New Bedford Railroad 0-6-6 Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class William Mason (Locobase 5585)

Data from reproduction of 1950 reprint of 1883 Recent Locomotives as hosted by [] (visited 2 June 2003). See also "Some Old Mason Engines," Railroad & Locomotive Engineering , December 1900, p. 535. The boiler pressure is an estimate. Mason's works number was 536.

Ironhorse129's commentary notes that this was the first locomotive in the United States using Egide Walschaert's radial valve gear. Australian ferroequinologist and live-steam enthusiast David Fletcher says that the Stephenson gear normally used wouldn't work for an engine whose drivers pivoted on a bogie as this Mason Bogie did. The distance between the lifting rod, which controls cutoff, and the engineer's actuating Johnson bar would vary and the engine would speed up or slow down as a consequence. The Walschaert layout allowed for placing the lifting rod up in front of the steam dome in an arrangement that fixed the distance.

The writer of the RLE article praised the William Mason's pulling power, saying: "There is possibly no engine today, of her dimensions, that could, under the conditions of the day and time, equal this engine for the amount of work done. Had she not had a bogie of old design, the late J N Lauder would have repaired her .... The engine could haul 125 long freight box cars, such as were used at the time between Mansfield and Fitchburg, and the grades were heavy, so Mr Hobart Piper, her engineer, informs us. "

Another 0-6-6T, Canada Atlantic 724, was the first and only Mason Bogie to run on Canadian rails and the first Canadian engine to use Walschaert's gear. See . NB: For an explanation of the use of the singular "Walschaert", see Locobase 11157.

Principal Dimensions by Steve Llanso of Sweat House Media
ClassWilliam Mason
Locobase ID5585
RailroadNew Bedford Railroad
Number in Class1
Road Numbers
Number Built1
BuilderWilliam Mason
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)8 / 2.44
Engine Wheelbase (ft / m)31 / 9.45
Ratio of driving wheelbase to overall engine wheebase 0.26
Overall Wheelbase (engine & tender) (ft / m)31 / 9.45
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)66,600 / 30,209
Engine Weight (lbs / kg)73,928 / 33,533
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)73,928
Tender Water Capacity (gals / ML)2530 / 9.58
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)
Minimum weight of rail (calculated) (lb/yd / kg/m)37 / 18.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)42 / 1067
Boiler Pressure (psi / kPa)125 / 8.60
High Pressure Cylinders (dia x stroke) (in / mm)16" x 24" / 406x610
Tractive Effort (lbs / kg)15,543 / 7050.19
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.28
Heating Ability
Firebox Area (sq ft / m2)126 / 11.71
Grate Area (sq ft / m2)22.17 / 2.06
Evaporative Heating Surface (sq ft / m2)1053 / 97.86
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)1053 / 97.86
Evaporative Heating Surface/Cylinder Volume188.54
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation2771
Same as above plus superheater percentage2771
Same as above but substitute firebox area for grate area15,750
Power L12637
Power MT261.87

All material Copyright ©
Wes Barris