NO. 3 LANGLEY MEMOIR ON MECHANICAL FLIGHT 233 



was machined to the form clearly shown in the photograph, Plate 77, where it 

 will be seen thai thin radiating ribs spaced one-quarter inch apart were formed 

 integral with the cylinder, the combustion chambers or beads being screwed on 



and brazed to the cylinders. After much delay the new cylinders were com- 

 pleted, and upon test it was found that while the radiating ribs assisted very 

 greatly iu keeping the engine cool, yet the valves were so small that the gas 

 was not able to get in and out of the cylinders rapidly enough to permit the 

 engine to furnish its full power. Even at this stage it would have been better 

 either to have made new cylinder heads with larger valves or to have made 

 entirely new cylinders and cylinder heads, bid in the effort to economize time 

 and money it seemed best to try to overcome part of the defect by adding an 

 auxiliary inlet valve. This was constructed, and upon test it was found that, 

 although the engine developed .'5.2 horse-power on the Prony brake at 1800 

 R.P.M., and even maintained 5.1 horse-power on the brake for a few seconds 

 when running at 3000 R. P. M., the ports leading from the valve chamber to the 

 cylinders were so small that they became heated after the engine had run for 

 '2 minutes and premature ignition occurred, which, of course, immediately and 

 very greatly reduced the power developed. 



It was decided, however, in view of the tests in which the engine had de- 

 veloped 3.2 horse-power at 1800 R. P.M., that there was sufficient margin of 

 power to enable it to propel the quarter-size model, even if it was not work- 

 ing at its best. After concluding the Prony-brake tests on the engine, it was 

 mounted in its proper position in the aerodrome frame and connected to the pro- 

 peller shafts. Some pendulum tests were then made, showing an average lift 

 o\' approximately 57 per ceut of the total flying weight. But it was found that 

 the propeller and transmission shafts and their bearings would not stand the 

 strain due to the increased power of the engine. Newer and stronger shafts 

 and bearings were, therefore, constructed and further pendulum tests were 

 made. It was then found that the transverse frame which supported the shafts 

 and bearings was too weak, and this was strengthened by substituting newer and 

 thicker tubing where it seemed necessary. 



These changes and repairs were all completed by October, 1901, and the 

 quarter-size model was at last, after months of delay, felt to be in a condition 

 which justified the expectation that its next flight would he entirely successful. 

 In view of the much more important work on the large aerodrome which de- 

 manded immediate attention the quarter-size model in this completed condition 

 was put aside. Nothing more was done with it until April, 1903, when some 

 shop tests were made preliminary to taking it to Quantico, where, on August 

 8, it made a successful flight, which is described in Chapter XII. 



26 



