Pennsylvania / Vandalia Line 4-6-2 "Pacific" Locomotives in the USA

Class K2 (Locobase 16277)

Data from Locomotive Testing Plant at Altoona, Penna, Bulletin No. 22, Comparison of Passenger Locomotives (Altoona, Pa: Pennsylvania Railroad Company, 1915), esp. 4-5.

Edson (Keystone Steam & Electric, 1974) notes that the K2 design was prepared by Fort Wayne while Altoona designed its K1. The K1 was not produced, so this was the first mass-produced Pacific acquired for the Pennsylvania and in such features as the 80" drivers and Belpaire firebox, it established the benchmarks for all the Keystone 4-6-2s to come.

Some of the subtleties of comparing efficiencies of saturated versus superheated boilers emerge in a comment 38 of the LTP's analysis cited above. "The evaporation for the saturated steam boiler K2 is the greatest," it reported. The report's explanation shed new light for Locobase when it explained that the result was "on account of the greater heat absorbing qualities of the boiler tube surrounded by water, as compared with a superheater tube surrounded by steam." ( Part 65 gives the ratio per square foot of superheater heating surface to water heating surface as between .268 to .426, the increase correlating with a growing proportion of superheater to saturated area.)

In other words, hot gases flowing through tubes gave up more heat to the surrounding water through the tubes' walls than the saturated steam flowing around superheater elements in superheater flues. Locobase wonders if the four-pass design of Schmidt Type A superheaters achieved ratios closer to even at the time the steam left for the cylinders.

Moreover, Part 143 summarized the benefits of superheating by noting that because superheating actually increased as the boiler was forced ("which would normally result in a lowering of efficency of the locomotive"). The authors summed up the superheater's role as acting "in a manner similar to a large accumulator or reservoir which gives up its energy when most needed, and at failry high efficiency."

A later finding--Part 60--notes the relatively high heating surface to grate area ratio was a factor in the "low" 15 pounds per hour per square foot (73 kg per hour per square metre) of total heating surface.

Very few of this class survived the 1930s, most being retired early in that decade.

Class K28 (Locobase 5693)

Data from "Pacific Locomotive for the Pennsylvania Lines West", The Railroad Gazette, Vol XLIII, No 9 (30 August 1907), pp. 238-240.

This was a single Lines West "Alco", but unlike the K29, which remained unique, this engine led to Pennsy's own K2 design. The grate was quite large, the piston valves relatively enormous at 16"(406 mm) diameter and 7" (279 mm) stroke, and the firebox radially stayed, but otherwise the K2s followed easily from this prototype.

Later superheated and redesignated K28s, when it had very nearly the same number of tubes and flues (200 & 30, vs 202 and 32) as the K2s.

Retirement and scrapping came in June 1933.

Class K29 (Locobase 7581)

Data from reproduction of 1913 Alco Bulletin 1016 on Richard Leonard's [] (accessed 16 June 2006). See also Locobase 3305, which discusses Locobase's suspicions about a mysterious entry in a 1921 table presented by an Alco designer. Works number was 50186 in December 1911.

Drury (1993) observes that "At some point Alco must have realized that even if it built an engine PRR would buy a thousand [examples] of [sic], Baldwin and Juniata would split the order." Even so, Edson (Keystone Steam & Electric, 1974) observes, the Alco K29 in many ways served as the forerunner for the K4 absent the Belpaire firebox.

This lone wolf soldiered on until 1929.

Class K2sa (Locobase 161)

Data from diagram scanned in by Robert Schoenberg of [] (viewed 11 April 2003). See also Locomotive Testing Plant at Altoona, Penna, Bulletin No. 22, Comparison of Passenger Locomotives (Altoona, Pa: Pennsylvania Railroad Company, 1915), esp. 4-5. (Many thanks to Chris Hohl for his 22 September 2017 email reporting unlikely boiler pressure values for 177 entries. A Locobase macro caused the error.)

Edson (Keystone Steam & Electric, 1974) notes that the K2 design was prepared by Fort Wayne while Altoona designed its K1. The K1 was not produced.

Soon after the K2 entered service in 1910, Altoona began upgrading them. 151 K2a were converted to K2s, and the 72 K2a that were built by Alco and Altoona from 1911-1913 were soon converted to K2sa. 72 K2sa were built from 1910-1913, all but 10 (Alco) built by Juniata. All had Belpaire fireboxes, 16" (406 mm) piston valves, and the 80" drivers. Some built with Crawford underfeed mechanical stokers that later removed when tests showed that they increased coal consumption.

Locobase believes it's worth quoting from a Classic Trains forum thread on "Steam commuter locomotives" started by Dave Klepper on 20 February 2015 , at [], last accessed 14 April 2017. In the course of the discussion, Klepper offered on 23 February a blunt appraisal of the K2s considerable deficiencies. Noting that few ever were fitted with power reverse, Klepper continues: "[T]he K2 Pacific was a notoriously inefficient locomotive, both in coal and water usage and in maintanace, the latter because of heavy valve-gear needing adjustment frequently. Its Johnson bar was heavy for the engineer to control."

"rfpjohn" quickly seconded Klepper's assessment, offering further details: "The reluctance of engineers to adjust valve settings under way on K2s, out of fear of being injured by the johnson bar throwing them into the front corner of the cab, may have been one of the reasons they were so inefficient and also would be cause for excessive wear in the valve gear and valves. I have also read that the trailing trucks had a bad habit of running hot and also disassembling at speed! Not good."

(rfpjohn later reported that, pursuant to an ICC order in the late 1930s, some did get power reverse.)

While Johnson-bar wrestling matches ending in broken bones weren't unique to the K2, it's understandable that such a prospect would bother Pennsy engineers.

Tom ("ACY") weighed in with a defense of the K2 on 26 February, offering this judgement: "I've always liked the PRR K2's and K3's, even though they were the odd man out on PRR's roster. The built-up, outside bearing trailing truck and oversized valve gear hanger stood out on a road that had very few other engines with these features (the USRA's being among the very few exceptions). In spite of PRR's 20-25 year retirement practice, some of these 1910-13 engines lasted until 1949."

Tom concurs, however, with a general view of their unsuitability on commuter runs: "I don't believe they fit well into commuter service, but they were used on secondary trains for a long time. Maybe the difficulties with the reverse lever constituted a major problem in service that required frequent stops and jackrabbit starts."

Very few of this class survived the 1930s, most being retired early in that decade.

Class K3s (Locobase 162)

Data from "Completion of the Forty-Thousandth Locomotive by the Baldwin Locomotive Works," Brotherhood of Locomotive Firemen and Enginemen's Magazine, Volume 55, No 11 (November 1913), pp. 619-623. See also DeGolyer, Volume 47, pp. 185+. (Many thanks to Chris Hohl for his 22 September 2017 email reporting unlikely boiler pressure values for 177 entries. A Locobase macro caused the error.) Works numbers were 39728-39730 in April 1913; 39764-39766, 39790-39802 in May; 39948-39954, 39993, 39995, 40000, 40074 in June 1913

Interim design between much more numerous K2 (225 built) and K4 (425 built). Intended for the Lines West routes, the K3 used the same boiler and Belpaire firebox as the K2sa. In the K3, however, the cylinder diameter grew by two inches, squaring the cylinder-stroke dimension. Arch tubes contributed 22.8 sq ft (2.12 sq m) to firebox heating surface area and relatively large 16" (406 mm) piston valves supplied steam to the cylinders. (The K4s used 12"/305 mm piston valves because tests showed little loss of efficiency in reducing the size while realizing a savings in weight.) K3s also were delivered with a mechanical stoker, which apparently was acceptable west of Pittsburgh, but not in those areas ruled by Altoona.

One of the K3 engines delivered in July 1913 was Baldwin's 40,000th locomotive. Road numbers ranged from 7004 to 8663. The Pennsy sold five of the class in October 1930--works 39730, 39764, 39792, 39952-39553--to the Norfolk & Western, which operated them as class E-3 (road numbers 500-504). By that time, the cylinders were equipped with 12" piston valves.

Class K4s (Locobase 159)

Data from tables in 1930 Locomotive Cyclopedia. See also DeGolyer, Volume 77, pp. 464+; and C D Young, Locomotive Testing Plant at Altoona, Penna, Bulletin No. 22, Comparison of Passenger Locomotives (Altoona, Pa: Pennsylvania Railroad Company, 1915), passim; and "Pacific and Mikado Type Locomotives, Pennsylvania R R", Railway Review, Volume 55, No 1 (4 July 1914), pp. 4-8. See also Robert Tufnell ,The Illustrated Encyclopedia of Railway Locomotives (London: Quarto Publishing Ltd, 1986). (Many thanks to Chris Hohl for his 22 September 2017 email reporting unlikely boiler pressure values for 177 entries. A Locobase macro caused the error; and for his 14 October 2019 email noting the Baldwin tender specs.)

Perhaps the archetypal 20th Century PRR locomotive, this design shared its boiler and firebox layout with the L-1 2-8-2s that appeared at the same time. See Locobase 32 -- the L1s entry -- for a comment on the unique design of Pennsy's Belpaire firebox.

425 K-4s entered service -- 350 constructed at Juniata and 75 at Baldwin. 1924-1928 locomotives numbered from 5350 to 5499, the Baldwin locos numbering 5400 to 5474. The Baldwin batch engine weight was 308,890 lb (140,110 kg) . The piston load per pound of reciprocating parts was 87 lb (39.5 kg), according to Railway Age (21 July 1916), which was 4.8% more than the E6 Atlantics, and 10.1% more than the Reading Pacifics.

The K-4 prototype generated 3,184 hp for 60 minutes running at 200-240 rpm (48-57 mph) and 60% cut-off. Other tests showed 1,275 indicated HP at 67 mph at 15% cut-off, 2,355 hp at 35% cut-off. Tufnell noted that at the most efficient steaming rate of 34,000 lb (15,422 kg)/hour, boiler efficiency was 76% and the engine burned fuel at the rate of 1.8 lb/ihp/hour (5,800 lb/hour).

See Locobases 161 and 16277 for extended discussions of superheater versus saturated boiler performance.

As with most Pennsy locomotives, the K-4 had a Belpaire firebox. (See Locobase 32 for a comment on the unique design of Pennsy's Belpaire firebox.) Direct heating surface area in the Baldwins included 62 sq ft (5.75 sq m) in the combustion chamber and 34.6 sq ft (3.2 sq m) in four arch tubes. Results of earlier tests at the Locomotive Testing Plant appear to dictated the boiler-grate, cylinder size, and tube length proportions, as they are essentially as prescribed in the conclusions of the test report.

Piston valves measured a relatively slender 12" (305 mm) in diameter, following the LTPs conclusion on page 131 that tests showed that reducing the diameter from the K2s and K3s cylinders' 16" would not cost them performance and would "secure the advantage of a uniform valve diameter and [a] reduction in weight."

Power reversing gear was fitted to the class in the 1920s and most received a mechanical stoker in the 1930s.

Sources differ on the size of the superheater with a couple of the diagrams reproduced by Schoenberg noting areas of 1,072 and 1,157 sq ft. But the majority of diagrams from all periods of K-4 service show the 943 sq ft (305 sq ft of firebox area) recorded in the specs.

The tender weight represents the larger 110 P75 tender. Smaller ones held 7,250 gallons of water and 13 1/2 tons of coal. Chris Hohl noted Baldwin's tenders for the 5400-5474 batch weighed 213,900 lb (97,024 kg) loaded with 11,000 US gallons(41,635 litres) and 13 tons (11.8 metrict tons) of coal.

Most K4s were hand-fired, which is often highlighted as backward thinking. See, however, John W Orr's excellent account of an engineer on the Pennsy (Set Up Running, published by PSU Press in 2001) in which he describes on pp. 116-117 the "bank-firing" technique used by a fireman on a K4. After laying the bed in an orthodox pattern, the fireman piled large amounts of coal, "especially in the corners", but left a bright fire in the middle. Stoking the fire during the K4s high-speed runs consisted of placing a few shovelsful of new coal in the bright fire patch, which kept the pressure at near pop-off point.

Class K4s - 3768 streamliner (Locobase 16454)

Data from PRR Steam Locomotive Diagrams supplied in August 2013 by Allen Stanley from his extensive Rail Data Exchange collection. See also on the Classic Streamliners website at [], last accessed 21 October 2019; and Lord K's " Sunday Streamline #28: Loewy Torpedoes" posted 17 April 2017 on his DieselPunks blog at [] . last accessed 21 October 2019. (Many thanks to Chris Hohl for his email commenting on several differences between the basic K4 entry (Locobase 159) and this streamliner. The spreadsheet and comments prompted Locobase to prepare this entry.)

When the Pennsy responded to a growing trend of fitting streamline casings to some of their existing passenger power, it recruited Raymond Loewy to design the shroud. Loewy, better known at the time for his work on the GG-1 electric motors, adapted many of the elements to a full casing on K4 3768. The shroud's outline effaced the characteristic Belapire firebox shoulders and extended over so much of the running gear as to show only the bottom half of the drivers that its engineers dubbed it the "Torpedo".

It had the gold pinstriping on both the engine and the dedicated tender. But this engine did not wear the Tuscan Red coat of paint so familiar to T1 and Baldwin Sharknose locomotive admirers. When it entered service, its casing had a bronze cast to it and later it would be repainted in Dark Green Locomotive Enamel (DGLE). Together with an impressive six-axle tender , the 3768 often headed up the famed Broadway Limited (although it probably needed to start the train with the help of a non-streamlined sister). The railroad didn't stop with locomotives--it bought 142 smoothsided cars limned in the same gold pinstriping as the engine and tender.

Mechanically, the locomotive was little changed from the long-running production version, but adhesion weight rose by almost 10 tons (9.3 metric tons) and engine weight increased by 15 tons (13.6 metric tons).

Four more engines, 1120, 2665, 3678, and 5338 received less cumbersome casings that left the running gear exposed and simplified maintenance. Together with the 3768, all four eventually discarded their streamlining.

Class K5 (Locobase 160)

Data from the 1930 Locomotive Cyclopedia tables. See also DeGolyer, Volume 81, 113+ for the Caprotti. (Many thanks to Chris Hohl for his 22 September 2017 email reporting unlikely boiler pressure values for 177 entries. A Locobase macro caused the error.)

5698 was built by Juniata with Walschaerts valve gear; called the General Butler. 5699 built by Baldwin with Caprotti poppet valve gear and called the Mussolini (because of its "Italian" valve gear). Both were fitted with a Worthington "PRR" Special Type S feedwater heater.

These were hand-bombers with a GDF that suggests the Herculean task facing the fireman. See Locobase 159 for a description of the "bank-firing" technique that saved the shoveller's back. The Caprotti gear on 5699 was later replaced by Walschaerts constant-lead radial valve gear.

Not considered a success.

Class VK1 / K21s (Locobase 7587)

Data from reproduction of 1913 Alco Bulletin 1016 on Richard Leonard's [] (accessed 16 June 2006). Edson's Keystone Steam & Electric (1974) shows that the class came in 3 batches: works# 47737-47740 in August 1910, 50631-50634 in February 1912, and 53971-53974 in July 1913

According to the notes in Bob Berkey's PRR Steam Locomotive Classification, the specs for these Indiana engines were similar to the Pennsy's K-2 and K-3 designs, but they were lighter, used a radial-stay firebox, and a different kind of trailing truck. They had 14" (356 mm) diameter piston valves. The first group was delivered with saturated boilers containing 383 2" tubes.

The Pennsy took them over in 1917 and scrapped them from December 1929-August 1930. One suspects the short lifetime is attributable to the relatively modest power dimensions, their Schenectady origins, and the small number of engines. This assessment is reinforced by an October 1910 account in Railway & Locomotive Engineering (p. 382) that emphasizes the easy gradients and wide-sweeping curves over which the Vandalia's trains had to travel. Perhaps when it came time to put them to more demanding use, the railroad found these locomotives would not serve.