PRR K5

PRR K5
Builder's photograph of Altoona-built K5, #5698.
Type and origin Power type Steam Builder #5698: PRR Altoona Works #5699: Baldwin Locomotive Works Serial number Altoona: 4205 Baldwin: 60660 Build date 1929 Total produced 2 Rebuild date 1937 Number rebuilt 1
Specifications Configuration: ​  • Whyte 4-6-2 Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Driver dia. 80 in (2.032 m) Adhesive weight 208,250 lb (94,460 kg) Loco weight 327,560 lb (148,580 kg) Tender type 130-P-75 Fuel type Coal Fuel capacity 22 short tons (20.0 t; 19.6 long tons) Water cap 12,475 US gal (47,220 l; 10,388 imp gal) Boiler pressure 250 psi (1.7 MPa) Heating surface 4,285 sq ft (398.1 m2) Superheater: ​  • Heating area 1,634 sq ft (151.8 m2) Cylinders 2 Cylinder size 27 in × 30 in (686 mm × 762 mm) Valve gear #5698: Walschaerts #5699: Caprotti, rebuilt to Walschaerts
Performance figures Tractive effort #5698: 54,675 lbf (243.21 kN) #5699: 58,092 lbf (258.41 kN) as built Factor of adh. 3.8
Career Operators Pennsylvania Railroad Class K5 Number in class 2 Numbers 5698–5699 Delivered 1929 Disposition Both scrapped

The Pennsylvania Railroad's class K5 was an experimental 4-6-2 "Pacific" type, built in 1929 to see if a larger Pacific than the standard K4s was worthwhile. Two prototypes were built, #5698 at the PRR's own Altoona Works, and #5699 by the Baldwin Locomotive Works. Although classified identically, the two locomotives differed in many aspects, as detailed below. They were both fitted with a much fatter boiler than the K4s, but dimensionally similar to those of the I1s 2-10-0 "Decapods". Most other dimensions were enlarged over the K4s as well; the exceptions being the 70 square feet (6.5 m²) grate area and the 80 in (2.032 m) drivers.

In comparison:

The K5's factor of adhesion was much worse than the K4s'. This is because the K5 was more powerful than the K4s but with little more weight on drivers (and thus adhesion). Factors of adhesion below 4 are often considered undesirable for steam locomotives, and the K5 design did prove to be rather less sure-footed because of it. For this reason, 4-8-2 "Mountain" and 4-8-4 "Northern" designs with more drivers (and thus a greater allowable weight on drivers within the same axle load limit) were generally considered preferable for locomotives as powerful as the K5.

Both K5 locomotives were given a 130-P-75 tender carrying 12,475 US gal (47,220 L; 10,388 imp gal) of water and 22 short tons (20.0 t; 19.6 long tons) of coal. Surprisingly for such large locomotives built at such a late date, both were equipped for hand firing. Both were fitted with Worthington-pattern feedwater heaters, power reverse, unflanged main drivers, and both used nickel steel boiler shells. As built, both carried their bell on the smokebox front, hung below the headlight; this arrangement was common on other roads but at the time unique on the PRR.

K5 #5698 was built at the PRR's Juniata Works (Juniata 4205 / 1929) in 1929, but having a works plate Altoona Works 4205 / 1929. This according to late Mr Ivan W. Saunders, Pittsburgh, Pa. A one-piece cast steel locomotive bed was used; this produced the locomotive frame, cylinders, and smokebox saddle as one giant steel casting. This casting was produced by Commonwealth Steel's Granite City, Illinois plant. This cast locomotive bed design was a successful trial, and was repeated on 1930s order for 100 M1a class 4-8-2 "Mountains", as was the Worthington feedwater heater with mixing chamber behind the stack.