotive Historical Society Bulletin, no. 58 (1942), pp. 18-31.

Another unusual Reading design, this one conceived by chief draftsman Edward O. Elliott. Add to the camelback with its enormous firebox (108" wide) a three-cylinder layout that originally was compound, later simpled as depicted here.

Edwin Alexander (1950) observes that this were the first Reading engines to have Walschaert valve gear. Warner reported that the original superheater was a Taylor design. This was a chamber some three feet (914 mm) long in the front boiler course. Warner concluded that it was probable " that the device ...gave only a very moderate degree of superheat." He noted that a later upgrade included the Schmidt type of superheater.

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Class P6-b (Locobase 4099)

Data from RDG 11 - 1926 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Additional data fromJ Snowden Bell, "Individual Paper on Three-Cylinder Locomotives", Report of proceedings of the ... annual convention of the American Railway Master Mechanics' Association, (American Railway Master Mechanics' Association, 1913), pp. 276-280; and Paul T. Warner, "Three-Cylinder Locomotives." The Railway and Locomotive Historical Society Bulletin, no. 58 (1942), pp. 18-31

The second of three trial three-cylinder camelback Atlantics (talk about an exclusive club!), this engine had a surprisingly high boiler pressure for the time. It was likely reduced soon after the 300 entered service. Warner noted that the heating surface area included a Taylor superheater. (See notes for engine 303, Locobase 2809)

Later superheated with a more conventional boiler; see Locobase 9459.

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Class P6-sb (Locobase 9459)

Locobase 4099 describes the second of three trial three-cylinder camelback Atlantics built by the Reading in the early teens.

As with the other experiments, operational reality soon dictated a conversion to a more conventional, but still camelback, layout. An oddity in this engine's boiler, however, is the provision of 18 1 3/4" tubes in addition to the 154 2" tubes shown in the specs. The superheater flues were slightly narrower than the conventional as well.

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Class P7-sb (Locobase 9448)

Data from RDG 11 - 1926 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Few railroads managed to make the 4-4-4 wheel arrangement work and the Reading fit the majority mold. Within a year of introducing its C1-a (Locobase 2810), the company rebuilt the quartet as 4-4-2s.

A principal difference was a 13.5 sq ft (1.25 sq m) drop in grate area, achieved by reducing firebox length by 18" (457 mm) to 126 1/4" (3.21 m),. Total wheelbase decreased by 4 feet (1,219 mm) as a much larger single-axle trailing truck (54"/1,372 mm) supported the firebox . Another drop was the 8 1/2 short ton (7.7 metric tonne) reduction in adhesion weight while weights on the trucks changed very little. The factor of adhesion changed relatively little from the C-1a's 4.1 because boiler pressure was reduced by 25 psi (1.72 bar). Piston valve diameter grew to 14" (356 mm).