Data from DeGolyer, Volume 60, pp. 355. Works numbers were 42554-42555 in October 1915.
Although apparently drawing from the design work that produced the two Morvi Railway Ten-wheelers a few months earlier (Locobase 14654), the SIR engines had a different purpose and were enlarged in several dimensions. They were fitted with a copper Belpaire firebox and 7" (179 mm) piston valves as well as the same number of tubes and flues. But all of the values were slightly higher and tractive effort augmented not just by a small increase in cylinder diameter but also a 19% decrease in driver diameter.
Data from "Narrow Gauge Locomotive, South Indian Railway", Locomotive Magazine, Volume XIX (15 July 1913), p. 170; and "Narrow Gauge Locomotive for the South Indian Railway", Engineer, Volume 115 (4 April 1913), pp. 357-358.
Robert White, South India's consulting engineer, ordered one of these locomotives with a saturated boiler (the standard BESA design) and the other four with superheaters. The design came with outside cylinders and 5 1/2" (140 mm) piston valves and a Belpaire firebox with a narrow grate.
. It's likely that White wanted to confirm the prevailing opinion of the great worth of superheaters by hedging his bet, especially as these were the first narrow-gauge locomotives to use superheaters. Presumably, he converted the fifth after a short time.
| Principal Dimensions by Steve Llanso of Middle Run Media | ||
|---|---|---|
| Class | B-79 | M |
| Locobase ID | 14657 | 20112 |
| Railroad | South Indian | South Indian |
| Country | India | India |
| Whyte | 4-6-0 | 4-6-0 |
| Number in Class | 2 | 5 |
| Road Numbers | B-79, B-80 | M 29 |
| Gauge | Metre | Metre |
| Number Built | 2 | 5 |
| Builder | Baldwin | Hawthorn Leslie |
| Year | 1915 | 1913 |
| Valve Gear | Walschaert | Walschaert |
| Locomotive Length and Weight | ||
| Driver Wheelbase (ft / m) | 12 / 3.66 | 12 / 3.66 |
| Engine Wheelbase (ft / m) | 21.08 / 6.43 | 21.12 / 6.44 |
| Ratio of driving wheelbase to overall engine wheelbase | 0.57 | 0.57 |
| Overall Wheelbase (engine & tender) (ft / m) | 42.10 / 12.83 | 42.14 / 12.84 |
| Axle Loading (Maximum Weight per Axle) (lbs / kg) | 20,160 / 9144 | |
| Weight on Drivers (lbs / kg) | 58,688 / 26,620 | 60,424 / 27,408 |
| Engine Weight (lbs / kg) | 77,728 / 35,257 | 79,803 / 36,198 |
| Tender Loaded Weight (lbs / kg) | 48,000 / 21,772 | 55,216 / 25,046 |
| Total Engine and Tender Weight (lbs / kg) | 125,728 / 57,029 | 135,019 / 61,244 |
| Tender Water Capacity (gals / ML) | 2400 / 9.09 | 2400 / 9.09 |
| Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) | 5.50 / 5 | 6.05 / 6 |
| Minimum weight of rail (calculated) (lb/yd / kg/m) | 33 / 16.50 | 34 / 17 |
| Geometry Relating to Tractive Effort | ||
| Driver Diameter (in / mm) | 48 / 1219 | 57 / 1448 |
| Boiler Pressure (psi / kPa) | 160 / 1100 | 170 / 1170 |
| High Pressure Cylinders (dia x stroke) (in / mm) | 16" x 22" / 406x559 | 16.5" x 22" / 419x559 |
| Tractive Effort (lbs / kg) | 15,957 / 7237.98 | 15,184 / 6887.35 |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | 3.68 | 3.98 |
| Heating Ability | ||
| Tubes (number - dia) (in / mm) | 87 - 1.75" / 44 | 87 - 1.75" / 44 |
| Flues (number - dia) (in / mm) | 15 - 5.25" / 133 | 15 - 5.25" / 133 |
| Flue/Tube length (ft / m) | 11.83 / 3.61 | 11.75 / 3.58 |
| Firebox Area (sq ft / m2) | 106 / 9.85 | 108 / 10.03 |
| Grate Area (sq ft / m2) | 16.80 / 1.56 | 16 / 1.49 |
| Evaporative Heating Surface (sq ft / m2) | 821 / 76.27 | 819 / 76.09 |
| Superheating Surface (sq ft / m2) | 207 / 19.23 | 195 / 18.12 |
| Combined Heating Surface (sq ft / m2) | 1028 / 95.50 | 1014 / 94.21 |
| Evaporative Heating Surface/Cylinder Volume | 160.36 | 150.42 |
| Computations Relating to Power Output (More Information) | ||
| Robert LeMassena's Power Computation | 2688 | 2720 |
| Same as above plus superheater percentage | 3226 | 3237 |
| Same as above but substitute firebox area for grate area | 20,352 | 21,848 |
| Power L1 | 8036 | 9237 |
| Power MT | 905.62 | 1011.06 |