Zerah Colburn was one of the most energetic locomotive designers of his time and one of the first to write about locomotives for a more general audience. He was in fact prolific both as a writer and as an inventor. In the early 1850s, Colburn's mind turned to finding a way for railroads hauling anthracite coal out of the Pennsylvania hills to use that fuel for their locomotives. This was no easy matter as such "hard" coals as anthracite did not burn well in the typical narrow and deep firebox in use at the time. The only possible way to create enough grate area for the soft draft and thin bed needed was to widen the grate as much as the loading gauge would allow.
In the case of this all-adhesion "Camel", that meant 7 feet 6 inches wide, which created another problem. At the time, the great concern over keeping the center of gravity low meant that such a grate could not be put over a set of drivers. Colburn's design resorte d to positioning the grate practically at rail height and behind the last coupled axle. The rectilinear firebox extended forward over the driver sets to the smokebox. The driver stood over the second coupled axle, behind a tall, thick cylinder that amounted to a dome and a huge stack with a wide bell. One effect of the peculiar was its need for an unusually long coupling bar - indeed, one of the design's weakest points was the difficulty linking it to its fuel supply.
The design did not originally go into service as Colburn had designed it. After the order was placed, Colburn left New Jersey Locomotive Works and the builder's superintendent of works John Brandt shortened the grate to 4 1/2 feet long, added a 4-foot long combustion chamber in the firebox ahead of the grate, and enlarged the tube diameter to 3 inches.
Once in service, that configuration flopped. One adjustment was to lengthen the firebox to Colburn's original 6-foot specification, the other was to reduce tube diameter to 2 1/2". Although the engine now steamed better, according to Sinclair, the Lehigh and its 5 stablemates were unpopular. For one thing, the LM writer notes, much of the weight was distributed towards the ends of the locomotive in the form of cylinders and the smokebox saddle on the front end, grate bars on the nether end. "[I]t will at once be seen that the placing of such relatively considerable masses of metal so far beyond the wheelbase must have had a tendency to cause a see-sawing motion of the whole engine around its center of gravity."
Yet Colburn had struck on the proper configuration for burning anthracite coal without using a combustion chamber. There were many observers, Sinclair among them, who argued that the so-called Wootten firebox that was widely adopted beginning in the 1889s would as correctly be described as a Colburn firebox.
|Specifications by Steve Llanso of Sweat House Media|
|Railroad||Delaware, Lackawanna &Western|
|Number in Class||6|
|Builder||New Jersey Locomotive|
|Locomotive Length and Weight|
|Ratio of driving wheelbase to overall engine wheebase||1|
|Overall Wheelbase (engine & tender)||48.33'|
|Axle Loading (Maximum Weight per Axle)|
|Weight on Drivers||73920 lbs|
|Engine Weight||73920 lbs|
|Tender Light Weight|
|Total Engine and Tender Weight|
|Tender Water Capacity|
|Tender Fuel Capacity (oil/coal)|
|Minimum weight of rail (calculated)||41 lb/yard|
|Geometry Relating to Tractive Effort|
|Boiler Pressure||100 psi|
|Cylinders (dia x stroke)||18" x 24"|
|Tractive Effort||13770 lbs|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||5.37|
|Grate Area||45 sq. ft|
|Evaporative Heating Surface||1008 sq. ft|
|Combined Heating Surface||1008 sq. ft|
|Evaporative Heating Surface/Cylinder Volume||142.60|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||4500|
|Same as above plus superheater percentage||4500|
|Same as above but substitute firebox area for grate area||0|