IgO BULLETIN 173, U. S. NATIONAL MUSEUM 



has since been incorporated in all plugs. Difficulty was experienced 

 from a coating of soot that formed on the porcelain and caused a 

 short circuit between the points. This was overcome by extending 

 the metal portion of the plug into the cylinder about three-quarters 

 of an inch beyond the porcelain. The terminal through the insulator 

 was also extended about half an inch and bent to co-act with a piece 

 of platinum on the inside wall of the plug. After this improvement 

 was made, no difficulty from short circuits was experienced. The 

 float-feed type of carburetor proved unsuitable as the tremor of the 

 frame caused the float to act as a pump, periodically flooding the 

 carburetor. Manly next tried a type, of mixing valve in which the 

 gasoline was fed through the valve seat of a lightly loaded valve 

 that opened when there was suction in the intake pipe. The amount 

 of gasoline was controlled by a pin valve. He then built and tested 

 several shapes and sizes of tanks filled with absorbent material that 

 was saturated with gasoline and the surplus drawn off before start- 

 ing. As the result of about one dozen tests he found the best type to 

 consist of a tank filled with small lumps of a porous cellular wood 

 (tupelo wood) initially saturated with gasoline and into which gaso- 

 line was fed through a distributing pipe as rapidly as it was taken 

 up by the air. Heated air was drawn from around the cylinders to 

 counteract the cooling effect of the evaporation within the carburetor. 

 A carburetor of this type kept the engine running at full speed even 

 when the aerodrome had turned completely over on its back. 



The full-size engine finally built is the 5-cylinder, water-cooled, 

 radial engine shown in the accompanying illustration. Construction 

 was started in the summer of 1901, and it was completed in December 

 of the same year. 



The engine cylinders each consist of a main outer shell of steel one- 

 sixteenth of an inch thick, near the bottom end of which was screwed 

 and brazed a suitable flange by which it was bolted to the supporting 

 frame drum or crank chamber. These shells, which were seamless 

 with the heads formed integral, were designed to be of sufficient 

 strength to withstand the force of the explosion in them, and in 

 order to provide a suitable wearing surface for the piston, a cast- 

 iron liner one-sixteenth of an inch thick was carefully shrunk into 

 them. At the side of the cylinder near the top was the combustion 

 chamber, machined out of a solid steel forging also forming the 

 port that entered the cylinder and was fastened to it by brazing. The 

 water jackets, which were formed of sheet steel 0.020 inch thick, were 

 also fastened to the cylinders by brazing. 



The pistons are of cast-iron having a slightly convex head rein- 

 forced by two deep but thin ribs. The head is approximately one- 

 eighth inch thick, the side walls above the wrist pin journal one- 

 quarter inch, and the skirt below the wrist pin about one-sixteenth 



