Turns out this 37mm was about the limit. There's talk of a 60mm experimental

It's not the recoil or the gun mount, or finding somebody crazy enough . . ,plenty of those

The only way to make a cannon light enough for use in an aircraft, is to make the gun barrel thinner. Metalurgy being what it was in 1916, that wasn't a very good idea

Wow, and they got that contraption up into the air with that tiny little propellor!

Apparently Georges Guynemer, fitted a 37mm single shot cannon that fired through his hollowed out prop shaft on his SPAD S.VII. also he claimed 2 victories with this weapon, I'm not sure how true this is but i do remember reading it somewhere

Sounds good, but I personally doubt it's veracity, engine technology being what it was in 1917

In WW2 the German fighters used a geared propellor to fire a cannon threw the prop hub. With the cannon itself being in the valley between the cylinders

In 1917 the geared propellor wasn't yet invented

I'll buy the foreward firing idea with the interrupter gear or mounted on the upper wing

Nonsense, geared propellers were routinely used on (a small number of types of, and production runs of) aircraft - not only EC either, as there were several chain driven CP types with the engines fuselage mounted and the propellers on the wings. Once you have chain drive you have 'gearing' as you can trivially change the relative diameter of sprockets even if you opt to use unity gearing.

The SE5 used some direct drive and some geared engine types, and there are others.

Quibbling, but the Seimens-Shuckert Rotaries are geared too, as they have contra-rotation of shaft and cylinders.


Retractable U/C also débuted during the war as well ~ and was particularly strikingly applied to a float-plane - sadly it was lost in an accident, but it looks really interesting...

Well then perhaps there is a mechanical drawing someplace showing how this was accomplished. Strange I've never seen one, have you

I should think with all these modern mechanical wonders, they would've not needed someone to turn the propellor for starting

Mechanical drawings of what, geared props or the SPAD XII cannon?

I have a choice ?

Firing thru the propeller shaft, this I've got to see. Taking a direct drive propeller setup, having your mechanic cobble together a geared propeller. Solely because you wish to fire a cannon

How about a 1918 US built example from the National Museum of the USAF?





Note the gear housing on the front view, the breach on the rear view.

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Uncleal, the gear-reduction Hispano was commonly used in the later part of the War, and was indeed the powerplant fitted to the SPAD XII Ca.I. This was the plane that had been armed with the thru-hub firing Hotchkiss 37mm cannon and was designed in part by Guynemer and used by him to score at least two of his victories. Fonck also used the SPAD XII, scoring 11 of his victories with the craft. It did however have a fair number of problems. It was quite nose-heavy for one thing. Also, the Hotchkiss was a single-fire weapon and reloading in flight was horrible as air pressure coming through the barrel when you opened the breech pushed the spent shell gas into the cockpit and damn near choked the pilot into unconsciousness.

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