18 BULLETIN 198, UNITED STATES NATIONAL MUSEUM 



The carriage body, to which are attached all the principal parts 

 of the driving mechanism, is constructed entirely of wood. The 

 boiler and engine are below the seat portion of the body, while the 

 back of the body accommodates the feed-water tank and the horizontal 

 extension of the smoke box, which forms the chimney of the burner. 

 Three levers, by means of which the engine and burner are controlled, 

 are situated at the driver's right hand. The steering is controlled by 

 a side bar, which operates the pivoted front wheels. Power was trans- 

 mitted by a chain from a 16-tooth sprocket on the crankshaft to a 40- 

 tooth sprocket mounted upon the differential gear on the divided rear 

 axle, at the ends of which the rear wheels are keyed. A pedal actuates 

 the external contracting brake band of the brake drum on the sprocket 

 of the differential unit. 



The underf rame is constructed of tubing and consists of two longi- 

 tudinal tubes brazed and bolted at each end to curved cross tubes, 

 which are themselves brazed to straight cross tubes of which the rear 

 one is divided at its center to receive the differential gear on the 

 rear axle. Additional stiffness is given to the underframe by stay 

 tubes and rods. The tread is 53 inches and the wheel base 58 inches. 



The boiler is of the vertical fire-tube type. It consists of a cylindri- 

 cal drum, formed by upper and lower tube plates, and a shell plate 

 strengthened by windings of steel piano wire to resist bursting. The 

 tube plates are connected by about 300 copper fire tubes. The heating 

 surface of the boiler consists of about 100 square inches of tube plate 

 surface and over 4,000 square inches of tube surface, a total of about 

 30 square feet. Below the lower tube plate is the fire box, which con- 

 tains the burner. The smoke box and drum of the boiler are thickly 

 lagged with asbestos. The water supply for the boiler was contained 

 in a horseshoe-shaped tank of about 15 gallons capacity. The supply 

 was drawn from the bottom of the tank and flowed to a feed pump, 

 which is attached to the engine frame and which was operated by a 

 rocking lever from one of the engine's cross heads. The water entered 

 the boiler at the lower tube plate, the water level in the boiler being 

 indicated by a gauge glass placed on the right side of the carriage 

 body. The small mirror near the brake pedal enabled the driver to 

 see the glass readily. 



The boiler was normally worked at 150 pounds pressure, as indicated 

 by the pressure gauge at the driver's right foot. 



The gasoline supply for the burner was contained in the cylindrical 

 tank suspended from the frame below the floorboard of the body, air 

 pressure being employed to maintain the supply. The air pressure 

 was indicated by another pressure gauge on the footboard. 



The engine is of the vertical, double-acting type having two cylin- 

 ders each 21/^ inches in bore and 3l^ inches in stroke. The cranks are 



