288 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1962 



Figure 19. — Fairchild-Caminez engine, transverse section. This was the only crankless 

 reciprocating engine to reach the stage of official approval (U.S. Dept. of Commerce 

 Approved type Certificate No. 1, June 1927). Later it was found to be impractical be- 

 cause of severe torque variation. 



1927) but proved impractical because of excessive vibration due to 

 torque variation. It was flown experimentally 1926-28. 



3. Sleeve-valve engines. The earliest development that I recall 

 of a sleeve-valve aircraft engine was the Belgian "Minerva," which 

 appeared in the 1920's, but never got beyond the experimental stage. 

 This was a "Knight" type, or double-sleeve engine. The single sleeve, 

 or "Burt-McCoUum" type, was exploited chiefly in England and finally 

 became operational in the Bristol line of aircraft radial engines, 

 including the "Hercules" (pi. 26, fig. 1) and the "Centaurus." These 

 engines were used by the British Air Force during World War II, and 

 are still being manufactured (1962). The Napier "Sabre," also using 

 the single-sleeve valve, was a 24-cylinder, liquid-cooled, two-crankshaft 



