Editing Synchronization gear (section)

==== The Birkigt gear ====
The [[SPAD S.VII]] was designed around Marc Birkigt's [[Hispano-Suiza 8|Hispano-Suiza engine]], and when the new fighter entered service in September 1916 it came armed with a single Vickers gun synchronized with a new gear provided by Birkigt for use with his engine. Unlike most other mechanical gears, the "SPAD gear" as it was often called, did without a pushrod altogether: the firing impulses being transmitted to the gun [[Torsion (mechanics)|torsionally]] by a moving ''oscillating'' shaft, which rotated through about a quarter of a revolution, alternately clockwise and anticlockwise. This oscillation was more mechanically efficient than the reciprocating motion of a push rod, permitting higher speeds. Officially known as the ''Système de Synchronisation pour Vickers Type II (moteurs fixes)'' the Birkigt gear was later adapted to control two guns, and remained in use in French service up to the time of the Second World War.<ref name=Woodman16>Woodman 1989, p. 198.</ref>