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Old 11-04-2018, 11:08 PM   #1
Django
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Default Gun vibration & standby compass

If you check out this video at 7:30 in an A-10C cockpit as the gun fires the vibration causes the standby compass to swirl around. I think it would be nice to see this effect in the sim.
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Old 11-05-2018, 02:27 AM   #2
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The gun itself doesn't cause it. Deceleration causes it.

Funny, because acceleration does affect the whiskey compass (it will tilt and swing on the takeoff roll.)
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Old 11-06-2018, 01:02 AM   #3
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Quote:
Originally Posted by Emmy View Post
Deceleration causes it.
Do you mean recoil???
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Old 11-06-2018, 01:19 AM   #4
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There's a certain negative thrust associated with the gun firing. Accelerations cause compass errors as you can see with every turn, pitch up/down, etc. in that video.

But the "whiskey" compass alcohol fluid is absolutely being vibrated by the gun firing. Bubbles are produced by vigorous vibration. It's almost like there's not enough fluid in the instrument. You can't fill a sealed casing 100% with an incompressible fluid or bad things happen but it didn't need to be that empty.

It'd be a cool visual effect to model in the sim.
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Old 11-09-2018, 04:59 PM   #5
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Quote:
Originally Posted by Django View Post
If you check out this video at 7:30 in an A-10C cockpit as the gun fires the vibration causes the standby compass to swirl around. I think it would be nice to see this effect in the sim.
Been looking for a mod to do the same thing since I first saw that video.

Always felt the Cannon was lackluster compared to the visceral experience it appears to be irl.
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Old 11-10-2018, 02:29 AM   #6
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Vibration causes the compass to spin. Something worth noting in the video is that you can see the miniscus at the top of the compass fluid, so the compass has been leaking and isn't all the way full like it should be. This is one sure way we have of checking to see if a compass is completely empty of fluid. We tap on the compass housing, and if the card spins, the compass needs to be overhauled. Ideally, when a compass is overhauled and refilled, the refilling is done by completely submerging the compass in a clean container of compass fluid. The compass is then rotated and rolled over and checked/rechecked for air bubbles to show up behind the glass to chase any residual air out of the fluid. Once we see no bubbles, the filler cap is installed while the compass is still submerged. There is a rubber diaphragm in the back of the Airpath compasses which compensates for changes in air pressure. So, as long as the integrity of the seals on the compass is good, there should be no air inside it to cause foaming. The fluid is there to keep the compass from being affected by vibration. The gun on the A-10 will vibrate it enough to cause it to move, but it won't spin if the case is completely filled.
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Old 11-10-2018, 01:43 PM   #7
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Quote:
Originally Posted by eaglecash867 View Post
Vibration causes the compass to spin. Something worth noting in the video is that you can see the miniscus at the top of the compass fluid, so the compass has been leaking .....

Thank you for the detailed explanation
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Old 11-10-2018, 02:07 PM   #8
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No problem!
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Old 11-11-2018, 03:16 AM   #9
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Quote:
Originally Posted by eaglecash867 View Post
Vibration causes the compass to spin. ... but it won't spin if the case is completely filled.
Quote:
Originally Posted by AMVI_Groove View Post
Thank you for the detailed explanation
+1 awesome!
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Old 11-11-2018, 06:05 AM   #10
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Quote:
Originally Posted by eaglecash867 View Post
Ideally, when a compass is overhauled and refilled, the refilling is done by completely submerging the compass in a clean container of compass fluid.
Ok now the Million Dollar question...what is "Clean Compass Fluid"? We always called them Whiskey Compasses...but I doubt that's what they are filled with now.

Great explanation.
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