Data from "American Locomotives in Japan", Locomotive Magazine, Volume XXIV, No. 3 (15 March 1918), p. 40; Akira Saito, "A Summary of Overview of Japan's Modern Steam Locomotives", based on his May 2000 Rail Magazine article and available on the web from 2004 at [] . and "JGR Class 9020" in Locomotive Wiki at [], last accessed 13 January 2024.. Works numbers were 49829-49834 in March 1911.
Among the Mallet articulated locomotives eventually operated in Japan, ths sextet were among the first. Alco had already supplied these engines as 0-4-4-0 Mallets, a small design that Akira Saito dismissed as training vehicles. To improve their roadability, the shops added a leading truck to this Mallet articulated all-adhesion design.
Piston valves supplied live steam to the rear engine unit; slide valves sufficed for the low-pressure cylinders in the leading unit.
Whatever the IGR may have expected from these engines, they did not deliver a satsifactory result. All were discarded by 1925.
| Principal Dimensions by Steve Llanso of Middle Run Media | |
|---|---|
| Class | 9020 |
| Locobase ID | 20206 |
| Railroad | Imperial Government Railways (JGR) |
| Country | Japan |
| Whyte | 2-4-4-0 |
| Number in Class | 6 |
| Road Numbers | 9020-9025 |
| Gauge | 3'6" |
| Number Built | 6 |
| Builder | Alco-Schenectady |
| Year | 1911 |
| Valve Gear | Walschaert |
| Locomotive Length and Weight | |
| Driver Wheelbase (ft / m) | 7 / 2.13 |
| Engine Wheelbase (ft / m) | 22.67 / 6.91 |
| Ratio of driving wheelbase to overall engine wheelbase | 0.31 |
| Overall Wheelbase (engine & tender) (ft / m) | 22.67 / 6.91 |
| Axle Loading (Maximum Weight per Axle) (lbs / kg) | |
| Weight on Drivers (lbs / kg) | 117,500 / 53,297 |
| Engine Weight (lbs / kg) | 117,500 / 53,297 |
| Tender Loaded Weight (lbs / kg) | 62,350 / 28,282 |
| Total Engine and Tender Weight (lbs / kg) | 179,850 / 81,579 |
| Tender Water Capacity (gals / ML) | 3240 / 12.27 |
| Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) | 3 / 3 |
| Minimum weight of rail (calculated) (lb/yd / kg/m) | 49 / 24.50 |
| Geometry Relating to Tractive Effort | |
| Driver Diameter (in / mm) | 49 / 1245 |
| Boiler Pressure (psi / kPa) | 180 / 1240 |
| High Pressure Cylinders (dia x stroke) (in / mm) | 15.5" x 24" / 394x610 |
| Low Pressure Cylinders (dia x stroke) (in / mm) | 24.5" x 24" / 622x610 |
| Tractive Effort (lbs / kg) | 25,715 / 11664.14 |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | 4.57 |
| Heating Ability | |
| Tubes (number - dia) (in / mm) | 176 - 2.25" / 57 |
| Flues (number - dia) (in / mm) | - 5.5" / 140 |
| Flue/Tube length (ft / m) | 16.83 / 5.13 |
| Firebox Area (sq ft / m2) | 117.80 / 10.94 |
| Grate Area (sq ft / m2) | 21.40 / 1.99 |
| Evaporative Heating Surface (sq ft / m2) | 1864 / 173.17 |
| Superheating Surface (sq ft / m2) | |
| Combined Heating Surface (sq ft / m2) | 1864 / 173.17 |
| Evaporative Heating Surface/Cylinder Volume | 355.63 |
| Computations Relating to Power Output (More Information) | |
| Robert LeMassena's Power Computation | 3852 |
| Same as above plus superheater percentage | 3852 |
| Same as above but substitute firebox area for grate area | 21,204 |
| Power L1 | 2754 |
| Power MT | 206.69 |