Locomotives: The Great Debate
American locomotives were worked very hard during the nineteenth century because like the jetliners of today, they were expensive capital goods, and their owners were intent on realizing maximum use from a major investment. Between 1840 and 1870 main-line locomotives normally cost eight to ten thousand dollars each. This was very big money for the period. Engines ran twenty to thirty thousand miles a year, consuming about twelve hundred cords of wood in the process. In 1851, operating costs, including fuel, wages, water, depreciation, and oil, came to thirty-one cents a mile.
There was general agreement during most of the century on a single pattern of engine. The eight-wheel, or American, type—illustrated by the Saranak—was the universal engine for freight and passenger trains. The details varied considerably from maker to maker and from railroad to railroad, but the overall proportions and arrangement did not. Other wheel arrangements were employed for switching and other service, but all the engines in the Pittsfield picture are most likely standard eight-wheelers.
The consensus on a general design did not extend to at least one important area. Should the cylinders be placed inside the frames or outside? The argument was fundamental to the basic plan of the locomotive’s running gear, and as with so many opposing views in engineering, there were two strong sides to the disagreement.
The advocates of inside-cylinder engines argued persuasively that placing the engine’s reciprocating parts (pistons! crossheads, and connecting rods) nearer the center line made a locomotive oscillate much less from side to side and thus made it safer to operate and easier on the track. Greater thermal efficiency was possible because the cylinders were insulated and warmed by heat otherwise lost through the smokebox. The dry or steam delivery pipe, inside the smokebox, was protected from radiation losses and so helped promote fuel efficiency.
Opponents of this arrangement pointed out that the advantages of insiders were canceled by the trade-offs of using a crank axle, having machinery hidden away beneath the engine, and having a size restriction imposed by trying to pack the connecting rods and valve gear inside the frames. Inspection, repair, and oiling of the working parts were very much impeded by the inside arrangement, and cylinder size was forever limited. But the chief argument against the insiders was the crank axle. The only way to transmit the power of the piston to the wheels was with axles that incorporated two cranks set at ninety degrees—one for each cylinder. To withstand the forces they were normally subjected to, they were made very heavy, and they were expensive to forges because of their intricate shape. Worst of all, they broke frequently, lasting three years at best. They were likely tql break when under the greatest stress—when the engine was running fast—and so became a mischievous cause of accidents.
Nonetheless, New England railroaders held loyal to insiders through the middle 1850s. A few were built as late as the 1870s. The older gentlemen sitting around at the Pittsfield roundhouse date mostly from the 1840s and so are insiders almost to the machine; the preference for the crank-axle engine was at its peak among New England railroads when they were produced. The Saranak in the same picture is, by contrast, an outside-cylinder engine, a fact evident from the cylinder visible between and just above the small leading wheels.
