Editing Synchronization gear (section)

=== France ===
The French ''Aviation Militaire'' was fortunate in that they were able to standardise on two reasonably satisfactory synchronization gears – one adapted for rotary engines, and the other for "stationary" (in-line) ones – almost from the beginning.

[[File:Alkan-Hamy gear in Nieuport.jpg|thumb|Nieuport 17 with machine gun synchronized by Alkan-Hamy system. The large reel behind the machine gun is a take-up spool for the ammunition belt and has nothing to do with the synchronization gear. Note how the push rod has effectively become part of the gun]]

==== The Alkan-Hamy gear ====
The first French synchronizer was developed by ''Sergeant-Mécanicien'' Robert Alkan and ''Ingénieur du Génie maritime'' Hamy. It was based closely on the definitive Fokker ''Stangensteuerung'' gear: the main difference being that the push rod was installed within the Vickers gun, using a redundant steam tube in the cooling jacket. This mitigated a major drawback of other push rod gears in that the rod, being supported for its whole length, was much less liable to distortion or breakage. Vickers guns modified to take this gear can be distinguished by the housing for the push rod's spring, projecting from the front of the gun like a second barrel. This gear was first installed and air-tested in a [[Nieuport 12]], on 2 May 1916, and other pre-production gears were fitted to contemporary Morane-Saulnier and Nieuport fighters. The Alkan-Hamy gear was standardised as the ''Système de Synchronisation pour Vickers Type I (moteurs rotatifs)'', becoming available in numbers in time for the arrival of the [[Nieuport 17]] at the front in mid 1916, as the standard gear for forward-firing guns of rotary-engine French aircraft.<ref name=Woodman15>Woodman 1989, pp. 197–198.</ref>

The [[Nieuport 28]] used a different gear – now known only through American documentation, where it is described as the "Nieuport Synchronizing gear" or the "Gnome gear".<ref name=Woodman17>Woodman 1989, p. 199.</ref> A spinning drive shaft, driven by the rotating crankcase of the Nieuport's 160 CV [[Gnome Monosoupape|Gnome 9N Monosoupape]] rotary engine, drove two separately adjustable trigger motors – each imparting firing impulses to its gun by means of its own short rod.<ref name=Hamady1>Hamady 2008 pp. 222–223.</ref> Photographic evidence suggests that an earlier version of this gear, controlling a single gun, might have been fitted to the [[Nieuport 17#Derivatives|Nieuport 23]] and the [[Hanriot HD.1]].

==== 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>