Data from DeGolyer, Volume 35, p. 176 and "Locomotive Performance on the Chicago Great Western" Railway Age Gazette, Volume 57, No 18 (30 October 1914), pp. 796-798. (Thanks to Chris Hohl for his 17 March 2019 email noting the correct tender fuel capacity.) Works numbers were 35365-35374 in October 1910.
Firebox heating surface included 25 sq ft (2.32 sq m) of "water tubes."
The design was essentially identical to the Western Maryland M-1a engines produced in the same month; see Locobase 13938.
After March 1914 tests among ten each of the CGW's Consolidations (Locobase 3090), these Mallets, and the newer Mikados (Locobase 3093) over the Eastern Division between Oelwein, Iowa and Stockton, Ill, the Railway Age Gazette summarized the Prairie Mallet's performance: "It is surprising to note the relatively small amount of gross tons per mile for the Mallet locomotives with such a high percentage of gross to potential ton miles." It isn't surprising, therefore, to find these engines moving on to the Clinchfield by 1916. The CGW simply found the Mikados they were buying more suitable to their requirements.
Picked up by the Clinchfield after the Chicago Great Western found them unsuitable, they lasted only a few years. As Drury (1993) comments: "Their early retirement in 1925 is probably a good indication of their performance."
Data from "Converted Mallet Locomotives for the Chicago Great Western", Railway Age Gazette, Volume 54 (4 November 1910), pp. 867-869.
It wasn't unheard of for a railroad to convert a simple-expansion freight locomotive to a compound Mallet, but it was rare. Locobase 16300 describes a single Erie 2-6-8-0 conversion from one of their 2-8-0s and Locobase 16380 concerns a very similar Great Northern 2-6-8-0 conversion.
CGW accomplished this modification in 1910 by ordering a new "Mallet kit" front end from Baldwin and fitting them to three F3 mixed-traffic Prairies from 1902 (Locobase 4166). The back end changed very little. The rear, high-pressure cylinders still used their 11" (279 mm) piston valves.
The front end contained 400 2" (51 mm) tubes, each 8 ft 11 in (2.72 sq m) in a feed water heater bundle. CGW included the 1,700 sq ft (157.94 sq m) calculated from that bundle, which raised the tube surface total to 4,924 sq ft (457.46 sq m). (See, e.g., Locobase 3558 for more discussion of the feed water heater design.) The low pressure cylinders took their steam from 15" (381 mm) piston valves.
Very few articulateds had such small grate and firebox areas when compared to their putative evaporative heating surface areas. Deducting the feed water tubes reveals the actual high-pressure ratio of 65:1, however. Yet the cobbled-together assembly apparently was as unsatisfactory as its ungainly appearance.
In 1915, the CGW has removed the Mallet kit, fitted four-wheel bogies, thus creating three K-6s Pacifics (see Locobase 4176).
Principal Dimensions by Steve Llanso of Middle Run Media | ||
---|---|---|
Class | H1 | H2 |
Locobase ID | 3091 | 16525 |
Railroad | Chicago Great Western (CGW) | Chicago Great Western (CGW) |
Country | USA | USA |
Whyte | 2-6-6-2 | 2-6-6-2 |
Number in Class | 10 | 3 |
Road Numbers | 600-609 | 650-652 |
Gauge | Std | Std |
Number Built | 10 | |
Builder | Baldwin | CGW |
Year | 1910 | 1910 |
Valve Gear | Walschaert | Stephenson |
Locomotive Length and Weight | ||
Driver Wheelbase (ft / m) | 20 / 6.10 | 22.92 / 6.99 |
Engine Wheelbase (ft / m) | 45.33 / 13.82 | 51.83 / 15.80 |
Ratio of driving wheelbase to overall engine wheelbase | 0.44 | 0.44 |
Overall Wheelbase (engine & tender) (ft / m) | 72 / 21.95 | 80.54 / 24.55 |
Axle Loading (Maximum Weight per Axle) (lbs / kg) | ||
Weight on Drivers (lbs / kg) | 307,000 / 139,253 | 265,000 / 120,202 |
Engine Weight (lbs / kg) | 353,100 / 160,164 | 367,500 / 166,695 |
Tender Loaded Weight (lbs / kg) | 146,900 / 66,633 | 98,500 / 44,679 |
Total Engine and Tender Weight (lbs / kg) | 500,000 / 226,797 | 466,000 / 211,374 |
Tender Water Capacity (gals / ML) | 8000 / 30.30 | 8000 / 30.30 |
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) | 16 / 15 | 12.50 / 11 |
Minimum weight of rail (calculated) (lb/yd / kg/m) | 85 / 42.50 | 74 / 37 |
Geometry Relating to Tractive Effort | ||
Driver Diameter (in / mm) | 57 / 1448 | 63 / 1600 |
Boiler Pressure (psi / kPa) | 205 / 1410 | 200 / 1380 |
High Pressure Cylinders (dia x stroke) (in / mm) | 23" x 32" / 584x813 | 21" x 28" / 533x711 |
Low Pressure Cylinders (dia x stroke) (in / mm) | 35" x 32" / 889x813 | 35" x 28" / 889x711 |
Tractive Effort (lbs / kg) | 72,284 / 32787.51 | 49,000 / 22226.05 |
Factor of Adhesion (Weight on Drivers/Tractive Effort) | 4.25 | 5.41 |
Heating Ability | ||
Tubes (number - dia) (in / mm) | 450 - 2.25" / 57 | 352 - 2" / 51 |
Flues (number - dia) (in / mm) | ||
Flue/Tube length (ft / m) | 21 / 6.40 | 16.66 / 5.08 |
Firebox Area (sq ft / m2) | 250 / 23.23 | 154 / 14.31 |
Grate Area (sq ft / m2) | 78 / 7.25 | 49.30 / 4.58 |
Evaporative Heating Surface (sq ft / m2) | 5789 / 538.01 | 5078 / 471.76 |
Superheating Surface (sq ft / m2) | ||
Combined Heating Surface (sq ft / m2) | 5789 / 538.01 | 5078 / 471.76 |
Evaporative Heating Surface/Cylinder Volume | 376.25 | 452.57 |
Computations Relating to Power Output (More Information) | ||
Robert LeMassena's Power Computation | 15,990 | 9860 |
Same as above plus superheater percentage | 15,990 | 9860 |
Same as above but substitute firebox area for grate area | 51,250 | 30,800 |
Power L1 | 3847 | 3939 |
Power MT | 165.76 | 196.62 |