Lehigh Valley 4-6-2 "Pacific" Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class K-1 (Locobase 11099)

Data from "Locomotive Building," The Railway Gazette, Vol XXXIX, No 24 (15 December 1905), p. 191. See also Baldwin Locomotive Works Specification for Engines as digitized by the DeGolyer Library of Southern Methodist University, Volume 28, pp. 46 and 200.. Works numbers were 26353 in August 1905, 26712 in October, 27752-27753 in March 1906, 27864-27866 in April.

These were the only camelback Pacifics to be built for any railroad. The layout resulted in a profile of a Ten-wheeler immediately followed by its enormous Wootten firebox, which was supported by the trailing axle.

2004-2006 wer rebuilt in 1919 and 1921 as K-3 conventional-cab Pacifics; see Locobase

Class K-2 1/2 (Locobase 1361)

Data from "Anthracite Burning Pacific Type Locomotive", Railway Age, Vol. 56, No 10 (6 March 1914), pp. 473-475.

The RA report noted that these Pacifics were designed to work over the Easton-Sayre (PA) Division. The maximum grades on this run were (westbound) the 33.7 mile (54.25 km) climb from Mauch Chunk (later Jim Thorpe) to Glen Summit, which had a maximum grade of 1.25% and, eastbound, the Wilkes-Barre -- Glen Summit section, which maxed out at 1.8% during its 19.6 mile (31.6 km) ascent. Over this line the Pacifics were designed to haul 550-ton passenger trains westbound, 360-ton trains eastbound.

The grate size tells you this was an anthracite burner with a Wootten firebox. RA acknowledged that the factor of adhesion is relatively low and notes that "it was necessary to design the valve gear to obtain a rotative effort as nearly constant as possible." The 14" (356 mm) piston valves were set up to have the relatively generous lap of 1 1/4", which RA comments "is apparently responsible for the even turning movement." Although RA doesn't mention it, the lead in these valves of 5/16" was also relatively high and would also have contributed to the smooth reciprocation of the motion.

The first 2/1/2 left service in 1937 with the last not retiring until 1950.

Class K-3/K-4 (Locobase 3087)

Data from LV 3 - 1934 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Raildata collection.

These followed the new-build K2 1/2s (Locobase 1361) and had identical principal dimensions. K3s 2026-2031 were rebuilds of Camelbacks as conventional cabs, but retained the Wootten firebox. 2026 had been K-1 2004 and 2034-2035 were ex-K-1 2005-2006 (Locobase 1361). 2028-2034 rebuilt seven K-2s, which were themselves modifications of the I-1 Prairies delivered by Baldwin in 1902 (Locobase 12614).

K4s (2050-2064) had conventional fireboxes burning bituminous coal; the data relates to these engines.

Class K-5/K-5 1/2 (Locobase 446)

Data from Railway Age Gazette, 27 April 1917. Data confirmed and supplemented by table in January 1917 issue of Railway Mechanical Engineer (RME) and LV 3 - 1934 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Raildata collection. See also DeGolyer, Vol 59, pp. 168-203.Works numbers were


December 44582-44587, 44629-44631, 44675-44676


January 44817-44819, 44832-44834, 44905-44906, 44917-44918, 44928-44929; February 45045-45046, 45077-45079, 45123-45124


November 50675; December 50941


January 51033-51034, 51079, 51118, 51154-51155; February 51254-51255, 51305-51306, 51339, 51383; March 51478, 51516, 51555-51556, 51584, 51637.

Firebox burned bituminous coal; its heating surface area included 100 sq ft (9.3 sq m) in the combustion chamber and 40 sq ft (3.7 sq m) in five arch tubes. Tube/flue layout was identical to the R-class 2-10-2s built in the same year, but the latter had 21-foot-long tubes. Piston valves measured 14" (356 mm) in diameter.

Lehigh Valley built several K classes. The first 30 entered service in early 1917; 20 more delivered by the end of the year. Operated as dual-service fast-freight/heavy passenger locomotives between Manchester, NY and Coxton, Pa (175 miles) over a ruling grade of 0.4%. A 50-car freight made the trip in 5 1/2 hours. Also used in heavy passenger service on the Wyoming division (Pittson-Athens) .

Although they started out with 192,200 lb on the drivers (301,500 lb for the engine), upgrades and additions increased both weights by five tons. They also trailed much larger tenders over time, starting out with 158,500 lb loaded and carrying 8,000 gal of water and 12 1/2 tons of coal.

Several K-series engines (including #2102) were streamlined for the John Wilkes express service.

Class K6b (Locobase 147)

Data from tables in 1930 Locomotive Cyclopedia. See also the Black Diamond Express web page at http://gold.mylargescale.com/scottychaos/BlackDiamondExpress/BDE-page3.html, last accessed 6 December 2013. Works numbers were Alco-Brooks 65255-65256 in January 1924 and 65257-64 in February (road numbers were 2090-2099). (Thanks to Chris Hohl for his 13 September 2012 query concering the actual make up of this class.)

Firebox had combustion chamber. These had axle loadings almost four tons lighter than those of the K 5 1/2 (Locobase 446). These engines had a 10,400 lb booster to increase starting TE. Lehigh Valley's Sayre shops converted two K-3s to K-6bs in June 1925 and August 1926; these had the two lowest road numbers of the class.

Three were later streamlined. 2093 and 2089 received the treatment in 1939, 2097 in 1940. Their Otto Kuhler-designed casings were black with red valences and trimmed with white pinstripes. All of the top hamper (domes, stack, safety valve stand) were shrouded in a narrow casing that ended at the smoke box edge. The engine had a cone-shaped fairing capping the smokebox front.

Specifications by Steve Llanso of Sweat House Media
ClassK-1K-2 1/2K-3/K-4K-5/K-5 1/2K6b
Locobase ID11099 1361 3087 446 147
RailroadLehigh Valley (LV)Lehigh Valley (LV)Lehigh Valley (LV)Lehigh Valley (LV)Lehigh Valley (LV)
Number in Class911335012
Road Numbers2001-20072010-20202021-2035, 2050-20642100-21492088-2099
Number Built911205012
BuilderBurnham, Williams & CoLV-SayreLVBaldwinSeveral
Valve GearStephensonWalschaertWalschaertBaker or WalschaertBaker
Locomotive Length and Weight
Driver Wheelbase13.50'13.67'13.67'13.67'13.67'
Engine Wheelbase33.75'35.58'36.08'36.50'
Ratio of driving wheelbase to overall engine wheebase 0.40 0.38 0.38 0.37
Overall Wheelbase (engine & tender)63.15'76.36'68.06'68.85'73'
Axle Loading (Maximum Weight per Axle)55760 lbs68330 lbs60400 lbs
Weight on Drivers140000 lbs161940 lbs162080 lbs204560 lbs181000 lbs
Engine Weight220000 lbs262160 lbs262540 lbs311900 lbs291000 lbs
Tender Light Weight139600 lbs163860 lbs222200 lbs197500 lbs
Total Engine and Tender Weight359600 lbs426400 lbs534100 lbs488500 lbs
Tender Water Capacity6500 gals7000 gals8500 gals12000 gals10500 gals
Tender Fuel Capacity (oil/coal)12 tons12 tons13.5 tons17.5 tons15 tons
Minimum weight of rail (calculated)78 lb/yard90 lb/yard90 lb/yard114 lb/yard101 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter76.50"77"77"73"77"
Boiler Pressure200 psi215 psi215 psi205 psi215 psi
Cylinders (dia x stroke)22" x 28"25" x 28"25" x 28"27" x 28"25" x 28"
Tractive Effort30116 lbs41534 lbs41534 lbs48723 lbs41534 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.65 3.90 3.90 4.20 4.36
Heating Ability
Firebox Area207.50 sq. ft268 sq. ft322 sq. ft369 sq. ft328 sq. ft
Grate Area80 sq. ft87 sq. ft65 sq. ft75 sq. ft75.30 sq. ft
Evaporative Heating Surface3854 sq. ft3787 sq. ft3325 sq. ft4105 sq. ft3285 sq. ft
Superheating Surface812 sq. ft741 sq. ft980 sq. ft945 sq. ft
Combined Heating Surface3854 sq. ft4599 sq. ft4066 sq. ft5085 sq. ft4230 sq. ft
Evaporative Heating Surface/Cylinder Volume312.85238.06209.02221.23206.50
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation1600018705139751537516190
Same as above plus superheater percentage1600022072164911829619751
Same as above but substitute firebox area for grate area4150067992816919001886034
Power L11012521568201271985423294
Power MT478.32880.87821.31641.92851.18


If you have any railroad data such as diagram books, rail station plans or anything else that you would be willing to share, please contact us.