Vauclain Compound - History

History

The Vauclain compound was introduced in 1889 through U.S. Patent 406,011 by its namesake and the then general superintendent of Baldwin and eventually president of the company, Samuel M. Vauclain. Soon most Baldwin customers were operating some examples; a brochure from 1900 lists sales to 140 customers, including large fleets to such Class I railroads as the Baltimore and Ohio Railroad, the Chicago, Milwaukee and St. Paul Railway, the Erie Railroad, the Lehigh Valley Railroad, the Norfolk and Western Railway, and the Philadelphia and Reading Railroad. Many other lines purchased one or two as samples. Vauclain was awarded the Elliott Cresson Medal of the Franklin Institute in 1891 for the locomotive design; in recommending award, the reviewing committee wrote,

"Your committee, in conclusion, find that in view of the state of art, the Vauclain compound locomotive is a distinctly new and original type of locomotive. It is the most marked departure from the usual construction of engines, that has elicited general satisfaction wherever introduced, and in view of the reliable and satisfactory performance in service under the largest variations of conditions, immunity from total disablement, ready adaptability within limits of space incapable of accommodating other compound engines, and general applicability to and utility in railway service, it is, in the opinion of your committee, deserving of recognition by the award of the Elliott Cresson Medal of the Franklin Institute, which they hereby recommend."

This popularity, however, was short-lived. Significant maintenance difficulties appeared, particularly with uneven forces wear on the crosshead guides. The two cylinders were supposed to be proportioned so as to do equal work (with the low pressure being three times larger than the high); but since the steam passed between the low and high pressure cylinder is always expanded, even before cutoff, the force produced in the low pressure cylinder varies differently from that in the high pressure cylinder. The complex valve assembly and the starter valve also led to increased maintenance costs. The introduction of the superheater was the final nail in the coffin, as it increased efficiency further and was much easier to maintain.

All of the compounding machinery was contained in the valve chest, which in American locomotives (in the days before one piece cast frames) was integral with the smokebox saddle. The whole unit therefore could be unbolted and replaced with conventional single expansion cylinders. That was the typical fate of Vauclain compounds: when the time came for a major overhaul, the compound machinery and Stephenson valve gear were removed, and the engine was rebuilt with superheating, Walschaerts valve gear, and conventional cylinders.

Ironically, two of the four surviving Manitou and Pike's Peak Railway locomotives were converted to compounding after experience with M&PP #4, built in 1893 and at present the only operating Vauclain compound. (Vauclain himself had travelled to the line to deal with operational issues with the original engines in their pre-compounding state.) All six steam locomotives of the line were of this type.