Camden & Amboy 0-4-0 "Switcher" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class John Bull (Locobase 3312)

See also John H White, Jr, A History of the American Locomotive: Its Development: 1830-1880 (New York: Dover Publications, 1979 - original publication in 1968)

Robert L. Stevens worked out this design with Robert Stephenson himself in England in 1831. It was, says White (1968), a Sampson-class design with one important difference -- a low dome boiler. This construction, specified by Stevens, "lacks the one merit of the Bury [high-dome] design, ample steam room. It retains the defects of the dome boiler, namely, a difficult and expensive construction with limited grate area." Although the tube number and diameter were originally as described in the data, White notes that an inspection of the boiler showed 74 tubes of 1 3/4" and cites an 1891 pamphlet on the John Bull as having 62 tubes of 2" diameter. (Project Gutenberg's 1891 Scientific American Supplement, [], accessed 27 April 2007, gives 62 tubes as well.)

Inside cylinders, a tall stack, twin thin safety valve columns, outside crank and side rods, and a frame girdling the boiler at midline characterized the locomotive as built. Eleven days after he began, Isaac Dripps had assembled the John Bull for a trial run, but regular operations didn't begin for two years because the road wasn't ready.

For most of its career, however, the John Bull looked quite different. The steam dome was moved forward to just behind the tall, spark-arresting stack. Engineers now rode in a large cab ahead of a covered tender.

More important, Stevens soon added a leading truck anchored to pins that extended from both ends of the lead axle. The frame extended well forward of the smokebox with the long "cowcatcher" probing still farther. The result was an apparatus that rose and fell like a helmet visor, but didn't not move side to side; the lead axle, however, now had 1" lateral play. To accommodate the frame, Stevens removed the coupling rods, which converted the John Bull to a 2-2-2-0, although the second "2" was of equal diameter to the driver.

Stevens claimed "uniform and complete" success with this innovation. In the 1832 report of the railroad, he reported a run with 10 cars (weight of stone and iron equivalent to 340 passengers) over the steepest grades and around the sharpest curves with no binding and reaching speeds of over 30 mph. Because the original alignment of the C&A was so smooth, level, and straight, the John Bull and sisters ran for nearly 30 years even at the reduced tractive effort afforded by the addition of the leading truck.

Principal Dimensions by Steve Llanso of Sweat House Media

ClassJohn Bull
Locobase ID3312
RailroadCamden & Amboy
Number in Class4
Road Numbers
Number Built4
Valve Gear
Locomotive Length and Weight
Driver Wheelbase (ft / m)
Engine Wheelbase (ft / m) 4.58
Ratio of driving wheelbase to overall engine wheelbase
Overall Wheelbase (engine & tender) (ft / m)
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)20,000 / 9072
Engine Weight (lbs / kg)20,000 / 9072
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)
Tender Water Capacity (gals / ML)1150 / 4.36
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)2 / 2
Minimum weight of rail (calculated) (lb/yd / kg/m)17 / 8.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)54 / 1372
Boiler Pressure (psi / kPa)40 / 2.80
High Pressure Cylinders (dia x stroke) (in / mm)9" x 20" / 229x508
Tractive Effort (lbs / kg)1020 / 462.66
Factor of Adhesion (Weight on Drivers/Tractive Effort)19.61
Heating Ability
Tubes (number - dia) (in / mm)82 - 1.625" / 41
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m) 6.75 / 2.06
Firebox Area (sq ft / m2)34.80 / 3.23
Grate Area (sq ft / m2)10.07 / 0.94
Evaporative Heating Surface (sq ft / m2)297 / 27.60
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)297 / 27.60
Evaporative Heating Surface/Cylinder Volume202.04
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation403
Same as above plus superheater percentage403
Same as above but substitute firebox area for grate area1392
Power L11153
Power MT254.19

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Wes Barris