How were machine guns synchronised to fire thru the propellor on the Me 109?

[Stovepipe]

Hi all,
How was it done? I know that the ammunition was electrically fired, but how was the act of interruption carried out? was it by electrical or some kind of timed mechanical means? One source said was dependent on the magneto timing, another said there was a cam device fitted to the prop shaft that created an interruption based on RPM? How was it done in the field?

 

[muttly]

I"m guessing a geared device. Anyone with more knowledge on this subject
please chime in.

 

[riggerrob]

As an aside, the 20 mm motor kanons installed in Me.109 did not need interrupter gear because they fired straight through the prop hub. Motor kanons were completely outside the crankcase. They lay between the cylinder banks and only fired through the hollow propeller speed reduction unit.
Motor kanons were invented by Hsipano-Suiza during World War 1. A few French fighters (e.g. Dewoitine) were equipped with motor-kanons at the start of WW2 and H-S licensed the 12Y engine design to Klimov in the Soviet Union, so many Yak, Lavovchin, etc. fighters also got motor-kanons.

 

[1635yankee]

Well, Wikipedia has an article: https://en.wikipedia.org/wiki/Synchronization_gear which is, as is common with encyclopedia articles, full of reasonable citations. AG (Tony) Williams also has an article (https://quarryhs.co.uk/Synchro.pdf) on his website.

 

[Apophenia]

... another said there was a cam device fitted to the prop shaft that created an interruption based on RPM...

I assume that this "cam device" is actually a reference to the oscillating block mechanism:

MG17 Belt Feed Mechanism

The MG17 is one of the lesser-known German machine guns used in WWII, used for aircraft armament. Mechanically, the MG17 is basically the same as the MG15 ground gun, but with some aircraft-specifi…

www.forgottenweapons.com

 

[Stovepipe]

I have read that the timing was done by affecting the ignition system,ie, the magnetos were involved in the firing sequence.

 

[riggerrob]

I have read that the timing was done by affecting the ignition system,ie, the magnetos were involved in the firing sequence.

Ignition system and magnetos still dominate.
Ignition system tells firing pin when NOT to fire.