NO. 3 LAXOI.KY MEMOIB OX MECHANICAL FLIGHT 239 



tests iii which the engine was run for ten consecutive hours at full power it 

 showed no signs whatever of overheating. As this new form of connecting rod 

 bearing- for the crank pin had never been tried before, the precaution was taken 

 to leave the threads on the crank pin for the cone mils, so that if this new 

 hearing should not prove successful the old plan of having the connecting rod 

 shoes bear directly on the crank pin could be reverted to. These threads are 

 clearly seen in Plate 78 and were never removed from the crank pin, though 

 their removal would have added considerably to the area of the hearing sur- 

 face of the main connecting rod, had more bearing surface seemed necessary. 



The lubrication of the main crank-shaft bearing and of the crank pin was 

 effected by means of a small oil cup, fastened to the port bed plate, which fed 

 oil through a hole in the huh of the drum to a circular groove formed in the 

 hronze bushing in the hub. The crank shaft being hollow, a hole was drilled 

 through it in line with the groove in the bushing, and the oil was then led from 

 the interior of the crank shaft through a pipe connected to the plug in the end 

 thereof, and through a hole drilled in the crank arm to the hollow crank pin. 

 Small holes through the crank pin permitted oil to pass to the exterior thereof 

 and thus oil the bearing of the main connecting rod. Small holes through the 

 sleeve and hushing of the main connecting rod fed oil under the shoes of the 

 other four connect iua: rods, the small holes being placed in oil grooves formed 

 in the interior of the hronze bushing. The lubrication of the pistons was ef 

 fected by means of small crescent-shaped oil cups fastened to the outer wall 

 of the cylinders, which distributed the oil equidistantly around the circumfer- 

 ence of the pistons, through small tubes which projected through correspond- 

 ing holes drilled in the cylinder wall. These oil cups for the cylinders were, 

 while small, of sufficient size to furnish a supply for approximately one hour, 

 and were so positioned on each cylinder as to have a gravity feed. It may be 

 mentioned here that while there were many parts of the engine which were 

 of unprecedented lightness there was nothing which excelled these oil cups in 

 this respect, as they were made of sheet steel .003 of an inch thick, riveted and 

 soldered up. The crank-shaft bearing in the starboard drum was oiled from 

 an oil cup mounted on the outside of the bed plate and connected by a pipe to 

 a hole in the inner wall of the drum, which was connected to the oil grooves in 

 the bronze bushing in the hub of the drum. 



The first set of pistons for this engine were similar in design to those 

 shown in the assembled, drawings, except that they had side walls and heads 

 which were twice as thick as those shown. These lighter pistons were constructed 

 later, and were just as good as the earlier and heavier ones. It will be noted 

 that the pistons have two deep but thin ribs reinforcing the head. The pis- 

 tons were slightly tapered from the middle, where they were .005 inch smaller 

 than the cylinder bore, toward the outer end, where they were .007.") inch smaller 



