Rock Island 4-6-2 "Pacific" Type Locomotives

Class Details by Steve Llanso

Class P-28 (Locobase 5349)

Data from a table published in AERJ in July 1904 (reference back to Oct 1902, p 351). Additional data from RI 11 - 1904 Locomotive Classification and Diagrams supplied in May 2005 by Allen Stanley from his extensive collection. See also "Report of Committee on Power ...Descriptions of Standard Types of Locomotives", AERJ, Vol (March 1905), pp. 84-85.

Drury (1993) notes they had inside piston valves. The Rock's Committee on Power offered this class as the model for their standard Pacific design. "For very heavy passenger service on divisions with steep grades this type, with a deep firebox and large amount of heating surface, great steaming capacity, and high tractive effort, may be more generally depended upon than any other type of locomotive."

That may been the intent, but Schenectady's 1905 class (Locobase 5366) enlarged the cylinder volume and increased the tube count by 28

It's not clear if they were ever superheated, but as they were retired in 1935-1936, it seems unlikely.

Class P-31 (Locobase 14466)

Data from "Equipment and Supplies - Locomotive Building", Railway Age Gazette, Vol XLVIII, No 7 (18 February 1910), p. 384.

These Pacifics were enlargements of the P-32s of 1905 that rolled on taller drivers. The grate and firebox were unchanged as was the tube count in the boiler, but tube length grew by 14 inches (356 mm). Other differences included the adoption of Walschaert's outside radial valve gear and more adhesion weight.

The whole class was later superheated; see Locobase 8353.

Class P-31 - superheated (Locobase 8354)

Data from RI 1 - 1942 Locomotive Diagrams book supplied in May 2005 by Allen Stanley from his extensive collection.

As delivered in 1909 from Alco's Schenectady works, these engines already were fitted with piston valves and Walschaert valve gear (Locobase 14466). Consequently, the superheating upgrade that started a few years later resembled that of the P-32 (Locobase 8353) except for the greater cylinder volume and the longer flues. Some substituted new cast-steel trailing trucks with 10,198-lb tractive-effort Delta boosters and were redesignated P-33-B. A few retained their 26 sq ft of arch tubes, but others replaced the arch tubes with 58 sq ft of thermic syphons at the cost of two small tubes. Although the overall heating surface gain amounted to 12 sq ft, direct heating surface increased by 32 sq ft. This latter figure is shown in the full specifications.

As with the P-32, P-31 retirements began in 1936 and ended many years later. In the case of the P-31s, the last locomotive was withdrawn in 1953.

Class P-32 (Locobase 5366)

The data comes a table published in AERJ in July 1904 (reference back to Oct 1902, p 351). See also "Pacific Type Passenger Locomotive", American Engineer and Railroad Journal, Vol 79, No 8 (August 1905), pp. 282-283.

A larger version of the P-28, the P-32s had a somewhat more generous tube count. Drury (1993) notes that although they came with outside-bearing trailing trucks, the P-32s retained slide valves on all but four of this class.

The whole class was later superheated; see Locobase 8353.

Class P-32 - superheated (Locobase 8353)

Data from RI 1 - 1942 Locomotive Diagrams book supplied in May 2005 by Allen Stanley from his extensive collection.

As noted in the earlier version, these were big, saturated-steam locomotives with slide valves. An upgrade to superheating involved a series of changes that were typical of such a transformation. The slide valves were replaced by 12" piston valves and these were actuated by outside Walschaert radial valve gear.

The firebox was untouched (although the 23.6 sq ft of arch tubes added to the firebox heating surface may have been come later), but the boiler was reworked in the usual fashion with dozens of small tubes replaced by the superheater flues. A less usual change was the 1" increase in cylinder diameter.

Retirements from this class stretched over a 14-year period from 1936-1950.

Class P-33 (Locobase 1194)

Data from RI 1 - 1942 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection. Firebox heating surface includes 58 sq ft of syphons. The design was originally supplied with 26 sq ft of arch tubes.

Following on from the P-31 class that arrived the year before (Locobase 8354), this class had larger-diameter fire tubes and was delivered with a superheater already installed. Although 59,500 doesn't seem to be a high Grate Demand Factor, Drury (1993) says that the small grate was overmatched by the 25 x 28 cylinders originally fitted by Alco-Schenectady. These engines soon received the smaller cylinders indicated in the specifications. Some later substituted new cast-steel trailing trucks with 10,198-lb tractive-effort Delta boosters

(Note: the official name of the Rock Island was the Chicago, Rock Island, & Pacific or CRI&P.)

Class P-40 (Locobase 1193)

Data from Railway Age (9 January 1914), revised and supplemented by RI 1 - 1942 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection Firebox heating surface included 25.4 sq ft of arch tubes.

Improved P-33s (Locobase 1194) by Alco-Brooks that featured a larger grate that allowed restoration of the 25 1/2" x 28" cylinders that had overpowered the smaller grate. American Vandium Facts for March 1914 pointed out that these engines had vanadium cast steel frames, which had been introduced on the Rock Island in 1912.

The 1914 Railway Age published comments by WJ Tollerton, Chief Mechanical Superintendent, who noted that on one run, one of these Pacifics hauled a 12-car, 900-ton train began climbing a 6-mile-long 1% grade at 35 mph and maintained an average speed of 27 mph.

Retirements began in the late 1930s with the last engine leaving in 1952. Unlike earlier Pacifics on the Rock, this class didn't receive trailing truck boosters or thermic syphons.

Class P-46 (Locobase 142)

Data from 1930 Locomotive Cyclopedia table. (Thanks to Chris Hohl for his November 2013 email identifying the valve gear.)

Firebox had 106 sq ft (9.85 sq m) of thermic syphons. Compare with L&N #295 (Locobase 149) and MP #6000 (Locobase 152) for very similar dimensions. One engine of a standard Alco three-cylinder design modified slightly for the three different railroads. Lasted only until 1934 and was scrapped in 1939."


Specifications by Steve Llanso
ClassP-28P-31P-31 - superheatedP-32P-32 - superheatedP-33P-40P-46
Locobase ID5349 14466 8354 5366 8353 1194 1193 142
RailroadRock Island (CRI & P)Rock Island (CRI & P)Rock Island (CRI & P)Rock Island (CRI & P)Rock Island (CRI & P)Rock Island (CRI & P)Rock Island (CRI & P)Rock Island (CRI & P)
Whyte4-6-24-6-24-6-24-6-24-6-24-6-24-6-24-6-2
Road Numbers801-830862-894862-894831-861831-861895-944950-979999
GaugeStdStdStdStdStdStdStdStd
BuilderAlco-BrooksAlco-SchenectadyCRIPAlco-SchenectadyCRIPAlco-SchenectadyAlco-BrooksAlco-Brooks
Year19031910191719051920191019131924
Valve GearStephensonWalschaertWalschaertStephensonWalschaertWalschaertBakerWalschaert
Locomotive Length and Weight
Driver Wheelbase12.33'12.33'13'12.33'12.33'13'13'13.50'
Engine Wheelbase31.83'32'34.67'32'32'34.17'33.83'36.58'
Ratio of driving wheelbase to overall engine wheebase 0.39 0.39 0.37 0.39 0.39 0.38 0.38 0.37
Overall Wheelbase (engine & tender)58.75'61.08'65.67'61.08'61.08'65.67'69.46'74.50'
Axle Loading (Maximum Weight per Axle)
Weight on Drivers130000 lbs148000 lbs147750 lbs143500 lbs146500 lbs151500 lbs174500 lbs187000 lbs
Engine Weight192800 lbs227000 lbs226950 lbs212000 lbs216000 lbs243025 lbs281500 lbs301000 lbs
Tender Light Weight141500 lbs150000 lbs150640 lbs150000 lbs150000 lbs150640 lbs194000 lbs196000 lbs
Total Engine and Tender Weight334300 lbs377000 lbs377590 lbs362000 lbs366000 lbs393665 lbs475500 lbs497000 lbs
Tender Water Capacity7000 gals7500 gals7900 gals7500 gals7500 gals7500 gals8500 gals10900 gals
Tender Fuel Capacity (oil/coal)13 tons13 tons13 tons13 tons13 tons3250 gals4400 gals16 tons
Minimum weight of rail (calculated) on which locomotive could run72 lb/yard82 lb/yard82 lb/yard80 lb/yard81 lb/yard84 lb/yard97 lb/yard104 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter69"73"74"69"69"74"74"74"
Boiler Pressure200 psi185 psi185 psi200 psi190 psi185 psi190 psi190 psi
Cylinders (dia x stroke)21" x 26"23" x 28"23" x 28"22" x 26"23" x 26"23.5" x 28"25.5" x 28"22.5" x 28" (3)
Tractive Effort28250 lbs31907 lbs31476 lbs31004 lbs32192 lbs32859 lbs39736 lbs46404 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.60 4.64 4.69 4.63 4.55 4.61 4.39 4.03
Heating Ability
Firebox Area164 sq. ft179.41 sq. ft238 sq. ft179.41 sq. ft203.45 sq. ft238 sq. ft238 sq. ft378 sq. ft
Grate Area42.20 sq. ft44.80 sq. ft45 sq. ft44.80 sq. ft44.80 sq. ft45 sq. ft63 sq. ft66.80 sq. ft
Evaporative Heating Surface3104 sq. ft3555 sq. ft2995 sq. ft3354 sq. ft2821 sq. ft2951 sq. ft3514 sq. ft3527 sq. ft
Superheating Surface676 sq. ft596 sq. ft739 sq. ft805 sq. ft933 sq. ft
Combined Heating Surface3104 sq. ft3555 sq. ft3671 sq. ft3354 sq. ft3417 sq. ft3690 sq. ft4319 sq. ft4460 sq. ft
Evaporative Heating Surface/Cylinder Volume297.81264.03222.44293.20225.63209.94212.32182.48
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation8440828883258960851283251197012692
Same as above plus superheater percentage8440828898248960995999901424415357
Same as above but substitute firebox area for grate area3280033191519553588245227528365381286902
Power L18659744217402854716082175181691816748
Power MT440.53332.57778.98393.93726.03764.76641.22592.35

Photos

Reference

Credits

Introduction and roster provided by Richard Duley. Class details and specifications provided by Steve Llanso of Sweat House Media.