[HN Gopher] Sync Gear: How World War I Fighters Avoided Damaging...
___________________________________________________________________
Sync Gear: How World War I Fighters Avoided Damaging Their Own
Propellers
Author : thunderbong
Score : 27 points
Date : 2023-08-09 02:36 UTC (1 days ago)
(HTM) web link (hartzellprop.com)
(TXT) w3m dump (hartzellprop.com)
| ortusdux wrote:
| Reminds me of Intermeshing-rotor helicopters
|
| https://en.wikipedia.org/wiki/Intermeshing-rotor_helicopter
| nescioquid wrote:
| Serious question: why not just move the guns so they do not shoot
| through the props?
|
| I've always assumed there was a reason for it that required
| solving the engineering problem in the first place. But now I
| wonder whether it was just simply easier to invent the 'sync
| gear' than deal with whatever problems ensue from moving the
| guns.
|
| > Sync gear, also known as an interrupter or gun synchronizer,
| was developed during World War I to ensure that...
|
| Was the sync gear an application or adaptation of an existing
| technique?
| cpgxiii wrote:
| > why not just move the guns so they do not shoot through the
| props?
|
| You can mount guns in the wing, as seen on many WWII fighters,
| or run through the center of propeller shaft. These approaches
| have significant benefits, notably the rate of fire is not
| limited by propeller speed and number of blades, as well as
| having much more room to work with when wing-mounting (or the
| case of the P-39/P-63, having significant volume in the nose).
|
| However, these approaches have some significant limitations,
| particularly for WWI-era aircraft. Most importantly, the wings
| of WWI aircraft were not strong enough to survive the stresses
| of mounting (and firing) machine guns. Wings of WWII and later
| metal aircraft are vastly stronger than the early wood, fabric,
| and wire bracing wings of most WWI aircraft. Through-propeller
| mountings are fundamentally incompatible with radial and rotary
| engines, and really only work with V-type inline engines.
| Relatively few WWI fighters were fitted with such engines. Also
| notable, wing-mounted guns must be angled inwards to converge
| at a desired range, and to be effective a pilot wants a
| gunsight that helps them estimate range to target. Such
| gunsights didn't exist in WWI, and so fuselage-mounted guns are
| easier to aim with basic sights.
| triceratops wrote:
| My guess: it's easier for the pilot to aim a gun that he's
| sitting directly behind. If the guns were mounted under the
| wings or whatever, it would be much harder.
| throwbadubadu wrote:
| Much easier aiming if its at the center (like no ""focal
| point""), and then the early ones also had only one, balance!
| But both uneducated guesses.
|
| focal point: not sure if its the right term here, what I mean
| is: If you put the guns far to the side and still let them
| shoot straight you have drastically reduced the chance to hit a
| plane flying in front. And if you point them inwards you have
| only one good distance (where bullets cross, like focal point)
| where you hit well.
| psunavy03 wrote:
| Because if the gun is mounted on the centerline of the
| aircraft, it's more natural for the pilot to aim. Also, you can
| fire out to the full range of the ammunition.
|
| Guns mounted on the wings had to be canted inward so that their
| pattern of fire intersects at some distance in front of the
| aircraft, so you only get the full firepower of all your guns
| at or around that specific range.
|
| https://en.wikipedia.org/wiki/Gun_harmonisation
| guessbest wrote:
| Three reasons, 1) Easier to line up barrel with target, 2)
| Easier to clear jams especially given the colder air
| temperature at altitude (up to 12k feet), 3) Easier to replace
| belt when out of ammo with a box of ammo behind the pilot.
| littlestymaar wrote:
| Tangentially related: you may wonder why they didn't use a pusher
| propeller[1] in the first place. After all, if the propeller is
| behind you, then you don't have an issue shooting in front of
| you, so why didn't they do it? It's because a pusher propeller
| stabilizes the plane a lot, when you start turning, the propeller
| applies a force that want to bring it back to its original
| direction, whereas the puller propeller have the opposite effect,
| making them much more maneuverable, which is the most important
| factor in a dogfight.
|
| See this excellent Twitter thread if you want to know more about
| the mechanical properties of both designs:
| https://nitter.42l.fr/F22124509/status/1538990570684784645#m
|
| [1]: a pusher propeller is behind the plane, "pushing" it instead
| of the more common "puller propeller" located in front. For
| examples of pusher propeller designs, look at popular UCAVs out
| there, like MQ-9 Reaper and Bayraktar TB2.
| jfk13 wrote:
| Indeed, some pushers were used early in WW1; e.g.
| https://en.wikipedia.org/wiki/Royal_Aircraft_Factory_F.E.2
|
| But as you say, the puller turned out to be superior.
| knodi123 wrote:
| Why not both?
|
| https://en.wikipedia.org/wiki/Dornier_Do_335
| fsckboy wrote:
| > _making them much more maneuverable, which is the most
| important factor in a dogfight_
|
| as an example problem in statistics class in grad school, we
| showed that the intuition that maneuverability is most
| important in a dogfight is incorrect, that it's speed (fly in,
| take a few shots, zoom away, lather rinse repeat) and that's
| why WWII fighters were so designed
|
| of course, all else being equal, maneuverability is good, but
| all else is not equal, there are aerodynamic tradeoffs
| littlestymaar wrote:
| Note that WWI and WWII offered a very different fighting
| environment for pilots, so what's true in one environment
| doesn't necessarily apply to the other (especially since for
| WWII fighters, the ability to intercept and shoot down enemy
| bombers was a very important design consideration).
|
| I'd be curious to learn more about your statistics example
| though.
| HeyLaughingBoy wrote:
| "Speed is Life."
| vwcx wrote:
| Thanks, that thread is an excellent discussion of the
| differences. I had never considered the exhaust contamination
| of the propeller feed air in a pusher design.
| joshstrange wrote:
| The article was pretty sparse on how it was done technically and
| the video completely skips over it. It just shows slow motion of
| it working but (and I skipped around a tiny bit but I think I got
| all the actual talking, there is only so much slow motion of the
| same thing over and over I can stand) never actually explains the
| mechanism.
|
| Sidenote, I'm sure they took all the needed safety precautions
| but it sure seemed like they were standing in front of the gun
| barrel in a few shots which made me super anxious. I knew nothing
| was going to happen (since it was posted on YouTube) but it just
| felt felt dangerous.
| fsckboy wrote:
| > _I 'm sure they took all the needed safety precautions_
|
| no they didn't, one of the most prominent advocates working on
| this problem was killed by a ricochet. let me see if I can find
| it...
| WJW wrote:
| It's just a lever holding back the firing pin until the
| propellor is past a certain point even if the trigger is
| actuated. One of those brilliant inventions that is trivial if
| you know the secret but very tricky to discover if you don't.
| __loam wrote:
| We should celebrate simple elegance more than rampant
| complexity.
| mcpackieh wrote:
| The article doesn't really say much about this, but it's an
| interesting topic. There were several ways these kind of systems
| were implemented, using mechanical linkages, hydraulics, or
| electrically using solenoids.
|
| Animation of a mechanical link system:
| https://www.youtube.com/watch?v=j1OxWxYAGlc
|
| Hydraulic: https://www.youtube.com/watch?v=8Oh1pLl1--Y
___________________________________________________________________
(page generated 2023-08-10 23:01 UTC)