Editing Synchronization gear (section)

=== United Kingdom ===
[[File:Bristol Scout with Vickers Challenger.jpg|thumb|upright=.75|Mounting of synchronized Vickers gun on Bristol Scout, using the Vickers-Challenger gear: note long push rod at awkward angle]]
British gun synchronization got off to a quick but rather shaky start. The early mechanical synchronization gears turned out to be inefficient and unreliable and full standardisation on the very satisfactory hydraulic "C.C." gear was not accomplished until November 1917. Synchronized guns seem to have been rather unpopular with British fighter pilots well into 1917 and the over-wing Lewis gun, on its [[Foster mounting]], remained the weapon for Nieuports in British service, being also initially considered as the main weapon of the [[Royal Aircraft Factory S.E.5|S.E.5]].<ref name=Cheesman4>Cheesman 1960, p. 181.</ref> Significantly, early problems with the C.C. gear were considered one of the ''less'' pressing matters for No. 56 squadron in March 1917, busy getting their new S.E.5 fighters combat worthy before they went to France, since they had the over-wing Lewis to fall back on!<ref name=Pengellyp153>Pengelly 2010, p. 153.</ref> [[Albert Ball|Ball]] actually had his Vickers gun removed altogether for a while, to save weight.<ref name=Hare2p52>Hare 2013, p. 52.</ref>

==== The Vickers-Challenger gear ====
[[File:RE 8 with Vickers Challenger.jpg|thumb|left|Much neater, more practical application of the Vickers-Challenger gear for the synchronized Vickers gun of an R.E.8]]
The first British synchronizer gear was built by the manufacturer of the machine-gun for which it was designed: it went into production in December 1915. [[George Henry Challenger|George Challenger]], the designer, was at the time an engineer at Vickers. In principle it closely resembled the first form of the Fokker gear, although this was not because it was a copy (as is sometimes reported) it was not until April 1916 that a captured Fokker was available for technical analysis. The fact is that both gears were based closely on the Saulnier patent. The first version was driven by a reduction gear attached to a rotary engine oil pump spindle as in Saulnier's design and a small impulse-generating cam was mounted externally on the port side of the forward fuselage where it was readily accessible for adjustment.<ref name=Woodman9>Woodman 1989, pp. 187–189.</ref>

Unfortunately, when the gear was fitted to types such as the [[Bristol Scout]] and the [[Sopwith 1½ Strutter]], which had rotary engines and their forward-firing machine gun in front of the cockpit, the long push rod linking the gear to the gun had to be mounted at an awkward angle, in which it was liable to twisting and deformation as well as expansion and contraction due to temperature changes.

For this reason the [[Royal Aircraft Factory B.E.12|B.E.12]], the [[Royal Aircraft Factory R.E.8|R.E.8]] and Vickers' own [[Vickers FB 19|FB 19]] mounted their forward-firing machine guns on the port side of the fuselage so that a relatively short version of the push rod could be linked directly to the gun.

This worked reasonably well although the "awkward" position of the gun, which precluded direct sighting, was initially much criticised. It proved less of a problem than was at first supposed once it was realized that it was the aircraft that was aimed rather than the gun itself. The last aircraft type to be fitted with the Vickers-Challenger gear, the R.E.8, retained the port-side position of the gun even after most were retrofitted with the C.C. gear from mid 1917.

==== The Scarff-Dibovski gear ====
[[File:Scarff Dibovsky cam gear.png|thumb|upright|Cam gear of the Scarff Dibovsky]]

Lieutenant Victor Dibovski, an officer of the [[Imperial Russian Navy]], while serving as a member of a mission to England to observe and report on British aircraft production methods, suggested a synchronization gear of his own design. According to Russian sources, this gear had already been tested in Russia, with mixed results,<ref name=Kulikov1>Kulikov 2013, pp. 13–14.</ref> although it is possible that the earlier Dibovski gear was actually a deflector system rather than a true synchronizer. In any case, Warrant Officer F. W. Scarff worked with Dibovski to develop and realize the gear, which worked on the familiar cam and rider principle, the connection to the gun being by the usual push rod and a rather complicated series of levers. It was [[gear]]ed in order to slow the rate that firing impulses were delivered to the gun (and hence improve reliability, although not the rate of fire). The gear was ordered for the RNAS and followed the Vickers-Challenger gear into production by a matter of weeks. It was more adaptable to rotary engines than the Vickers-Challenger, but apart from early Sopwith 1½ Strutters built to RNAS orders in 1916, and possibly some early [[Sopwith Pup]]s, no actual applications seem to have been recorded.<ref name=Woodman10>Woodman 1989, pp. 189–190.</ref>

==== Ross and other "miscellaneous" gears ====
The Ross gear was an interim, field-built gear designed in 1916 specifically to replace the unsuitable Vickers-Challenger gears in the 1½ Strutters of the [[No. 70 Squadron RAF|RFC's No.70 Squadron]].<ref group="Note">It is likely that the Scarff-Dibovski gear – being Navy issue, would not have been readily available for this purpose.</ref> Officially it was designed by Captain Ross of No.70, although it has been suggested that a flight-sergeant working under Captain Ross was largely responsible. The gear was apparently used only on 1½ Strutters, but [[No. 45 Squadron RAF|No. 45]] squadron used at least some examples of the gear, as well as No. 70. It was replaced by the Sopwith-Kauper gear when that gear became available.<ref name=Woodman12>Woodman 1989, p. 192.</ref>

[[Norman Macmillan (RAF officer)|Norman Macmillan]], writing some years after the event, claimed that the Ross gear had a very slow rate of fire, but that it left the original trigger intact, so that it was possible "in a really tight corner" to "fire the gun direct without the gear, and get the normal rate of fire of the ground gun". Macmillan claimed that propellers with up to twenty hits nonetheless got their aircraft home.<ref name=Bruce1>Bruce 1966, p. 7.</ref> Some aspects of this information are hard to reconcile with the way a synchronized gun actually worked, and may well be a matter of Macmillan's memory playing tricks.<ref name=Woodman12/>

Another "field made" synchronizer was the ARSIAD: produced by the ''Aeroplane Repair Section of the No.1 Aircraft Depot'' in 1916. Little specific seems to be known about it; although it may have been fitted to some early R.E.8s for which no Vickers-Challenger gears could be found.<ref name=Woodman12/>

[[Airco]] and [[Armstrong Whitworth Aircraft|Armstrong Whitworth]] both designed their own gears specifically for their own aircraft. Standardisation on the [[hydraulic]] C.C. gear (described below) occurred before either had been produced in numbers.<ref name=Woodman13>Woodman 1989, pp. 192–193.</ref> Only [[Sopwith Aviation Company|Sopwith]]s' gear (next section) was to go into production.

==== The Sopwith-Kauper gear ====
[[File:Sopwith-Kauper gear.png|thumb|A diagram from the maintenance manual for installation of Sopwith-Kauper synchronization (Mk.III) gear in early production [[Sopwith Camel]]s (1917)]]

The first mechanical synchronization gears fitted to early Sopwith fighters were so unsatisfactory that in mid 1916 Sopwiths had an improved gear designed by their foreman of works [[Harry Kauper]], a friend and colleague of fellow Australian [[Harry Hawker]].<ref name=Woodman11>Woodman 1989, pp. 191–192.</ref> This gear was specifically intended to overcome the faults of earlier gears. Patents connected with the extensively modified Mk.II and Mk.III versions were applied for in January and June 1917.

Mechanical efficiency was improved by reversing the action of the push rod. The firing impulse was generated at a low point of the cam instead of at the lobe of the cam as in Saulnier's patent. Thus the force on the rod was exerted by tension rather than compression, (or in less technical language, the trigger motor worked by being "pulled" rather than "pushed") which enabled the rod to be lighter, minimising its inertia so that it could operate faster (at least in early versions of the gear, each revolution of the cam wheel produced two firing impulses instead of one). A single firing lever engaged the gear and fired the gun in one action, rather than the gear having to be "turned on" and then fired, as with some earlier gears.

2,750 examples of the Sopwith-Kauper gear were installed in service aircraft: as well as being the standard gear for the Sopwith Pup and [[Sopwith Triplane|Triplane]] it was fitted to many early [[Sopwith Camel|Camel]]s, and replaced earlier gears in 1½ Strutters and other Sopwith types. However, by November 1917, in spite of several modifications, it was becoming evident that even the Sopwith-Kauper gear suffered from the inherent limitations of mechanical gears. Camel squadrons, in particular, reported that propellers were frequently being "shot through", the gears having a tendency to "run away". Wear and tear, as well as the increased rate of fire of the Vickers gun and higher engine speeds were responsible for this decline in performance and reliability. By this time the teething problems of the hydraulic C.C. gear had been overcome and it was made standard for all British aircraft, including Sopwiths.<ref name=Woodman11/>

==== The Constantinesco synchronization gear ====
[[File:C.C. gear.png|thumb|U.S. Patent office drawing for C.C. Synchronization gear. The pump-like component was the oil reservoir, and was situated in the cockpit. Lifting its handle ensured there was adequate hydraulic pressure to operate the gear]]

Major Colley, the [[Chief Experimental Officer]] and Artillery Adviser at the War Office Munitions Invention Department, became interested in [[George Constantinescu|George Constantinesco's]] theory of [[Wave Transmission]], and worked with him to determine how his invention could be put to practical use, finally hitting on the notion of developing a synchronization gear based on it. Major Colley used his contacts in the [[Royal Flying Corps]] and the [[Royal Artillery]] (his own corps) to obtain the loan of a Vickers machine gun and 1,000 rounds of ammunition.

Constantinesco drew on his work with rock drills to develop a synchronization gear using his wave transmission system.<ref name=Woodman131>Woodman 1989, p. 195.</ref> In May 1916, he prepared the first drawing and an experimental model of what became known as the Constantinesco Fire Control Gear or the "C.C. (Constantinesco-Colley) Gear".  The first provisional patent application for the Gear was submitted on 14 July 1916 (No. 512).

At first, the meticulous Constantinesco was dissatisfied with the odd slightly deviant hit on his test disc. It was found that carefully inspecting the ammunition cured this fault (common, of course, to all such gears); with good quality rounds, the performance of the gear pleased even its creator.<ref>{{Cite web|url=https://www.inventricity.com/the-sound-man-george-constantinesco|title=The Sound Man – George Constantinesco}}</ref> [[Archibald Low|A. M. Low]] who commanded the [[British unmanned aerial vehicles of World War I|Royal Flying Corps secret Experimental Works at Feltham]] was involved in the testing. The system was perfected by Constantinesco in collaboration with the [[Fleet Street]] printer and engineer Walter Haddon at the Haddon Engineering Works in Honeypot Lane, Alperton.<ref>"The Dawn of the Drone" Steve Mills 2019 Casemate Publishers. p 233</ref> The first working C.C. gear was air-tested in a B.E.2c in August 1916.<ref name=Sweetman1>Sweetman 2010, p. 111.</ref>

The new gear had several advantages over all mechanical gears: the rate of fire was greatly improved, the synchronization was much more accurate, and above all it was readily adaptable to any type of engine and airframe, instead of needing a specially designed impulse generator for each type of engine and special linkages for each type of aircraft.<ref name=Cheesman3>Cheesman 1960, p. 180.</ref> In the long run (provided it was properly maintained and adjusted) it also proved far more durable and less prone to failure.<ref name=Woodman14>Woodman 1989, p. 196.</ref>

[[No. 55 Squadron RAF|No. 55 Squadron's]] [[Airco DH.4|DH.4s]] arrived in France on 6 March 1917 fitted with the new gear,<ref name=Cheesman3/> followed shortly after by [[No. 48 Squadron RAF|No. 48 squadron's]] [[Bristol F.2|Bristol Fighters]] and [[No. 56 Squadron RAF|No. 56 Squadron's]] [[Royal Aircraft Factory S.E.5|S.E.5s]]. Early production models had some teething troubles in service, as ground crew learned to service and adjust the new gears, and pilots to operate them.<ref name=Woodman14>Woodman 1989, p. 196.</ref> It was late in 1917 before a version of the gear that could operate twin guns became available, so that the first Sopwith Camels had to be fitted with the Sopwith-Kauper gear instead.

From November 1917 the gear finally became standard; being fitted to all new British aircraft with synchronized guns from that date up to the [[Gloster Gladiator]] of 1937.

Over 6,000 gears were fitted to machines of the Royal Flying Corps and the Royal Naval Air Service between March and December 1917.  Twenty thousand more "Constantinesco-Colley" gun synchronization systems were fitted to British military aircraft between January and October 1918, during the period when the [[Royal Air Force]] was formed from the two earlier services on April 1, 1918. A total of 50,000 gears were manufactured during the twenty years it was standard equipment.

==== The Betteridge gear ====
[[File:Aerial Warfare 1914-1918 Q66257.jpg|thumb|A synchronized Vickers gun fitted to a test stand; an electric motor drives a structure that simulates the propeller]]
The C.C. gear was not the only hydraulic gear to be proposed; in 1917 Air Mechanic A.R. Betteridge of [[No. 1 Squadron RAAF|No.1 Squadron Australian Flying Corps]] built and tested a gear of his own design while serving with his unit in Palestine. No official interest was expressed in this device; possibly the C.C. gear was already in prospect.<ref name=Woodman12a>Woodman 1989, p. 193.</ref> The illustration seems very likely to be of the test rig for this gear.