Because of tremendous demand for mass transportation over long distances in this Country, railroad equipment has become less and less suited for small transportation needs; but a large amount of small-unit transportation exists which can earn a profit for the railroads if they have the equipment best suited to handle it. Gasoline-propelled rail-cars have demonstrated their ability to meet the needs of this small-unit traffic. Types of such rail-cars now operating range from 25-passenger or 10 tons of freight capacity to 60-passenger or 30 tons of freight capacity; in certain services, their capacity can be increased by using trailers and by running them in trains operated by one driver at the front end, who has them under multiple-unit control, at speeds up to 50 m.p.h. and for from 20 to 50 cents per car-mile. Recently developed rail-cars are about 55 ft. long, have a useful car-floor area 9 ft. wide, weigh about 60,000 lb. when loaded and require about 1 hp. for each 500 lb. of weight.
Rail-cars propelled by electricity from storage-batteries, by electricity from a gasoline-engine-driven generator through electric motors on the axles and by similar means from power generated by a Diesel engine are mentioned, as well as hydraulic transmissions used instead of electric drive, and cars equipped with large single engines and mechanical transmissions, with comments on their varied performance. Development of multiple-unit control for rail-cars has not presented great difficulties, the main one being sufficient dependability of the power unit for its operation without attendance. This system of control and the mode of synchronous operation of several power units are treated briefly and the rail-car field is surveyed.
Specific rail-car development as reported in the paper includes the reasons governing the determination to use an individual power unit of 60 hp., clutch requirements and design and other elements that can be compounded in various ways to produce rail-cars capable of meeting almost any one requirement. The rail-car design adopted by the company the author represents is analyzed, this being a four-wheel power-truck having an engine and transmission and driving to one axle, as well as gasoline supply, cooling and exhaust systems, an air compressor and an electric generator; a car body suited to the needs of the purchaser; and control equipment, these three elements making possible many combinations to meet specific services, some of which are mentioned. The detail design of the various units is then discussed in sequence.