how did propellor warplanes shoot their machine guns through the propellor?
In: 2413
There were several “fixes” to the problem tried in WW1: Here they are in the order they were implemented:
1 – Avoid the problem entirely by building a plane with a pusher propeller (engine in the rear). Con: These pusher planes had poor performance.
2 – Put the gun up high on the top wing so it can shoot forward just above the propeller. Con: Pilot can’t sight the gun since it’s not in front of his eyes. Also it’s hard to change the ammo drum up there.
3 – Go ahead and shoot the gun through the propeller anyway, but affix armored metal wedges to the propeller blades at the spot the bullets will be hitting. Most bullets miss the blades and go straight through, but the ones that don’t get slapped aside by the metal wedge. Con: The engine rattles like mad whenever the propeller wedge slaps a bullet aside. The wear from this meant engines had to be replaced after just a handful of flights. Also, bullets that happen to hit the wedge straight-on would ricochet back toward the pilot, which isn’t ideal.
4 – Create an “interrupter” mechanism driven by the engine’s rotation. The interrupter is a mechanical part linked to the engine’s shaft that will interfere with the trigger mechanism of the machine gun when the engine’s drive shaft has rotated into certain positions. The interrupter stops the trigger from working during the split second in which the bullet would hit the propeller if it was fired right then. Then the interrupter rotates out of the way and the machine gun trigger will work again, until the engine rotates around again to that spot and the interrupter halts the mechanism. Thus let’s say you graph the machine gun’s timing of bullets and it would normally be like this:
|
|—bullet—bullet—bullet—bullet—bullet—bullet—bullet—> time
|
With the interrupter mechanism, it might end up looking more like this:
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|—bullet—bullet————bullet—bullet————bullet—> time
| ^ ^
| Interrupter says “no”. Interrupter says “no”.
5 – Instead of having the engine *suppress* the firing of the gun at certain times, have the engine *be* the trigger that fires the gun. In other words, design the gun to use the cycling motion of the engine *as* its triggering mechanism. Then, just like, say, an engine piston moving into the right position causes a the spark plug to spark, you have the gun fired By the engine moving into the right position where it triggers the gun. Thus instead of interrupting the normal flow of the machine gun, the machine gun is fired totally in sync with the engine’s movements. A gun might be arranged to fire a bullet at, say, at 3 or 4 specific points of the engine’s rotation. When you use this method, the pilot’s trigger isn’t so much firing the machine gun, as it is just connecting the machine gun to the engine mechanism that fires it.
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