interrupter gear or machine gun synchronizer

This was recorded in the Canada Aviation Museum in Ottawa, Ontario.
Interrupter gear : From Wikipedia, the free encyclopedia
An interrupter gear is a device used on military aircraft and warships in order to allow them to target opponents without damaging themselves.
The term covers two related technologies: the first, more accurately referred to as synchronization gear, or a gun synchronizer, is attached to the armament of a tractor-type craft so that it can fire through the arc of a spinning propeller without the bullets striking the blades. Introduced during the First World War, the gun synchronizer was a significant development in the history of aerial warfare and remained in operational use until the Korean War, after which the universal adoption of propeller-less jet aircraft rendered such gears unnecessary.
The other, true interrupter gear stops the firing of the machine gun when some part of the aircraft is in the way. For much of the early history of the fighter aircraft this was limited to the propeller. This would change with the introduction of gun turret mounts on bomber aircraft.
Though their effects were the same, there was a subtle difference between the concept of the interrupter and the synchronizer. A machine gun fitted with interrupter gear had the trigger normally enabled and the interrupter mechanism would disable the trigger when a propeller blade was in the way. A machine gun fitted with synchronization gear had the trigger normally disabled and the synchronizer mechanism would enable the trigger when the propeller was clear, essentially with the rotating parts of the engine (the crankshaft and other parts connected to it with an inline engine, the crankcase with a rotary engine) firing the gun. In reality, the technical difficulties associated with reliably halting, or co-ordinating, the firing of a Maxim-type machine gun meant that no working interrupter system was ever developed - all successful implementations used the concept of synchronization.

[@NJA2k8]

As a kid, I just thought that they prayed for the best and hoped it didn't hit the propellers that were spinning so fast lol

[@MyAngelReimu]

LOL

[@Yildun28]

The earliest fighter did exactly that, the Morane Monoplane. But it was also equipped with a deflector to help save the propeller from the roughly 5-10% of the bullets that hit it. upload.wikimedia.org/wikipedia/commons/1/1c/Morane-Saulnier_Type_N.jpg

[@toxicatto6074]

same, i thought there's a chance of the bullet got the propeller

[@bruhdenegressive7887]

Same but now I know

[@batozorange]

They did, actually. At least until the invention of the synchronized gear.

[@connardman]

Such ingenuity. I imagined something far more complex than that. It's so simple, it's beautiful.

[@williamdiaz8599]

Same. I was thinking it interrupted the firing sequence. Now I see it automates it essentially

[@thomasraskopf5747]

This means that the RPM of the engine modifies the cyclic rate of fire. Your gun fires faster or slower depending on the speed of the engine. Cool engineering!

[@advoc8tr]

Also means it is a semi-automatic gun not a 'machine' gun in the tradition sense. The cam is basically a trigger pull and release.

[@samburkes7552]

@@advoc8tr Grey area there, but for most part, you're correct..A matter of semantics.

[@paulmarchi1393]

@@samburkes7552 Not grey. They tried making automatic guns work with synchronization gears like that and never really managed. The best solution is to use a semi-automatic gun as shown in the video.

[@samburkes7552]

@@paulmarchi1393 Don't quite agree with that there. A firearm like that is either full auto, or semi-auto.Way I logically view it, being a ballistics expert in a gun store, it's full-auto until the cam system "interrupts", or stops the bolt from going into battery, firing the gun, or the cam actuation system dictates whether the gun continues firing or not..

[@mommayp8353]

This answers a question I've always been asking myself, how do they shoot without hitting the blades!

[@guiltygearcore]

Me too.

[@peterp696]

In WW1 most engines were like this. It's called "Rotary engine" The cylinders span around with the propeller to help them cool down.

[@HoHoMoMoo]

😂 I knew there was some mathematics involved now I can rest in peace...

[@FLIGHTCOMPANY]

I've always wondered.

[@magnarshirt7960]

Me too, haha. Science

[@Ryan57x_]

Anyone else interested in knowing how this worked after watching the Slow Mo Guys's video?

[@96dragonhunter]

I don't even know who they are

[@albertlalmuanpuia7024]

I've always search this..now i see

[@dumdumlegacy3251]

Yep

[@thankyouforyourcompliance7386]

Exactly.

[@JohnRamboPT]

hahaha exactly why i'm here very good hahahaha

[@jiznvamerike]

Battlefield 1 brought me here wondering.. Shit's amazing!

[@amjadal-bittar5638]

same

[@gbsavc]

Same

[@deano50z]

Haha that's crazy me too man!! Curiosity wonders...

[@zodiac308]

fuck yeah it is amazing!

[@warlordianx23]

same here my friend

[@generalmaul4615]

That's freakin smart. I always wondered how older planes never shot themselves down while shooting their guns.

[@zombiedoggie2732]

before a capture of a few German planes, the allies had metal on the backs of their props to deflect any bullets hitting them.

[@RM172011]

slo mo guys brought me here

[@adamdow8083]

RM172011 same

[@Felisargyle]

They didn’t explain it :(

[@MarshmallowMasta]

@Marc Opie: Some did, take a look at the SE5a aircraft, they had a Maxim gun mounted on the nose to be fired through the propeller and a Lewis machine gun mounted on the top of the wing that fired over the propeller. There are other examples like the Nieuport 11 which had a Lewis mounted above the wing as well. The problem with this is you then have to account for convergence, in WW2 on say a BF-109, the cannons are mounted on the wings, outside of the propeller's arc, because of this they had to set up the guns in such a way that the two guns were basically shooting perpendicular to each other so that at say 3000 yards the bullet from each gun would, in a perfect world without gravity, wind and imperfection, would collide at a single point. This means if you're say 2000 yards from a target and you're aiming directly at the tail of an enemy aircraft, when you pull the trigger, your bullets will actually hit on each side of the point you're aiming at, rather than hitting the tail where your gun sight is pointed because you're too close so the ammunition hasn't gone far enough to hit that convergence point. I'm sure there's more to it and other reasons but that's one major downside of having guns mounted outside the propeller.

[@samburkes7552]

Cheeky Donkey, most exactly correct. Its,the job of Ordnance to properly "zero-point"/harmonize all the guns, usually, as found out recently, zeroed about 500yds, a workable distance..The RAF employed slightly different harmonization zero points. This concept, along with the employment of the reflex gunsight sitting ahead of the pilot, is not all that different than the bore-sighting of a hi-powered hunting rifle, using the optical bore-sight as a tool with the scope mounted...I work in a gunshop here in Miss, this being an adjunct to my other gun-cleaning duties..Thnx

[@ScoutSniper3124]

Their first idea was steel plates on the propellers at the point the bullets hit. I'm guessing this worked for a bit, but eventually even the steel would start to fail, and there goes the prop.

[@thurbine2411]

And that makes the propellers heavier and less efficient which is a big problem

[@TheGreatSeraphim]

So simple yet my brain could not figure it out till I found out about the interrupter gear.

[@MyAngelReimu]

TheGreatSeraphim I don't think it's simple.

[@baathgang1707]

The complicated part is the disconnector, the mechanism in of its self is very ingenous

[@Destro]

PhillyD sent me

[@Burningwipf]

same here

[@ATiOX]

Same here. Damn this is badass.

[@claytonstatusjc]

Destro lol same👊

[@yctan97]

This 2 minutes video is so much more informative than many 30 minutes video featuring some guys talking about stuffs no one asked for. Thank you.

[@reynaldoflores4522]

What's so brilliant is its basic simplicity !

[@cubescubescubescaptain3708]

War thunder brought me here

[@mixnmatchflavourbleach2313]

Ive pressed this machine's button so much growing up! An awesome demonstation!

[@filmidioten]

Thanks for sharing! Ever since my grandpa told me about this system I was confused and always wondered what this system looked like in reality :) It's sort of quite insane really, think of the speed in all this, when they're in actual combat.

[@samburkes7552]

..Yes, most exactly, tho pretty reliable..unless a gun jams. And that can happen, specially at hi altitudes!

[@matzeelsemann9729]

Wow, thanks for that video. I've always been asking myself how it was possible that machine guns could be mounted behind the propeller without damaging it in combat.

[@JessePeterson94]

Holy crap...the technology that was created so long ago is so smart.

[@samsignorelli]

Primitive....but primitive doesn't mean stupid.

[@samburkes7552]

@@samsignorelli Most exactly correct!! The concept was carried over even into WW2. The Germans, Italians, Japanese , even the US, carried over that mechanical/ballistic system on their single-engined fighters!

[@Bernieo153]

I've wondered about this many times before and never figured out how it works. The new Battlefield trailer triggered my wondering again and I finally decided to get to the bottom of it lol.

[@aceofdeath0285]

holy shit me too lol

[@gibbs-13]

I was always wondering this. This means, theoretically we can shoot vertical through a helicopter propeller, can't we?

[@brandon-munson]

We'll Yeah but why the hell would you want to do that??

[@leonelalmeida7921]

@@brandon-munson Direct on the spot!👍🤣🤣🤣🤣🤣🤣🤣

[@KuroHebi]

I knew there was some kind of synchronization mechanism controlling the MG's firing that would make it so that a bullet wouldn't hit a prop, but I never fully understood how it worked until now.

[@andwhatsnew]

I finally understand now.

[@oliverpaivaniemi4242]

this thing saved me with my history essay thank you so much lmao

[@SilverMiraii]

Ok now it all makes sense, I was looking at war thunder and wondering, wtf is this shit, the guns fire through the propeller ?

[@joepurmort16]

+Silver Mirai Right LOL

[@BaHaEzZz]

+Silver Mirai knowing that electronic circuits didn't exist at the time of WW1 i was wonder how they did it

[@Sean-xu5ti]

So funny. I'm here because I wanted to learn how they do it also. Actually I learned a year ago and forgot. Ha. So cool.

[@BaHaEzZz]

iTheGeek well, they still had little practical use. I'm guessing the device was purely mechanical

[@MrHws5mp]

Most of this gear was mechanical, but there were examples of electrical interuptor gear in WWII. Problaby the most famous was the Fw-190 which had a 20mm cannon in each wing root synched to fire through the prop. Because this particular cannon (the MG 151) fired it's rounds with an electric charge rather than a firing pin, it was very easy and reliable to arrange an electrical switch on the prop shaft that cut the firing circuit at the moment a blade was in the way.

[@SirRoxo]

totally came here because of the Slo-mo Guys

[@unbindallgaming7556]

technology aside, this is an awesome museum piece with the lights indicating components and actually being able to see it in action

[@omfgimgettingpissed]

So simple once you know how it's done. Thanks for posting.

[@smaarof]

I,ve always wondered how the front mounted machine guns on ww2 planes avoided shooting off the propellers. Thanks for answering my decades old question.

[@samburkes7552]

..Same mech. concept, poss. updated. Our early Curtiss P-40 Hawk fighters(AVG, Flying Tigers) had two cowl-mounted synchro mach.guns, plus what they mounted in the wings.

[@DustyEggSauce]

As a kid, I always thought it would only allow fire at certain times when the gun was out of sync with the propellers. However I never took into account that planes fly at different speeds for different situations. But wow, seeing how simple the solution is blows my mind hahah! So clever, that's amazing!

[@carpo719]

thank you! I was trying to explain this to my kids.... and realized I never knew how it worked!

[@JonathanS89]

That's pretty awesome, I always wondered how this was achieved.

[@gavmcdonald7684]

If I remember my history correctly this gave the Central powers a massive advantage during WWI until the Allies caught up to the fact that forward firing machine guns were far better than other alternatives, if you could develop a working Synch' gear that is.

[@ROMANABSOLUT]

The Synchronization gear or a gun synchronizer invented by the ROMANIAN George Constantinescu (1881-1965) . I wonder myself WHY does this short video clip NOT mention HIS name ?!? His hydraulic machine gun synchronization gear allowed airplane-mounted guns to shoot between the spinning blades of the propeller. The Constantinesco synchronization gear (or "CC" gear) was first used operationally on the D.H.4s of No. 55 squadron R.F.C. from March 1917, during World War I, and rapidly became standard equipment, replacing a variety of mechanical gears. It continued to be used by the Royal Air Force until World War II - the Gloster Gladiator being the last British fighter to be equipped with "CC" gear.

[@carlosrios8837]

The first fighter equipped with an interrupter gear was the Fokker Eindecker.

[@stukafaust]

This demonstration is brilliant. I really wondered about how this worked and now I have it much clearer in my mind.

[@timboinozify]

Because the recording person moved - you don't get to hear - if this IS what the recorded narrator says - that ALL MG's or cannon firing through a propeller disk, right up until end WWII - are in semi-automatic mode. ? Yes. That is, the gun can't fire a burst of rounds, just one round at a time, triggered by the engine / propeller, so that the rounds go between the blades. That's a very important concept and it is the main reason why the cyclic rate of fire of guns firing through the propeller was so much lower. Once constants speed / variable pitch propellers came in this ROF became relatively fixed. The only way to avoid this ROF issue was to fire a single gun through the propeller mechanism. And this was usually a Heavy MG or cannon by WWII, to maximise the effectiveness of a nose mounted gun.

[@klawstraphobia]

+Timothy Bailey All the guns that I have fired shot only one round at a time, no matter what mode the selector was set on.

[@defenderoftheadverb]

So the machine gun is set up for semi-auto fire and the propellor cam pulls the trigger. Those props went at about 1200 to 1400 RPM and the guns typically cycled at about 500 to 600 RPM so the gun either missed a cycle when the trigger pulled before it was ready or the cam trigger was disabled by the gun until it had cycled or the guns were altered to cycle at more than double their normal rate.

[@eldinswe]

Watching Porco Rosso on netflix and asking myself this question led me here. That is some genious engineering

[@oriontigley5089]

So cool! It's the little inventions that are so often overlooked, that leads to the greatness of today

[@BrandonKent136]

Cool to see this, because my great grandfather is the one that helped design this!

[@LucasMillerMTB]

Brandon Kent cool dude

[@ArchevalsArchives]

Marc Opie having the gun mounted on the center of the plane allows for straight firing where as if you're firing from the wing the guns are slanted inwards slightly to make the bullets cross at a certain point in front of the plane which reduces accuracy if a target is past that crossing point in the path of the bullets

[@BFaluup]

Thanks for posting this....ever since i heard of the synchronized machine gun i wondered how they could have done it.

[@justaguy4real]

Incredible with how fast that the prop is spinning that the firing sequence is even faster from time of chambering round they explosive process shooting out bullet so fast and repeating to next cycle.

[@AliAhmadi-hq9pj]

Wow. That’s the best engineering ever

[@Wyrmwould]

I completely understand how this works, but it still looks terribly risky. It must have occasionally become desynchronized and hit the blades. I can't imagine that it never happened like that.

[@blabby102]

WTF, all the radial engine cylinders also rotate?

[@allenroth24]

Not all of em do, but some did.

[@blabby102]

Allen Roth Really? The engine rotates along with the propeller? Are you sure?

[@khristoferthomason2296]

Yes. The two basic types of radials are called rotary-type radial and static-type radial. Rotary radials produced the greatest horsepower for their weight. The cylinders of a rotary-type radial engine are mounted radially around a small crankcase and rotate with the prop, while the crankshaft remains stationary, mounted to the firewall. The biggest disadvantage was the torque produced by the large rotating mass of the prop and the cylinders. A large number of WWI pilots died, mainly on takeoff, because so much torque made the aircraft difficult to control. This difficulty, coupled with carburetion, lubrication and exhaust system problems, limited development. Static type radials have the crankcase mounted stationary to the firewall, while the crankshaft rotates like most radial engines from post-WWI and on.

[@blabby102]

Khristofer Thomason Thanks for the awesome explanation. It sounds crazy that the engine works in "reverse". I can imagine balancing such a large rotating mass would be difficult.

[@CrisURace]

Khristofer Thomason Holy Jezus, i never knew that...:o An I am a big airplane fan :D Never thought I will be so amazed after a certain age... :o

[@perolito83]

Awesome, very creative solution.

[@TheNugler]

This is so intelligent

[@BifronsCandle]

Never knew about this. Always thought they just mounted the guns as close to the rotatory as possible, without damaging it.

[@mrabhi100k]

Thankyou Sir or Mam,for the video.. and hail to the designer...

[@yotaiji012]

Simple but ingenious

[@northstarpolaris1]

Marc Opie In WWI the prop had to be a specific size to get the new invention in the sky. Mounting the gun on the side would be a very difficult task when trying to fire straight at an opponent. In WWII with mounting guns in the wings and having a compete elaborate electrical firing unit to get it to work with deflection (how much in front of a turning target); it then became possible to mount weapons there and zero the gun angle to the center for convergence. Basically, in 1915 there was no technology to mount from the side. You wouldn't be able to clear jams or judge where you firing would likely land. But in WWII jams became less and less a problem with better feeding system for rounds to chamber thus you see a lot of US planes with it wing mounted machine guns. The Germans and Japanese still used this sync of firing through props for better straights shots rather than zeroing wing mounted guns without the deflection calculation in their cockpits because they just didn't have the technology.

[@Stiffybeaver]

Anthony Faulkner or however you spell it, his invention! Just saw it on the WW1 documentary lol curious how it worked

[@d2cuadrados510]

can't belive I actually spent a whole day thinking how they did this.

[@arazr.khojasteh5032]

Thank you

[@Corrieography]

Something I've never thought I'd be curious about. Very nice.

[@davo1093]

Very cool. Clever too

[@LordChaosHavik]

Ahh man god to finally actually know how this was done.

[@xKarma_411]

Canada I'm coming to that museum

[@maxlange5517]

Makes you wonder who invented this genius piece ? Oh was it a german? Of course it was

[@ColHogan-le5yk]

What a great display they created there!

[@BlackrabbitStudios11]

okay, mystery solved on how propellers weren't getting blown off during dogfights. though i recon at some point that mechanism failed, and I'm pretty sure they did given the time period, so i gotta look up cases of those

[@GiantSavage117]

The way it was made, if the mechanism fails the gun wont fire at all, unless the pilot does something to disconnect the gun, or jury rig it, from the sync gear. Which would have probably been possible in the early planes, while in flight, but later planes had the guns housed in the fuselage which would make disconnecting them impossible in flight. Also the guns were semi-automatic and used the rotation of the propeller to provide a pretty decent rate of fire for the time period. Which means it would be awfully hard to use in a combat situation without the sync gear. I know this is kind of late and you have probably already figured this out. But I felt like passing on my knowledge anyway.

[@AFCoulthard]

Thanks for posting this.

[@SuperStarwarsfan101]

I've known about this technology for a while, but always wondered how it worked

[@ChucksSEADnDEAD]

Marc Opie I'd need to read up more on WWI dogfighting, but I think the primary reason would be reloading and clearing jams.

[@SillyPutty3700]

That is the 1st time I have ever seen a whole engine rotate. I would love to see how the fuel lines and electrical cables connect to it.

[@kkhagerty6315]

Jonathan DeWitt it was pretty common for these old aircraft, almost all of them had a rotary engine

[@wilburross9709]

It is crazy and fascinating engineering. From what I remember, the engines were 2-stroke and the hub that was bolted to the airframe, that the engine rotated on, was hollow and a carburetor was bolted backwards to it. This fed the caster oil fuel mixture into the crankcase to cool and lube it first before being transferred into the combustion chamber to be burnt. I don't know for certain, but I imagine the transfer passage for the intake was part of the cylinder casting, like it is for 2-stroke engines today. Not sure how they fired the ignition, but with the whole engine rotating and each cylinder firing in the same position of the rotation, they could have got away with having an electrode from the magneto/coil sticking out to come in contact with and fire each spark plug as it rotated past. That would have been cool. All of this to try to get each cylinder out into the slipstream to keep an air-cooled engine cool.

[@wilburross9709]

Just watched the video again and this engine has overhead intake valves. You can see the single pushrod in front of each cylinder to open and close the valve and the external 'transfer port' at the back of the engine leading from the crankcase to the intake valve of each cylinder.

[@Ihavetopushmycar]

Smithsonian out by Dulles in Virginia....Literally, not figuratively, knew the second I saw they grey floor and the description behind the plane Awesome vid!

[@lukehefler1395]

How would that ever be figurative?

[@Willcism]

No man, this is in my hometown of Ottawa, like 5 minutes from my house. That's the Canadian Aviation Museum.

[@stewie.mullen9793]

Will Crow yeah, the ottawa aviation museum

[@failtolawl]

what a great exhibit

[@pauls5745]

re: the opening text, craft like F4U Corsair, P51 Mustang, P47 Thunderbolt etc. already were using wing-mounted armaments to eliminate the trouble of synchronized guns while giving a broader cone of fire for single-engine craft and freed up horsepower. jet propulsion was an unrelated development imo

[@rob_olmstead]

Early models (like the one used by Roland Garros) used reinforced propellers to deflect bullets that could hit, according to a book I'm reading. During the war, Garros was forced to land in enemy soil, and his plane was dent to Anthony Fokker, who modified it to fire syncronised without hitting the propellers. Can you confirm?

[@rob_olmstead]

Every place credits the interrupting gear to a different inventor.

[@dominic677969]

That was really helpful thank you.

[@Senorgusanos]

Very informative...I'd always wondered how those guns fired through their propellers

[@2828terey]

Amazing to think we had this precise technology even back then.

[@mrcrowley3891]

you mean a disk with a notch and a cable? we had much more than that lol

[@ulukbekzhumaliev2588]

I don't understand why the guns must be put behind the propeller; but not on a different part of the plane.

[@jessyjack]

Poster should indicate in the description that this is a display in the Canadian Aviation and Space Museum in Ottawa, Canada.

[@PeterPasieka]

Thanks for the post, I didn't even realize it didn't say where I recorded this.

[@greenteaespresso4348]

Ahhhh this museum is really amazing, y'all should go check it out!

[@martinholourenco1706]

thanks for posting

[@dreunderscore3314]

anyone reacted like "so that's how those bullets doesn't hit the fucking propeller"?

[@dr.strangelove6118]

Epic history brought me here

[@caviestcaveman8691]

simple and elegant and beautiful

[@billybobjo99]

this would go perfect for part of my National History Day Project!!!

[@lala1lala722]

Yosemite Sam brought me here after all those years...

[@andylebrecht4377]

Thank you so much. This vid is exactly what i was looking for.

[@MakkaP]

Slo mo guys :D

[@jx592]

Remember kangaroo jack when it went off sync?

[@PhuongNguyen-ht4tl]

this replies my question

[@beatbox20fmj]

Awesome, I always knew how it worked but never seen a close up view till now.

[@HunterTag]

finally a good way to see this

[@Paints0763]

Absolutely fascinating.

[@davesuiter]

The British suffered heavy losses after the Germans installed interrupters; designed by, I kid you not, Fokker.

[@threeuniquefingers]

So does this mean, the higher the rpm the better the firing frequency? Or does the propeller speed reduce/increase to a set frequency for firing?

[@kevinmcguinness6526]

Thanks for the video man

[@localextremist2839]

i was like How the fuck does the MG Shoot throught the proppelers without hitting it

[@HasanRizviMagic]

Good technology

[@hyennussquatch4597]

But the propeller has 2 blades and it interrupts only once per revolution. Am i missing something?

[@PeterPasieka]

The engine in flight would be spinning around 2000 revolutions per minute. I'm guessing this is spinning at 30RPM? In combat, it would seem like a continuous spray of bullets coming out of the guns.

[@seandoxtator3700]

This always got me thinking n wanted a video explaining it more