Chicago & Alton 2-6-6-2 "Mallet Mogul" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class K1 (Locobase 16357)

Data from "Mallet Articulated Compound for the Chicago & Alton", Railway & Locomotive Engineering, Volume 23, No 7 (July 1910), p. 274. (Thanks to Chris Hohl for his 18 June 2018 email and spreadsheet detailing this earlier version of the K1 at Locobase 9102 and prompting this new entry.) Works numbers were 47539-47541 in April 1910.

In the same year that Brooks delivered the first of its L1 Mikados to the Alton (Locobase 9100), it supplied this trio of light Mallets. They borrowed the same boiler design, but lengthened the tubes by a foot and included more flues. R&LE used an interesting comparison when it calculated that the boiler's total area was "a little more than half the space enclosed between the bags on a baseball field."

Like the Mikes, the HP cylinders had 14" (356 mm) piston valves. The LP cylinders used double-ported slide valves.

The R&LE report notes that the L1s could handle a 4,000-ton train from the Girard coal district near Atlanta, "...[e]xcept on the grade between Lawndale and Atlanta, which is 0.85 Per cent" To allow the Mikes to take the heavy trains all the way to Chicago, these Mallets were assigned to pusher service on the Atlanta hill.

One was sold almost immediately (April 1911) to the Chesapeake & Ohio and classed as an H-3, although it was quite different from the Chessie's other H-3s. In short order, the loner would be renumbered 750, 799, 699, the latter in 1915. A decade later it would take number 1290. It served the C & O until the late 1920s and was scrapped in April 1930..

The other two persisted in pusher service, but apparently revealed a shortage of steam. The culprit lay in the firebox, which measured 108 1/8" (2.75 m) long and 66" (1.68 m) wide, adequate for the L1 2-8-2s, but seriously underscaled for the much bigger Mallets. The two Alton survivors were soon fitted with new boilers holding superheaters and a larger grate; see Locobase 9102.

Class K1 - superheated/KK-3 (Locobase 9102)

Data from C&A 12-1920 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Locobase 16357 describes the original trio of saturated-boiler Mallets delivered by Brooks in 1910. 700--the class leader--was sold to the C&O in 1911. 701-702 were later renumbered 700-701.

The other two apparently failed to meet promised power estimates and were rebuilt to an extent far beyond the usual superheater upgrade. There was the usual sacrifice of small tubes for larger-diameter flues (in this case 173 small tubes for 38 flues) in the boiler, although the superheater ratio of 21% of the combined heating surface area was unusually high for a converstion. Also unusual was the change in firebox. Its heating surface area decreased considerably, but the grate was lengthened by 37" to 145 1/8" (3.69 m) and widened 6" to 72" (1.83 m), increasing its area 22% and reducing its EHS/grate ratio from 95.9:1 to 66.4:1.

Adhesion weight dramatically increased by 31,700 lb (14,379 kg) and engine weight grew by 37,794 lb (17,143 kg).

When the Alton was aken over by the Baltimore & Ohio in 1930, the pair then traveled east, but into storage rather than into service. There they languished until scrapped in April 1938.

Principal Dimensions by Steve Llanso of Sweat House Media
ClassK1K1 - superheated/KK-3
Locobase ID16,357 9102
RailroadChicago & Alton (C&A)Chicago & Alton (C&A)
Number in Class32
Road Numbers700-702701-702/700-701
Number Built3
Valve GearWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)11 / 3.3511 / 3.35
Engine Wheelbase (ft / m)48.08 / 14.6548.08 / 14.65
Ratio of driving wheelbase to overall engine wheebase 0.23 0.23
Overall Wheelbase (engine & tender) (ft / m)76.57 / 23.3474.62 / 22.74
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)286,300 / 129,864318,900 / 144,244
Engine Weight (lbs / kg)327,300 / 148,461365,094 / 165,563
Tender Loaded Weight (lbs / kg)171,000 / 77,564205,600 / 93,259
Total Engine and Tender Weight (lbs / kg)498,300 / 226,025570,694 / 258,822
Tender Water Capacity (gals / ML)8500 / 32.2011,000 / 41.67
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)14 / 12.7018 / 16.40
Minimum weight of rail (calculated) (lb/yd / kg/m)80 / 4089 / 44.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)62 / 157562 / 1575
Boiler Pressure (psi / kPa)200 / 13.80200 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)22" x 30" / 559x76222" x 30" / 559x762
Low Pressure Cylinders (dia x stroke) (in / mm)35" x 30" / 889x76235" x 30" / 889x762
Tractive Effort (lbs / kg)57,075 / 25888.8257,075 / 25888.82
Factor of Adhesion (Weight on Drivers/Tractive Effort) 5.02 5.59
Heating Ability
Firebox Area (sq ft / m2)300 / 27.87237 / 22.02
Grate Area (sq ft / m2)49.70 / 4.6263.30 / 5.88
Evaporative Heating Surface (sq ft / m2)4766 / 442.774205 / 390.65
Superheating Surface (sq ft / m2)1117 / 103.77
Combined Heating Surface (sq ft / m2)4766 / 442.775322 / 494.42
Evaporative Heating Surface/Cylinder Volume361.09318.58
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation994012,660
Same as above plus superheater percentage994015,319
Same as above but substitute firebox area for grate area60,00057,354
Power L138769554
Power MT179.08396.29

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