This pocket rocket was built for a mountain narrow-gauge that operated in Western Colorado and Utah. The long water tanks extended from the cab to the middle of the front engine unit. Steam was led forward under the boiler jacket in a dry pipe to the superheater as usual, but returned for the rear cylinders in two heavily lagged external pipes that branched around the stack and dropped down to the cylinders behind the water tanks on each side. The cylinders were supplied by 8" (203 mm) piston valves with 5" (127 mm) travel.
The leading truck was equalized with the front unit's drivers and could swing 6 3/4" (171 mm) to each side. The rear, bissell truck was equalized with the rear driving set.
These Mallet Prairie Tanks could handle twice the train load on the 5% grade that ruled, wrangling 240 tons (218 tonnes) up such a slope. On the 1.1% grade between Watson and Dragon, 51 was rated at 1,150 tons (1,045 tonnes). At the other extreme, the 7.5% grade between Atehea and Baxter Pass brought the tonnage rating down to 145 tons (131.8 tonnes).
Bill Pratt (http://home.bresnan.net/~bpratt15/a_longer_history.htm, accessed 9 Jan 2006 and at the time recommended as an excellent site covering the Uintah Railroad past and present; alas apparently no longer active), notes that as delivered the 50 had one steam dome in the middle of the boiler. After an engineer negotiating the five miles of 7 1/2% adverse grade realized the water glass was showing empty, a second steam dome was installed near the cab.
http://loggingmallets.railfan.net notes that the Uintah sold off both locomotives in 1940 to Sumpter Valley in Oregon, where they operated until 1947 as 250 & 251. Still yoked in their joint destiny, the two engines then went to the International Railways of Central America in Escuintla, Guatemala. 251 retired first in 1962 and 250 followed in 1964.
|Principal Dimensions by Steve Llanso of Sweat House Media|
|Number in Class||2|
|Locomotive Length and Weight|
|Driver Wheelbase (ft / m)||7.67 / 2.34|
|Engine Wheelbase (ft / m)||38.25 / 11.66|
|Ratio of driving wheelbase to overall engine wheebase||0.20|
|Overall Wheelbase (engine & tender) (ft / m)||38.25 / 11.66|
|Axle Loading (Maximum Weight per Axle) (lbs / kg)||30,240 / 13,717|
|Weight on Drivers (lbs / kg)||194,000 / 87,997|
|Engine Weight (lbs / kg)||236,300 / 107,184|
|Tender Loaded Weight (lbs / kg)|
|Total Engine and Tender Weight (lbs / kg)||236,300|
|Tender Water Capacity (gals / ML)||2600 / 9.85|
|Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)||4.50 / 4.10|
|Minimum weight of rail (calculated) (lb/yd / kg/m)||54 / 27|
|Geometry Relating to Tractive Effort|
|Driver Diameter (in / mm)||42 / 1067|
|Boiler Pressure (psi / kPa)||210 / 14.50|
|High Pressure Cylinders (dia x stroke) (in / mm)||15" x 22" / 381x559 (4)|
|Tractive Effort (lbs / kg)||42,075 / 19084.92|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.61|
|Firebox Area (sq ft / m2)||125 / 11.61|
|Grate Area (sq ft / m2)||37.40 / 3.47|
|Evaporative Heating Surface (sq ft / m2)||2100 / 195.09|
|Superheating Surface (sq ft / m2)||505 / 46.92|
|Combined Heating Surface (sq ft / m2)||2605 / 242.01|
|Evaporative Heating Surface/Cylinder Volume||233.35|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||7854|
|Same as above plus superheater percentage||9346|
|Same as above but substitute firebox area for grate area||31,238|