THREE FAMOUS EARLY AERO ENGINES — MEYER 359 



The Clement engine had two tasks to perform: the propulsion of 

 a lighter-than-air craft, and the operation of a blower [fan] to aid 

 in maintaining the rigidity and therefore the structural mtegrity of 

 the dirigible's envelope [balloon]. 



As Santos Dumont stated above, this motor would propel his dimin- 

 utive airship up to 15 m.p.h. Forcing it much beyond this speed would 

 not have been practical because of the envelope's great resistance to 

 the passage of the air. If a considerably more powerful engine had 

 been installed, it would have weighed so much that little or no ballast 

 could have been carried. This would have prevented safe aerial 

 navigation. 



The blower, as mentioned above, merely forced air under low pres- 

 sure into a flexible compartment on the underside of the gas bag. 

 This compensated for any reduction in stiffness of the airship's 

 envelope due to a loss of lifting gas caused by leakage or purposeful 

 releasing of the gas. Probably only a fraction of 1 horsepower was 

 needed for this purpose. 



This particular engme was apparently designed for the Clement 

 Autocyclette motorcycle which was sold in 1903. However, its light 

 weight and reasonably good weight/power ratio made it an ideal 

 engine for the diminutive airship. 



From 1903 until the advent of World War II, this motorcycle type 

 of engine (two air-cooled cylinders in V-configuration) was being 

 manufactured for single-place heavier-than-air craft. Below are 

 listed some examples. 



British J.A.P. of 1909. 

 French Farcot of 1913. 

 British Blackburne of 1923. 

 American Indian of 1925. 

 British Anzani of 1936. 



Engines with their cylinders arranged horizontally on either side 

 of the crankshaft (horizontally opposed) eventually replaced power- 

 plants having the V-arrangement of the Clement. The advantages of 

 the former type are more smoothness (the reciprocating parts coun- 

 terbalanced each other) and better visibility (the cylinders did not 

 protrude above the crankcase). This type gave way in turn to the 

 four-cylinder engine in the same configuration. This four-cylinder 

 version offered more smootliness owing to more frequent and smaller 

 power impulses, as well as greater safety, for the loss of one cylinder 

 would not cause a forced landing. After World War II most single- 

 seat airplanes were powered by the four-cylinder horizontally opposed 

 air-cooled engine. The Clement motorcycle type of engine therefore 

 appears to have influenced aircraft engine design for single-seat air- 

 planes directly for 35 years, and indirectly for more than 50 years. 



625325—62 ^24 



