THREE FAMOUS EARLY AERO ENGINES — MEYER 361 



On May 6, 1900, lie visited Balzer in New York City to find out ex- 

 actly what had been accomplished, and to see what might be done to im- 

 prove the engine's efficiency. He tested the engine and found it pro- 

 ducing only 4 hp., and this low output could be maintained for only 

 a few minutes. After working on the problem for several weeks, 

 Manly succeeded in obtaining a continuous rating of 8 hp. at 350 r.p.m. 

 This being only two-thirds of the necessary power, the project was 

 abandoned. 



Manly spent the next three months searching for a suitable engine 

 among the American and European manufacturers without success. 

 As a last resort, he decided to redesign the Balzer engine. 



By September 18, 1900, he had modified it with Balzer's help so 

 that it developed I8I/2 hp. at 715 r.p.m. It differed from its original 

 configuration by having stationary instead of rotating cylinders, and 

 the cylinders water cooled with damp cloths instead of being air 

 cooled. Later the ignition system was changed from the low-ten- 

 sion make-and-break type (which was difficult to keep in time and 

 in good operating condition) to the modern high-tension type using 

 spark plugs. Considerable weight was saved by having a single coil 

 and distributor for all five cylinders instead of a separate one for 

 each. INIanly designed and made his own spark plugs which had a 

 reliability far exceeding those available. He accomplished this by 

 extending the metal portion of the plug and the terminals into the 

 cylinder and beyond the insulator, thereby preventing soot deposits 

 from forming and causing short circuits. With these improvements 

 the engine developed 21.5 hp. at 825 r.p.m. while weighing but 120 

 pounds. 



By this time it was realized that more than 24 hp. would be needed, 

 for the aerodrome, as Langley called his flying machine, would weigh 

 more than the original calculations indicated. (Smithsonian Insti- 

 tution Information Leaflet No. 29 describes the aerodrome project.) 

 Since it had been demonstrated that a single engine would develop 

 sufficient horsepower, the heavier and more complicated dual-engine 

 concept was abandoned. The engine was therefore redesigned by 

 Manly, with larger cylinders, to give 40 hp. with all the cylinders 

 operating, or 28 hp. with one cylinder "dead." He used some of 

 Balzer's men and equipment. 



Four particularly important features were incorporated in the 

 engine : 



1. Instead of the usual single-walled cylinder, the following double- 

 walled construction was employed, making the cylinders stronger 

 and lighter: an outer seamless shell, with an integrally formed head, 

 made of YiQ-in. steel, providing the strength. To act as the wearing 

 surface for the piston, a cast-iron liner, also i/ig in. thick, was shrunk 



