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.
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.
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 In the case of the P-31s, the last locomotive was withdrawn in 1953.
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.
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.
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.)
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.
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|
|Class||P-28||P-31||P-31 - superheated||P-32||P-32 - superheated||P-33||P-40||P-46|
|Railroad||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)||Rock Island (CRI & P)|
|Locomotive Length and Weight|
|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 Drivers||130000 lbs||148000 lbs||147750 lbs||143500 lbs||146500 lbs||151500 lbs||174500 lbs||187000 lbs|
|Engine Weight||192800 lbs||227000 lbs||226950 lbs||212000 lbs||216000 lbs||243025 lbs||281500 lbs||301000 lbs|
|Tender Light Weight||141500 lbs||150000 lbs||150640 lbs||150000 lbs||150000 lbs||150640 lbs||194000 lbs||196000 lbs|
|Total Engine and Tender Weight||334300 lbs||377000 lbs||377590 lbs||362000 lbs||366000 lbs||393665 lbs||475500 lbs||497000 lbs|
|Tender Water Capacity||7000 gals||7500 gals||7900 gals||7500 gals||7500 gals||7500 gals||8500 gals||10900 gals|
|Tender Fuel Capacity (oil/coal)||13 tons||13 tons||13 tons||13 tons||13 tons||3250 gals||4400 gals||16 tons|
|Minimum weight of rail (calculated) on which locomotive could run||72 lb/yard||82 lb/yard||82 lb/yard||80 lb/yard||81 lb/yard||84 lb/yard||97 lb/yard||104 lb/yard|
|Geometry Relating to Tractive Effort|
|Boiler Pressure||200 psi||185 psi||185 psi||200 psi||190 psi||185 psi||190 psi||190 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 Effort||28250 lbs||31907 lbs||31476 lbs||31004 lbs||32192 lbs||32859 lbs||39736 lbs||46404 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|
|Firebox Area||164 sq. ft||179.41 sq. ft||238 sq. ft||179.41 sq. ft||203.45 sq. ft||238 sq. ft||238 sq. ft||378 sq. ft|
|Grate Area||42.20 sq. ft||44.80 sq. ft||45 sq. ft||44.80 sq. ft||44.80 sq. ft||45 sq. ft||63 sq. ft||66.80 sq. ft|
|Evaporative Heating Surface||3104 sq. ft||3555 sq. ft||2995 sq. ft||3354 sq. ft||2821 sq. ft||2951 sq. ft||3514 sq. ft||3527 sq. ft|
|Superheating Surface||676 sq. ft||596 sq. ft||739 sq. ft||805 sq. ft||933 sq. ft|
|Combined Heating Surface||3104 sq. ft||3555 sq. ft||3671 sq. ft||3354 sq. ft||3417 sq. ft||3690 sq. ft||4319 sq. ft||4460 sq. ft|
|Evaporative Heating Surface/Cylinder Volume||297.81||264.03||222.44||293.20||225.63||209.94||212.32||182.48|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||8440||8288||8325||8960||8512||8325||11970||12692|
|Same as above plus superheater percentage||8440||8288||9824||8960||9959||9990||14244||15357|
|Same as above but substitute firebox area for grate area||32800||33191||51955||35882||45227||52836||53812||86902|